Now all queues allocators come without abounce limit by default,
dm doesn't have to override this anymore.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
A target driver support zoned block devices and exposing it as such may
receive REQ_OP_ZONE_REPORT request for the user to determine the mapped
device zone configuration. To process properly such request, the target
driver may need to remap the zone descriptors provided in the report
reply. The helper function dm_remap_zone_report() does this generically
using only the target start offset and length and the start offset
within the target device.
dm_remap_zone_report() will remap the start sector of all zones
reported. If the report includes sequential zones, the write pointer
position of these zones will also be remapped.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
A REQ_OP_ZONE_REPORT bio is not a medium access command. Its number of
sectors indicates the maximum size allowed for the report reply size and
not an amount of sectors accessed from the device. REQ_OP_ZONE_REPORT
bios should thus not be split depending on the target device maximum I/O
length but passed as-is. Note that it is the responsability of the
target to remap and format the report reply.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The REQ_OP_ZONE_RESET bio has no payload and zero sectors. Its position
is the only information used to indicate the zone to reset on the
device. Due to its zero length, this bio is not cloned and sent to the
target through the non-flush case in __split_and_process_bio(). Add an
additional case in that function to call __split_and_process_non_flush()
without checking the clone info size.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Add the ability to poll on the /dev/mapper/control device. The select
or poll function waits until any event happens on any dm device since
opening the /dev/mapper/control device. When select or poll returns the
device as readable, we must close and reopen the device to wait for new
dm events.
Usage:
1. open the /dev/mapper/control device
2. scan the event numbers of all devices we are interested in and process
them
3. call select, poll or epoll on the handle (it waits until some new event
happens since opening the device)
4. close the /dev/mapper/control handle
5. go to step 1
The next commit allows to re-arm the polling without closing and
reopening the device.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This patch converts bioset_create() to not create a workqueue by
default, so alloctions will never trigger punt_bios_to_rescuer(). It
also introduces a new flag BIOSET_NEED_RESCUER which tells
bioset_create() to preserve the old behavior.
All callers of bioset_create() that are inside block device drivers,
are given the BIOSET_NEED_RESCUER flag.
biosets used by filesystems or other top-level users do not
need rescuing as the bio can never be queued behind other
bios. This includes fs_bio_set, blkdev_dio_pool,
btrfs_bioset, xfs_ioend_bioset, and one allocated by
target_core_iblock.c.
biosets used by md/raid do not need rescuing as
their usage was recently audited and revised to never
risk deadlock.
It is hoped that most, if not all, of the remaining biosets
can end up being the non-rescued version.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Credit-to: Ming Lei <ming.lei@redhat.com> (minor fixes)
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
"flags" arguments are often seen as good API design as they allow
easy extensibility.
bioset_create_nobvec() is implemented internally as a variation in
flags passed to __bioset_create().
To support future extension, make the internal structure part of the
API.
i.e. add a 'flags' argument to bioset_create() and discard
bioset_create_nobvec().
Note that the bio_split allocations in drivers/md/raid* do not need
the bvec mempool - they should have used bioset_create_nobvec().
Suggested-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Allow device-mapper to route flush operations to the
per-target implementation. In order for the device stacking to work we
need a dax_dev and a pgoff relative to that device. This gives each
layer of the stack the information it needs to look up the operation
pointer for the next level.
This conceptually allows for an array of mixed device drivers with
varying flush implementations.
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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Merge tag 'v4.12-rc5' into for-4.13/block
We've already got a few conflicts and upcoming work depends on some of the
changes that have gone into mainline as regression fixes for this series.
Pull in 4.12-rc5 to resolve these conflicts and make it easier on down stream
trees to continue working on 4.13 changes.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Allow device-mapper to route copy_from_iter operations to the
per-target implementation. In order for the device stacking to work we
need a dax_dev and a pgoff relative to that device. This gives each
layer of the stack the information it needs to look up the operation
pointer for the next level.
This conceptually allows for an array of mixed device drivers with
varying copy_from_iter implementations.
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Replace bi_error with a new bi_status to allow for a clear conversion.
Note that device mapper overloaded bi_error with a private value, which
we'll have to keep arround at least for now and thus propagate to a
proper blk_status_t value.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Turn the error paramter into a pointer so that target drivers can change
the value, and make sure only DM_ENDIO_* values are returned from the
methods.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Instead use the special DM_MAPIO_KILL return value to return -EIO just
like we do for the request based path. Note that dm-log-writes returned
-ENOMEM in a few places, which now becomes -EIO instead. No consumer
treats -ENOMEM special so this shouldn't be an issue (and it should
use a mempool to start with to make guaranteed progress).
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Commit b685d3d65a ("block: treat REQ_FUA and REQ_PREFLUSH as
synchronous") removed REQ_SYNC flag from WRITE_{FUA|PREFLUSH|...}
definitions. generic_make_request_checks() however strips REQ_FUA and
REQ_PREFLUSH flags from a bio when the storage doesn't report volatile
write cache and thus write effectively becomes asynchronous which can
lead to performance regressions.
Fix the problem by making sure all bios which are synchronous are
properly marked with REQ_SYNC.
Fixes: b685d3d65a ("block: treat REQ_FUA and REQ_PREFLUSH as synchronous")
Cc: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
* Region media error reporting: A libnvdimm region device is the parent
to one or more namespaces. To date, media errors have been reported via
the "badblocks" attribute attached to pmem block devices for namespaces
in "raw" or "memory" mode. Given that namespaces can be in "device-dax"
or "btt-sector" mode this new interface reports media errors
generically, i.e. independent of namespace modes or state. This
subsequently allows userspace tooling to craft "ACPI 6.1 Section
9.20.7.6 Function Index 4 - Clear Uncorrectable Error" requests and
submit them via the ioctl path for NVDIMM root bus devices.
* Introduce 'struct dax_device' and 'struct dax_operations': Prompted by
a request from Linus and feedback from Christoph this allows for dax
capable drivers to publish their own custom dax operations. This fixes
the broken assumption that all dax operations are related to a
persistent memory device, and makes it easier for other architectures
and platforms to add customized persistent memory support.
* 'libnvdimm' core updates: A new "deep_flush" sysfs attribute is
available for storage appliance applications to manually trigger memory
controllers to drain write-pending buffers that would otherwise be
flushed automatically by the platform ADR (asynchronous-DRAM-refresh)
mechanism at a power loss event. Support for "locked" DIMMs is included
to prevent namespaces from surfacing when the namespace label data area
is locked. Finally, fixes for various reported deadlocks and crashes,
also tagged for -stable.
* ACPI / nfit driver updates: General updates of the nfit driver to add
DSM command overrides, ACPI 6.1 health state flags support, DSM payload
debug available by default, and various fixes.
Acknowledgements that came after the branch was pushed:
commmit 565851c972 "device-dax: fix sysfs attribute deadlock"
Tested-by: Yi Zhang <yizhan@redhat.com>
commit 23f4984483 "libnvdimm: rework region badblocks clearing"
Tested-by: Toshi Kani <toshi.kani@hpe.com>
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Merge tag 'libnvdimm-for-4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm
Pull libnvdimm updates from Dan Williams:
"The bulk of this has been in multiple -next releases. There were a few
late breaking fixes and small features that got added in the last
couple days, but the whole set has received a build success
notification from the kbuild robot.
Change summary:
- Region media error reporting: A libnvdimm region device is the
parent to one or more namespaces. To date, media errors have been
reported via the "badblocks" attribute attached to pmem block
devices for namespaces in "raw" or "memory" mode. Given that
namespaces can be in "device-dax" or "btt-sector" mode this new
interface reports media errors generically, i.e. independent of
namespace modes or state.
This subsequently allows userspace tooling to craft "ACPI 6.1
Section 9.20.7.6 Function Index 4 - Clear Uncorrectable Error"
requests and submit them via the ioctl path for NVDIMM root bus
devices.
- Introduce 'struct dax_device' and 'struct dax_operations': Prompted
by a request from Linus and feedback from Christoph this allows for
dax capable drivers to publish their own custom dax operations.
This fixes the broken assumption that all dax operations are
related to a persistent memory device, and makes it easier for
other architectures and platforms to add customized persistent
memory support.
- 'libnvdimm' core updates: A new "deep_flush" sysfs attribute is
available for storage appliance applications to manually trigger
memory controllers to drain write-pending buffers that would
otherwise be flushed automatically by the platform ADR
(asynchronous-DRAM-refresh) mechanism at a power loss event.
Support for "locked" DIMMs is included to prevent namespaces from
surfacing when the namespace label data area is locked. Finally,
fixes for various reported deadlocks and crashes, also tagged for
-stable.
- ACPI / nfit driver updates: General updates of the nfit driver to
add DSM command overrides, ACPI 6.1 health state flags support, DSM
payload debug available by default, and various fixes.
Acknowledgements that came after the branch was pushed:
- commmit 565851c972 "device-dax: fix sysfs attribute deadlock":
Tested-by: Yi Zhang <yizhan@redhat.com>
- commit 23f4984483 "libnvdimm: rework region badblocks clearing"
Tested-by: Toshi Kani <toshi.kani@hpe.com>"
* tag 'libnvdimm-for-4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm: (52 commits)
libnvdimm, pfn: fix 'npfns' vs section alignment
libnvdimm: handle locked label storage areas
libnvdimm: convert NDD_ flags to use bitops, introduce NDD_LOCKED
brd: fix uninitialized use of brd->dax_dev
block, dax: use correct format string in bdev_dax_supported
device-dax: fix sysfs attribute deadlock
libnvdimm: restore "libnvdimm: band aid btt vs clear poison locking"
libnvdimm: fix nvdimm_bus_lock() vs device_lock() ordering
libnvdimm: rework region badblocks clearing
acpi, nfit: kill ACPI_NFIT_DEBUG
libnvdimm: fix clear length of nvdimm_forget_poison()
libnvdimm, pmem: fix a NULL pointer BUG in nd_pmem_notify
libnvdimm, region: sysfs trigger for nvdimm_flush()
libnvdimm: fix phys_addr for nvdimm_clear_poison
x86, dax, pmem: remove indirection around memcpy_from_pmem()
block: remove block_device_operations ->direct_access()
block, dax: convert bdev_dax_supported() to dax_direct_access()
filesystem-dax: convert to dax_direct_access()
Revert "block: use DAX for partition table reads"
ext2, ext4, xfs: retrieve dax_device for iomap operations
...
whether blocks should migrate to/from the cache. The bio-prison-v2
interface supports this improvement by enabling direct dispatch of
work to workqueues rather than having to delay the actual work
dispatch to the DM cache core. So the dm-cache policies are much more
nimble by being able to drive IO as they see fit. One immediate
benefit from the improved latency is a cache that should be much more
adaptive to changing workloads.
- Add a new DM integrity target that emulates a block device that has
additional per-sector tags that can be used for storing integrity
information.
- Add a new authenticated encryption feature to the DM crypt target that
builds on the capabilities provided by the DM integrity target.
- Add MD interface for switching the raid4/5/6 journal mode and update
the DM raid target to use it to enable aid4/5/6 journal write-back
support.
- Switch the DM verity target over to using the asynchronous hash crypto
API (this helps work better with architectures that have access to
off-CPU algorithm providers, which should reduce CPU utilization).
- Various request-based DM and DM multipath fixes and improvements from
Bart and Christoph.
- A DM thinp target fix for a bio structure leak that occurs for each
discard IFF discard passdown is enabled.
- A fix for a possible deadlock in DM bufio and a fix to re-check the
new buffer allocation watermark in the face of competing admin changes
to the 'max_cache_size_bytes' tunable.
- A couple DM core cleanups.
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Merge tag 'for-4.12/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper updates from Mike Snitzer:
- A major update for DM cache that reduces the latency for deciding
whether blocks should migrate to/from the cache. The bio-prison-v2
interface supports this improvement by enabling direct dispatch of
work to workqueues rather than having to delay the actual work
dispatch to the DM cache core. So the dm-cache policies are much more
nimble by being able to drive IO as they see fit. One immediate
benefit from the improved latency is a cache that should be much more
adaptive to changing workloads.
- Add a new DM integrity target that emulates a block device that has
additional per-sector tags that can be used for storing integrity
information.
- Add a new authenticated encryption feature to the DM crypt target
that builds on the capabilities provided by the DM integrity target.
- Add MD interface for switching the raid4/5/6 journal mode and update
the DM raid target to use it to enable aid4/5/6 journal write-back
support.
- Switch the DM verity target over to using the asynchronous hash
crypto API (this helps work better with architectures that have
access to off-CPU algorithm providers, which should reduce CPU
utilization).
- Various request-based DM and DM multipath fixes and improvements from
Bart and Christoph.
- A DM thinp target fix for a bio structure leak that occurs for each
discard IFF discard passdown is enabled.
- A fix for a possible deadlock in DM bufio and a fix to re-check the
new buffer allocation watermark in the face of competing admin
changes to the 'max_cache_size_bytes' tunable.
- A couple DM core cleanups.
* tag 'for-4.12/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (50 commits)
dm bufio: check new buffer allocation watermark every 30 seconds
dm bufio: avoid a possible ABBA deadlock
dm mpath: make it easier to detect unintended I/O request flushes
dm mpath: cleanup QUEUE_IF_NO_PATH bit manipulation by introducing assign_bit()
dm mpath: micro-optimize the hot path relative to MPATHF_QUEUE_IF_NO_PATH
dm: introduce enum dm_queue_mode to cleanup related code
dm mpath: verify __pg_init_all_paths locking assumptions at runtime
dm: verify suspend_locking assumptions at runtime
dm block manager: remove an unused argument from dm_block_manager_create()
dm rq: check blk_mq_register_dev() return value in dm_mq_init_request_queue()
dm mpath: delay requeuing while path initialization is in progress
dm mpath: avoid that path removal can trigger an infinite loop
dm mpath: split and rename activate_path() to prepare for its expanded use
dm ioctl: prevent stack leak in dm ioctl call
dm integrity: use previously calculated log2 of sectors_per_block
dm integrity: use hex2bin instead of open-coded variant
dm crypt: replace custom implementation of hex2bin()
dm crypt: remove obsolete references to per-CPU state
dm verity: switch to using asynchronous hash crypto API
dm crypt: use WQ_HIGHPRI for the IO and crypt workqueues
...
I/O errors triggered by multipathd incorrectly not enabling the no-flush
flag for DM_DEVICE_SUSPEND or DM_DEVICE_RESUME are hard to debug. Add
more logging to make it easier to debug this.
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Introduce an enumeration type for the queue mode. This patch does
not change any functionality but makes the DM code easier to read.
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Ensure that the assumptions about the caller holding suspend_lock
are checked at runtime if lockdep is enabled.
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Now that all the producers and consumers of dax interfaces have been
converted to using dax_operations on a dax_device, remove the block
device direct_access enabling.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Arrange for dm to lookup the dax services available from member devices.
Update the dax-capable targets, linear and stripe, to route dax
operations to the underlying device. Changes the target-internal
->direct_access() method to more closely align with the dax_operations
->direct_access() calling convention.
Cc: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
A dm-crypt on dm-integrity device incorrectly advertises an integrity
profile on the DM crypt device. It can be seen in the files
"/sys/block/dm-*/integrity/*" that both dm-integrity and dm-crypt target
advertise the integrity profile. That is incorrect, only the
dm-integrity target should advertise the integrity profile.
A general problem in DM is that if we have a DM device that depends on
another device with an integrity profile, the upper device will always
advertise the integrity profile, even when the target driver doesn't
support handling integrity data.
Most targets don't support integrity data, so we provide a whitelist of
targets that support it (linear, delay and striped). The targets that
support passing integrity data to the lower device are marked with the
flag DM_TARGET_PASSES_INTEGRITY. The DM core will now advertise
integrity data on a DM device only if all the targets support the
integrity data.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Allocate a dax_device to represent the capacity of a device-mapper
instance. Provide a ->direct_access() method via the new dax_operations
indirection that mirrors the functionality of the current direct_access
support via block_device_operations. Once fs/dax.c has been converted
to use dax_operations the old dm_blk_direct_access() will be removed.
A new helper dm_dax_get_live_target() is introduced to separate some of
the dm-specifics from the direct_access implementation.
This enabling is only for the top-level dm representation to upper
layers. Converting target direct_access implementations is deferred to a
separate patch.
Cc: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Copy & paste from the REQ_OP_WRITE_SAME code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Currently only dm and md/raid5 bios trigger
trace_block_bio_complete(). Now that we have bio_chain() and
bio_inc_remaining(), it is not possible, in general, for a driver to
know when the bio is really complete. Only bio_endio() knows that.
So move the trace_block_bio_complete() call to bio_endio().
Now trace_block_bio_complete() pairs with trace_block_bio_queue().
Any bio for which a 'queue' event is traced, will subsequently
generate a 'complete' event.
There are a few cases where completion tracing is not wanted.
1/ If blk_update_request() has already generated a completion
trace event at the 'request' level, there is no point generating
one at the bio level too. In this case the bi_sector and bi_size
will have changed, so the bio level event would be wrong
2/ If the bio hasn't actually been queued yet, but is being aborted
early, then a trace event could be confusing. Some filesystems
call bio_endio() but do not want tracing.
3/ The bio_integrity code interposes itself by replacing bi_end_io,
then restoring it and calling bio_endio() again. This would produce
two identical trace events if left like that.
To handle these, we introduce a flag BIO_TRACE_COMPLETION and only
produce the trace event when this is set.
We address point 1 above by clearing the flag in blk_update_request().
We address point 2 above by only setting the flag when
generic_make_request() is called.
We address point 3 above by clearing the flag after generating a
completion event.
When bio_split() is used on a bio, particularly in blk_queue_split(),
there is an extra complication. A new bio is split off the front, and
may be handle directly without going through generic_make_request().
The old bio, which has been advanced, is passed to
generic_make_request(), so it will trigger a trace event a second
time.
Probably the best result when a split happens is to see a single
'queue' event for the whole bio, then multiple 'complete' events - one
for each component. To achieve this was can:
- copy the BIO_TRACE_COMPLETION flag to the new bio in bio_split()
- avoid generating a 'queue' event if BIO_TRACE_COMPLETION is already set.
This way, the split-off bio won't create a queue event, the original
won't either even if it re-submitted to generic_make_request(),
but both will produce completion events, each for their own range.
So if generic_make_request() is called (which generates a QUEUED
event), then bi_endio() will create a single COMPLETE event for each
range that the bio is split into, unless the driver has explicitly
requested it not to.
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Commit 79bd99596b ("blk: improve order of bio handling in generic_make_request()")
changed current->bio_list so that it did not contain *all* of the
queued bios, but only those submitted by the currently running
make_request_fn.
There are two places which walk the list and requeue selected bios,
and others that check if the list is empty. These are no longer
correct.
So redefine current->bio_list to point to an array of two lists, which
contain all queued bios, and adjust various code to test or walk both
lists.
Signed-off-by: NeilBrown <neilb@suse.com>
Fixes: 79bd99596b ("blk: improve order of bio handling in generic_make_request()")
Signed-off-by: Jens Axboe <axboe@fb.com>
Fix up affected files that include this signal functionality via sched.h.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
tweaks.
- Add journal support to the DM raid target to close the 'write hole' on
raid 4/5/6.
- Fix dm-cache corruption, due to rounding bug, when cache exceeds 2TB.
- Add 'metadata2' feature to dm-cache to separate the dirty bitset out
from other cache metadata. This improves speed of shutting down
a large cache device (which implies writing out dirty bits).
- Fix a memory leak during dm-stats data structure destruction.
- Fix a DM multipath round-robin path selector performance regression
that was caused by less precise balancing across all paths.
- Lastly, introduce a DM core fix for a long-standing DM snapshot
deadlock that is rooted in the complexity of the device stack used in
conjunction with block core maintaining bios on current->bio_list to
manage recursion in generic_make_request(). A more comprehensive fix
to block core (and its hook in the cpu scheduler) would be wonderful
but this DM-specific fix is pragmatic considering how difficult it has
been to make progress on a generic fix.
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Merge tag 'dm-4.11-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper updates from Mike Snitzer:
- Fix dm-raid transient device failure processing and other smaller
tweaks.
- Add journal support to the DM raid target to close the 'write hole'
on raid 4/5/6.
- Fix dm-cache corruption, due to rounding bug, when cache exceeds 2TB.
- Add 'metadata2' feature to dm-cache to separate the dirty bitset out
from other cache metadata. This improves speed of shutting down a
large cache device (which implies writing out dirty bits).
- Fix a memory leak during dm-stats data structure destruction.
- Fix a DM multipath round-robin path selector performance regression
that was caused by less precise balancing across all paths.
- Lastly, introduce a DM core fix for a long-standing DM snapshot
deadlock that is rooted in the complexity of the device stack used in
conjunction with block core maintaining bios on current->bio_list to
manage recursion in generic_make_request(). A more comprehensive fix
to block core (and its hook in the cpu scheduler) would be wonderful
but this DM-specific fix is pragmatic considering how difficult it
has been to make progress on a generic fix.
* tag 'dm-4.11-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (22 commits)
dm: flush queued bios when process blocks to avoid deadlock
dm round robin: revert "use percpu 'repeat_count' and 'current_path'"
dm stats: fix a leaked s->histogram_boundaries array
dm space map metadata: constify dm_space_map structures
dm cache metadata: use cursor api in blocks_are_clean_separate_dirty()
dm persistent data: add cursor skip functions to the cursor APIs
dm cache metadata: use dm_bitset_new() to create the dirty bitset in format 2
dm bitset: add dm_bitset_new()
dm cache metadata: name the cache block that couldn't be loaded
dm cache metadata: add "metadata2" feature
dm cache metadata: use bitset cursor api to load discard bitset
dm bitset: introduce cursor api
dm btree: use GFP_NOFS in dm_btree_del()
dm space map common: memcpy the disk root to ensure it's arch aligned
dm block manager: add unlikely() annotations on dm_bufio error paths
dm cache: fix corruption seen when using cache > 2TB
dm raid: cleanup awkward branching in raid_message() option processing
dm raid: use mddev rather than rdev->mddev
dm raid: use read_disk_sb() throughout
dm raid: add raid4/5/6 journaling support
...
Commit df2cb6daa4 ("block: Avoid deadlocks with bio allocation by
stacking drivers") created a workqueue for every bio set and code
in bio_alloc_bioset() that tries to resolve some low-memory deadlocks
by redirecting bios queued on current->bio_list to the workqueue if the
system is low on memory. However other deadlocks (see below **) may
happen, without any low memory condition, because generic_make_request
is queuing bios to current->bio_list (rather than submitting them).
** the related dm-snapshot deadlock is detailed here:
https://www.redhat.com/archives/dm-devel/2016-July/msg00065.html
Fix this deadlock by redirecting any bios on current->bio_list to the
bio_set's rescue workqueue on every schedule() call. Consequently,
when the process blocks on a mutex, the bios queued on
current->bio_list are dispatched to independent workqueus and they can
complete without waiting for the mutex to be available.
The structure blk_plug contains an entry cb_list and this list can contain
arbitrary callback functions that are called when the process blocks.
To implement this fix DM (ab)uses the onstack plug's cb_list interface
to get its flush_current_bio_list() called at schedule() time.
This fixes the snapshot deadlock - if the map method blocks,
flush_current_bio_list() will be called and it redirects bios waiting
on current->bio_list to appropriate workqueues.
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1267650
Depends-on: df2cb6daa4 ("block: Avoid deadlocks with bio allocation by stacking drivers")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
.. at least for unprivileged users. Before we called into the SCSI
ioctl code to allow excemptions for a few SCSI passthrough ioctls,
but this is pretty unsafe and except for this call dm knows nothing
about SCSI ioctls.
As the SCSI ioctl code is now optional, we really don't want to
drag it in for DM, and the exception is not very useful anyway.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@kernel.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
We will want to have struct backing_dev_info allocated separately from
struct request_queue. As the first step add pointer to backing_dev_info
to request_queue and convert all users touching it. No functional
changes in this patch.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
DM already calls blk_mq_alloc_request on the request_queue of the
underlying device if it is a blk-mq device. But now that we allow drivers
to allocate additional data and initialize it ahead of time we need to do
the same for all drivers. Doing so and using the new cmd_size
infrastructure in the block layer greatly simplifies the dm-rq and mpath
code, and should also make arbitrary combinations of SQ and MQ devices
with SQ or MQ device mapper tables easily possible as a further step.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
. some locking improvements in DM bufio
. add Kconfig option to disable the DM block manager's extra locking
which mainly serves as a developer tool
. a few bug fixes to DM's persistent-data
. a couple changes to prepare for multipage biovec support in the block
layer
. various improvements and cleanups in the DM core, DM cache, DM raid
and DM crypt
. add ability to have DM crypt use keys from the kernel key retention
service
. add a new "error_writes" feature to the DM flakey target, reads are
left unchanged in this mode
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Merge tag 'dm-4.10-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper updates from Mike Snitzer:
- various fixes and improvements to request-based DM and DM multipath
- some locking improvements in DM bufio
- add Kconfig option to disable the DM block manager's extra locking
which mainly serves as a developer tool
- a few bug fixes to DM's persistent-data
- a couple changes to prepare for multipage biovec support in the block
layer
- various improvements and cleanups in the DM core, DM cache, DM raid
and DM crypt
- add ability to have DM crypt use keys from the kernel key retention
service
- add a new "error_writes" feature to the DM flakey target, reads are
left unchanged in this mode
* tag 'dm-4.10-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (40 commits)
dm flakey: introduce "error_writes" feature
dm cache policy smq: use hash_32() instead of hash_32_generic()
dm crypt: reject key strings containing whitespace chars
dm space map: always set ev if sm_ll_mutate() succeeds
dm space map metadata: skip useless memcpy in metadata_ll_init_index()
dm space map metadata: fix 'struct sm_metadata' leak on failed create
Documentation: dm raid: define data_offset status field
dm raid: fix discard support regression
dm raid: don't allow "write behind" with raid4/5/6
dm mpath: use hw_handler_params if attached hw_handler is same as requested
dm crypt: add ability to use keys from the kernel key retention service
dm array: remove a dead assignment in populate_ablock_with_values()
dm ioctl: use offsetof() instead of open-coding it
dm rq: simplify use_blk_mq initialization
dm: use blk_set_queue_dying() in __dm_destroy()
dm bufio: drop the lock when doing GFP_NOIO allocation
dm bufio: don't take the lock in dm_bufio_shrink_count
dm bufio: avoid sleeping while holding the dm_bufio lock
dm table: simplify dm_table_determine_type()
dm table: an 'all_blk_mq' table must be loaded for a blk-mq DM device
...
Pull block layer updates from Jens Axboe:
"This is the main block pull request this series. Contrary to previous
release, I've kept the core and driver changes in the same branch. We
always ended up having dependencies between the two for obvious
reasons, so makes more sense to keep them together. That said, I'll
probably try and keep more topical branches going forward, especially
for cycles that end up being as busy as this one.
The major parts of this pull request is:
- Improved support for O_DIRECT on block devices, with a small
private implementation instead of using the pig that is
fs/direct-io.c. From Christoph.
- Request completion tracking in a scalable fashion. This is utilized
by two components in this pull, the new hybrid polling and the
writeback queue throttling code.
- Improved support for polling with O_DIRECT, adding a hybrid mode
that combines pure polling with an initial sleep. From me.
- Support for automatic throttling of writeback queues on the block
side. This uses feedback from the device completion latencies to
scale the queue on the block side up or down. From me.
- Support from SMR drives in the block layer and for SD. From Hannes
and Shaun.
- Multi-connection support for nbd. From Josef.
- Cleanup of request and bio flags, so we have a clear split between
which are bio (or rq) private, and which ones are shared. From
Christoph.
- A set of patches from Bart, that improve how we handle queue
stopping and starting in blk-mq.
- Support for WRITE_ZEROES from Chaitanya.
- Lightnvm updates from Javier/Matias.
- Supoort for FC for the nvme-over-fabrics code. From James Smart.
- A bunch of fixes from a whole slew of people, too many to name
here"
* 'for-4.10/block' of git://git.kernel.dk/linux-block: (182 commits)
blk-stat: fix a few cases of missing batch flushing
blk-flush: run the queue when inserting blk-mq flush
elevator: make the rqhash helpers exported
blk-mq: abstract out blk_mq_dispatch_rq_list() helper
blk-mq: add blk_mq_start_stopped_hw_queue()
block: improve handling of the magic discard payload
blk-wbt: don't throttle discard or write zeroes
nbd: use dev_err_ratelimited in io path
nbd: reset the setup task for NBD_CLEAR_SOCK
nvme-fabrics: Add FC LLDD loopback driver to test FC-NVME
nvme-fabrics: Add target support for FC transport
nvme-fabrics: Add host support for FC transport
nvme-fabrics: Add FC transport LLDD api definitions
nvme-fabrics: Add FC transport FC-NVME definitions
nvme-fabrics: Add FC transport error codes to nvme.h
Add type 0x28 NVME type code to scsi fc headers
nvme-fabrics: patch target code in prep for FC transport support
nvme-fabrics: set sqe.command_id in core not transports
parser: add u64 number parser
nvme-rdma: align to generic ib_event logging helper
...
After QUEUE_FLAG_DYING has been set any code that is waiting in
get_request() should be woken up. But to get this behaviour
blk_set_queue_dying() must be used instead of only setting
QUEUE_FLAG_DYING.
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Some drivers often use external bvec table, so introduce
this helper for this case. It is always safe to access the
bio->bi_io_vec in this way for this case.
After converting to this usage, it will becomes a bit easier
to evaluate the remaining direct access to bio->bi_io_vec,
so it can help to prepare for the following multipage bvec
support.
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Fixed up the new O_DIRECT cases.
Signed-off-by: Jens Axboe <axboe@fb.com>
Remove the WRITE_* and READ_SYNC wrappers, and just use the flags
directly. Where applicable this also drops usage of the
bio_set_op_attrs wrapper.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
- A couple .request_fn request-based DM NULL pointer fixes
- A fix for a DM target reference count leak, on target load error, that
prevented associated DM target kernel module(s) from being removed
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Merge tag 'dm-4.9-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper fixes from Mike Snitzer:
- a couple DM raid and DM mirror fixes
- a couple .request_fn request-based DM NULL pointer fixes
- a fix for a DM target reference count leak, on target load error,
that prevented associated DM target kernel module(s) from being
removed
* tag 'dm-4.9-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
dm table: fix missing dm_put_target_type() in dm_table_add_target()
dm rq: clear kworker_task if kthread_run() returned an error
dm: free io_barrier after blk_cleanup_queue call
dm raid: fix activation of existing raid4/10 devices
dm mirror: use all available legs on multiple failures
dm mirror: fix read error on recovery after default leg failure
dm raid: fix compat_features validation
dm_old_request_fn() has paths that access md->io_barrier. The party
destroying io_barrier should ensure that no future execution of
dm_old_request_fn() is possible. Move io_barrier destruction to below
blk_cleanup_queue() to ensure this and avoid a NULL pointer crash during
request-based DM device shutdown.
Cc: stable@vger.kernel.org # 4.3+
Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
A good practice is to prefix the names of functions by the name
of the subsystem.
The kthread worker API is a mix of classic kthreads and workqueues. Each
worker has a dedicated kthread. It runs a generic function that process
queued works. It is implemented as part of the kthread subsystem.
This patch renames the existing kthread worker API to use
the corresponding name from the workqueues API prefixed by
kthread_:
__init_kthread_worker() -> __kthread_init_worker()
init_kthread_worker() -> kthread_init_worker()
init_kthread_work() -> kthread_init_work()
insert_kthread_work() -> kthread_insert_work()
queue_kthread_work() -> kthread_queue_work()
flush_kthread_work() -> kthread_flush_work()
flush_kthread_worker() -> kthread_flush_worker()
Note that the names of DEFINE_KTHREAD_WORK*() macros stay
as they are. It is common that the "DEFINE_" prefix has
precedence over the subsystem names.
Note that INIT() macros and init() functions use different
naming scheme. There is no good solution. There are several
reasons for this solution:
+ "init" in the function names stands for the verb "initialize"
aka "initialize worker". While "INIT" in the macro names
stands for the noun "INITIALIZER" aka "worker initializer".
+ INIT() macros are used only in DEFINE() macros
+ init() functions are used close to the other kthread()
functions. It looks much better if all the functions
use the same scheme.
+ There will be also kthread_destroy_worker() that will
be used close to kthread_cancel_work(). It is related
to the init() function. Again it looks better if all
functions use the same naming scheme.
+ there are several precedents for such init() function
names, e.g. amd_iommu_init_device(), free_area_init_node(),
jump_label_init_type(), regmap_init_mmio_clk(),
+ It is not an argument but it was inconsistent even before.
[arnd@arndb.de: fix linux-next merge conflict]
Link: http://lkml.kernel.org/r/20160908135724.1311726-1-arnd@arndb.de
Link: http://lkml.kernel.org/r/1470754545-17632-3-git-send-email-pmladek@suse.com
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Borislav Petkov <bp@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use autoremove_wake_function() instead of default_wake_function()
to make the dm wait loops more similar to other wait loops in the
kernel. This patch does not change any functionality.
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Use signal_pending_state() instead of open-coding it. This patch does
not change any functionality but makes it possible to pass TASK_KILLABLE
as the second argument of dm_wait_for_completion(). See also commit
16882c1e96 ("sched: fix TASK_WAKEKILL vs SIGKILL race").
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Rename 'interruptible' into 'task_state' to make it clear that this
argument is a task state instead of a boolean. Also, change type from
int to long.
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Document the locking assumptions for the __bind() and __dm_suspend()
functions.
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This avoids that new requests are queued while __dm_destroy() is in
progress.
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
dm_resume() will return success (0) rather than -EINVAL if
!dm_suspended_md() upon retry within dm_resume().
Reset the error code at the start of dm_resume()'s retry loop.
Also, remove a useless assignment at the end of dm_resume().
Fixes: ffcc393641 ("dm: enhance internal suspend and resume interface")
Cc: stable@vger.kernel.org # 3.19+
Signed-off-by: Minfei Huang <mnghuan@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Since commit 63a4cc2486, bio->bi_rw contains flags in the lower
portion and the op code in the higher portions. This means that
old code that relies on manually setting bi_rw is most likely
going to be broken. Instead of letting that brokeness linger,
rename the member, to force old and out-of-tree code to break
at compile time instead of at runtime.
No intended functional changes in this commit.
Signed-off-by: Jens Axboe <axboe@fb.com>
Otherwise, there is potential for both DMF_SUSPENDED* and
DMF_NOFLUSH_SUSPENDING to not be set during dm_suspend() -- which is
definitely _not_ a valid state.
This fix, in conjuction with "dm rq: fix the starting and stopping of
blk-mq queues", addresses the potential for request-based DM multipath's
__multipath_map() to see !dm_noflush_suspending() during suspend.
Reported-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
1/ Replace pcommit with ADR / directed-flushing:
The pcommit instruction, which has not shipped on any product, is
deprecated. Instead, the requirement is that platforms implement either
ADR, or provide one or more flush addresses per nvdimm. ADR
(Asynchronous DRAM Refresh) flushes data in posted write buffers to the
memory controller on a power-fail event. Flush addresses are defined in
ACPI 6.x as an NVDIMM Firmware Interface Table (NFIT) sub-structure:
"Flush Hint Address Structure". A flush hint is an mmio address that
when written and fenced assures that all previous posted writes
targeting a given dimm have been flushed to media.
2/ On-demand ARS (address range scrub):
Linux uses the results of the ACPI ARS commands to track bad blocks
in pmem devices. When latent errors are detected we re-scrub the media
to refresh the bad block list, userspace can also request a re-scrub at
any time.
3/ Support for the Microsoft DSM (device specific method) command format.
4/ Support for EDK2/OVMF virtual disk device memory ranges.
5/ Various fixes and cleanups across the subsystem.
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Merge tag 'libnvdimm-for-4.8' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm
Pull libnvdimm updates from Dan Williams:
- Replace pcommit with ADR / directed-flushing.
The pcommit instruction, which has not shipped on any product, is
deprecated. Instead, the requirement is that platforms implement
either ADR, or provide one or more flush addresses per nvdimm.
ADR (Asynchronous DRAM Refresh) flushes data in posted write buffers
to the memory controller on a power-fail event.
Flush addresses are defined in ACPI 6.x as an NVDIMM Firmware
Interface Table (NFIT) sub-structure: "Flush Hint Address Structure".
A flush hint is an mmio address that when written and fenced assures
that all previous posted writes targeting a given dimm have been
flushed to media.
- On-demand ARS (address range scrub).
Linux uses the results of the ACPI ARS commands to track bad blocks
in pmem devices. When latent errors are detected we re-scrub the
media to refresh the bad block list, userspace can also request a
re-scrub at any time.
- Support for the Microsoft DSM (device specific method) command
format.
- Support for EDK2/OVMF virtual disk device memory ranges.
- Various fixes and cleanups across the subsystem.
* tag 'libnvdimm-for-4.8' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm: (41 commits)
libnvdimm-btt: Delete an unnecessary check before the function call "__nd_device_register"
nfit: do an ARS scrub on hitting a latent media error
nfit: move to nfit/ sub-directory
nfit, libnvdimm: allow an ARS scrub to be triggered on demand
libnvdimm: register nvdimm_bus devices with an nd_bus driver
pmem: clarify a debug print in pmem_clear_poison
x86/insn: remove pcommit
Revert "KVM: x86: add pcommit support"
nfit, tools/testing/nvdimm/: unify shutdown paths
libnvdimm: move ->module to struct nvdimm_bus_descriptor
nfit: cleanup acpi_nfit_init calling convention
nfit: fix _FIT evaluation memory leak + use after free
tools/testing/nvdimm: add manufacturing_{date|location} dimm properties
tools/testing/nvdimm: add virtual ramdisk range
acpi, nfit: treat virtual ramdisk SPA as pmem region
pmem: kill __pmem address space
pmem: kill wmb_pmem()
libnvdimm, pmem: use nvdimm_flush() for namespace I/O writes
fs/dax: remove wmb_pmem()
libnvdimm, pmem: flush posted-write queues on shutdown
...
later merged with 'for-4.8/core' to pickup the QUEUE_FLAG_DAX commits
that DM depends on to provide its DAX support
- clean up the bio-based vs request-based DM core code by moving the
request-based DM core code out to dm-rq.[hc]
- reinstate bio-based support in the DM multipath target (done with the
idea that fast storage like NVMe over Fabrics could benefit) -- while
preserving support for request_fn and blk-mq request-based DM mpath
- SCSI and DM multipath persistent reservation fixes that were
coordinated with Martin Petersen.
- the DM raid target saw the most extensive change this cycle; it now
provides reshape and takeover support (by layering ontop of the
corresponding MD capabilities)
- DAX support for DM core and the linear, stripe and error targets
- A DM thin-provisioning block discard vs allocation race fix that
addresses potential for corruption
- A stable fix for DM verity-fec's block calculation during decode
- A few cleanups and fixes to DM core and various targets
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Merge tag 'dm-4.8-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper updates from Mike Snitzer:
- initially based on Jens' 'for-4.8/core' (given all the flag churn)
and later merged with 'for-4.8/core' to pickup the QUEUE_FLAG_DAX
commits that DM depends on to provide its DAX support
- clean up the bio-based vs request-based DM core code by moving the
request-based DM core code out to dm-rq.[hc]
- reinstate bio-based support in the DM multipath target (done with the
idea that fast storage like NVMe over Fabrics could benefit) -- while
preserving support for request_fn and blk-mq request-based DM mpath
- SCSI and DM multipath persistent reservation fixes that were
coordinated with Martin Petersen.
- the DM raid target saw the most extensive change this cycle; it now
provides reshape and takeover support (by layering ontop of the
corresponding MD capabilities)
- DAX support for DM core and the linear, stripe and error targets
- a DM thin-provisioning block discard vs allocation race fix that
addresses potential for corruption
- a stable fix for DM verity-fec's block calculation during decode
- a few cleanups and fixes to DM core and various targets
* tag 'dm-4.8-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (73 commits)
dm: allow bio-based table to be upgraded to bio-based with DAX support
dm snap: add fake origin_direct_access
dm stripe: add DAX support
dm error: add DAX support
dm linear: add DAX support
dm: add infrastructure for DAX support
dm thin: fix a race condition between discarding and provisioning a block
dm btree: fix a bug in dm_btree_find_next_single()
dm raid: fix random optimal_io_size for raid0
dm raid: address checkpatch.pl complaints
dm: call PR reserve/unreserve on each underlying device
sd: don't use the ALL_TG_PT bit for reservations
dm: fix second blk_delay_queue() parameter to be in msec units not jiffies
dm raid: change logical functions to actually return bool
dm raid: use rdev_for_each in status
dm raid: use rs->raid_disks to avoid memory leaks on free
dm raid: support delta_disks for raid1, fix table output
dm raid: enhance reshape check and factor out reshape setup
dm raid: allow resize during recovery
dm raid: fix rs_is_recovering() to allow for lvextend
...
Change mapped device to implement direct_access function,
dm_blk_direct_access(), which calls a target direct_access function.
'struct target_type' is extended to have target direct_access interface.
This function limits direct accessible size to the dm_target's limit
with max_io_len().
Add dm_table_supports_dax() to iterate all targets and associated block
devices to check for DAX support. To add DAX support to a DM target the
target must only implement the direct_access function.
Add a new dm type, DM_TYPE_DAX_BIO_BASED, which indicates that mapped
device supports DAX and is bio based. This new type is used to assure
that all target devices have DAX support and remain that way after
QUEUE_FLAG_DAX is set in mapped device.
At initial table load, QUEUE_FLAG_DAX is set to mapped device when setting
DM_TYPE_DAX_BIO_BASED to the type. Any subsequent table load to the
mapped device must have the same type, or else it fails per the check in
table_load().
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
These two are confusing leftover of the old world order, combining
values of the REQ_OP_ and REQ_ namespaces. For callers that don't
special case we mostly just replace bi_rw with bio_data_dir or
op_is_write, except for the few cases where a switch over the REQ_OP_
values makes more sense. Any check for READA is replaced with an
explicit check for REQ_RAHEAD. Also remove the READA alias for
REQ_RAHEAD.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
So far we tried to rely on the SCSI 'all target ports' bit to register
all path, but for many setups this didn't work properly as the different
paths are seen as separate initiators to the target instead of multiple
ports of the same initiator. Because of that we'll stop setting the
'all target ports' bit in SCSI, and let device mapper handle iterating
over the device for each path and register them manually.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Allow a user to specify an optional feature 'queue_mode <mode>' where
<mode> may be "bio", "rq" or "mq" -- which corresponds to bio-based,
request_fn rq-based, and blk-mq rq-based respectively.
If the queue_mode feature isn't specified the default for the
"multipath" target is still "rq" but if dm_mod.use_blk_mq is set to Y
it'll default to mode "mq".
This new queue_mode feature introduces the ability for each multipath
device to have its own queue_mode (whereas before this feature all
multipath devices effectively had to have the same queue_mode).
This commit also goes a long way to eliminate the awkward (ab)use of
DM_TYPE_*, the associated filter_md_type() and other relatively fragile
and difficult to maintain code.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Add some seperation between bio-based and request-based DM core code.
'struct mapped_device' and other DM core only structures and functions
have been moved to dm-core.h and all relevant DM core .c files have been
updated to include dm-core.h rather than dm.h
DM targets should _never_ include dm-core.h!
[block core merge conflict resolution from Stephen Rothwell]
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
To avoid confusion between REQ_OP_FLUSH, which is handled by
request_fn drivers, and upper layers requesting the block layer
perform a flush sequence along with possibly a WRITE, this patch
renames REQ_FLUSH to REQ_PREFLUSH.
Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This adds a REQ_OP_FLUSH operation that is sent to request_fn
based drivers by the block layer's flush code, instead of
sending requests with the request->cmd_flags REQ_FLUSH bit set.
Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
The req operation REQ_OP is separated from the rq_flag_bits
definition. This converts the block layer drivers to
use req_op to get the op from the request struct.
Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Separate the op from the rq_flag_bits and have dm
set/get the bio using bio_set_op_attrs/bio_op.
Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
It looks like dm stats cares about the data direction
(READ vs WRITE) and does not need the bio/request flags.
Commands like REQ_FLUSH, REQ_DISCARD and REQ_WRITE_SAME
are currently always set with REQ_WRITE, so the extra check for
REQ_DISCARD in dm_stats_account_io is not needed.
This patch has it use the bio and request data_dir helpers
instead of accessing the bi_rw/cmd_flags directly. This makes
the next patches that remove the operation from the cmd_flags
and bi_rw easier, because we will no longer have the REQ_WRITE
bit set for operations like discards.
Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Commit c80914e81e ("dm: return error if bio_integrity_clone() fails
in clone_bio()") changed clone_bio() such that if it does return error
then the alloc_tio() created resources (both the bio that was allocated
to be a clone and the containing dm_target_io struct) will leak.
Fix this by calling free_tio() in __clone_and_map_data_bio()'s
clone_bio() error path.
Fixes: c80914e81e ("dm: return error if bio_integrity_clone() fails in clone_bio()")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
An "old" (.request_fn) DM 'struct request' stores a pointer to the
associated 'struct dm_rq_target_io' in rq->special.
dm_requeue_original_request(), previously named
dm_requeue_unmapped_original_request(), called dm_unprep_request() to
reset rq->special to NULL. But rq_end_stats() would go on to hit a NULL
pointer deference because its call to tio_from_request() returned NULL.
Fix this by calling rq_end_stats() _before_ dm_unprep_request()
Signed-off-by: Bryn M. Reeves <bmr@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Fixes: e262f34741 ("dm stats: add support for request-based DM devices")
Cc: stable@vger.kernel.org # 4.2+
clone_bio() now checks if bio_integrity_clone() returned an error rather
than just drop it on the floor.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
md->queue and q are the same thing in dm_old_init_request_queue() and
dm_mq_init_request_queue().
Also drop the temporary 'struct request_queue *q' in
dm_old_init_request_queue().
Signed-off-by: Bob Liu <bob.liu@oracle.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Saves 16 bytes by eliminating 4 4byte holes but more importantly:
numerous members that crossed cachelines were fixed.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Change the map pointer in 'struct mapped_device' from 'struct dm_table
__rcu *' to 'void __rcu *' to avoid the need for the dummy definition.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Allows user to control which NUMA node the memory for DM device
structures (e.g. mapped_device, request_queue, gendisk, blk_mq_tag_set)
is allocated from.
Defaults to NUMA_NO_NODE (-1). Allowable range is from -1 until the
last online NUMA node id.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This will allow DM multipath to use a portion of the blk-mq pdu space
for target data (e.g. struct dm_mpath_io).
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Rename various methods to have either a "dm_old" or "dm_mq" prefix.
Improve code comments to assist with understanding the duality of code
that handles both "dm_old" and "dm_mq" cases.
It is no much easier to quickly look at the code and _know_ that a given
method is either 1) "dm_old" only 2) "dm_mq" only 3) common to both.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Remove all fiddley code that propped up this support for a blk-mq
request-queue ontop of all .request_fn devices.
Testing has proven this niche request-based dm-mq mode to be buggy, when
testing fault tolerance with DM multipath, and there is no point trying
to preserve it.
Should help improve efficiency of pure dm-mq code and make code
maintenance less delicate.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
old_stop_queue() was checking blk_queue_stopped() without holding the
q->queue_lock.
dm_requeue_original_request() needed to check blk_queue_stopped(), with
q->queue_lock held, before calling blk_mq_kick_requeue_list(). And a
side-effect of that change is start_queue() must also call
blk_mq_kick_requeue_list().
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The blk_mq_tag_set is only needed for dm-mq support. There is point
wasting space in 'struct mapped_device' for non-dm-mq devices.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> # check kzalloc return
Allow user to change these values via module params or sysfs.
'dm_mq_nr_hw_queues' defaults to 1 (max 32).
'dm_mq_queue_depth' defaults to 2048 (up from 64, which proved far too
small under moderate sized workloads -- the dm-multipath device would
continuously block waiting for tags (requests) to become available).
The maximum is BLK_MQ_MAX_DEPTH (currently 10240).
Keep in mind the total number of pre-allocated requests per
request-based dm-mq device is 'dm_mq_nr_hw_queues' * 'dm_mq_queue_depth'
(currently 2048).
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
DM multipath is the only request-based DM target -- which only supports
tables with a single target that is immutable. Leverage this fact in
dm_request_fn().
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
DM multipath is the only dm-mq target. But that aside, request-based DM
only supports tables with a single target that is immutable. Leverage
this fact in dm_mq_queue_rq() by using the 'immutable_target' stored in
the mapped_device when the table was made active. This saves the need
to even take the read-side of the SRCU via dm_{get,put}_live_table.
If the active DM table does not have an immutable target (e.g. "error"
target was swapped in) then fallback to the slow-path where the target
is looked up from the live table.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The request-based DM support for checking queue congestion doesn't
require access to the live DM table.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Request-based DM's blk-mq support (dm-mq) was reported to be 50% slower
than if an underlying null_blk device were used directly. One of the
reasons for this drop in performance is that blk_insert_clone_request()
was calling blk_mq_insert_request() with @async=true. This forced the
use of kblockd_schedule_delayed_work_on() to run the blk-mq hw queues
which ushered in ping-ponging between process context (fio in this case)
and kblockd's kworker to submit the cloned request. The ftrace
function_graph tracer showed:
kworker-2013 => fio-12190
fio-12190 => kworker-2013
...
kworker-2013 => fio-12190
fio-12190 => kworker-2013
...
Fixing blk_insert_clone_request()'s blk_mq_insert_request() call to
_not_ use kblockd to submit the cloned requests isn't enough to
eliminate the observed context switches.
In addition to this dm-mq specific blk-core fix, there are 2 DM core
fixes to dm-mq that (when paired with the blk-core fix) completely
eliminate the observed context switching:
1) don't blk_mq_run_hw_queues in blk-mq request completion
Motivated by desire to reduce overhead of dm-mq, punting to kblockd
just increases context switches.
In my testing against a really fast null_blk device there was no benefit
to running blk_mq_run_hw_queues() on completion (and no other blk-mq
driver does this). So hopefully this change doesn't induce the need for
yet another revert like commit 621739b00e !
2) use blk_mq_complete_request() in dm_complete_request()
blk_complete_request() doesn't offer the traditional q->mq_ops vs
.request_fn branching pattern that other historic block interfaces
do (e.g. blk_get_request). Using blk_mq_complete_request() for
blk-mq requests is important for performance. It should be noted
that, like blk_complete_request(), blk_mq_complete_request() doesn't
natively handle partial completions -- but the request-based
DM-multipath target does provide the required partial completion
support by dm.c:end_clone_bio() triggering requeueing of the request
via dm-mpath.c:multipath_end_io()'s return of DM_ENDIO_REQUEUE.
dm-mq fix#2 is _much_ more important than #1 for eliminating the
context switches.
Before: cpu : usr=15.10%, sys=59.39%, ctx=7905181, majf=0, minf=475
After: cpu : usr=20.60%, sys=79.35%, ctx=2008, majf=0, minf=472
With these changes multithreaded async read IOPs improved from ~950K
to ~1350K for this dm-mq stacked on null_blk test-case. The raw read
IOPs of the underlying null_blk device for the same workload is ~1950K.
Fixes: 7fb4898e0 ("block: add blk-mq support to blk_insert_cloned_request()")
Fixes: bfebd1cdb ("dm: add full blk-mq support to request-based DM")
Cc: stable@vger.kernel.org # 4.1+
Reported-by: Sagi Grimberg <sagig@dev.mellanox.co.il>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Jens Axboe <axboe@kernel.dk>
Rename dm_get_live_table_for_ioctl to dm_grab_bdev_for_ioctl and have it
do the dm_{get,put}_live_table() rather than split those operations.
The dm_grab_bdev_for_ioctl() callers only care about the block_device
associated with a singleton DM device so there isn't any need to retain
a reference to the live DM table. It is sufficient to:
1) dm_get_live_table()
2) bdgrab() the bdev associated with the singleton table's target
3) dm_put_live_table()
4) bdput() the bdev
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
None of the callers actually used the returned target.
Also, just reuse bdev pointer passed to dm_blk_ioctl().
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
(Ab)using the @bdev passed to dm_blk_ioctl() opens the potential for
targets' .prepare_ioctl to fail if they go on to check the bdev for
!NULL.
Fixes: e56f81e0b0 ("dm: refactor ioctl handling")
Reported-by: Junichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
dm-mpath retries ioctl, when no path is readily available and the device
is configured to queue I/O in such a case. If you want to stop the retry
before multipathd decides to turn off queueing mode, you could send
signal for the process to exit from the loop.
However the check of fatal signal has not carried along when commit
6c182cd88d ("dm mpath: fix ioctl deadlock when no paths") moved the
loop from dm-mpath to dm core. As a result, we can't terminate such
a process in the retry loop.
Easy reproducer of the situation is:
# dmsetup create mp --table '0 1024 multipath 0 0 0 0'
# dmsetup message mp 0 'queue_if_no_path'
# sg_inq /dev/mapper/mp
then you should be able to terminate sg_inq by pressing Ctrl+C.
Fixes: 6c182cd88d ("dm mpath: fix ioctl deadlock when no paths")
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
No functional changes in this patch, but it prepares us for returning
a more useful cookie related to the IO that was queued up.
Signed-off-by: Jens Axboe <axboe@fb.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Acked-by: Keith Busch <keith.busch@intel.com>
users (e.g. kvm guests) that issued ioctls when a multipath device had
no available paths.
- Include Christoph's refactoring of DM's ioctl handling and add support
for passing through persistent reservations with DM multipath.
- All other changes are very simple cleanups.
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Merge tag 'dm-4.4-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper updates from Mike Snitzer:
"Smaller set of DM changes for this merge. I've based these changes on
Jens' for-4.4/reservations branch because the associated DM changes
required it.
- Revert a dm-multipath change that caused a regression for
unprivledged users (e.g. kvm guests) that issued ioctls when a
multipath device had no available paths.
- Include Christoph's refactoring of DM's ioctl handling and add
support for passing through persistent reservations with DM
multipath.
- All other changes are very simple cleanups"
* tag 'dm-4.4-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
dm switch: simplify conditional in alloc_region_table()
dm delay: document that offsets are specified in sectors
dm delay: capitalize the start of an delay_ctr() error message
dm delay: Use DM_MAPIO macros instead of open-coded equivalents
dm linear: remove redundant target name from error messages
dm persistent data: eliminate unnecessary return values
dm: eliminate unused "bioset" process for each bio-based DM device
dm: convert ffs to __ffs
dm: drop NULL test before kmem_cache_destroy() and mempool_destroy()
dm: add support for passing through persistent reservations
dm: refactor ioctl handling
Revert "dm mpath: fix stalls when handling invalid ioctls"
dm: initialize non-blk-mq queue data before queue is used
Pull block integrity updates from Jens Axboe:
""This is the joint work of Dan and Martin, cleaning up and improving
the support for block data integrity"
* 'for-4.4/integrity' of git://git.kernel.dk/linux-block:
block, libnvdimm, nvme: provide a built-in blk_integrity nop profile
block: blk_flush_integrity() for bio-based drivers
block: move blk_integrity to request_queue
block: generic request_queue reference counting
nvme: suspend i/o during runtime blk_integrity_unregister
md: suspend i/o during runtime blk_integrity_unregister
md, dm, scsi, nvme, libnvdimm: drop blk_integrity_unregister() at shutdown
block: Inline blk_integrity in struct gendisk
block: Export integrity data interval size in sysfs
block: Reduce the size of struct blk_integrity
block: Consolidate static integrity profile properties
block: Move integrity kobject to struct gendisk
Commit 54efd50bfd ("block: make
generic_make_request handle arbitrarily sized bios") makes it possible
for block devices to process large bios. In doing so that commit
allocates a new queue->bio_split bioset for each block device, this
bioset is used for allocating bios when the driver needs to split large
bios.
Each bioset allocates a workqueue process, thus the above commit
increases the number of processes allocated per block device.
DM doesn't need the queue->bio_split bioset, thus we can deallocate it.
This reduces the number of allocated processes per bio-based DM device
from 3 to 2. Also remove the call to blk_queue_split(), it is not
needed because DM does its own splitting.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Remove DM's unneeded NULL tests before calling these destroy functions,
now that they check for NULL, thanks to these v4.3 commits:
3942d2991 ("mm/slab_common: allow NULL cache pointer in kmem_cache_destroy()")
4e3ca3e03 ("mm/mempool: allow NULL `pool' pointer in mempool_destroy()")
The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)
// <smpl>
@@ expression x; @@
-if (x != NULL)
\(kmem_cache_destroy\|mempool_destroy\|dma_pool_destroy\)(x);
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This adds support to pass through persistent reservation requests
similar to the existing ioctl handling, and with the same limitations,
e.g. devices may only have a single target attached.
This is mostly intended for multipathing.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This moves the call to blkdev_ioctl and the argument checking to DM core
code, and only leaves a callout to find the block device to operate on
in the targets. This simplifies the code and allows us to pass through
ioctl-like command using other methods in the next patch.
Also split out a helper around calling the prepare_ioctl method that
will be reused for persistent reservation handling.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Commit bfebd1cdb4 ("dm: add full blk-mq
support to request-based DM") moves the initialization of the fields
backing_dev_info.congested_fn, backing_dev_info.congested_data and
queuedata from the function dm_init_md_queue (that is called when the
device is created) to dm_init_old_md_queue (that is called after the
device type is determined).
There is no locking when accessing these variables, thus it is possible
for other parts of the kernel to briefly see this data in a transient
state (e.g. queue->backing_dev_info.congested_fn initialized and
md->queue->backing_dev_info.congested_data uninitialized, resulting in
passing an incorrect parameter to the function dm_any_congested).
This queue data is left initialized for blk-mq devices even though they
that don't use it.
Fixes: bfebd1cdb4 ("dm: add full blk-mq support to request-based DM")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # v4.1+
Now that the integrity profile is statically allocated there is no work
to do when shutting down an integrity enabled block device.
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: James Bottomley <JBottomley@Odin.com>
Acked-by: NeilBrown <neilb@suse.com>
Acked-by: Keith Busch <keith.busch@intel.com>
Acked-by: Vishal Verma <vishal.l.verma@intel.com>
Tested-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
end_clone_bio() is a endio callback for clone bio and should check
and save the clone's bi_error for error reporting. However,
4246a0b63b ("block: add a bi_error field to struct bio") changed
the function to check the original bio's bi_error, which is 0.
Without this fix, clone's error is ignored and reported to the
original request as success. Thus data corruption will be observed.
Fixes: 4246a0b63b ("block: add a bi_error field to struct bio")
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
__dm_destroy() takes io_barrier SRCU lock (dm_get_live_table) and
suspend_lock in reverse order. Doing so can cause AB-BA deadlock:
__dm_destroy dm_swap_table
---------------------------------------------------
mutex_lock(suspend_lock)
dm_get_live_table()
srcu_read_lock(io_barrier)
dm_sync_table()
synchronize_srcu(io_barrier)
.. waiting for dm_put_live_table()
mutex_lock(suspend_lock)
.. waiting for suspend_lock
Fix this by taking the locks in proper order.
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Fixes: ab7c7bb6f4 ("dm: hold suspend_lock while suspending device during device deletion")
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
Pull device mapper update from Mike Snitzer:
- a couple small cleanups in dm-cache, dm-verity, persistent-data's
dm-btree, and DM core.
- a 4.1-stable fix for dm-cache that fixes the leaking of deferred bio
prison cells
- a 4.2-stable fix that adds feature reporting for the dm-stats
features added in 4.2
- improve DM-snapshot to not invalidate the on-disk snapshot if
snapshot device write overflow occurs; but a write overflow triggered
through the origin device will still invalidate the snapshot.
- optimize DM-thinp's async discard submission a bit now that late bio
splitting has been included in block core.
- switch DM-cache's SMQ policy lock from using a mutex to a spinlock;
improves performance on very low latency devices (eg. NVMe SSD).
- document DM RAID 4/5/6's discard support
[ I did not pull the slab changes, which weren't appropriate for this
tree, and weren't obviously the right thing to do anyway. At the very
least they need some discussion and explanation before getting merged.
Because not pulling the actual tagged commit but doing a partial pull
instead, this merge commit thus also obviously is missing the git
signature from the original tag ]
* tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
dm cache: fix use after freeing migrations
dm cache: small cleanups related to deferred prison cell cleanup
dm cache: fix leaking of deferred bio prison cells
dm raid: document RAID 4/5/6 discard support
dm stats: report precise_timestamps and histogram in @stats_list output
dm thin: optimize async discard submission
dm snapshot: don't invalidate on-disk image on snapshot write overflow
dm: remove unlikely() before IS_ERR()
dm: do not override error code returned from dm_get_device()
dm: test return value for DM_MAPIO_SUBMITTED
dm verity: remove unused mempool
dm cache: move wake_waker() from free_migrations() to where it is needed
dm btree remove: remove unused function get_nr_entries()
dm btree: remove unused "dm_block_t root" parameter in btree_split_sibling()
dm cache policy smq: change the mutex to a spinlock
Pull core block updates from Jens Axboe:
"This first core part of the block IO changes contains:
- Cleanup of the bio IO error signaling from Christoph. We used to
rely on the uptodate bit and passing around of an error, now we
store the error in the bio itself.
- Improvement of the above from myself, by shrinking the bio size
down again to fit in two cachelines on x86-64.
- Revert of the max_hw_sectors cap removal from a revision again,
from Jeff Moyer. This caused performance regressions in various
tests. Reinstate the limit, bump it to a more reasonable size
instead.
- Make /sys/block/<dev>/queue/discard_max_bytes writeable, by me.
Most devices have huge trim limits, which can cause nasty latencies
when deleting files. Enable the admin to configure the size down.
We will look into having a more sane default instead of UINT_MAX
sectors.
- Improvement of the SGP gaps logic from Keith Busch.
- Enable the block core to handle arbitrarily sized bios, which
enables a nice simplification of bio_add_page() (which is an IO hot
path). From Kent.
- Improvements to the partition io stats accounting, making it
faster. From Ming Lei.
- Also from Ming Lei, a basic fixup for overflow of the sysfs pending
file in blk-mq, as well as a fix for a blk-mq timeout race
condition.
- Ming Lin has been carrying Kents above mentioned patches forward
for a while, and testing them. Ming also did a few fixes around
that.
- Sasha Levin found and fixed a use-after-free problem introduced by
the bio->bi_error changes from Christoph.
- Small blk cgroup cleanup from Viresh Kumar"
* 'for-4.3/core' of git://git.kernel.dk/linux-block: (26 commits)
blk: Fix bio_io_vec index when checking bvec gaps
block: Replace SG_GAPS with new queue limits mask
block: bump BLK_DEF_MAX_SECTORS to 2560
Revert "block: remove artifical max_hw_sectors cap"
blk-mq: fix race between timeout and freeing request
blk-mq: fix buffer overflow when reading sysfs file of 'pending'
Documentation: update notes in biovecs about arbitrarily sized bios
block: remove bio_get_nr_vecs()
fs: use helper bio_add_page() instead of open coding on bi_io_vec
block: kill merge_bvec_fn() completely
md/raid5: get rid of bio_fits_rdev()
md/raid5: split bio for chunk_aligned_read
block: remove split code in blkdev_issue_{discard,write_same}
btrfs: remove bio splitting and merge_bvec_fn() calls
bcache: remove driver private bio splitting code
block: simplify bio_add_page()
block: make generic_make_request handle arbitrarily sized bios
blk-cgroup: Drop unlikely before IS_ERR(_OR_NULL)
block: don't access bio->bi_error after bio_put()
block: shrink struct bio down to 2 cache lines again
...
As generic_make_request() is now able to handle arbitrarily sized bios,
it's no longer necessary for each individual block driver to define its
own ->merge_bvec_fn() callback. Remove every invocation completely.
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Lars Ellenberg <drbd-dev@lists.linbit.com>
Cc: drbd-user@lists.linbit.com
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Yehuda Sadeh <yehuda@inktank.com>
Cc: Sage Weil <sage@inktank.com>
Cc: Alex Elder <elder@kernel.org>
Cc: ceph-devel@vger.kernel.org
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: dm-devel@redhat.com
Cc: Neil Brown <neilb@suse.de>
Cc: linux-raid@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: NeilBrown <neilb@suse.de> (for the 'md' bits)
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
[dpark: also remove ->merge_bvec_fn() in dm-thin as well as
dm-era-target, and resolve merge conflicts]
Signed-off-by: Dongsu Park <dpark@posteo.net>
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
The way the block layer is currently written, it goes to great lengths
to avoid having to split bios; upper layer code (such as bio_add_page())
checks what the underlying device can handle and tries to always create
bios that don't need to be split.
But this approach becomes unwieldy and eventually breaks down with
stacked devices and devices with dynamic limits, and it adds a lot of
complexity. If the block layer could split bios as needed, we could
eliminate a lot of complexity elsewhere - particularly in stacked
drivers. Code that creates bios can then create whatever size bios are
convenient, and more importantly stacked drivers don't have to deal with
both their own bio size limitations and the limitations of the
(potentially multiple) devices underneath them. In the future this will
let us delete merge_bvec_fn and a bunch of other code.
We do this by adding calls to blk_queue_split() to the various
make_request functions that need it - a few can already handle arbitrary
size bios. Note that we add the call _after_ any call to
blk_queue_bounce(); this means that blk_queue_split() and
blk_recalc_rq_segments() don't need to be concerned with bouncing
affecting segment merging.
Some make_request_fn() callbacks were simple enough to audit and verify
they don't need blk_queue_split() calls. The skipped ones are:
* nfhd_make_request (arch/m68k/emu/nfblock.c)
* axon_ram_make_request (arch/powerpc/sysdev/axonram.c)
* simdisk_make_request (arch/xtensa/platforms/iss/simdisk.c)
* brd_make_request (ramdisk - drivers/block/brd.c)
* mtip_submit_request (drivers/block/mtip32xx/mtip32xx.c)
* loop_make_request
* null_queue_bio
* bcache's make_request fns
Some others are almost certainly safe to remove now, but will be left
for future patches.
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ming Lei <ming.lei@canonical.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: dm-devel@redhat.com
Cc: Lars Ellenberg <drbd-dev@lists.linbit.com>
Cc: drbd-user@lists.linbit.com
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Jim Paris <jim@jtan.com>
Cc: Philip Kelleher <pjk1939@linux.vnet.ibm.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Oleg Drokin <oleg.drokin@intel.com>
Cc: Andreas Dilger <andreas.dilger@intel.com>
Acked-by: NeilBrown <neilb@suse.de> (for the 'md/md.c' bits)
Acked-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
[dpark: skip more mq-based drivers, resolve merge conflicts, etc.]
Signed-off-by: Dongsu Park <dpark@posteo.net>
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
In properly written code we should not assume that DM_MAPIO_SUBMITTED is
zero. We should test the return value for DM_MAPIO_SUBMITTED rather than
testing it for zero.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
A DM regression on 32 bit systems was reported against v4.2-rc3 here:
https://lkml.org/lkml/2015/7/29/401
Fix this by reverting both commit 1c220c69 ("dm: fix casting bug in
dm_merge_bvec()") and 148e51ba ("dm: improve documentation and code
clarity in dm_merge_bvec"). This combined revert is done to eliminate
the possibility of a partial revert in stable@ kernels.
In hindsight the correct fix, at the time 1c220c69 was applied to fix
the regression that 148e51ba introduced, should've been to simply revert
148e51ba.
Reported-by: Josh Boyer <jwboyer@fedoraproject.org>
Tested-by: Adam Williamson <awilliam@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.19+
Currently we have two different ways to signal an I/O error on a BIO:
(1) by clearing the BIO_UPTODATE flag
(2) by returning a Linux errno value to the bi_end_io callback
The first one has the drawback of only communicating a single possible
error (-EIO), and the second one has the drawback of not beeing persistent
when bios are queued up, and are not passed along from child to parent
bio in the ever more popular chaining scenario. Having both mechanisms
available has the additional drawback of utterly confusing driver authors
and introducing bugs where various I/O submitters only deal with one of
them, and the others have to add boilerplate code to deal with both kinds
of error returns.
So add a new bi_error field to store an errno value directly in struct
bio and remove the existing mechanisms to clean all this up.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Linux 4.2-rc1 Commit 0f20972f7b ("dm: factor out a common
cleanup_mapped_device()") moved a common cleanup code to a separate
function. Unfortunately, that commit incorrectly changed the order of
cleanup, so that it destroys the mapped_device's srcu structure
'io_barrier' before destroying its workqueue.
The function that is executed on the workqueue (dm_wq_work) uses the srcu
structure, thus it may use it after being freed. That results in a
crash in the LVM test suite's mirror-vgreduce-removemissing.sh test.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: 0f20972f7b ("dm: factor out a common cleanup_mapped_device()")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This reverts commit 9a0e609e3f.
(Resolved a conflict during revert due to commit bfebd1cdb4 that came
after)
This revert is motivated by a couple failure reports on request-based DM
multipath testbeds:
1) Netapp reported that their multipath fault injection test under heavy
IO load can stall longer than 300 seconds.
2) IBM reported elevated lock contention in their testbed (likely due to
increased back pressure due to IO not being dispatched as quickly):
https://www.redhat.com/archives/dm-devel/2015-July/msg00057.html
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 4.1+
ability to handle partial request completions -- otherwise with the
current SCSI LLDs these changes could lead to silent data corruption.
- Fix two DM version bumps that were missing from the initial 4.2 DM
pull request (enabled userspace lvm2 to know certain changes have been
made).
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Merge tag 'dm-4.2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper fixes from Mike Snitzer:
"Apologies for not pressing this request-based DM partial completion
issue further, it was an oversight on my part. We'll have to get it
fixed up properly and revisit for a future release.
- Revert block and DM core changes the removed request-based DM's
ability to handle partial request completions -- otherwise with the
current SCSI LLDs these changes could lead to silent data
corruption.
- Fix two DM version bumps that were missing from the initial 4.2 DM
pull request (enabled userspace lvm2 to know certain changes have
been made)"
* tag 'dm-4.2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
dm cache policy smq: fix "default" version to be 1.4.0
dm: bump the ioctl version to 4.32.0
Revert "block, dm: don't copy bios for request clones"
Revert "dm: do not allocate any mempools for blk-mq request-based DM"
This reverts commit 5f1b670d0b.
Justification for revert as reported in this dm-devel post:
https://www.redhat.com/archives/dm-devel/2015-June/msg00160.html
this change should not be pushed to mainline yet.
Firstly, Christoph has a newer version of the patch that fixes silent
data corruption problem:
https://www.redhat.com/archives/dm-devel/2015-May/msg00229.html
And the new version still depends on LLDDs to always complete requests
to the end when error happens, while block API doesn't enforce such a
requirement. If the assumption is ever broken, the inconsistency between
request and bio (e.g. rq->__sector and rq->bio) will cause silent data
corruption:
https://www.redhat.com/archives/dm-devel/2015-June/msg00022.html
Reported-by: Junichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
- blk-mq request-based DM no longer uses any mempools now that partial
completions are no longer handled as part of cloned requests
- DM raid cleanups and support for MD raid0
- DM cache core advances and a new stochastic-multi-queue (smq) cache
replacement policy
- smq is the new default dm-cache policy
- DM thinp cleanups and much more efficient large discard support
- DM statistics support for request-based DM and nanosecond resolution
timestamps
- Fixes to DM stripe, DM log-writes, DM raid1 and DM crypt
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Merge tag 'dm-4.2-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper updates from Mike Snitzer:
- DM core cleanups:
* blk-mq request-based DM no longer uses any mempools now that
partial completions are no longer handled as part of cloned
requests
- DM raid cleanups and support for MD raid0
- DM cache core advances and a new stochastic-multi-queue (smq) cache
replacement policy
* smq is the new default dm-cache policy
- DM thinp cleanups and much more efficient large discard support
- DM statistics support for request-based DM and nanosecond resolution
timestamps
- Fixes to DM stripe, DM log-writes, DM raid1 and DM crypt
* tag 'dm-4.2-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (39 commits)
dm stats: add support for request-based DM devices
dm stats: collect and report histogram of IO latencies
dm stats: support precise timestamps
dm stats: fix divide by zero if 'number_of_areas' arg is zero
dm cache: switch the "default" cache replacement policy from mq to smq
dm space map metadata: fix occasional leak of a metadata block on resize
dm thin metadata: fix a race when entering fail mode
dm thin: fail messages with EOPNOTSUPP when pool cannot handle messages
dm thin: range discard support
dm thin metadata: add dm_thin_remove_range()
dm thin metadata: add dm_thin_find_mapped_range()
dm btree: add dm_btree_remove_leaves()
dm stats: Use kvfree() in dm_kvfree()
dm cache: age and write back cache entries even without active IO
dm cache: prefix all DMERR and DMINFO messages with cache device name
dm cache: add fail io mode and needs_check flag
dm cache: wake the worker thread every time we free a migration object
dm cache: add stochastic-multi-queue (smq) policy
dm cache: boost promotion of blocks that will be overwritten
dm cache: defer whole cells
...
Pull cgroup writeback support from Jens Axboe:
"This is the big pull request for adding cgroup writeback support.
This code has been in development for a long time, and it has been
simmering in for-next for a good chunk of this cycle too. This is one
of those problems that has been talked about for at least half a
decade, finally there's a solution and code to go with it.
Also see last weeks writeup on LWN:
http://lwn.net/Articles/648292/"
* 'for-4.2/writeback' of git://git.kernel.dk/linux-block: (85 commits)
writeback, blkio: add documentation for cgroup writeback support
vfs, writeback: replace FS_CGROUP_WRITEBACK with SB_I_CGROUPWB
writeback: do foreign inode detection iff cgroup writeback is enabled
v9fs: fix error handling in v9fs_session_init()
bdi: fix wrong error return value in cgwb_create()
buffer: remove unusued 'ret' variable
writeback: disassociate inodes from dying bdi_writebacks
writeback: implement foreign cgroup inode bdi_writeback switching
writeback: add lockdep annotation to inode_to_wb()
writeback: use unlocked_inode_to_wb transaction in inode_congested()
writeback: implement unlocked_inode_to_wb transaction and use it for stat updates
writeback: implement [locked_]inode_to_wb_and_lock_list()
writeback: implement foreign cgroup inode detection
writeback: make writeback_control track the inode being written back
writeback: relocate wb[_try]_get(), wb_put(), inode_{attach|detach}_wb()
mm: vmscan: disable memcg direct reclaim stalling if cgroup writeback support is in use
writeback: implement memcg writeback domain based throttling
writeback: reset wb_domain->dirty_limit[_tstmp] when memcg domain size changes
writeback: implement memcg wb_domain
writeback: update wb_over_bg_thresh() to use wb_domain aware operations
...
Pull core block IO update from Jens Axboe:
"Nothing really major in here, mostly a collection of smaller
optimizations and cleanups, mixed with various fixes. In more detail,
this contains:
- Addition of policy specific data to blkcg for block cgroups. From
Arianna Avanzini.
- Various cleanups around command types from Christoph.
- Cleanup of the suspend block I/O path from Christoph.
- Plugging updates from Shaohua and Jeff Moyer, for blk-mq.
- Eliminating atomic inc/dec of both remaining IO count and reference
count in a bio. From me.
- Fixes for SG gap and chunk size support for data-less (discards)
IO, so we can merge these better. From me.
- Small restructuring of blk-mq shared tag support, freeing drivers
from iterating hardware queues. From Keith Busch.
- A few cfq-iosched tweaks, from Tahsin Erdogan and me. Makes the
IOPS mode the default for non-rotational storage"
* 'for-4.2/core' of git://git.kernel.dk/linux-block: (35 commits)
cfq-iosched: fix other locations where blkcg_to_cfqgd() can return NULL
cfq-iosched: fix sysfs oops when attempting to read unconfigured weights
cfq-iosched: move group scheduling functions under ifdef
cfq-iosched: fix the setting of IOPS mode on SSDs
blktrace: Add blktrace.c to BLOCK LAYER in MAINTAINERS file
block, cgroup: implement policy-specific per-blkcg data
block: Make CFQ default to IOPS mode on SSDs
block: add blk_set_queue_dying() to blkdev.h
blk-mq: Shared tag enhancements
block: don't honor chunk sizes for data-less IO
block: only honor SG gap prevention for merges that contain data
block: fix returnvar.cocci warnings
block, dm: don't copy bios for request clones
block: remove management of bi_remaining when restoring original bi_end_io
block: replace trylock with mutex_lock in blkdev_reread_part()
block: export blkdev_reread_part() and __blkdev_reread_part()
suspend: simplify block I/O handling
block: collapse bio bit space
block: remove unused BIO_RW_BLOCK and BIO_EOF flags
block: remove BIO_EOPNOTSUPP
...
This makes it possible to use dm stats with DM multipath.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
and the role of the separation is unclear. For cgroup support for
writeback IOs, a bdi will be updated to host multiple wb's where each
wb serves writeback IOs of a different cgroup on the bdi. To achieve
that, a wb should carry all states necessary for servicing writeback
IOs for a cgroup independently.
This patch moves bdi->state into wb.
* enum bdi_state is renamed to wb_state and the prefix of all enums is
changed from BDI_ to WB_.
* Explicit zeroing of bdi->state is removed without adding zeoring of
wb->state as the whole data structure is zeroed on init anyway.
* As there's still only one bdi_writeback per backing_dev_info, all
uses of bdi->state are mechanically replaced with bdi->wb.state
introducing no behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: drbd-dev@lists.linbit.com
Cc: Neil Brown <neilb@suse.de>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Introduce a single common method for cleaning up a DM device's
mapped_device. No functional change, just eliminates duplication of
delicate mapped_device cleanup code.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
More often than not a request that is requeued _is_ mapped (meaning the
clone request is allocated and clone->q is initialized). Rename
dm_requeue_unmapped_original_request() to avoid potential confusion due
to function name containing "unmapped".
Also, remove dm_requeue_unmapped_request() since callers can easily call
the dm_requeue_original_request() directly.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Do not allocate the io_pool mempool for blk-mq request-based DM
(DM_TYPE_MQ_REQUEST_BASED) in dm_alloc_rq_mempools().
Also refine __bind_mempools() to have more precise awareness of which
mempools each type of DM device uses -- avoids mempool churn when
reloading DM tables (particularly for DM_TYPE_REQUEST_BASED).
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
dm_merge_bvec() was originally added in f6fccb ("dm: introduce
merge_bvec_fn"). In that commit a value in sectors is converted to
bytes using << 9, and then assigned to an int. This code made
assumptions about the value of BIO_MAX_SECTORS.
A later commit 148e51 ("dm: improve documentation and code clarity in
dm_merge_bvec") was meant to have no functional change but it removed
the use of BIO_MAX_SECTORS in favor of using queue_max_sectors(). At
this point the cast from sector_t to int resulted in a zero value. The
fallout being dm_merge_bvec() would only allow a single page to be added
to a bio.
This interim fix is minimal for the benefit of stable@ because the more
comprehensive cleanup of passing a sector_t to all DM targets' merge
function will impact quite a few DM targets.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.19+
When stacking request-based dm device on non blk-mq device and
device-mapper target could not map the request (error target is used,
multipath target with all paths down, etc), the WARN_ON_ONCE() in
free_rq_clone() will trigger when it shouldn't.
The warning was added by commit aa6df8d ("dm: fix free_rq_clone() NULL
pointer when requeueing unmapped request"). But free_rq_clone() with
clone->q == NULL is valid usage for the case where
dm_kill_unmapped_request() initiates request cleanup.
Fix this false warning by just removing the WARN_ON -- it only generated
false positives and was never useful in catching the intended case
(completing clone request not being mapped e.g. clone->q being NULL).
Fixes: aa6df8d ("dm: fix free_rq_clone() NULL pointer when requeueing unmapped request")
Reported-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reported-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Use BLK_MQ_RQ_QUEUE_BUSY to requeue a blk-mq request directly from the
DM blk-mq device's .queue_rq. This cleans up the previous convoluted
handling of request requeueing that would return BLK_MQ_RQ_QUEUE_OK
(even though it wasn't) and then run blk_mq_requeue_request() followed
by blk_mq_kick_requeue_list().
Also, document that DM blk-mq ontop of old request_fn devices cannot
fail in clone_rq() since the clone request is preallocated as part of
the pdu.
Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
When stacking request-based DM on blk_mq device, request cloning and
remapping are done in a single call to target's clone_and_map_rq().
The clone is allocated and valid only if clone_and_map_rq() returns
DM_MAPIO_REMAPPED.
The "IS_ERR(clone)" check in map_request() does not cover all the
!DM_MAPIO_REMAPPED cases that are possible (E.g. if underlying devices
are not ready or unavailable, clone_and_map_rq() may return
DM_MAPIO_REQUEUE without ever having established an ERR_PTR). Fix this
by explicitly checking for a return that is not DM_MAPIO_REMAPPED in
map_request().
Without this fix, DM core may call setup_clone() for a NULL clone
and oops like this:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000068
IP: [<ffffffff81227525>] blk_rq_prep_clone+0x7d/0x137
...
CPU: 2 PID: 5793 Comm: kdmwork-253:3 Not tainted 4.0.0-nm #1
...
Call Trace:
[<ffffffffa01d1c09>] map_tio_request+0xa9/0x258 [dm_mod]
[<ffffffff81071de9>] kthread_worker_fn+0xfd/0x150
[<ffffffff81071cec>] ? kthread_parkme+0x24/0x24
[<ffffffff81071cec>] ? kthread_parkme+0x24/0x24
[<ffffffff81071fdd>] kthread+0xe6/0xee
[<ffffffff81093a59>] ? put_lock_stats+0xe/0x20
[<ffffffff81071ef7>] ? __init_kthread_worker+0x5b/0x5b
[<ffffffff814c2d98>] ret_from_fork+0x58/0x90
[<ffffffff81071ef7>] ? __init_kthread_worker+0x5b/0x5b
Fixes: e5863d9ad ("dm: allocate requests in target when stacking on blk-mq devices")
Reported-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 4.0+
Without kicking queue, requeued request may stay forever in
the queue if there are no other I/O activities to the device.
The original error had been in v2.6.39 with commit 7eaceaccab
("block: remove per-queue plugging"), which replaced conditional
plugging by periodic runqueue.
Commit 9d1deb83d4 in v4.1-rc1 removed the periodic runqueue
and the problem started to manifest.
Fixes: 9d1deb83d4 ("dm: don't schedule delayed run of the queue if nothing to do")
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Currently dm-multipath has to clone the bios for every request sent
to the lower devices, which wastes cpu cycles and ties down memory.
This patch instead adds a new REQ_CLONE flag that instructs req_bio_endio
to not complete bios attached to a request, which we set on clone
requests similar to bios in a flush sequence. With this change I/O
errors on a path failure only get propagated to dm-multipath, which
can then either resubmit the I/O or complete the bios on the original
request.
I've done some basic testing of this on a Linux target with ALUA support,
and it survives path failures during I/O nicely.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Commit 022333427a ("dm: optimize dm_mq_queue_rq to _not_ use kthread if
using pure blk-mq") mistakenly removed free_rq_clone()'s clone->q check
before testing clone->q->mq_ops. It was an oversight to discontinue
that check for 1 of the 2 use-cases for free_rq_clone():
1) free_rq_clone() called when an unmapped original request is requeued
2) free_rq_clone() called in the request-based IO completion path
The clone->q check made sense for case #1 but not for #2. However, we
cannot just reinstate the check as it'd mask a serious bug in the IO
completion case #2 -- no in-flight request should have an uninitialized
request_queue (basic block layer refcounting _should_ ensure this).
The NULL pointer seen for case #1 is detailed here:
https://www.redhat.com/archives/dm-devel/2015-April/msg00160.html
Fix this free_rq_clone() NULL pointer by simply checking if the
mapped_device's type is DM_TYPE_MQ_REQUEST_BASED (clone's queue is
blk-mq) rather than checking clone->q->mq_ops. This avoids the need to
dereference clone->q, but a WARN_ON_ONCE is added to let us know if an
uninitialized clone request is being completed.
Reported-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Commit bfebd1cdb4 ("dm: add full blk-mq support to request-based DM")
didn't properly account for the need to short-circuit re-initializing
DM's blk-mq request_queue if it was already initialized.
Otherwise, reloading a blk-mq request-based DM table (either manually
or via multipathd) resulted in errors, see:
https://www.redhat.com/archives/dm-devel/2015-April/msg00132.html
Fix is to only initialize the request_queue on the initial table load
(when the mapped_device type is assigned).
This is better than having dm_init_request_based_blk_mq_queue() return
early if the queue was already initialized because it elevates the
constraint to a more meaningful location in DM core. As such the
pre-existing early return in dm_init_request_based_queue() can now be
removed.
Fixes: bfebd1cdb4 ("dm: add full blk-mq support to request-based DM")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Add device specific modes to dm-verity to specify how corrupted
blocks should be handled. The following modes are defined:
- DM_VERITY_MODE_EIO is the default behavior, where reading a
corrupted block results in -EIO.
- DM_VERITY_MODE_LOGGING only logs corrupted blocks, but does
not block the read.
- DM_VERITY_MODE_RESTART calls kernel_restart when a corrupted
block is discovered.
In addition, each mode sends a uevent to notify userspace of
corruption and to allow further recovery actions.
The driver defaults to previous behavior (DM_VERITY_MODE_EIO)
and other modes can be enabled with an additional parameter to
the verity table.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Request-based DM's blk-mq support defaults to off; but a user can easily
change the default using the dm_mod.use_blk_mq module/boot option.
Also, you can check what mode a given request-based DM device is using
with: cat /sys/block/dm-X/dm/use_blk_mq
This change enabled further cleanup and reduced work (e.g. the
md->io_pool and md->rq_pool isn't created if using blk-mq).
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
dm_mq_queue_rq() is in atomic context so care must be taken to not
sleep -- as such GFP_ATOMIC is used for the md->bs bioset allocations
and dm-mpath's call to blk_get_request(). In the future the bioset
allocations will hopefully go away (by removing support for partial
completions of bios in a cloned request).
Also prepare for supporting DM blk-mq ontop of old-style request_fn
device(s) if a new dm-mod 'use_blk_mq' parameter is set. The kthread
will still be used to queue work if blk-mq is used ontop of old-style
request_fn device(s).
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Commit e5863d9ad ("dm: allocate requests in target when stacking on
blk-mq devices") served as the first step toward fully utilizing blk-mq
in request-based DM -- it enabled stacking an old-style (request_fn)
request_queue ontop of the underlying blk-mq device(s). That first step
didn't improve performance of DM multipath ontop of fast blk-mq devices
(e.g. NVMe) because the top-level old-style request_queue was severely
limited by the queue_lock.
The second step offered here enables stacking a blk-mq request_queue
ontop of the underlying blk-mq device(s). This unlocks significant
performance gains on fast blk-mq devices, Keith Busch tested on his NVMe
testbed and offered this really positive news:
"Just providing a performance update. All my fio tests are getting
roughly equal performance whether accessed through the raw block
device or the multipath device mapper (~470k IOPS). I could only push
~20% of the raw iops through dm before this conversion, so this latest
tree is looking really solid from a performance standpoint."
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Tested-by: Keith Busch <keith.busch@intel.com>
Otherwise, for sequential workloads, the dm_request_fn can allow
excessive request merging at the expense of increased service time.
Add a per-device sysfs attribute to allow the user to control how long a
request, that is a reasonable merge candidate, can be queued on the
request queue. The resolution of this request dispatch deadline is in
microseconds (ranging from 1 to 100000 usecs), to set a 20us deadline:
echo 20 > /sys/block/dm-7/dm/rq_based_seq_io_merge_deadline
The dm_request_fn's merge heuristic and associated extra accounting is
disabled by default (rq_based_seq_io_merge_deadline is 0).
This sysfs attribute is not applicable to bio-based DM devices so it
will only ever report 0 for them.
By allowing a request to remain on the queue it will block others
requests on the queue. But introducing a short dequeue delay has proven
very effective at enabling certain sequential IO workloads on really
fast, yet IOPS constrained, devices to build up slightly larger IOs --
yielding 90+% throughput improvements. Having precise control over the
time taken to wait for larger requests to build affords control beyond
that of waiting for certain IO sizes to accumulate (which would require
a deadline anyway). This knob will only ever make sense with sequential
IO workloads and the particular value used is storage configuration
specific.
Given the expected niche use-case for when this knob is useful it has
been deemed acceptable to expose this relatively crude method for
crafting optimal IO on specific storage -- especially given the solution
is simple yet effective. In the context of DM multipath, it is
advisable to tune this sysfs attribute to a value that offers the best
performance for the common case (e.g. if 4 paths are expected active,
tune for that; if paths fail then performance may be slightly reduced).
Alternatives were explored to have request-based DM autotune this value
(e.g. if/when paths fail) but they were quickly deemed too fragile and
complex to warrant further design and development time. If this problem
proves more common as faster storage emerges we'll have to look at
elevating a generic solution into the block core.
Tested-by: Shiva Krishna Merla <shivakrishna.merla@netapp.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Request-based DM's dm_request_fn() is so fast to pull requests off the
queue that steps need to be taken to promote merging by avoiding request
processing if it makes sense.
If the current request would've merged with previous request let the
current request stay on the queue longer.
Suggested-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Commit 7eaceaccab ("block: remove per-queue plugging") didn't justify
DM's use of a 100ms delay; such an extended delay is a liability when
there is reason to re-kick the queue.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
On really fast storage it can be beneficial to delay running the
request_queue to allow the elevator more opportunity to merge requests.
Otherwise, it has been observed that requests are being sent to
q->request_fn much quicker than is ideal on IOPS-bound backends.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The old dm_request() method used for q->make_request_fn had a branch for
request-based DM support but it isn't needed given that
dm_init_request_based_queue() sets it to the standard blk_queue_bio()
anyway.
Cleanup dm_init_md_queue() to be DM device-type agnostic and have
dm_setup_md_queue() properly finish queue setup based on DM device-type
(bio-based vs request-based).
A followup block patch can be made to remove the export for
blk_queue_bio() now that DM no longer calls it directly.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
DM multipath is the only caller of blk_lld_busy() -- which calls a
queue's lld_busy_fn hook. Request-based DM doesn't support stacking
multipath devices so there is no reason to register the lld_busy_fn hook
on a multipath device's queue using blk_queue_lld_busy().
As such, remove functions dm_lld_busy and dm_table_any_busy_target.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
__dm_get_module_param() could be useful for future DM module parameters
besides those related to "reserved_ios".
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Commit c4db59d31e ("fs: don't reassign dirty inodes to
default_backing_dev_info") exposed DM to a latent race in free_dev() vs
add_disk() in relation to management of the device's minor number.
Fix this by refactoring free_dev() to match cleanup order of the
alloc_dev() error path. Move cleanup of the gendisk, queue, and bdev
to _before_ the cleanup of the idr managed minor number.
Also, purely due to cleanup that fell out during the free_dev() audit:
- adjust dm_blk_close() to access the gendisk's private_data under
the _minor_lock spinlock.
- move __dm_destroy()'s dm_get_live_table() call out from under the
_minor_lock spinlock.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1202449
Reported-by: Zdenek Kabelac <zkabelac@redhat.com>
Reported-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The "dm snapshot: suspend origin when doing exception handover" commit
fixed a exception store handover bug associated with pending exceptions
to the "snapshot-origin" target.
However, a similar problem exists in snapshot merging. When snapshot
merging is in progress, we use the target "snapshot-merge" instead of
"snapshot-origin". Consequently, during exception store handover, we
must find the snapshot-merge target and suspend its associated
mapped_device.
To avoid lockdep warnings, the target must be suspended and resumed
without holding _origins_lock.
Introduce a dm_hold() function that grabs a reference on a
mapped_device, but unlike dm_get(), it doesn't crash if the device has
the DMF_FREEING flag set, it returns an error in this case.
In snapshot_resume() we grab the reference to the origin device using
dm_hold() while holding _origins_lock (_origins_lock guarantees that the
device won't disappear). Then we release _origins_lock, suspend the
device and grab _origins_lock again.
NOTE to stable@ people:
When backporting to kernels 3.18 and older, use dm_internal_suspend and
dm_internal_resume instead of dm_internal_suspend_fast and
dm_internal_resume_fast.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
In the function snapshot_resume we perform exception store handover. If
there is another active snapshot target, the exception store is moved
from this target to the target that is being resumed.
The problem is that if there is some pending exception, it will point to
an incorrect exception store after that handover, causing a crash due to
dm-snap-persistent.c:get_exception()'s BUG_ON.
This bug can be triggered by repeatedly changing snapshot permissions
with "lvchange -p r" and "lvchange -p rw" while there are writes on the
associated origin device.
To fix this bug, we must suspend the origin device when doing the
exception store handover to make sure that there are no pending
exceptions:
- introduce _origin_hash that keeps track of dm_origin structures.
- introduce functions __lookup_dm_origin, __insert_dm_origin and
__remove_dm_origin that manipulate the origin hash.
- modify snapshot_resume so that it calls dm_internal_suspend_fast() and
dm_internal_resume_fast() on the origin device.
NOTE to stable@ people:
When backporting to kernels 3.12-3.18, use dm_internal_suspend and
dm_internal_resume instead of dm_internal_suspend_fast and
dm_internal_resume_fast.
When backporting to kernels older than 3.12, you need to pick functions
dm_internal_suspend and dm_internal_resume from the commit
fd2ed4d252.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
__dm_destroy() must take the suspend_lock so that its presuspend and
postsuspend calls do not race with an internal suspend.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
The function dm_get_md finds a device mapper device with a given dev_t,
increases the reference count and returns the pointer.
dm_get_md calls dm_find_md, dm_find_md takes _minor_lock, finds the
device, tests that the device doesn't have DMF_DELETING or DMF_FREEING
flag, drops _minor_lock and returns pointer to the device. dm_get_md then
calls dm_get. dm_get calls BUG if the device has the DMF_FREEING flag,
otherwise it increments the reference count.
There is a possible race condition - after dm_find_md exits and before
dm_get is called, there are no locks held, so the device may disappear or
DMF_FREEING flag may be set, which results in BUG.
To fix this bug, we need to call dm_get while we hold _minor_lock. This
patch renames dm_find_md to dm_get_md and changes it so that it calls
dm_get while holding the lock.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
stacking ontop of blk-mq devices. This blk-mq support changes the
model request-based DM uses for cloning a request to relying on
calling blk_get_request() directly from the underlying blk-mq device.
Early consumer of this code is Intel's emerging NVMe hardware; thanks
to Keith Busch for working on, and pushing for, these changes.
- A few other small fixes and cleanups across other DM targets.
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Merge tag 'dm-3.20-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper changes from Mike Snitzer:
- The most significant change this cycle is request-based DM now
supports stacking ontop of blk-mq devices. This blk-mq support
changes the model request-based DM uses for cloning a request to
relying on calling blk_get_request() directly from the underlying
blk-mq device.
An early consumer of this code is Intel's emerging NVMe hardware;
thanks to Keith Busch for working on, and pushing for, these changes.
- A few other small fixes and cleanups across other DM targets.
* tag 'dm-3.20-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
dm: inherit QUEUE_FLAG_SG_GAPS flags from underlying queues
dm snapshot: remove unnecessary NULL checks before vfree() calls
dm mpath: simplify failure path of dm_multipath_init()
dm thin metadata: remove unused dm_pool_get_data_block_size()
dm ioctl: fix stale comment above dm_get_inactive_table()
dm crypt: update url in CONFIG_DM_CRYPT help text
dm bufio: fix time comparison to use time_after_eq()
dm: use time_in_range() and time_after()
dm raid: fix a couple integer overflows
dm table: train hybrid target type detection to select blk-mq if appropriate
dm: allocate requests in target when stacking on blk-mq devices
dm: prepare for allocating blk-mq clone requests in target
dm: submit stacked requests in irq enabled context
dm: split request structure out from dm_rq_target_io structure
dm: remove exports for request-based interfaces without external callers
Pull core block IO changes from Jens Axboe:
"This contains:
- A series from Christoph that cleans up and refactors various parts
of the REQ_BLOCK_PC handling. Contributions in that series from
Dongsu Park and Kent Overstreet as well.
- CFQ:
- A bug fix for cfq for realtime IO scheduling from Jeff Moyer.
- A stable patch fixing a potential crash in CFQ in OOM
situations. From Konstantin Khlebnikov.
- blk-mq:
- Add support for tag allocation policies, from Shaohua. This is
a prep patch enabling libata (and other SCSI parts) to use the
blk-mq tagging, instead of rolling their own.
- Various little tweaks from Keith and Mike, in preparation for
DM blk-mq support.
- Minor little fixes or tweaks from me.
- A double free error fix from Tony Battersby.
- The partition 4k issue fixes from Matthew and Boaz.
- Add support for zero+unprovision for blkdev_issue_zeroout() from
Martin"
* 'for-3.20/core' of git://git.kernel.dk/linux-block: (27 commits)
block: remove unused function blk_bio_map_sg
block: handle the null_mapped flag correctly in blk_rq_map_user_iov
blk-mq: fix double-free in error path
block: prevent request-to-request merging with gaps if not allowed
blk-mq: make blk_mq_run_queues() static
dm: fix multipath regression due to initializing wrong request
cfq-iosched: handle failure of cfq group allocation
block: Quiesce zeroout wrapper
block: rewrite and split __bio_copy_iov()
block: merge __bio_map_user_iov into bio_map_user_iov
block: merge __bio_map_kern into bio_map_kern
block: pass iov_iter to the BLOCK_PC mapping functions
block: add a helper to free bio bounce buffer pages
block: use blk_rq_map_user_iov to implement blk_rq_map_user
block: simplify bio_map_kern
block: mark blk-mq devices as stackable
block: keep established cmd_flags when cloning into a blk-mq request
block: add blk-mq support to blk_insert_cloned_request()
block: require blk_rq_prep_clone() be given an initialized clone request
blk-mq: add tag allocation policy
...
For blk-mq request-based DM the responsibility of allocating a cloned
request is transfered from DM core to the target type. Doing so
enables the cloned request to be allocated from the appropriate
blk-mq request_queue's pool (only the DM target, e.g. multipath, can
know which block device to send a given cloned request to).
Care was taken to preserve compatibility with old-style block request
completion that requires request-based DM _not_ acquire the clone
request's queue lock in the completion path. As such, there are now 2
different request-based DM target_type interfaces:
1) the original .map_rq() interface will continue to be used for
non-blk-mq devices -- the preallocated clone request is passed in
from DM core.
2) a new .clone_and_map_rq() and .release_clone_rq() will be used for
blk-mq devices -- blk_get_request() and blk_put_request() are used
respectively from these hooks.
dm_table_set_type() was updated to detect if the request-based target is
being stacked on blk-mq devices, if so DM_TYPE_MQ_REQUEST_BASED is set.
DM core disallows switching the DM table's type after it is set. This
means that there is no mixing of non-blk-mq and blk-mq devices within
the same request-based DM table.
[This patch was started by Keith and later heavily modified by Mike]
Tested-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
For blk-mq request-based DM the responsibility of allocating a cloned
request will be transfered from DM core to the target type.
To prepare for conditionally using this new model the original
request's 'special' now points to the dm_rq_target_io because the
clone is allocated later in the block layer rather than in DM core.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Switch to having request-based DM enqueue all prep'ed requests into work
processed by another thread. This allows request-based DM to invoke
block APIs that assume interrupt enabled context (e.g. blk_get_request)
and is a prerequisite for adding blk-mq support to request-based DM.
The new kernel thread is only initialized for request-based DM devices.
multipath_map() is now always in irq enabled context so change multipath
spinlock (m->lock) locking to always disable interrupts.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Request-based DM support for blk-mq devices requires that
dm_rq_target_io structures not be allocated with an embedded request
structure. The request-based DM target (e.g. dm-multipath) must
allocate the request from the blk-mq devices' request_queue using
blk_get_request().
The unfortunate side-effect of this change is old-style request-based DM
support will no longer use contiguous memory for the dm_rq_target_io and
request structures for each clone.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Christoph Hellwig