The main point of calling __smp_call_function_single() is to send
an IPI in a pure asynchronous way. By embedding a csd in an object,
a caller can send the IPI without waiting for a previous one to complete
as is required by smp_call_function_single() for example. As such,
sending this kind of IPI can be safe even when irqs are disabled.
This flexibility comes at the expense of the caller who then needs to
synchronize the csd lifecycle by himself and make sure that IPIs on a
single csd are serialized.
This is how __smp_call_function_single() works when wait = 0 and this
usecase is relevant.
Now there don't seem to be any usecase with wait = 1 that can't be
covered by smp_call_function_single() instead, which is safer. Lets look
at the two possible scenario:
1) The user calls __smp_call_function_single(wait = 1) on a csd embedded
in an object. It looks like a nice and convenient pattern at the first
sight because we can then retrieve the object from the IPI handler easily.
But actually it is a waste of memory space in the object since the csd
can be allocated from the stack by smp_call_function_single(wait = 1)
and the object can be passed an the IPI argument.
Besides that, embedding the csd in an object is more error prone
because the caller must take care of the serialization of the IPIs
for this csd.
2) The user calls __smp_call_function_single(wait = 1) on a csd that
is allocated on the stack. It's ok but smp_call_function_single()
can do it as well and it already takes care of the allocation on the
stack. Again it's more simple and less error prone.
Therefore, using the underscore prepend API version with wait = 1
is a bad pattern and a sign that the caller can do safer and more
simple.
There was a single user of that which has just been converted.
So lets remove this option to discourage further users.
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@fb.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Make sure we have a proper pairing between starting and requeueing
requests. Move the dma drain and REQ_END setup into blk_mq_start_request,
and make sure blk_mq_requeue_request properly undoes them, giving us
a pair of function to prepare and unprepare a request without leaving
side effects.
Together this ensures we always clean up properly after
BLK_MQ_RQ_QUEUE_BUSY returns from ->queue_rq.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
rq->errors never has been part of the communication protocol between drivers
and the block stack and most drivers will not have initialized it.
Return -EIO to upper layers when the driver returns BLK_MQ_RQ_QUEUE_ERROR
unconditionally. If a driver want to return a different error it can easily
do so by returning success after calling blk_mq_end_io itself.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Witch to using a preallocated flush_rq for blk-mq similar to what's done
with the old request path. This allows us to set up the request properly
with a tag from the actually allowed range and ->rq_disk as needed by
some drivers. To make life easier we also switch to dynamic allocation
of ->flush_rq for the old path.
This effectively reverts most of
"blk-mq: fix for flush deadlock"
and
"blk-mq: Don't reserve a tag for flush request"
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Rework I/O completions to work more like the old code path. blk_mq_end_io
now stays out of the business of deferring completions to others CPUs
and calling blk_mark_rq_complete. The latter is very important to allow
completing requests that have timed out and thus are already marked completed,
the former allows using the IPI callout even for driver specific completions
instead of having to reimplement them.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
This patch adds the missing bio_integrity_enabled() +
bio_integrity_prep() setup into blk_mq_make_request()
in order to use DIF protection with scsi-mq.
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
Make blk-mq handle the dma_drain_size field the same way as the old request
path.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
This is neede for proper SG_IO operation as well as various uses of
blk_execute_rq from the SCSI midlayer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Reserving a tag (request) for flush to avoid dead lock is a overkill. A
tag is valuable resource. We can track the number of flush requests and
disallow having too many pending flush requests allocated. With this
patch, blk_mq_alloc_request_pinned() could do a busy nop (but not a dead
loop) if too many pending requests are allocated and new flush request
is allocated. But this should not be a problem, too many pending flush
requests are very rare case.
I verified this can fix the deadlock caused by too many pending flush
requests.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
'struct page' has two list_head fields: 'lru' and 'list'. Conveniently,
they are unioned together. This means that code can use them
interchangably, which gets horribly confusing.
The blk-mq made the logical decision to try to use page->list. But, that
field was actually introduced just for the slub code. ->lru is the right
field to use outside of slab/slub.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
__smp_call_function_single already avoids multiple IPIs by internally
queing up the items, and now also is available for non-SMP builds as
a trivially correct stub, so there is no need to wrap it. If the
additional lock roundtrip cause problems my patch to convert the
generic IPI code to llists is waiting to get merged will fix it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_rq_init() is called in req's complete handler to initialize
the request, so the members of start_time and start_time_ns might
become inaccurate when it is allocated in future.
The patch initializes the two members in blk_mq_rq_ctx_init() to
fix the problem.
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_mq_free_queue() is called from release handler of
queue kobject, so it needn't be called from drivers.
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This patch moves synchronization on mq->delay_work
from blk_mq_free_queue() to blk_sync_queue(), so that
blk_sync_queue can work on mq.
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_mq_drain_queue() is introduced so that we can drain
mq queue inside blk_cleanup_queue().
Also don't accept new requests any more if queue is marked
as dying.
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Merge tag 'v3.13-rc6' into for-3.14/core
Needed to bring blk-mq uptodate, since changes have been going in
since for-3.14/core was established.
Fixup merge issues related to the immutable biovec changes.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Conflicts:
block/blk-flush.c
fs/btrfs/check-integrity.c
fs/btrfs/extent_io.c
fs/btrfs/scrub.c
fs/logfs/dev_bdev.c
If accounting is on, we will do the IO completion accounting after
we have freed the request. Fix that by moving it sooner instead.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If __GFP_WAIT isn't set and we fail allocating, when we go
to drop the reference on the ctx, we will attempt to dereference
the NULL rq. Fix that.
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If disk stats are enabled on the queue, a request needs to
be marked with REQ_IO_STAT for accounting to be active on
that request. This fixes an issue with virtio-blk not
showing up in /proc/diskstats after the conversion to
blk-mq.
Add QUEUE_FLAG_MQ_DEFAULT, setting stats and same cpu-group
completion on by default.
Reported-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pull second round of block driver updates from Jens Axboe:
"As mentioned in the original pull request, the bcache bits were pulled
because of their dependency on the immutable bio vecs. Kent re-did
this part and resubmitted it, so here's the 2nd round of (mostly)
driver updates for 3.13. It contains:
- The bcache work from Kent.
- Conversion of virtio-blk to blk-mq. This removes the bio and request
path, and substitutes with the blk-mq path instead. The end result
almost 200 deleted lines. Patch is acked by Asias and Christoph, who
both did a bunch of testing.
- A removal of bootmem.h include from Grygorii Strashko, part of a
larger series of his killing the dependency on that header file.
- Removal of __cpuinit from blk-mq from Paul Gortmaker"
* 'for-linus' of git://git.kernel.dk/linux-block: (56 commits)
virtio_blk: blk-mq support
blk-mq: remove newly added instances of __cpuinit
bcache: defensively handle format strings
bcache: Bypass torture test
bcache: Delete some slower inline asm
bcache: Use ida for bcache block dev minor
bcache: Fix sysfs splat on shutdown with flash only devs
bcache: Better full stripe scanning
bcache: Have btree_split() insert into parent directly
bcache: Move spinlock into struct time_stats
bcache: Kill sequential_merge option
bcache: Kill bch_next_recurse_key()
bcache: Avoid deadlocking in garbage collection
bcache: Incremental gc
bcache: Add make_btree_freeing_key()
bcache: Add btree_node_write_sync()
bcache: PRECEDING_KEY()
bcache: bch_(btree|extent)_ptr_invalid()
bcache: Don't bother with bucket refcount for btree node allocations
bcache: Debug code improvements
...
We've switched over every architecture that supports SMP to it, so
remove the new useless config variable.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The new blk-mq code added new instances of __cpuinit usage.
We removed this a couple versions ago; we now want to remove
the compat no-op stubs. Introducing new users is not what
we want to see at this point in time, as it will break once
the stubs are gone.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We switched to plug mq_list for mq, but some code are still using old list.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The flush state machine takes in a struct request, which then is
submitted multiple times to the underling driver. The old block code
requeses the same request for each of those, so it does not have an
issue with tapping into the request pool. The new one on the other hand
allocates a new request for each of the actualy steps of the flush
sequence. If have already allocated all of the tags for IO, we will
fail allocating the flush request.
Set aside a reserved request just for flushes.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add a helper to iterate over all hw queues and stop them. This is useful
for driver that implement PM suspend functionality.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Modified to just call blk_mq_stop_hw_queue() by Jens.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux currently has two models for block devices:
- The classic request_fn based approach, where drivers use struct
request units for IO. The block layer provides various helper
functionalities to let drivers share code, things like tag
management, timeout handling, queueing, etc.
- The "stacked" approach, where a driver squeezes in between the
block layer and IO submitter. Since this bypasses the IO stack,
driver generally have to manage everything themselves.
With drivers being written for new high IOPS devices, the classic
request_fn based driver doesn't work well enough. The design dates
back to when both SMP and high IOPS was rare. It has problems with
scaling to bigger machines, and runs into scaling issues even on
smaller machines when you have IOPS in the hundreds of thousands
per device.
The stacked approach is then most often selected as the model
for the driver. But this means that everybody has to re-invent
everything, and along with that we get all the problems again
that the shared approach solved.
This commit introduces blk-mq, block multi queue support. The
design is centered around per-cpu queues for queueing IO, which
then funnel down into x number of hardware submission queues.
We might have a 1:1 mapping between the two, or it might be
an N:M mapping. That all depends on what the hardware supports.
blk-mq provides various helper functions, which include:
- Scalable support for request tagging. Most devices need to
be able to uniquely identify a request both in the driver and
to the hardware. The tagging uses per-cpu caches for freed
tags, to enable cache hot reuse.
- Timeout handling without tracking request on a per-device
basis. Basically the driver should be able to get a notification,
if a request happens to fail.
- Optional support for non 1:1 mappings between issue and
submission queues. blk-mq can redirect IO completions to the
desired location.
- Support for per-request payloads. Drivers almost always need
to associate a request structure with some driver private
command structure. Drivers can tell blk-mq this at init time,
and then any request handed to the driver will have the
required size of memory associated with it.
- Support for merging of IO, and plugging. The stacked model
gets neither of these. Even for high IOPS devices, merging
sequential IO reduces per-command overhead and thus
increases bandwidth.
For now, this is provided as a potential 3rd queueing model, with
the hope being that, as it matures, it can replace both the classic
and stacked model. That would get us back to having just 1 real
model for block devices, leaving the stacked approach to dm/md
devices (as it was originally intended).
Contributions in this patch from the following people:
Shaohua Li <shli@fusionio.com>
Alexander Gordeev <agordeev@redhat.com>
Christoph Hellwig <hch@infradead.org>
Mike Christie <michaelc@cs.wisc.edu>
Matias Bjorling <m@bjorling.me>
Jeff Moyer <jmoyer@redhat.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Frederic Weisbecker