The unit of max_io_len is sector instead of byte (spotted through
code review), so fix it.
Fixes: 3b1a94c88b ("dm zoned: drive-managed zoned block device target")
Cc: stable@vger.kernel.org
Signed-off-by: Hou Tao <houtao1@huawei.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
per-device reclaim should select zones on that device only.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Remove the hard-coded limit of two devices and support an unlimited
number of additional zoned devices.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Random and sequential zones should be part of the respective
device structure to make arbitration between devices possible.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Instead of having one reclaim workqueue for the entire set we should
be allocating a reclaim workqueue per device; doing so will reduce
contention and should boost performance for a multi-device setup.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Add a pointer, to the containing device, within struct dm_zone and
kill dmz_zone_to_dev().
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Instead of lumping emulated zones together with random zones we
should be handling them as separate 'cache' zones. This improves
code readability and allows an easier implementation of different
cache policies.
Also add additional allocation flags, to separate the type (cache,
random, or sequential) from the purpose (eg reclaim).
Also switch the allocation policy to not use random zones as buffer
zones if cache zones are present. This avoids a performance drop when
all cache zones are used.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
When building arm32 allyesconfig:
ld.lld: error: undefined symbol: __aeabi_uldivmod
>>> referenced by dm-zoned-target.c
>>> md/dm-zoned-target.o:(dmz_ctr) in archive drivers/built-in.a
dmz_fixup_devices uses DIV_ROUND_UP with variables of type sector_t. As
such, it should be using DIV_ROUND_UP_SECTOR_T, which handles this
automatically.
Fixes: 70978208ec91 ("dm zoned: metadata version 2")
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
DMDEBUG will already add a newline to the logging messages, so we
shouldn't be adding it to the message itself.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Implement handling for metadata version 2. The new metadata adds a
label and UUID for the device mapper device, and additional UUID for
the underlying block devices.
It also allows for an additional regular drive to be used for
emulating random access zones. The emulated zones will be placed
logically in front of the zones from the zoned block device, causing
the superblocks and metadata to be stored on that device.
The first zone of the original zoned device will be used to hold
another, tertiary copy of the metadata; this copy carries a generation
number of 0 and is never updated; it's just used for identification.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Replace the 'target' pointer in the bio context with the
device pointer as this is what's actually used.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Use the dmz_zone_to_dev() mapping function to remove the
'dev' argument from reclaim.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Introduce accessors dmz_dev_is_dying() and dmz_check_dev() to
avoid having to reference the devices directly.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Introduce dmz_metadata_label() to format the device-mapper device
name and use it instead of the device name of the underlying device.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Move fields from the device structure into the metadata structure
and provide accessor functions.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Instead of calculating the zone index by the offset within the
zone array store the index within the structure itself. With that
the helper dmz_id() is pointless and can be replaced with accessing
the ->id value directly.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Add callback for 'dmsetup message' to allow the reclaim process
to be triggered manually.
Eg.
dmsetup message /dev/dm-X 0 message
will start the reclaim process even if the default threshold
of 50 percent of free random zones is not reached.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Add callback to supply information for 'dmsetup status'
and 'dmsetup table'. The output for 'dmsetup status' is
0 <size> zoned <nr_zones> zones <nr_unmap_rnd>/<nr_rnd> random <nr_unmap_seq>/<nr_seq> sequential
where <nr_unmap_rnd> is the number of unmapped (ie free) random zones,
<nr_rnd> the total number of random zones, <nr_unmap_seq> the number
of unmapped sequential zones, and <nr_seq> the total number of
sequential zones.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Changes made during the 5.6 cycle warrant bumping the version number
for DM core and the targets modified by this commit.
It should be noted that dm-thin, dm-crypt and dm-raid already had
their target version bumped during the 5.6 merge window.
Signed-off-by; Mike Snitzer <snitzer@redhat.com>
Dm-zoned initializes reference counters of new chunk works with zero
value and refcount_inc() is called to increment the counter. However, the
refcount_inc() function handles the addition to zero value as an error
and triggers the warning as follows:
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 7 PID: 1506 at lib/refcount.c:25 refcount_warn_saturate+0x68/0xf0
...
CPU: 7 PID: 1506 Comm: systemd-udevd Not tainted 5.4.0+ #134
...
Call Trace:
dmz_map+0x2d2/0x350 [dm_zoned]
__map_bio+0x42/0x1a0
__split_and_process_non_flush+0x14a/0x1b0
__split_and_process_bio+0x83/0x240
? kmem_cache_alloc+0x165/0x220
dm_process_bio+0x90/0x230
? generic_make_request_checks+0x2e7/0x680
dm_make_request+0x3e/0xb0
generic_make_request+0xcf/0x320
? memcg_drain_all_list_lrus+0x1c0/0x1c0
submit_bio+0x3c/0x160
? guard_bio_eod+0x2c/0x130
mpage_readpages+0x182/0x1d0
? bdev_evict_inode+0xf0/0xf0
read_pages+0x6b/0x1b0
__do_page_cache_readahead+0x1ba/0x1d0
force_page_cache_readahead+0x93/0x100
generic_file_read_iter+0x83a/0xe40
? __seccomp_filter+0x7b/0x670
new_sync_read+0x12a/0x1c0
vfs_read+0x9d/0x150
ksys_read+0x5f/0xe0
do_syscall_64+0x5b/0x180
entry_SYSCALL_64_after_hwframe+0x44/0xa9
...
After this warning, following refcount API calls for the counter all fail
to change the counter value.
Fix this by setting the initial reference counter value not zero but one
for the new chunk works. Instead, do not call refcount_inc() via
dmz_get_chunk_work() for the new chunks works.
The failure was observed with linux version 5.4 with CONFIG_REFCOUNT_FULL
enabled. Refcount rework was merged to linux version 5.5 by the
commit 168829ad09 ("Merge branch 'locking-core-for-linus' of
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip"). After this
commit, CONFIG_REFCOUNT_FULL was removed and the failure was observed
regardless of kernel configuration.
Linux version 4.20 merged the commit 092b564876 ("dm zoned: target: use
refcount_t for dm zoned reference counters"). Before this commit, dm
zoned used atomic_t APIs which does not check addition to zero, then this
fix is not necessary.
Fixes: 092b564876 ("dm zoned: target: use refcount_t for dm zoned reference counters")
Cc: stable@vger.kernel.org # 5.4+
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Simplify the arguments to blkdev_nr_zones by passing a gendisk instead
of the block_device and capacity. This also removes the need for
__blkdev_nr_zones as all callers are outside the fast path and can
deal with the additional branch.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Commit 75d66ffb48 added backing device health checks and as a part
of these checks, check_events() block ops template call is invoked in
dm-zoned mapping path as well as in reclaim and flush path. Calling
check_events() with ATA or SCSI backing devices introduces a blocking
scsi_test_unit_ready() call being made in sd_check_events(). Even though
the overhead of calling scsi_test_unit_ready() is small for ATA zoned
devices, it is much larger for SCSI and it affects performance in a very
negative way.
Fix this performance regression by executing check_events() only in case
of any I/O errors. The function dmz_bdev_is_dying() is modified to call
only blk_queue_dying(), while calls to check_events() are made in a new
helper function, dmz_check_bdev().
Reported-by: zhangxiaoxu <zhangxiaoxu5@huawei.com>
Fixes: 75d66ffb48 ("dm zoned: properly handle backing device failure")
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
dm-zoned is observed to lock up or livelock in case of hardware
failure or some misconfiguration of the backing zoned device.
This patch adds a new dm-zoned target function that checks the status of
the backing device. If the request queue of the backing device is found
to be in dying state or the SCSI backing device enters offline state,
the health check code sets a dm-zoned target flag prompting all further
incoming I/O to be rejected. In order to detect backing device failures
timely, this new function is called in the request mapping path, at the
beginning of every reclaim run and before performing any metadata I/O.
The proper way out of this situation is to do
dmsetup remove <dm-zoned target>
and recreate the target when the problem with the backing device
is resolved.
Fixes: 3b1a94c88b ("dm zoned: drive-managed zoned block device target")
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Some errors are ignored in the I/O path during queueing chunks
for processing by chunk works. Since at least these errors are
transient in nature, it should be possible to retry the failed
incoming commands.
The fix -
Errors that can happen while queueing chunks are carried upwards
to the main mapping function and it now returns DM_MAPIO_REQUEUE
for any incoming requests that can not be properly queued.
Error logging/debug messages are added where needed.
Fixes: 3b1a94c88b ("dm zoned: drive-managed zoned block device target")
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
My static checker complains about this line from dmz_get_zoned_device()
aligned_capacity = dev->capacity & ~(blk_queue_zone_sectors(q) - 1);
The problem is that "aligned_capacity" and "dev->capacity" are sector_t
type (which is a u64 under most configs) but blk_queue_zone_sectors(q)
returns a u32 so the higher 32 bits in aligned_capacity are cleared to
zero. This patch adds a cast to address the issue.
Fixes: 114e025968 ("dm zoned: ignore last smaller runt zone")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
There is no need to have DM core split discards on behalf of a DM target
now that blk_queue_split() handles splitting discards based on the
queue_limits. A DM target just needs to set max_discard_sectors,
discard_granularity, etc, in queue_limits.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
struct bioctx includes the ref refcount_t to track the number of I/O
fragments used to process a target BIO as well as ensure that the zone
of the BIO is kept in the active state throughout the lifetime of the
BIO. However, since decrementing of this reference count is done in the
target .end_io method, the function bio_endio() must be called multiple
times for read and write target BIOs, which causes problems with the
value of the __bi_remaining struct bio field for chained BIOs (e.g. the
clone BIO passed by dm core is large and splits into fragments by the
block layer), resulting in incorrect values and inconsistencies with the
BIO_CHAIN flag setting. This is turn triggers the BUG_ON() call:
BUG_ON(atomic_read(&bio->__bi_remaining) <= 0);
in bio_remaining_done() called from bio_endio().
Fix this ensuring that bio_endio() is called only once for any target
BIO by always using internal clone BIOs for processing any read or
write target BIO. This allows reference counting using the target BIO
context counter to trigger the target BIO completion bio_endio() call
once all data, metadata and other zone work triggered by the BIO
complete.
Overall, this simplifies the code too as the target .end_io becomes
unnecessary and differences between read and write BIO issuing and
completion processing disappear.
Fixes: 3b1a94c88b ("dm zoned: drive-managed zoned block device target")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
(.request_fn) from request-based DM. Jens has already started
preparing for complete removal of the legacy IO path in 4.21 but this
earlier removal of support from DM has been coordinated with Jens (as
evidenced by the commit being attributed to him). Making
request-based DM exclussively blk-mq only cleans up that portion of DM
core quite nicely.
- Convert the thinp and zoned targets over to using refcount_t where
applicable.
- A couple fixes to the DM zoned target for refcounting and other races
buried in the implementation of metadata block creation and use.
- Small cleanups to remove redundant unlikely() around a couple
WARN_ON_ONCE().
- Simplify how dm-ioctl copies from userspace, eliminating some
potential for a malicious user trying to change the executed ioctl
after its processing has begun.
- Tweaked DM crypt target to use the DM device name when naming the
various workqueues created for a particular DM crypt device (makes the
N workqueues for a DM crypt device more easily understood and enhances
user's accounting capabilities at a glance via "ps")
- Small fixup to remove dead branch in DM writecache's memory_entry().
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Merge tag 'for-4.20/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper updates from Mike Snitzer:
- The biggest change this cycle is to remove support for the legacy IO
path (.request_fn) from request-based DM.
Jens has already started preparing for complete removal of the legacy
IO path in 4.21 but this earlier removal of support from DM has been
coordinated with Jens (as evidenced by the commit being attributed to
him).
Making request-based DM exclussively blk-mq only cleans up that
portion of DM core quite nicely.
- Convert the thinp and zoned targets over to using refcount_t where
applicable.
- A couple fixes to the DM zoned target for refcounting and other races
buried in the implementation of metadata block creation and use.
- Small cleanups to remove redundant unlikely() around a couple
WARN_ON_ONCE().
- Simplify how dm-ioctl copies from userspace, eliminating some
potential for a malicious user trying to change the executed ioctl
after its processing has begun.
- Tweaked DM crypt target to use the DM device name when naming the
various workqueues created for a particular DM crypt device (makes
the N workqueues for a DM crypt device more easily understood and
enhances user's accounting capabilities at a glance via "ps")
- Small fixup to remove dead branch in DM writecache's memory_entry().
* tag 'for-4.20/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
dm writecache: remove disabled code in memory_entry()
dm zoned: fix various dmz_get_mblock() issues
dm zoned: fix metadata block ref counting
dm raid: avoid bitmap with raid4/5/6 journal device
dm crypt: make workqueue names device-specific
dm: add dm_table_device_name()
dm ioctl: harden copy_params()'s copy_from_user() from malicious users
dm: remove unnecessary unlikely() around WARN_ON_ONCE()
dm zoned: target: use refcount_t for dm zoned reference counters
dm thin: use refcount_t for thin_c reference counting
dm table: require that request-based DM be layered on blk-mq devices
dm: rename DM_TYPE_MQ_REQUEST_BASED to DM_TYPE_REQUEST_BASED
dm: remove legacy request-based IO path
Introduce the blkdev_nr_zones() helper function to get the total
number of zones of a zoned block device. This number is always 0 for a
regular block device (q->limits.zoned == BLK_ZONED_NONE case).
Replace hard-coded number of zones calculation in dmz_get_zoned_device()
with a call to this helper.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The API surrounding refcount_t should be used in place of atomic_t
when variables are being used as reference counters. This API can
prevent issues such as counter overflows and use-after-free
conditions. Within the dm zoned target stack, the atomic_t API is
used for bioctx->ref and cw->refcount. Change these to use
refcount_t, avoiding the issues mentioned.
Signed-off-by: John Pittman <jpittman@redhat.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Tested-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Eliminate most holes in DM data structures that were modified by
commit 6f1c819c21 ("dm: convert to bioset_init()/mempool_init()").
Also prevent structure members from unnecessarily spanning cache
lines.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Convert dm to embedded bio sets.
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Use the fmode_t that is passed to dm_blk_ioctl() rather than
inconsistently (varies across targets) drop it on the floor by
overriding it with the fmode_t stored in 'struct dm_dev'.
All the persistent reservation functions weren't using the fmode_t they
got back from .prepare_ioctl so remove them.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The SCSI layer allows ZBC drives to have a smaller last runt zone. For
such a device, specifying the entire capacity for a dm-zoned target
table entry fails because the specified capacity is not aligned on a
device zone size indicated in the request queue structure of the
device.
Fix this problem by ignoring the last runt zone in the entry length
when seting up the dm-zoned target (ctr method) and when iterating table
entries of the target (iterate_devices method). This allows dm-zoned
users to still easily setup a target using the entire device capacity
(as mandated by dm-zoned) or the aligned capacity excluding the last
runt zone.
While at it, replace direct references to the device queue chunk_sectors
limit with calls to the accessor blk_queue_zone_sectors().
Reported-by: Peter Desnoyers <pjd@ccs.neu.edu>
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This way we don't need a block_device structure to submit I/O. The
block_device has different life time rules from the gendisk and
request_queue and is usually only available when the block device node
is open. Other callers need to explicitly create one (e.g. the lightnvm
passthrough code, or the new nvme multipathing code).
For the actual I/O path all that we need is the gendisk, which exists
once per block device. But given that the block layer also does
partition remapping we additionally need a partition index, which is
used for said remapping in generic_make_request.
Note that all the block drivers generally want request_queue or
sometimes the gendisk, so this removes a layer of indirection all
over the stack.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Use GFP_NOIO for memory allocations in the I/O path. Other memory
allocations in the initialization path can use GFP_KERNEL.
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The value REQ_OP_FLUSH is only used by the block code for
request-based devices.
Remove the tests for REQ_OP_FLUSH from the bio-based dm-zoned-target.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The dm-zoned device mapper target provides transparent write access
to zoned block devices (ZBC and ZAC compliant block devices).
dm-zoned hides to the device user (a file system or an application
doing raw block device accesses) any constraint imposed on write
requests by the device, equivalent to a drive-managed zoned block
device model.
Write requests are processed using a combination of on-disk buffering
using the device conventional zones and direct in-place processing for
requests aligned to a zone sequential write pointer position.
A background reclaim process implemented using dm_kcopyd_copy ensures
that conventional zones are always available for executing unaligned
write requests. The reclaim process overhead is minimized by managing
buffer zones in a least-recently-written order and first targeting the
oldest buffer zones. Doing so, blocks under regular write access (such
as metadata blocks of a file system) remain stored in conventional
zones, resulting in no apparent overhead.
dm-zoned implementation focus on simplicity and on minimizing overhead
(CPU, memory and storage overhead). For a 14TB host-managed disk with
256 MB zones, dm-zoned memory usage per disk instance is at most about
3 MB and as little as 5 zones will be used internally for storing metadata
and performing buffer zone reclaim operations. This is achieved using
zone level indirection rather than a full block indirection system for
managing block movement between zones.
dm-zoned primary target is host-managed zoned block devices but it can
also be used with host-aware device models to mitigate potential
device-side performance degradation due to excessive random writing.
Zoned block devices can be formatted and checked for use with the dm-zoned
target using the dmzadm utility available at:
https://github.com/hgst/dm-zoned-tools
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>
[Mike Snitzer partly refactored Damien's original work to cleanup the code]
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Hou Tao