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>
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>
Commit febf715 ("block: require blk_rq_prep_clone() be given an
initialized clone request") introduced a regression by calling
blk_rq_init() on the original request rather than the clone
request that is passed to setup_clone().
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Fixes: febf71588c ("block: require blk_rq_prep_clone() be given an initialized clone request")
Signed-off-by: Jens Axboe <axboe@fb.com>
Prepare to allow blk_rq_prep_clone() to accept clone requests that were
allocated from blk-mq request queues. As such the blk_rq_prep_clone()
caller must first initialize the clone request.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Commit ffcc393641 ("dm: enhance internal suspend and resume interface")
attempted to handle multiple internal suspends on the same device, but
it did that incorrectly. When these functions are called in this order
on the same device the device is no longer suspended, but it should be:
dm_internal_suspend_noflush
dm_internal_suspend_noflush
dm_internal_resume
Fix this bug by maintaining an 'internal_suspend_count' and resuming
the device when this count drops to zero.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
In bio-based DM's clone_endio(), when target_type doesn't implement
.end_io (e.g. linear) r will be always be initialized 0. So if a
WRITE SAME bio fails WRITE SAME will not be disabled as intended.
Fix this by initializing r to error, rather than 0, in clone_endio().
Signed-off-by: Alex Chen <alex.chen@huawei.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Fixes: 7eee4ae2db ("dm: disable WRITE SAME if it fails")
Cc: stable@vger.kernel.org
Pull block layer driver updates from Jens Axboe:
- NVMe updates:
- The blk-mq conversion from Matias (and others)
- A stack of NVMe bug fixes from the nvme tree, mostly from Keith.
- Various bug fixes from me, fixing issues in both the blk-mq
conversion and generic bugs.
- Abort and CPU online fix from Sam.
- Hot add/remove fix from Indraneel.
- A couple of drbd fixes from the drbd team (Andreas, Lars, Philipp)
- With the generic IO stat accounting from 3.19/core, converting md,
bcache, and rsxx to use those. From Gu Zheng.
- Boundary check for queue/irq mode for null_blk from Matias. Fixes
cases where invalid values could be given, causing the device to hang.
- The xen blkfront pull request, with two bug fixes from Vitaly.
* 'for-3.19/drivers' of git://git.kernel.dk/linux-block: (56 commits)
NVMe: fix race condition in nvme_submit_sync_cmd()
NVMe: fix retry/error logic in nvme_queue_rq()
NVMe: Fix FS mount issue (hot-remove followed by hot-add)
NVMe: fix error return checking from blk_mq_alloc_request()
NVMe: fix freeing of wrong request in abort path
xen/blkfront: remove redundant flush_op
xen/blkfront: improve protection against issuing unsupported REQ_FUA
NVMe: Fix command setup on IO retry
null_blk: boundary check queue_mode and irqmode
block/rsxx: use generic io stats accounting functions to simplify io stat accounting
md: use generic io stats accounting functions to simplify io stat accounting
drbd: use generic io stats accounting functions to simplify io stat accounting
md/bcache: use generic io stats accounting functions to simplify io stat accounting
NVMe: Update module version major number
NVMe: fail pci initialization if the device doesn't have any BARs
NVMe: add ->exit_hctx() hook
NVMe: make setup work for devices that don't do INTx
NVMe: enable IO stats by default
NVMe: nvme_submit_async_admin_req() must use atomic rq allocation
NVMe: replace blk_put_request() with blk_mq_free_request()
...
rcu_dereference() should be used in sections protected by rcu_read_lock.
For writers, holding some kind of mutex or lock,
rcu_dereference_protected() is the way to go, adding explicit lockdep
bits.
In __unbind(), we are the last user of this mapped device, so can use
the constant '1' instead of a lockdep_is_held(), not consistent with
other uses of rcu_dereference_protected() which use md->suspend_lock
mutex.
Reported-by: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: 33423974bf ("dm: Use rcu_dereference() for accessing rcu pointer")
Cc: Pranith Kumar <bobby.prani@gmail.com>
[snitzer: allow lines longer than 80 columns, refine subject]
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Rename dm_internal_{suspend,resume} to dm_internal_{suspend,resume}_fast
-- dm-stats will continue using these methods to avoid all the extra
suspend/resume logic that is not needed in order to quickly flush IO.
Introduce dm_internal_suspend_noflush() variant that actually calls the
mapped_device's target callbacks -- otherwise target-specific hooks are
avoided (e.g. dm-thin's thin_presuspend and thin_postsuspend). Common
code between dm_internal_{suspend_noflush,resume} and
dm_{suspend,resume} was factored out as __dm_{suspend,resume}.
Update dm_internal_{suspend_noflush,resume} to always take and release
the mapped_device's suspend_lock. Also update dm_{suspend,resume} to be
aware of potential for DM_INTERNAL_SUSPEND_FLAG to be set and respond
accordingly by interruptibly waiting for the DM_INTERNAL_SUSPEND_FLAG to
be cleared. Add lockdep annotation to dm_suspend() and dm_resume().
The existing DM_SUSPEND_FLAG remains unchanged.
DM_INTERNAL_SUSPEND_FLAG is set by dm_internal_suspend_noflush() and
cleared by dm_internal_resume().
Both DM_SUSPEND_FLAG and DM_INTERNAL_SUSPEND_FLAG may be set if a device
was already suspended when dm_internal_suspend_noflush() was called --
this can be thought of as a "nested suspend". A "nested suspend" can
occur with legacy userspace dm-thin code that might suspend all active
thin volumes before suspending the pool for resize.
But otherwise, in the normal dm-thin-pool suspend case moving forward:
the thin-pool will have DM_SUSPEND_FLAG set and all active thins from
that thin-pool will have DM_INTERNAL_SUSPEND_FLAG set.
Also add DM_INTERNAL_SUSPEND_FLAG to status report. This new
DM_INTERNAL_SUSPEND_FLAG state is being reported to assist with
debugging (e.g. 'dmsetup info' will report an internally suspended
device accordingly).
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
The DM thin-pool target now must undo the changes performed during
pool_presuspend() so introduce presuspend_undo hook in target_type.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
When creating new devices dm_sync_table() calls
synchronize_rcu_expedited(), causing _all_ pending RCU pointers to be
flushed. This causes a latency overhead that is especially noticeable
when creating lots of devices.
And all of this is pointless as there are no old maps to be
disconnected, and hence no stale pointers which would need to be
cleared up.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Annotate the map field with __rcu since this is a rcu pointer which is checked
by sparse.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The map field in 'struct mapped_device' is an rcu pointer. Use rcu_dereference()
while accessing it.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
These code changes do not introduce a functional change.
But bio_add_page() will never attempt to build up a bio larger than
queue_max_sectors(). Similarly, bio_get_nr_vecs() is also bound by
queue_max_sectors(). Therefore, there is no point in allowing
dm_merge_bvec() to answer "how many sectors can a bio have at this
offset?" with anything larger than queue_max_sectors(). Using
queue_max_sectors() rather than BIO_MAX_SECTORS serves to more
accurately convey the limits that are being imposed.
Also, use unlikely() to clarify the fact that the defensive code in
dm_merge_bvec() relative to max_size going negative shouldn't ever
happen -- if it does happen there is a bug in the block layer for
requesting larger than dm_merge_bvec()'s initial response for a given
offset. Also, update a comment in dm_merge_bvec() relative to
max_hw_sectors_kb. And fix empty newline whitespace.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Until this change, when loading a new DM table, DM core would re-open
all of the devices in the DM table. Now, DM core will avoid redundant
device opens (and closes when destroying the old table) if the old
table already has a device open using the same mode. This is achieved
by managing reference counts on the table_devices that DM core now
stores in the mapped_device structure (rather than in the dm_table
structure). So a mapped_device's active and inactive dm_tables' dm_dev
lists now just point to the dm_devs stored in the mapped_device's
table_devices list.
This improvement in DM core's device reference counting has the
side-effect of fixing a long-standing limitation of the multipath
target: a DM multipath table couldn't include any paths that were unusable
(failed). For example: if all paths have failed and you add a new,
working, path to the table; you can't use it since the table load would
fail due to it still containing failed paths. Now a re-load of a
multipath table can include failed devices and when those devices become
active again they can be used instantly.
The device list code in dm.c isn't a straight copy/paste from the code in
dm-table.c, but it's very close (aside from some variable renames). One
subtle difference is that find_table_device for the tables_devices list
will only match devices with the same name and mode. This is because we
don't want to upgrade a device's mode in the active table when an
inactive table is loaded.
Access to the mapped_device structure's tables_devices list requires a
mutex (tables_devices_lock), so that tables cannot be created and
destroyed concurrently.
Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Since DM core uses bio_clone_fast() for both bio-based and request-based
DM devices there is no need for DM's bioset to have a bvec mempool.
With this patch, on arch with 4KB page for example, memory usage will be
reduced by 64KB for each bio-based DM device and 1MB for each
request-based DM device.
For example, when you create 10,000 bio-based DM devices and 1,000
request-based DM devices, memory usage of biovec under no load is:
# grep biovec /proc/slabinfo
biovec-256 418068 418068 4096 ...
biovec-128 0 0 2048 ...
biovec-64 0 0 1024 ...
biovec-16 0 0 256 ...
With this patch series applied, the usage becomes:
# grep biovec /proc/slabinfo
biovec-256 116 116 4096 ...
biovec-128 0 0 2048 ...
biovec-64 0 0 1024 ...
biovec-16 0 0 256 ...
So 4096 * (418068 - 116) = 1.6GB of memory is saved in this example.
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
alloc_tio() uses bio_alloc_bioset() to allocate a clone-bio for a bio.
alloc_tio() takes the number of bvecs to allocate for the clone-bio.
However, with v3.14's immutable biovec changes DM now uses
__bio_clone_fast() and no longer needs to allocate bvecs.
In practice, the 'nr_iovecs' passed to alloc_tio() is always effectively
0. __clone_and_map_simple_bio() looked like it was passing non-zero
nr_iovecs, but its value was always within the range of inline bvecs and
no allocation actually happened. If allocation happened, the BUG_ON() in
__bio_clone_fast() would've triggered.
Remove the nr_iovecs parameter from alloc_tio() to prevent possible
future bio_alloc_bioset() mis-use of a new bioset interface that will no
longer allow bvecs to be allocated.
Also fix extra whitespace before the __bio_clone_fast() call in
__clone_and_map_simple_bio().
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The commit 2c140a246d ("dm: allow remove to be deferred") introduced a
deferred removal feature for the device mapper. When this feature is
used (by passing a flag DM_DEFERRED_REMOVE to DM_DEV_REMOVE_CMD ioctl)
and the user tries to remove a device that is currently in use, the
device will be removed automatically in the future when the last user
closes it.
Device mapper used the system workqueue to perform deferred removals.
However, some targets (dm-raid1, dm-mpath, dm-stripe) flush work items
scheduled for the system workqueue from their destructor. If the
destructor itself is called from the system workqueue during deferred
removal, it introduces a possible deadlock - the workqueue tries to flush
itself.
Fix this possible deadlock by introducing a new workqueue for deferred
removals. We allocate just one workqueue for all dm targets. The
ability of dm targets to process IOs isn't dependent on deferred removal
of unused targets, so a deadlock due to shared workqueue isn't possible.
Also, cleanup local_init() to eliminate potential for returning success
on failure.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.13+
to only process a portion of a bio, the remainder being sent in the
next bio. This enables the old dm snapshot-origin target to only
split write bios on chunk boundaries, read bios are now sent to the
origin device unchanged.
. Add DM core support for disabling WRITE SAME if the underlying SCSI
layer disables it due to command failure.
. Reduce lock contention in DM's bio-prison.
. A few small cleanups and fixes to dm-thin and dm-era.
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Merge tag 'dm-3.16-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper updates from Mike Snitzer:
"This pull request is later than I'd have liked because I was waiting
for some performance data to help finally justify sending the
long-standing dm-crypt cpu scalability improvements upstream.
Unfortunately we came up short, so those dm-crypt changes will
continue to wait, but it seems we're not far off.
. Add dm_accept_partial_bio interface to DM core to allow DM targets
to only process a portion of a bio, the remainder being sent in the
next bio. This enables the old dm snapshot-origin target to only
split write bios on chunk boundaries, read bios are now sent to the
origin device unchanged.
. Add DM core support for disabling WRITE SAME if the underlying SCSI
layer disables it due to command failure.
. Reduce lock contention in DM's bio-prison.
. A few small cleanups and fixes to dm-thin and dm-era"
* tag 'dm-3.16-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
dm thin: update discard_granularity to reflect the thin-pool blocksize
dm bio prison: implement per bucket locking in the dm_bio_prison hash table
dm: remove symbol export for dm_set_device_limits
dm: disable WRITE SAME if it fails
dm era: check for a non-NULL metadata object before closing it
dm thin: return ENOSPC instead of EIO when error_if_no_space enabled
dm thin: cleanup noflush_work to use a proper completion
dm snapshot: do not split read bios sent to snapshot-origin target
dm snapshot: allocate a per-target structure for snapshot-origin target
dm: introduce dm_accept_partial_bio
dm: change sector_count member in clone_info from sector_t to unsigned
There is no need for code other than DM core to use dm_set_device_limits
so remove its EXPORT_SYMBOL_GPL. Also, cleanup a couple whitespace nits.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Add DM core support for disabling WRITE SAME on first failure to both
request-based and bio-based targets. The need to disable WRITE SAME
stems from SCSI enabling it by default but then disabling it when it
fails. When SCSI does this it returns "permanent target failure, do
not retry" using -EREMOTEIO. Update DM core to only disable WRITE SAME
on failure if the returned error is -EREMOTEIO.
Commit f84cb8a4 ("dm mpath: disable WRITE SAME if it fails")
implemented multipath specific disabling of WRITE SAME if it fails.
However, as that commit detailed, the multipath-only solution doesn't go
far enough if bio-based DM targets are stacked ontop of the
request-based dm-multipath target (as is commonly done using dm-linear
to support partitions on multipath devices, via kpartx).
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Tested-by: Alex Chen <alex.chen@huawei.com>
