linux-stable.git/drivers/md, branch v4.19.86

bcache: recal cached_dev_sectors on detach

2019-11-24T07:20:38+00:00

[ Upstream commit 46010141da6677b81cc77f9b47f8ac62bd1cbfd3 ]

Recal cached_dev_sectors on cached_dev detached, as recal done on
cached_dev attached.

Update the cached_dev_sectors before bcache_device_detach called
as bcache_device_detach will set bcache_device->c to NULL.

Signed-off-by: Shenghui Wang 
Signed-off-by: Coly Li 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

bcache: account size of buckets used in uuid write to ca->meta_sectors_written

2019-11-24T07:20:38+00:00

[ Upstream commit 7a55948d38eb9b274cbbdd56dc1dd4b96ebfbe04 ]

UUIDs are considered as metadata. __uuid_write should add the number
of buckets (in sectors) written to disk to ca->meta_sectors_written.
Currently only 1 bucket is used in uuid write.

Steps to test:
1) create a fresh backing device and a fresh cache device separately.
   The backing device didn't attach to any cache set.
2) cd /sys/block//bcache
   cat metadata_written      // record the output value
   cat bucket_size
3) attach the backing device to cache set
4) cat metadata_written
   The output value is almost the same as the value in step 2
   before the change.
   After the change, the value is bigger about 1 bucket size.

Signed-off-by: Shenghui Wang 
Reviewed-by: Tang Junhui 
Signed-off-by: Coly Li 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

md: allow metadata updates while suspending an array - fix

2019-11-24T07:19:58+00:00

[ Upstream commit 059421e041eb461fb2b3e81c9adaec18ef03ca3c ]

Commit 35bfc52187f6 ("md: allow metadata update while suspending.")
added support for allowing md_check_recovery() to still perform
metadata updates while the array is entering the 'suspended' state.
This is needed to allow the processes of entering the state to
complete.

Unfortunately, the patch doesn't really work.  The test for
"mddev->suspended" at the start of md_check_recovery() means that the
function doesn't try to do anything at all while entering suspend.

This patch moves the code of updating the metadata while suspending to
*before* the test on mddev->suspended.

Reported-by: Jeff Mahoney 
Fixes: 35bfc52187f6 ("md: allow metadata update while suspending.")
Signed-off-by: NeilBrown 
Signed-off-by: Shaohua Li 
Signed-off-by: Sasha Levin

bcache: fix input overflow to writeback_rate_minimum

2019-11-06T12:05:20+00:00

[ Upstream commit dab71b2db98dcdd4657d151b01a7be88ce10f9d1 ]

dc->writeback_rate_minimum is type unsigned integer variable, it is set
via sysfs interface, and converte from input string to unsigned integer
by d_strtoul_nonzero(). When the converted input value is larger than
UINT_MAX, overflow to unsigned integer happens.

This patch fixes the overflow by using sysfs_strotoul_clamp() to
convert input string and limit the value in range [1, UINT_MAX], then
the overflow can be avoided.

Signed-off-by: Coly Li 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

dm snapshot: rework COW throttling to fix deadlock

2019-11-06T12:05:11+00:00

[ Upstream commit b21555786f18cd77f2311ad89074533109ae3ffa ]

Commit 721b1d98fb517a ("dm snapshot: Fix excessive memory usage and
workqueue stalls") introduced a semaphore to limit the maximum number of
in-flight kcopyd (COW) jobs.

The implementation of this throttling mechanism is prone to a deadlock:

1. One or more threads write to the origin device causing COW, which is
   performed by kcopyd.

2. At some point some of these threads might reach the s->cow_count
   semaphore limit and block in down(&s->cow_count), holding a read lock
   on _origins_lock.

3. Someone tries to acquire a write lock on _origins_lock, e.g.,
   snapshot_ctr(), which blocks because the threads at step (2) already
   hold a read lock on it.

4. A COW operation completes and kcopyd runs dm-snapshot's completion
   callback, which ends up calling pending_complete().
   pending_complete() tries to resubmit any deferred origin bios. This
   requires acquiring a read lock on _origins_lock, which blocks.

   This happens because the read-write semaphore implementation gives
   priority to writers, meaning that as soon as a writer tries to enter
   the critical section, no readers will be allowed in, until all
   writers have completed their work.

   So, pending_complete() waits for the writer at step (3) to acquire
   and release the lock. This writer waits for the readers at step (2)
   to release the read lock and those readers wait for
   pending_complete() (the kcopyd thread) to signal the s->cow_count
   semaphore: DEADLOCK.

The above was thoroughly analyzed and documented by Nikos Tsironis as
part of his initial proposal for fixing this deadlock, see:
https://www.redhat.com/archives/dm-devel/2019-October/msg00001.html

Fix this deadlock by reworking COW throttling so that it waits without
holding any locks. Add a variable 'in_progress' that counts how many
kcopyd jobs are running. A function wait_for_in_progress() will sleep if
'in_progress' is over the limit. It drops _origins_lock in order to
avoid the deadlock.

Reported-by: Guruswamy Basavaiah 
Reported-by: Nikos Tsironis 
Reviewed-by: Nikos Tsironis 
Tested-by: Nikos Tsironis 
Fixes: 721b1d98fb51 ("dm snapshot: Fix excessive memory usage and workqueue stalls")
Cc: stable@vger.kernel.org # v5.0+
Depends-on: 4a3f111a73a8c ("dm snapshot: introduce account_start_copy() and account_end_copy()")
Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer 
Signed-off-by: Sasha Levin

dm snapshot: introduce account_start_copy() and account_end_copy()

2019-11-06T12:05:10+00:00

[ Upstream commit a2f83e8b0c82c9500421a26c49eb198b25fcdea3 ]

This simple refactoring moves code for modifying the semaphore cow_count
into separate functions to prepare for changes that will extend these
methods to provide for a more sophisticated mechanism for COW
throttling.

Signed-off-by: Mikulas Patocka 
Reviewed-by: Nikos Tsironis 
Signed-off-by: Mike Snitzer 
Signed-off-by: Sasha Levin

dm cache: fix bugs when a GFP_NOWAIT allocation fails

2019-10-29T08:20:03+00:00

commit 13bd677a472d534bf100bab2713efc3f9e3f5978 upstream.

GFP_NOWAIT allocation can fail anytime - it doesn't wait for memory being
available and it fails if the mempool is exhausted and there is not enough
memory.

If we go down this path:
  map_bio -> mg_start -> alloc_migration -> mempool_alloc(GFP_NOWAIT)
we can see that map_bio() doesn't check the return value of mg_start(),
and the bio is leaked.

If we go down this path:
  map_bio -> mg_start -> mg_lock_writes -> alloc_prison_cell ->
  dm_bio_prison_alloc_cell_v2 -> mempool_alloc(GFP_NOWAIT) ->
  mg_lock_writes -> mg_complete
the bio is ended with an error - it is unacceptable because it could
cause filesystem corruption if the machine ran out of memory
temporarily.

Change GFP_NOWAIT to GFP_NOIO, so that the mempool code will properly
wait until memory becomes available. mempool_alloc with GFP_NOIO can't
fail, so remove the code paths that deal with allocation failure.

Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer 
Signed-off-by: Greg Kroah-Hartman

md/raid0: fix warning message for parameter default_layout

2019-10-29T08:19:37+00:00

[ Upstream commit 3874d73e06c9b9dc15de0b7382fc223986d75571 ]

The message should match the parameter, i.e. raid0.default_layout.

Fixes: c84a1372df92 ("md/raid0: avoid RAID0 data corruption due to layout confusion.")
Cc: NeilBrown 
Reported-by: Ivan Topolsky 
Signed-off-by: Song Liu 
Signed-off-by: Sasha Levin

md/raid0: avoid RAID0 data corruption due to layout confusion.

2019-10-05T11:10:12+00:00

[ Upstream commit c84a1372df929033cb1a0441fb57bd3932f39ac9 ]

If the drives in a RAID0 are not all the same size, the array is
divided into zones.
The first zone covers all drives, to the size of the smallest.
The second zone covers all drives larger than the smallest, up to
the size of the second smallest - etc.

A change in Linux 3.14 unintentionally changed the layout for the
second and subsequent zones.  All the correct data is still stored, but
each chunk may be assigned to a different device than in pre-3.14 kernels.
This can lead to data corruption.

It is not possible to determine what layout to use - it depends which
kernel the data was written by.
So we add a module parameter to allow the old (0) or new (1) layout to be
specified, and refused to assemble an affected array if that parameter is
not set.

Fixes: 20d0189b1012 ("block: Introduce new bio_split()")
cc: stable@vger.kernel.org (3.14+)
Acked-by: Guoqing Jiang 
Signed-off-by: NeilBrown 
Signed-off-by: Song Liu 
Signed-off-by: Sasha Levin

md: only call set_in_sync() when it is expected to succeed.

2019-10-05T11:10:10+00:00

commit 480523feae581ab714ba6610388a3b4619a2f695 upstream.

Since commit 4ad23a976413 ("MD: use per-cpu counter for
writes_pending"), set_in_sync() is substantially more expensive: it
can wait for a full RCU grace period which can be 10s of milliseconds.

So we should only call it when the cost is justified.

md_check_recovery() currently calls set_in_sync() every time it finds
anything to do (on non-external active arrays).  For an array
performing resync or recovery, this will be quite often.
Each call will introduce a delay to the md thread, which can noticeable
affect IO submission latency.

In md_check_recovery() we only need to call set_in_sync() if
'safemode' was non-zero at entry, meaning that there has been not
recent IO.  So we save this "safemode was nonzero" state, and only
call set_in_sync() if it was non-zero.

This measurably reduces mean and maximum IO submission latency during
resync/recovery.

Reported-and-tested-by: Jack Wang 
Fixes: 4ad23a976413 ("MD: use per-cpu counter for writes_pending")
Cc: stable@vger.kernel.org (v4.12+)
Signed-off-by: NeilBrown 
Signed-off-by: Song Liu 
Signed-off-by: Greg Kroah-Hartman