linux-stable.git/drivers/md, branch v3.2.63

md/raid6: avoid data corruption during recovery of double-degraded RAID6

2014-09-13T22:41:45+00:00

commit 9c4bdf697c39805078392d5ddbbba5ae5680e0dd upstream.

During recovery of a double-degraded RAID6 it is possible for
some blocks not to be recovered properly, leading to corruption.

If a write happens to one block in a stripe that would be written to a
missing device, and at the same time that stripe is recovering data
to the other missing device, then that recovered data may not be written.

This patch skips, in the double-degraded case, an optimisation that is
only safe for single-degraded arrays.

Bug was introduced in 2.6.32 and fix is suitable for any kernel since
then.  In an older kernel with separate handle_stripe5() and
handle_stripe6() functions the patch must change handle_stripe6().

Fixes: 6c0069c0ae9659e3a91b68eaed06a5c6c37f45c8
Cc: Yuri Tikhonov 
Cc: Dan Williams 
Reported-by: "Manibalan P" 
Tested-by: "Manibalan P" 
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1090423
Signed-off-by: NeilBrown 
Acked-by: Dan Williams 
Signed-off-by: Ben Hutchings

md/raid1,raid10: always abort recover on write error.

2014-09-13T22:41:40+00:00

commit 2446dba03f9dabe0b477a126cbeb377854785b47 upstream.

Currently we don't abort recovery on a write error if the write error
to the recovering device was triggerd by normal IO (as opposed to
recovery IO).

This means that for one bitmap region, the recovery might write to the
recovering device for a few sectors, then not bother for subsequent
sectors (as it never writes to failed devices).  In this case
the bitmap bit will be cleared, but it really shouldn't.

The result is that if the recovering device fails and is then re-added
(after fixing whatever hardware problem triggerred the failure),
the second recovery won't redo the region it was in the middle of,
so some of the device will not be recovered properly.

If we abort the recovery, the region being processes will be cancelled
(bit not cleared) and the whole region will be retried.

As the bug can result in data corruption the patch is suitable for
-stable.  For kernels prior to 3.11 there is a conflict in raid10.c
which will require care.

Original-from: jiao hui 
Reported-and-tested-by: jiao hui 
Signed-off-by: NeilBrown 
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings

dm io: fix a race condition in the wake up code for sync_io

2014-08-06T17:07:37+00:00

commit 10f1d5d111e8aed46a0f1179faf9a3cf422f689e upstream.

There's a race condition between the atomic_dec_and_test(&io->count)
in dec_count() and the waking of the sync_io() thread.  If the thread
is spuriously woken immediately after the decrement it may exit,
making the on stack io struct invalid, yet the dec_count could still
be using it.

Fix this race by using a completion in sync_io() and dec_count().

Reported-by: Minfei Huang 
Signed-off-by: Joe Thornber 
Signed-off-by: Mike Snitzer 
Acked-by: Mikulas Patocka 
[bwh: Backported to 3.2: use wait_for_completion() as wait_for_completion_io()
 is not available]
Signed-off-by: Ben Hutchings

md: flush writes before starting a recovery.

2014-08-06T17:07:33+00:00

commit 133d4527eab8d199a62eee6bd433f0776842df2e upstream.

When we write to a degraded array which has a bitmap, we
make sure the relevant bit in the bitmap remains set when
the write completes (so a 're-add' can quickly rebuilt a
temporarily-missing device).

If, immediately after such a write starts, we incorporate a spare,
commence recovery, and skip over the region where the write is
happening (because the 'needs recovery' flag isn't set yet),
then that write will not get to the new device.

Once the recovery finishes the new device will be trusted, but will
have incorrect data, leading to possible corruption.

We cannot set the 'needs recovery' flag when we start the write as we
do not know easily if the write will be "degraded" or not.  That
depends on details of the particular raid level and particular write
request.

This patch fixes a corruption issue of long standing and so it
suitable for any -stable kernel.  It applied correctly to 3.0 at
least and will minor editing to earlier kernels.

Reported-by: Bill 
Tested-by: Bill 
Link: http://lkml.kernel.org/r/53A518BB.60709@sbcglobal.net
Signed-off-by: NeilBrown 
Signed-off-by: Ben Hutchings

md: always set MD_RECOVERY_INTR when aborting a reshape or other "resync".

2014-07-11T12:33:43+00:00

commit 3991b31ea072b070081ca3bfa860a077eda67de5 upstream.

If mddev->ro is set, md_to_sync will (correctly) abort.
However in that case MD_RECOVERY_INTR isn't set.

If a RESHAPE had been requested, then ->finish_reshape() will be
called and it will think the reshape was successful even though
nothing happened.

Normally a resync will not be requested if ->ro is set, but if an
array is stopped while a reshape is on-going, then when the array is
started, the reshape will be restarted.  If the array is also set
read-only at this point, the reshape will instantly appear to success,
resulting in data corruption.

Consequently, this patch is suitable for any -stable kernel.

Signed-off-by: NeilBrown 
Signed-off-by: Ben Hutchings

md: avoid possible spinning md thread at shutdown.

2014-06-09T12:29:08+00:00

commit 0f62fb220aa4ebabe8547d3a9ce4a16d3c045f21 upstream.

If an md array with externally managed metadata (e.g. DDF or IMSM)
is in use, then we should not set safemode==2 at shutdown because:

1/ this is ineffective: user-space need to be involved in any 'safemode' handling,
2/ The safemode management code doesn't cope with safemode==2 on external metadata
   and md_check_recover enters an infinite loop.

Even at shutdown, an infinite-looping process can be problematic, so this
could cause shutdown to hang.

Signed-off-by: NeilBrown 
Signed-off-by: Ben Hutchings

dm thin: fix dangling bio in process_deferred_bios error path

2014-04-30T15:23:24+00:00

commit fe76cd88e654124d1431bb662a0fc6e99ca811a5 upstream.

If unable to ensure_next_mapping() we must add the current bio, which
was removed from the @bios list via bio_list_pop, back to the
deferred_bios list before all the remaining @bios.

Signed-off-by: Mike Snitzer 
Acked-by: Joe Thornber 
Signed-off-by: Ben Hutchings

md/raid5: Fix CPU hotplug callback registration

2014-04-01T23:58:51+00:00

commit 789b5e0315284463617e106baad360cb9e8db3ac upstream.

Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	register_cpu_notifier(&foobar_cpu_notifier);

	put_online_cpus();

This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).

Interestingly, the raid5 code can actually prevent double initialization and
hence can use the following simplified form of callback registration:

	register_cpu_notifier(&foobar_cpu_notifier);

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	put_online_cpus();

A hotplug operation that occurs between registering the notifier and calling
get_online_cpus(), won't disrupt anything, because the code takes care to
perform the memory allocations only once.

So reorganize the code in raid5 this way to fix the deadlock with callback
registration.

Cc: linux-raid@vger.kernel.org
Fixes: 36d1c6476be51101778882897b315bd928c8c7b5
Signed-off-by: Oleg Nesterov 
[Srivatsa: Fixed the unregister_cpu_notifier() deadlock, added the
free_scratch_buffer() helper to condense code further and wrote the changelog.]
Signed-off-by: Srivatsa S. Bhat 
Signed-off-by: NeilBrown 
Signed-off-by: Ben Hutchings

md/raid5: fix long-standing problem with bitmap handling on write failure.

2014-04-01T23:58:43+00:00

commit 9f97e4b128d2ea90a5f5063ea0ee3b0911f4c669 upstream.

Before a write starts we set a bit in the write-intent bitmap.
When the write completes we clear that bit if the write was successful
to all devices.  However if the write wasn't fully successful we
should not clear the bit.  If the faulty drive is subsequently
re-added, the fact that the bit is still set ensure that we will
re-write the data that is missing.

This logic is mediated by the STRIPE_DEGRADED flag - we only clear the
bitmap bit when this flag is not set.
Currently we correctly set the flag if a write starts when some
devices are failed or missing.  But we do *not* set the flag if some
device failed during the write attempt.
This is wrong and can result in clearing the bit inappropriately.

So: set the flag when a write fails.

This bug has been present since bitmaps were introduces, so the fix is
suitable for any -stable kernel.

Reported-by: Ethan Wilson 
Signed-off-by: NeilBrown 
[bwh: Backported to 3.2: adjust context, indentation]
Signed-off-by: Ben Hutchings

dm sysfs: fix a module unload race

2014-04-01T23:58:43+00:00

commit 2995fa78e423d7193f3b57835f6c1c75006a0315 upstream.

This reverts commit be35f48610 ("dm: wait until embedded kobject is
released before destroying a device") and provides an improved fix.

The kobject release code that calls the completion must be placed in a
non-module file, otherwise there is a module unload race (if the process
calling dm_kobject_release is preempted and the DM module unloaded after
the completion is triggered, but before dm_kobject_release returns).

To fix this race, this patch moves the completion code to dm-builtin.c
which is always compiled directly into the kernel if BLK_DEV_DM is
selected.

The patch introduces a new dm_kobject_holder structure, its purpose is
to keep the completion and kobject in one place, so that it can be
accessed from non-module code without the need to export the layout of
struct mapped_device to that code.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer 
[bwh: Backported to 3.2:
 - Adjust context
 - Remove paranoid check of container_of() result in dm_get_from_kobject(),
   which would now be incorrect
 - Include  in dm-builtin.c, included indirectly upstream]
Signed-off-by: Ben Hutchings