linux-stable.git/drivers/md, branch v3.2.62

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

dm space map common: make sure new space is used during extend

2014-04-01T23:58:41+00:00

commit 12c91a5c2d2a8e8cc40a9552313e1e7b0a2d9ee3 upstream.

When extending a low level space map we should update nr_blocks at
the start so the new space is used for the index entries.

Otherwise extend can fail, e.g.: sm_metadata_extend call sequence
that fails:
 -> sm_ll_extend
    -> dm_tm_new_block -> dm_sm_new_block -> sm_bootstrap_new_block
    => returns -ENOSPC because smm->begin == smm->ll.nr_blocks

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

dm: wait until embedded kobject is released before destroying a device

2014-04-01T23:58:41+00:00

commit be35f486108227e10fe5d96fd42fb2b344c59983 upstream.

There may be other parts of the kernel holding a reference on the dm
kobject.  We must wait until all references are dropped before
deallocating the mapped_device structure.

The dm_kobject_release method signals that all references are dropped
via completion.  But dm_kobject_release doesn't free the kobject (which
is embedded in the mapped_device structure).

This is the sequence of operations:
* when destroying a DM device, call kobject_put from dm_sysfs_exit
* wait until all users stop using the kobject, when it happens the
  release method is called
* the release method signals the completion and should return without
  delay
* the dm device removal code that waits on the completion continues
* the dm device removal code drops the dm_mod reference the device had
* the dm device removal code frees the mapped_device structure that
  contains the kobject

Using kobject this way should avoid the module unload race that was
mentioned at the beginning of this thread:
https://lkml.org/lkml/2014/1/4/83

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer 
Signed-off-by: Ben Hutchings