linux-stable.git/drivers/md/raid5.c, branch linux-3.10.y

md/raid5: limit request size according to implementation limits

2017-06-20T06:02:58+00:00

commit e8d7c33232e5fdfa761c3416539bc5b4acd12db5 upstream.

Current implementation employ 16bit counter of active stripes in lower
bits of bio->bi_phys_segments. If request is big enough to overflow
this counter bio will be completed and freed too early.

Fortunately this not happens in default configuration because several
other limits prevent that: stripe_cache_size * nr_disks effectively
limits count of active stripes. And small max_sectors_kb at lower
disks prevent that during normal read/write operations.

Overflow easily happens in discard if it's enabled by module parameter
"devices_handle_discard_safely" and stripe_cache_size is set big enough.

This patch limits requests size with 256Mb - 8Kb to prevent overflows.

Signed-off-by: Konstantin Khlebnikov 
Cc: Shaohua Li 
Cc: Neil Brown 
Signed-off-by: Shaohua Li 
Signed-off-by: Willy Tarreau

md/raid5: Compare apples to apples (or sectors to sectors)

2016-06-07T08:42:47+00:00

commit e7597e69dec59b65c5525db1626b9d34afdfa678 upstream.

'max_discard_sectors' is in sectors, while 'stripe' is in bytes.

This fixes the problem where DISCARD would get disabled on some larger
RAID5 configurations (6 or more drives in my testing), while it worked
as expected with smaller configurations.

Fixes: 620125f2bf8 ("MD: raid5 trim support")
Cc: stable@vger.kernel.org v3.7+
Signed-off-by: Jes Sorensen 
Signed-off-by: Shaohua Li 
Signed-off-by: Willy Tarreau

md/raid5: don't record new size if resize_stripes fails.

2015-06-06T06:19:59+00:00

commit 6e9eac2dcee5e19f125967dd2be3e36558c42fff upstream.

If any memory allocation in resize_stripes fails we will return
-ENOMEM, but in some cases we update conf->pool_size anyway.

This means that if we try again, the allocations will be assumed
to be larger than they are, and badness results.

So only update pool_size if there is no error.

This bug was introduced in 2.6.17 and the patch is suitable for
-stable.

Fixes: ad01c9e3752f ("[PATCH] md: Allow stripes to be expanded in preparation for expanding an array")
Signed-off-by: NeilBrown 
Signed-off-by: Greg Kroah-Hartman

md/raid5: Fix livelock when array is both resyncing and degraded.

2015-03-06T22:40:53+00:00

commit 26ac107378c4742978216be1005b7291b799c7b2 upstream.

Commit a7854487cd7128a30a7f4f5259de9f67d5efb95f:
  md: When RAID5 is dirty, force reconstruct-write instead of read-modify-write.

Causes an RCW cycle to be forced even when the array is degraded.
A degraded array cannot support RCW as that requires reading all data
blocks, and one may be missing.

Forcing an RCW when it is not possible causes a live-lock and the code
spins, repeatedly deciding to do something that cannot succeed.

So change the condition to only force RCW on non-degraded arrays.

Reported-by: Manibalan P 
Bisected-by: Jes Sorensen 
Tested-by: Jes Sorensen 
Signed-off-by: NeilBrown 
Fixes: a7854487cd7128a30a7f4f5259de9f67d5efb95f
Signed-off-by: Greg Kroah-Hartman

md/raid5: fetch_block must fetch all the blocks handle_stripe_dirtying wants.

2015-01-30T01:40:57+00:00

commit 108cef3aa41669610e1836fe638812dd067d72de upstream.

It is critical that fetch_block() and handle_stripe_dirtying()
are consistent in their analysis of what needs to be loaded.
Otherwise raid5 can wait forever for a block that won't be loaded.

Currently when writing to a RAID5 that is resyncing, to a location
beyond the resync offset, handle_stripe_dirtying chooses a
reconstruct-write cycle, but fetch_block() assumes a
read-modify-write, and a lockup can happen.

So treat that case just like RAID6, just as we do in
handle_stripe_dirtying.  RAID6 always does reconstruct-write.

This bug was introduced when the behaviour of handle_stripe_dirtying
was changed in 3.7, so the patch is suitable for any kernel since,
though it will need careful merging for some versions.

Cc: stable@vger.kernel.org (v3.7+)
Fixes: a7854487cd7128a30a7f4f5259de9f67d5efb95f
Reported-by: Henry Cai 
Signed-off-by: NeilBrown 
Signed-off-by: Greg Kroah-Hartman

md/raid5: disable 'DISCARD' by default due to safety concerns.

2014-10-09T19:18:43+00:00

commit 8e0e99ba64c7ba46133a7c8a3e3f7de01f23bd93 upstream.

It has come to my attention (thanks Martin) that 'discard_zeroes_data'
is only a hint.  Some devices in some cases don't do what it
says on the label.

The use of DISCARD in RAID5 depends on reads from discarded regions
being predictably zero.  If a write to a previously discarded region
performs a read-modify-write cycle it assumes that the parity block
was consistent with the data blocks.  If all were zero, this would
be the case.  If some are and some aren't this would not be the case.
This could lead to data corruption after a device failure when
data needs to be reconstructed from the parity.

As we cannot trust 'discard_zeroes_data', ignore it by default
and so disallow DISCARD on all raid4/5/6 arrays.

As many devices are trustworthy, and as there are benefits to using
DISCARD, add a module parameter to over-ride this caution and cause
DISCARD to work if discard_zeroes_data is set.

If a site want to enable DISCARD on some arrays but not on others they
should select DISCARD support at the filesystem level, and set the
raid456 module parameter.
    raid456.devices_handle_discard_safely=Y

As this is a data-safety issue, I believe this patch is suitable for
-stable.
DISCARD support for RAID456 was added in 3.7

Cc: Shaohua Li 
Cc: "Martin K. Petersen" 
Cc: Mike Snitzer 
Cc: Heinz Mauelshagen 
Acked-by: Martin K. Petersen 
Acked-by: Mike Snitzer 
Fixes: 620125f2bf8ff0c4969b79653b54d7bcc9d40637
Signed-off-by: NeilBrown 
[bwh: Backported to 3.10: adjust context]
Signed-off-by: Ben Hutchings 
Signed-off-by: Greg Kroah-Hartman

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

2014-09-17T16:04:00+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: Greg Kroah-Hartman

md/raid5: Fix CPU hotplug callback registration

2014-02-22T20:41:29+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: Greg Kroah-Hartman

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

2014-02-06T19:08:12+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 
Signed-off-by: Greg Kroah-Hartman

md/raid5: Fix possible confusion when multiple write errors occur.

2014-01-25T16:27:12+00:00

commit 1cc03eb93245e63b0b7a7832165efdc52e25b4e6 upstream.

commit 5d8c71f9e5fbdd95650be00294d238e27a363b5c
    md: raid5 crash during degradation

Fixed a crash in an overly simplistic way which could leave
R5_WriteError or R5_MadeGood set in the stripe cache for devices
for which it is no longer relevant.
When those devices are removed and spares added the flags are still
set and can cause incorrect behaviour.

commit 14a75d3e07c784c004b4b44b34af996b8e4ac453
    md/raid5: preferentially read from replacement device if possible.

Fixed the same bug if a more effective way, so we can now revert
the original commit.

Reported-and-tested-by: Alexander Lyakas 
Fixes: 5d8c71f9e5fbdd95650be00294d238e27a363b5c
Signed-off-by: NeilBrown 
Signed-off-by: Greg Kroah-Hartman