md/raid5: avoid livelock caused by non-aligned writes.

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commit a40687ff73 upstream.

If a stripe in a raid6 array received a write to each data block while
the array is degraded, and if any of these writes to a missing device
are not page-aligned, then a live-lock happens.

In this case the P and Q blocks need to be read so that the part of
the missing block which is *not* being updated by the write can be
constructed.  Due to a logic error, these blocks are not loaded, so
the update cannot proceed and the stripe is 'handled' repeatedly in an
infinite loop.

This bug is unlikely as most writes are page aligned.  However as it
can lead to a livelock it is suitable for -stable.  It was introduced
in 3.16.

Fixed: 67f455486d
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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NeilBrown 2014-08-13 09:48:45 +10:00 • committed by Greg Kroah-Hartman

parent ae2a024488

commit 706d916414

1 changed files with 1 additions and 1 deletions

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drivers/md/raid5.c

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