md/raid1: make sure resync waits for conflicting writes to complete.

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commit 2f73d3c55d upstream.

The resync/recovery process for raid1 was recently changed
so that writes could happen in parallel with resync providing
they were in different regions of the device.

There is a problem though:  While a write request will always
wait for conflicting resync to complete, a resync request
will *not* always wait for conflicting writes to complete.

Two changes are needed to fix this:

1/ raise_barrier (which waits until it is safe to do resync)
   must wait until current_window_requests is zero
2/ wait_battier (which waits at the start of a new write request)
   must update current_window_requests if the request could
   possible conflict with a concurrent resync.

As concurrent writes and resync can lead to data loss,
this patch is suitable for -stable.

Fixes: 79ef3a8aa1
Cc: majianpeng <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

NeilBrown 2014-09-10 15:01:49 +10:00 • committed by Greg Kroah-Hartman

parent dd777df4dd

commit 0fdbd42fb0

1 changed files with 4 additions and 2 deletions

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drivers/md/raid1.c

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