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dm raid1: set discard_zeroes_data_unsupported

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We can't guarantee that REQ_DISCARD on dm-mirror zeroes the data even if
the underlying disks support zero on discard.  So this patch sets
ti->discard_zeroes_data_unsupported.

For example, if the mirror is in the process of resynchronizing, it may
happen that kcopyd reads a piece of data, then discard is sent on the
same area and then kcopyd writes the piece of data to another leg.
Consequently, the data is not zeroed.

The flag was made available by commit 983c7db347
(dm crypt: always disable discard_zeroes_data).

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mikulas Patocka 2012-07-20 14:25:07 +01:00 committed by Alasdair G Kergon
parent 650d2a06b4
commit 7c8d3a42fe
1 changed files with 1 additions and 0 deletions
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drivers/md/dm-raid1.c
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@ -1084,6 +1084,7 @@ static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
ti->split_io = dm_rh_get_region_size(ms->rh);
ti->num_flush_requests = 1;
ti->num_discard_requests = 1;
ti->discard_zeroes_data_unsupported = 1;
ms->kmirrord_wq = alloc_workqueue("kmirrord",
WQ_NON_REENTRANT | WQ_MEM_RECLAIM, 0);