[ 091/221] dm: disable WRITE SAME

[Greg Kroah-Hartman]

3.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mike Snitzer <snitzer@xxxxxxxxxx>

commit c1a94672a830e01d58c7c7e8de530c3f136d6ff2 upstream.

WRITE SAME bios are not yet handled correctly by device-mapper so
disable their use on device-mapper devices by setting
max_write_same_sectors to zero.

As an example, a ciphertext device is incompatible because the data
gets changed according to the location at which it written and so the
dm crypt target cannot support it.

Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Cc: Milan Broz <mbroz@xxxxxxxxxx>
Signed-off-by: Alasdair G Kergon <agk@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/md/dm-table.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1445,6 +1445,8 @@ void dm_table_set_restrictions(struct dm
 	else
 		queue_flag_clear_unlocked(QUEUE_FLAG_NONROT, q);
 
+	q->limits.max_write_same_sectors = 0;
+
 	dm_table_set_integrity(t);
 
 	/*


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