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[3.8,079/116] dm thin: update discard_granularity to reflect the thin-pool blocksize

Message ID 1406067727-19683-80-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa July 22, 2014, 10:21 p.m. UTC 
3.8.13.27 -stable review patch.  If anyone has any objections, please let me know.

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

From: Lukas Czerner <lczerner@redhat.com>

commit 09869de57ed2728ae3c619803932a86cb0e2c4f8 upstream.

DM thinp already checks whether the discard_granularity of the data
device is a factor of the thin-pool block size.  But when using the
dm-thin-pool's discard passdown support, DM thinp was not selecting the
max of the underlying data device's discard_granularity and the
thin-pool's block size.

Update set_discard_limits() to set discard_granularity to the max of
these values.  This enables blkdev_issue_discard() to properly align the
discards that are sent to the DM thin device on a full block boundary.
As such each discard will now cover an entire DM thin-pool block and the
block will be reclaimed.

Reported-by: Zdenek Kabelac <zkabelac@redhat.com>
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/md/dm-thin.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
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Patch

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index ca954b1..3d183ca 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -2479,7 +2479,8 @@  static void set_discard_limits(struct pool_c *pt, struct queue_limits *limits)
 	 */
 	if (pt->adjusted_pf.discard_passdown) {
 		data_limits = &bdev_get_queue(pt->data_dev->bdev)->limits;
-		limits->discard_granularity = data_limits->discard_granularity;
+		limits->discard_granularity = max(data_limits->discard_granularity,
+						  pool->sectors_per_block << SECTOR_SHIFT);
 	} else if (block_size_is_power_of_two(pool))
 		limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT;
 	else