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dm thin: update discard_granularity to reflect the thin-pool blocksize

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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>
Cc: stable@vger.kernel.org
This commit is contained in:
Lukas Czerner 2014-06-11 12:28:43 -04:00 committed by Mike Snitzer
parent adcc44472b
commit 09869de57e
1 changed files with 2 additions and 1 deletions
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3
drivers/md/dm-thin.c
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@ -3094,7 +3094,8 @@ 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
limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT;
}