Currently if the underlying device is discard capable and the
discard_passdown is enabled, the discard_granularity will be inherited
from that device.
This will pose a problem in the case that the device discard_granularity
is smaller than thin volume chunk size, because in that case discard
requests will not be chunk size aligned so it will be ignored by
dm-thin.
Fix this by setting thin volume discard granularity to the bigger of the
two max(device discard_granularity, thin volume chunk size). Strictly
speaking it is not necessary to get the bigger of the two, because
the thin volume chunk size will always be >= device discard_granularity.
However I believe that the reason for this is only because dm-thin can
not handle discard requests bigger than chunk size which is hopefully
going to change soon. This way it is future proof.
RHBZ: 1106856
Reported-by: Zdenek Kabelac <zkabelac@xxxxxxxxxxxxxxxxx>
Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
---
drivers/md/dm-thin.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 242ac2e..fdd7089 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -3068,7 +3068,9 @@ 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;
}
--
1.8.3.1
--
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