[PATCH 4.9 01/22] block: break discard submissions into the user defined size

Greg Kroah-Hartman
2018-12-28T12:17:16Z

[ Upstream commit af097f5d199e2aa3ab3ef777f0716e487b8f7b08 ]

Don't build discards bigger than what the user asked for, if the
user decided to limit the size by writing to 'discard_max_bytes'.

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/blk-lib.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 46fe9248410d..d8b89c58af3d 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -63,10 +63,16 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
unsigned int req_sects;
sector_t end_sect, tmp;

- /* Make sure bi_size doesn't overflow */
- req_sects = min_t(sector_t, nr_sects, UINT_MAX >> 9);
+ /*
+ * Issue in chunks of the user defined max discard setting,
+ * ensuring that bi_size doesn't overflow
+ */
+ req_sects = min_t(sector_t, nr_sects,
+ q->limits.max_discard_sectors);
+ if (req_sects > UINT_MAX >> 9)
+ req_sects = UINT_MAX >> 9;

- /**
+ /*
* If splitting a request, and the next starting sector would be
* misaligned, stop the discard at the previous aligned sector.
*/
--
2.19.1