block: break discard submissions into the user defined size

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>

diff --git a/block/blk-lib.c b/block/blk-lib.c
index a676084..8faa70f 100644 (file)
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -62,10 +62,16 @@ 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.
                 */