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>

1 files changed, 9 insertions, 3 deletions

diff --git a/block/blk-lib.c b/block/blk-lib.c
index a676084d4740..8faa70f26fcd 100644
--- 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.
                  */