block: don't deal with discard limit in blkdev_issue_discard()

blk_queue_split() does respect this limit via bio splitting, so no
need to do that in blkdev_issue_discard(), then we can align to
normal bio submit(bio_add_page() & submit_bio()).

More importantly, this patch fixes one issue introduced in a22c4d7e34402cc
("block: re-add discard_granularity and alignment checks"), in which
zero discard bio may be generated in case of zero alignment.

Fixes: a22c4d7e34402ccdf3 ("block: re-add discard_granularity and alignment checks")
Cc: stable@vger.kernel.org
Cc: Ming Lin <ming.l@ssi.samsung.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Xiao Ni <xni@redhat.com>
Tested-by: Mariusz Dabrowski <mariusz.dabrowski@intel.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 2 insertions, 26 deletions

diff --git a/block/blk-lib.c b/block/blk-lib.c
index d1b9dd03da25..bbd44666f2b5 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -29,9 +29,7 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 {
         struct request_queue *q = bdev_get_queue(bdev);
         struct bio *bio = *biop;
-        unsigned int granularity;
         unsigned int op;
-        int alignment;
         sector_t bs_mask;
 
         if (!q)
@@ -54,38 +52,16 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
         if ((sector | nr_sects) & bs_mask)
                 return -EINVAL;
 
-        /* Zero-sector (unknown) and one-sector granularities are the same.  */
-        granularity = max(q->limits.discard_granularity >> 9, 1U);
-        alignment = (bdev_discard_alignment(bdev) >> 9) % granularity;
-
         while (nr_sects) {
-                unsigned int req_sects;
-                sector_t end_sect, tmp;
+                unsigned int req_sects = nr_sects;
+                sector_t end_sect;
 
-                /*
-                 * 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)
                         goto fail;
                 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.
-                 */
                 end_sect = sector + req_sects;
-                tmp = end_sect;
-                if (req_sects < nr_sects &&
-                    sector_div(tmp, granularity) != alignment) {
-                        end_sect = end_sect - alignment;
-                        sector_div(end_sect, granularity);
-                        end_sect = end_sect * granularity + alignment;
-                        req_sects = end_sect - sector;
-                }
 
                 bio = next_bio(bio, 0, gfp_mask);
                 bio->bi_iter.bi_sector = sector;