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Subject[PATCH 4.4 72/88] block: dont deal with discard limit in blkdev_issue_discard()
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ming Lei <ming.lei@redhat.com>

commit 744889b7cbb56a64f957e65ade7cb65fe3f35714 upstream.

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>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
block/blk-lib.c | 28 ++--------------------------
1 file changed, 2 insertions(+), 26 deletions(-)

--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -43,8 +43,6 @@ int blkdev_issue_discard(struct block_de
DECLARE_COMPLETION_ONSTACK(wait);
struct request_queue *q = bdev_get_queue(bdev);
int type = REQ_WRITE | REQ_DISCARD;
- unsigned int granularity;
- int alignment;
struct bio_batch bb;
struct bio *bio;
int ret = 0;
@@ -56,10 +54,6 @@ int blkdev_issue_discard(struct block_de
if (!blk_queue_discard(q))
return -EOPNOTSUPP;

- /* 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;
-
if (flags & BLKDEV_DISCARD_SECURE) {
if (!blk_queue_secdiscard(q))
return -EOPNOTSUPP;
@@ -72,8 +66,8 @@ int blkdev_issue_discard(struct block_de

blk_start_plug(&plug);
while (nr_sects) {
- unsigned int req_sects;
- sector_t end_sect, tmp;
+ unsigned int req_sects = nr_sects;
+ sector_t end_sect;

bio = bio_alloc(gfp_mask, 1);
if (!bio) {
@@ -81,28 +75,10 @@ int blkdev_issue_discard(struct block_de
break;
}

- /*
- * 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.
- */
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->bi_iter.bi_sector = sector;
bio->bi_end_io = bio_batch_end_io;

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