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    Subject[PATCH 4.18 014/350] block: dont deal with discard limit in blkdev_issue_discard()
    Date
    4.18-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: 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
    @@ -29,9 +29,7 @@ int __blkdev_issue_discard(struct block_
    {
    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_
    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;

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