The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 744889b7cbb56a64f957e65ade7cb65fe3f35714 Mon Sep 17 00:00:00 2001

From: Ming Lei ming.lei@redhat.com Date: Fri, 12 Oct 2018 15:53:10 +0800 Subject: [PATCH] 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

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;