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Commit a22c4d7e authored by Ming Lin's avatar Ming Lin Committed by Jens Axboe
Browse files

block: re-add discard_granularity and alignment checks 



In commit b49a0871("block: remove split code in
blkdev_issue_{discard,write_same}"), discard_granularity and alignment
checks were removed. Ideally, with bio late splitting, the upper layers
shouldn't need to depend on device's limits.

Christoph reported a discard regression on the HGST Ultrastar SN100 NVMe
device when mkfs.xfs. We have not found the root cause yet.

This patch re-adds discard_granularity and alignment checks by reverting
the related changes in commit b49a0871. The good thing is now we can
remove the 2G discard size cap and just use UINT_MAX to avoid bi_size
overflow.

Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Tested-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarMing Lin <ming.l@ssi.samsung.com>
Reviewed-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 23d88271

block/blk-lib.c

+22 −9
Original line number Diff line number Diff line
@@ -26,13 +26,6 @@ static void bio_batch_end_io(struct bio *bio) 
	bio_put(bio);

}



/*

 * Ensure that max discard sectors doesn't overflow bi_size and hopefully

 * it is of the proper granularity as long as the granularity is a power

 * of two.

 */

#define MAX_BIO_SECTORS ((1U << 31) >> 9)



/**

 * blkdev_issue_discard - queue a discard

 * @bdev:	blockdev to issue discard for
@@ -50,6 +43,8 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, 
	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;
@@ -61,6 +56,10 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, 
	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;
@@ -74,7 +73,7 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, 
	blk_start_plug(&plug);

	while (nr_sects) {

		unsigned int req_sects;

		sector_t end_sect;

		sector_t end_sect, tmp;



		bio = bio_alloc(gfp_mask, 1);

		if (!bio) {
@@ -82,8 +81,22 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, 
			break;

		}



		req_sects = min_t(sector_t, nr_sects, MAX_BIO_SECTORS);

		/* Make sure bi_size doesn't overflow */

		req_sects = min_t(sector_t, nr_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;