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Commit 8dd2cb7e authored by Shaohua Li's avatar Shaohua Li Committed by Jens Axboe
Browse files

block: discard granularity might not be power of 2 



In MD raid case, discard granularity might not be power of 2, for example, a
4-disk raid5 has 3*chunk_size discard granularity. Correct the calculation for
such cases.

Reported-by: default avatarNeil Brown <neilb@suse.de>
Signed-off-by: default avatarShaohua Li <shli@fusionio.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 75274551

block/blk-lib.c

+13 −10
Original line number Diff line number Diff line
@@ -43,8 +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 max_discard_sectors;

	unsigned int granularity, alignment, mask;

	sector_t max_discard_sectors;

	sector_t granularity, alignment;

	struct bio_batch bb;

	struct bio *bio;

	int ret = 0;
@@ -57,15 +57,16 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, 


	/* Zero-sector (unknown) and one-sector granularities are the same.  */

	granularity = max(q->limits.discard_granularity >> 9, 1U);

	mask = granularity - 1;

	alignment = (bdev_discard_alignment(bdev) >> 9) & mask;

	alignment = bdev_discard_alignment(bdev) >> 9;

	alignment = sector_div(alignment, granularity);



	/*

	 * Ensure that max_discard_sectors is of the proper

	 * granularity, so that requests stay aligned after a split.

	 */

	max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);

	max_discard_sectors = round_down(max_discard_sectors, granularity);

	sector_div(max_discard_sectors, granularity);

	max_discard_sectors *= granularity;

	if (unlikely(!max_discard_sectors)) {

		/* Avoid infinite loop below. Being cautious never hurts. */

		return -EOPNOTSUPP;
@@ -83,7 +84,7 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, 


	while (nr_sects) {

		unsigned int req_sects;

		sector_t end_sect;

		sector_t end_sect, tmp;



		bio = bio_alloc(gfp_mask, 1);

		if (!bio) {
@@ -98,10 +99,12 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, 
		 * misaligned, stop the discard at the previous aligned sector.

		 */

		end_sect = sector + req_sects;

		if (req_sects < nr_sects && (end_sect & mask) != alignment) {

			end_sect =

				round_down(end_sect - alignment, granularity)

				+ alignment;

		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;

		}

block/blk-settings.c

+3 −3
Original line number Diff line number Diff line
@@ -611,7 +611,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, 
			bottom = b->discard_granularity + alignment;



			/* Verify that top and bottom intervals line up */

			if (max(top, bottom) & (min(top, bottom) - 1))

			if ((max(top, bottom) % min(top, bottom)) != 0)

				t->discard_misaligned = 1;

		}
@@ -619,8 +619,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, 
						      b->max_discard_sectors);

		t->discard_granularity = max(t->discard_granularity,

					     b->discard_granularity);

		t->discard_alignment = lcm(t->discard_alignment, alignment) &

			(t->discard_granularity - 1);

		t->discard_alignment = lcm(t->discard_alignment, alignment) %

			t->discard_granularity;

	}



	return ret;

include/linux/blkdev.h

+4 −3
Original line number Diff line number Diff line
@@ -1188,13 +1188,14 @@ static inline int queue_discard_alignment(struct request_queue *q) 


static inline int queue_limit_discard_alignment(struct queue_limits *lim, sector_t sector)

{

	unsigned int alignment = (sector << 9) & (lim->discard_granularity - 1);

	sector_t alignment = sector << 9;

	alignment = sector_div(alignment, lim->discard_granularity);



	if (!lim->max_discard_sectors)

		return 0;



	return (lim->discard_granularity + lim->discard_alignment - alignment)

		& (lim->discard_granularity - 1);

	alignment = lim->discard_granularity + lim->discard_alignment - alignment;

	return sector_div(alignment, lim->discard_granularity);

}



static inline int bdev_discard_alignment(struct block_device *bdev)