Commit e3cc28ea authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: refactor discard bio size limiting 



Move all the logic to limit the discard bio size into a common helper
so that it is better documented.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Acked-by: default avatarColy Li <colyli@suse.de>
Reviewed-by: default avatarChaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220415045258.199825-23-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 5c4b4a5c

block/blk-lib.c

+29 −30
Original line number Diff line number Diff line
@@ -10,6 +10,32 @@ 


#include "blk.h"



static sector_t bio_discard_limit(struct block_device *bdev, sector_t sector)

{

	unsigned int discard_granularity =

		bdev_get_queue(bdev)->limits.discard_granularity;

	sector_t granularity_aligned_sector;



	if (bdev_is_partition(bdev))

		sector += bdev->bd_start_sect;



	granularity_aligned_sector =

		round_up(sector, discard_granularity >> SECTOR_SHIFT);



	/*

	 * Make sure subsequent bios start aligned to the discard granularity if

	 * it needs to be split.

	 */

	if (granularity_aligned_sector != sector)

		return granularity_aligned_sector - sector;



	/*

	 * Align the bio size to the discard granularity to make splitting the bio

	 * at discard granularity boundaries easier in the driver if needed.

	 */

	return round_down(UINT_MAX, discard_granularity) >> SECTOR_SHIFT;

}



int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,

		sector_t nr_sects, gfp_t gfp_mask, int flags,

		struct bio **biop)
@@ -17,7 +43,7 @@ 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 op;

	sector_t bs_mask, part_offset = 0;

	sector_t bs_mask;



	if (bdev_read_only(bdev))

		return -EPERM;
@@ -48,36 +74,9 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector, 
	if (!nr_sects)

		return -EINVAL;



	/* In case the discard request is in a partition */

	if (bdev_is_partition(bdev))

		part_offset = bdev->bd_start_sect;



	while (nr_sects) {

		sector_t granularity_aligned_lba, req_sects;

		sector_t sector_mapped = sector + part_offset;



		granularity_aligned_lba = round_up(sector_mapped,

				q->limits.discard_granularity >> SECTOR_SHIFT);



		/*

		 * Check whether the discard bio starts at a discard_granularity

		 * aligned LBA,

		 * - If no: set (granularity_aligned_lba - sector_mapped) to

		 *   bi_size of the first split bio, then the second bio will

		 *   start at a discard_granularity aligned LBA on the device.

		 * - If yes: use bio_aligned_discard_max_sectors() as the max

		 *   possible bi_size of the first split bio. Then when this bio

		 *   is split in device drive, the split ones are very probably

		 *   to be aligned to discard_granularity of the device's queue.

		 */

		if (granularity_aligned_lba == sector_mapped)

			req_sects = min_t(sector_t, nr_sects,

					  bio_aligned_discard_max_sectors(q));

		else

			req_sects = min_t(sector_t, nr_sects,

					  granularity_aligned_lba - sector_mapped);



		WARN_ON_ONCE((req_sects << 9) > UINT_MAX);

		sector_t req_sects =

			min(nr_sects, bio_discard_limit(bdev, sector));



		bio = blk_next_bio(bio, bdev, 0, op, gfp_mask);

		bio->bi_iter.bi_sector = sector;

block/blk.h

+0 −14
Original line number Diff line number Diff line
@@ -346,20 +346,6 @@ static inline unsigned int bio_allowed_max_sectors(struct request_queue *q) 
	return round_down(UINT_MAX, queue_logical_block_size(q)) >> 9;

}



/*

 * The max bio size which is aligned to q->limits.discard_granularity. This

 * is a hint to split large discard bio in generic block layer, then if device

 * driver needs to split the discard bio into smaller ones, their bi_size can

 * be very probably and easily aligned to discard_granularity of the device's

 * queue.

 */

static inline unsigned int bio_aligned_discard_max_sectors(

					struct request_queue *q)

{

	return round_down(UINT_MAX, q->limits.discard_granularity) >>

			SECTOR_SHIFT;

}



/*

 * Internal io_context interface

 */