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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: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Coly Li <colyli@suse.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220415045258.199825-23-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2022-04-15 06:52:53 +02:00 committed by Jens Axboe
parent 5c4b4a5c6f
commit e3cc28ea28
2 changed files with 29 additions and 44 deletions
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59
block/blk-lib.c
View File

@ -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;

14
block/blk.h
View File

@ -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
*/