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block: Implement support for WRITE SAME

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The WRITE SAME command supported on some SCSI devices allows the same
block to be efficiently replicated throughout a block range. Only a
single logical block is transferred from the host and the storage device
writes the same data to all blocks described by the I/O.

This patch implements support for WRITE SAME in the block layer. The
blkdev_issue_write_same() function can be used by filesystems and block
drivers to replicate a buffer across a block range. This can be used to
efficiently initialize software RAID devices, etc.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Martin K. Petersen
2012-09-18 12:19:27 -04:00
committed by Jens Axboe
parent f31dc1cd49
commit 4363ac7c13
11 changed files with 181 additions and 6 deletions
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29
include/linux/blkdev.h
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@@ -270,6 +270,7 @@ struct queue_limits {
unsigned int io_min;
unsigned int io_opt;
unsigned int max_discard_sectors;
unsigned int max_write_same_sectors;
unsigned int discard_granularity;
unsigned int discard_alignment;
@@ -614,9 +615,20 @@ static inline bool blk_check_merge_flags(unsigned int flags1,
if ((flags1 & REQ_SECURE) != (flags2 & REQ_SECURE))
return false;
if ((flags1 & REQ_WRITE_SAME) != (flags2 & REQ_WRITE_SAME))
return false;
return true;
}
static inline bool blk_write_same_mergeable(struct bio *a, struct bio *b)
{
if (bio_data(a) == bio_data(b))
return true;
return false;
}
/*
* q->prep_rq_fn return values
*/
@@ -818,6 +830,9 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
if (unlikely(cmd_flags & REQ_DISCARD))
return q->limits.max_discard_sectors;
if (unlikely(cmd_flags & REQ_WRITE_SAME))
return q->limits.max_write_same_sectors;
return q->limits.max_sectors;
}
@@ -886,6 +901,8 @@ extern void blk_queue_max_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);
extern void blk_queue_max_discard_sectors(struct request_queue *q,
unsigned int max_discard_sectors);
extern void blk_queue_max_write_same_sectors(struct request_queue *q,
unsigned int max_write_same_sectors);
extern void blk_queue_logical_block_size(struct request_queue *, unsigned short);
extern void blk_queue_physical_block_size(struct request_queue *, unsigned int);
extern void blk_queue_alignment_offset(struct request_queue *q,
@@ -1016,6 +1033,8 @@ static inline struct request *blk_map_queue_find_tag(struct blk_queue_tag *bqt,
extern int blkdev_issue_flush(struct block_device *, gfp_t, sector_t *);
extern int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
sector_t nr_sects, gfp_t gfp_mask, unsigned long flags);
extern int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
sector_t nr_sects, gfp_t gfp_mask, struct page *page);
extern int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
sector_t nr_sects, gfp_t gfp_mask);
static inline int sb_issue_discard(struct super_block *sb, sector_t block,
@@ -1193,6 +1212,16 @@ static inline unsigned int bdev_discard_zeroes_data(struct block_device *bdev)
return queue_discard_zeroes_data(bdev_get_queue(bdev));
}
static inline unsigned int bdev_write_same(struct block_device *bdev)
{
struct request_queue *q = bdev_get_queue(bdev);
if (q)
return q->limits.max_write_same_sectors;
return 0;
}
static inline int queue_dma_alignment(struct request_queue *q)
{
return q ? q->dma_alignment : 511;