path: root/include/linux/blkdev.h
diff options
authorMartin K. Petersen <martin.petersen@oracle.com>2012-09-18 12:19:27 -0400
committerJens Axboe <axboe@kernel.dk>2012-09-20 14:31:45 +0200
commit4363ac7c13a9a4b763c6e8d9fdbfc2468f3b8ca4 (patch)
tree010b05699eb9544b9cdfe5e1b3affdaea80132e7 /include/linux/blkdev.h
parentf31dc1cd490539e2b62a126bc4dc2495b165d772 (diff)
block: Implement support for WRITE SAME
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>
Diffstat (limited to 'include/linux/blkdev.h')
1 files changed, 29 insertions, 0 deletions
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 90f7abe8f18..1756001210d 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -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;