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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 <[email protected]>
Acked-by: Mike Snitzer <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Martin K. Petersen 2012-09-18 12:19:27 -04:00 • committed by Jens Axboe
commit 4363ac7c13
11 changed files with 181 additions and 6 deletions
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16
block/blk-settings.c
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@ -113,6 +113,7 @@ void blk_set_default_limits(struct queue_limits *lim)
lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
lim->max_sectors = lim->max_hw_sectors = BLK_SAFE_MAX_SECTORS;
lim->max_write_same_sectors = 0;
lim->max_discard_sectors = 0;
lim->discard_granularity = 0;
lim->discard_alignment = 0;
@ -144,6 +145,7 @@ void blk_set_stacking_limits(struct queue_limits *lim)
lim->max_segments = USHRT_MAX;
lim->max_hw_sectors = UINT_MAX;
lim->max_sectors = UINT_MAX;
lim->max_write_same_sectors = UINT_MAX;
}
EXPORT_SYMBOL(blk_set_stacking_limits);
@ -285,6 +287,18 @@ void blk_queue_max_discard_sectors(struct request_queue *q,
}
EXPORT_SYMBOL(blk_queue_max_discard_sectors);
/**
* blk_queue_max_write_same_sectors - set max sectors for a single write same
* @q: the request queue for the device
* @max_write_same_sectors: maximum number of sectors to write per command
**/
void blk_queue_max_write_same_sectors(struct request_queue *q,
unsigned int max_write_same_sectors)
{
q->limits.max_write_same_sectors = max_write_same_sectors;
}
EXPORT_SYMBOL(blk_queue_max_write_same_sectors);
/**
* blk_queue_max_segments - set max hw segments for a request for this queue
* @q: the request queue for the device
@ -510,6 +524,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
t->max_write_same_sectors = min(t->max_write_same_sectors,
b->max_write_same_sectors);
t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,