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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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13
block/blk-sysfs.c
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@ -180,6 +180,13 @@ static ssize_t queue_discard_zeroes_data_show(struct request_queue *q, char *pag
return queue_var_show(queue_discard_zeroes_data(q), page);
}
static ssize_t queue_write_same_max_show(struct request_queue *q, char *page)
{
return sprintf(page, "%llu\n",
(unsigned long long)q->limits.max_write_same_sectors << 9);
}
static ssize_t
queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
{
@ -385,6 +392,11 @@ static struct queue_sysfs_entry queue_discard_zeroes_data_entry = {
.show = queue_discard_zeroes_data_show,
};
static struct queue_sysfs_entry queue_write_same_max_entry = {
.attr = {.name = "write_same_max_bytes", .mode = S_IRUGO },
.show = queue_write_same_max_show,
};
static struct queue_sysfs_entry queue_nonrot_entry = {
.attr = {.name = "rotational", .mode = S_IRUGO | S_IWUSR },
.show = queue_show_nonrot,
@ -432,6 +444,7 @@ static struct attribute *default_attrs[] = {
&queue_discard_granularity_entry.attr,
&queue_discard_max_entry.attr,
&queue_discard_zeroes_data_entry.attr,
&queue_write_same_max_entry.attr,
&queue_nonrot_entry.attr,
&queue_nomerges_entry.attr,
&queue_rq_affinity_entry.attr,