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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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Documentation/ABI/testing/sysfs-block
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@@ -206,3 +206,17 @@ Description:
when a discarded area is read the discard_zeroes_data
parameter will be set to one. Otherwise it will be 0 and
the result of reading a discarded area is undefined.
What: /sys/block/<disk>/queue/write_same_max_bytes
Date: January 2012
Contact: Martin K. Petersen <martin.petersen@oracle.com>
Description:
Some devices support a write same operation in which a
single data block can be written to a range of several
contiguous blocks on storage. This can be used to wipe
areas on disk or to initialize drives in a RAID
configuration. write_same_max_bytes indicates how many
bytes can be written in a single write same command. If
write_same_max_bytes is 0, write same is not supported
by the device.