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authorMartin K. Petersen <martin.petersen@oracle.com>2015-01-21 04:06:30 +0300
committerJens Axboe <axboe@fb.com>2015-01-21 20:41:46 +0300
commitd93ba7a5a97c9f315bacdcdb8de4e5f368e7b396 (patch)
tree08ed637d3982f9c87e5334d42e2f7a3670867876 /block/partitions
parentc6ce194325cef342313e3d27620411ce90a89c50 (diff)
downloadlinux-d93ba7a5a97c9f315bacdcdb8de4e5f368e7b396.tar.xz
block: Add discard flag to blkdev_issue_zeroout() function
blkdev_issue_discard() will zero a given block range. This is done by way of explicit writing, thus provisioning or allocating the blocks on disk. There are use cases where the desired behavior is to zero the blocks but unprovision them if possible. The blocks must deterministically contain zeroes when they are subsequently read back. This patch adds a flag to blkdev_issue_zeroout() that provides this variant. If the discard flag is set and a block device guarantees discard_zeroes_data we will use REQ_DISCARD to clear the block range. If the device does not support discard_zeroes_data or if the discard request fails we will fall back to first REQ_WRITE_SAME and then a regular REQ_WRITE. Also update the callers of blkdev_issue_zero() to reflect the new flag and make sb_issue_zeroout() prefer the discard approach. Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
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