• Martin K. Petersen's avatar
    block: Add discard flag to blkdev_issue_zeroout() function · d93ba7a5
    Martin K. Petersen authored
    blkdev_issue_discard() will zero a given block range. This is done by
    way of explicit writing, thus provisioning or allocating the blocks on
    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: default avatarMartin K. Petersen <martin.petersen@oracle.com>
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    Signed-off-by: default avatarJens Axboe <axboe@fb.com>
ioctl.c 10.7 KB