• Ilya Dryomov's avatar
    block: cope with WRITE ZEROES failing in blkdev_issue_zeroout() · c894755d
    Ilya Dryomov authored
    commit d5ce4c31d6df518dd8f63bbae20d7423c5018a6c upstream.
    
    sd_config_write_same() ignores ->max_ws_blocks == 0 and resets it to
    permit trying WRITE SAME on older SCSI devices, unless ->no_write_same
    is set.  Because REQ_OP_WRITE_ZEROES is implemented in terms of WRITE
    SAME, blkdev_issue_zeroout() may fail with -EREMOTEIO:
    
      $ fallocate -zn -l 1k /dev/sdg
      fallocate: fallocate failed: Remote I/O error
      $ fallocate -zn -l 1k /dev/sdg  # OK
      $ fallocate -zn -l 1k /dev/sdg  # OK
    
    The following calls succeed because sd_done() sets ->no_write_same in
    response to a sense that would become BLK_STS_TARGET/-EREMOTEIO, causing
    __blkdev_issue_zeroout() to fall back to generating ZERO_PAGE bios.
    
    This means blkdev_issue_zeroout() must cope with WRITE ZEROES failing
    and fall back to manually zeroing, unless BLKDEV_ZERO_NOFALLBACK is
    specified.  For BLKDEV_ZERO_NOFALLBACK case, return -EOPNOTSUPP if
    sd_done() has just set ->no_write_same thus indicating lack of offload
    support.
    
    Fixes: c20cfc27 ("block: stop using blkdev_issue_write_same for zeroing")
    Cc: Hannes Reinecke <hare@suse.com>
    Reviewed-by: 's avatarChristoph Hellwig <hch@lst.de>
    Reviewed-by: 's avatarMartin K. Petersen <martin.petersen@oracle.com>
    Signed-off-by: 's avatarIlya Dryomov <idryomov@gmail.com>
    Signed-off-by: 's avatarJens Axboe <axboe@kernel.dk>
    Cc: Janne Huttunen <janne.huttunen@nokia.com>
    Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    c894755d