• Christoph Hellwig's avatar
    cleanup blockdev_direct_IO locking · 1e431f5c
    Christoph Hellwig authored
    Currently the locking in blockdev_direct_IO is a mess, we have three different
    locking types and very confusing checks for some of them.  The most
    complicated one is DIO_OWN_LOCKING for reads, which happens to not actually be
    This patch gets rid of the DIO_OWN_LOCKING - as mentioned above the read case
    is unused anyway, and the write side is almost identical to DIO_NO_LOCKING.
    The difference is that DIO_NO_LOCKING always sets the create argument for
    the get_blocks callback to zero, but we can easily move that to the actual
    get_blocks callbacks.  There are four users of the DIO_NO_LOCKING mode:
    gfs already ignores the create argument and thus is fine with the new
    version, ocfs2 only errors out if create were ever set, and we can remove
    this dead code now, the block device code only ever uses create for an
    error message if we are fully beyond the device which can never happen,
    and last but not least XFS will need the new behavour for writes.
    Now we can replace the lock_type variable with a flags one, where no flag
    means the DIO_NO_LOCKING behaviour and DIO_LOCKING is kept as the first
    flag.  Separate out the check for not allowing to fill holes into a separate
    flag, although for now both flags always get set at the same time.
    Also revamp the documentation of the locking scheme to actually make sense.
    Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
direct-io.c 33.3 KB