• Christoph Hellwig's avatar
    vfs: pull btrfs clone API to vfs layer · 04b38d60
    Christoph Hellwig authored
    The btrfs clone ioctls are now adopted by other file systems, with NFS
    and CIFS already having support for them, and XFS being under active
    development.  To avoid growth of various slightly incompatible
    implementations, add one to the VFS.  Note that clones are different from
    file copies in several ways:
     - they are atomic vs other writers
     - they support whole file clones
     - they support 64-bit legth clones
     - they do not allow partial success (aka short writes)
     - clones are expected to be a fast metadata operation
    Because of that it would be rather cumbersome to try to piggyback them on
    top of the recent clone_file_range infrastructure.  The converse isn't
    true and the clone_file_range system call could try clone file range as
    a first attempt to copy, something that further patches will enable.
    Based on earlier work from Peng Tao.
    Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
ioctl.c 16.4 KB