• Zach Brown's avatar
    vfs: add copy_file_range syscall and vfs helper · 29732938
    Zach Brown authored
    Add a copy_file_range() system call for offloading copies between
    regular files.
    This gives an interface to underlying layers of the storage stack which
    can copy without reading and writing all the data.  There are a few
    candidates that should support copy offloading in the nearer term:
    - btrfs shares extent references with its clone ioctl
    - NFS has patches to add a COPY command which copies on the server
    - SCSI has a family of XCOPY commands which copy in the device
    This system call avoids the complexity of also accelerating the creation
    of the destination file by operating on an existing destination file
    descriptor, not a path.
    Currently the high level vfs entry point limits copy offloading to files
    on the same mount and super (and not in the same file).  This can be
    relaxed if we get implementations which can copy between file systems
    Signed-off-by: default avatarZach Brown <zab@redhat.com>
    [Anna Schumaker: Change -EINVAL to -EBADF during file verification,
                     Change flags parameter from int to unsigned int,
                     Add function to include/linux/syscalls.h,
                     Check copy len after file open mode,
                     Don't forbid ranges inside the same file,
                     Use rw_verify_area() to veriy ranges,
                     Use file_out rather than file_in,
                     Add COPY_FR_REFLINK flag]
    Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
sys_ni.c 7 KB