• Andrew Morton's avatar
    [PATCH] sys_sync_file_range() · f79e2abb
    Andrew Morton authored
    Remove the recently-added LINUX_FADV_ASYNC_WRITE and LINUX_FADV_WRITE_WAIT
    fadvise() additions, do it in a new sys_sync_file_range() syscall instead.
    - It's more flexible.  Things which would require two or three syscalls with
      fadvise() can be done in a single syscall.
    - Using fadvise() in this manner is something not covered by POSIX.
    The patch wires up the syscall for x86.
    The sycall is implemented in the new fs/sync.c.  The intention is that we can
    move sys_fsync(), sys_fdatasync() and perhaps sys_sync() into there later.
    Documentation for the syscall is in fs/sync.c.
    A test app (sync_file_range.c) is in
    The available-to-GPL-modules do_sync_file_range() is for knfsd: "A COMMIT can
    say NFS_DATA_SYNC or NFS_FILE_SYNC.  I can skip the ->fsync call for
    NFS_DATA_SYNC which is hopefully the more common."
    Note: the `async' writeout mode SYNC_FILE_RANGE_WRITE will turn synchronous if
    the queue is congested.  This is trivial to fix: add a new flag bit, set
    wbc->nonblocking.  But I'm not sure that we want to expose implementation
    details down to that level.
    Note: it's notable that we can sync an fd which wasn't opened for writing.
    Same with fsync() and fdatasync()).
    Note: the code takes some care to handle attempts to sync file contents
    outside the 16TB offset on 32-bit machines.  It makes such attempts appear to
    succeed, for best 32-bit/64-bit compatibility.  Perhaps it should make such
    requests fail...
    Cc: Nick Piggin <nickpiggin@yahoo.com.au>
    Cc: Michael Kerrisk <mtk-manpages@gmx.net>
    Cc: Ulrich Drepper <drepper@redhat.com>
    Cc: Neil Brown <neilb@cse.unsw.edu.au>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
fadvise.c 3.11 KB