statx: NFS: Return enhanced file attributes
Return enhanced file atrributes from the NFS filesystem. This includes the
following:
(1) STATX_ATTR_AUTOMOUNT is set on referral or submount directories that
are automounted upon. NFS shows one directory with a different FSID,
but the local VFS has two: the mountpoint directory (fabricated) and
the root of the filesystem mounted upon it.
Furthermore, what nfs_getattr() does can be controlled as follows:
(1) If AT_STATX_DONT_SYNC is indicated then this will suppress the
flushing of outstanding writes and the rereading of the inode's
attributes with the server as detailed below.
(2) Otherwise:
(a) If AT_STATX_FORCE_SYNC is indicated, or mtime or ctime are
requested then the outstanding writes will be written to the
server first.
(b) The inode's attributes will be reread from the server:
(i) if AT_STATX_FORCE_SYNC is indicated;
(ii) if atime is requested (and atime updating is not suppressed by
a mount flag); or
(iii) if the cached attributes have expired;
If the inode isn't synchronised, then the cached attributes will be used -
even if expired - without reference to the server.
Example output:
[root@andromeda ~]# /tmp/test-statx /warthog
statx(/warthog) = 0
results=7ff
Size: 4096 Blocks: 8 IO Block: 1048576 directory
Device: 00:26 Inode: 2 Links: 21
Access: (0555/dr-xr-xr-x) Uid: 0 Gid: 0
Access: 2016-11-25 11:56:06.460465738+0000
Modify: 2016-09-08 20:39:46.785788707+0100
Change: 2016-09-08 20:39:46.785788707+0100
Note that the NFS4 protocol potentially provides a creation time that could
be passed through this interface and system, hidden and archive values that
could be passed as attributes. There is also a backup time that could be
exposed.
Signed-off-by: David Howells <dhowells@redhat.com>
1 file changed
