[PATCH 4/6] statx: NFS: Return enhanced file attributes

David Howells
2016-04-29T12:58:06Z

Return enhanced file atrributes from the NFS filesystem. This includes the
following:

(1) The change attribute as st_version if NFSv4.

(2) STATX_INFO_AUTOMOUNT and STATX_INFO_FABRICATED are set on referral or
submount directories that are automounted upon. NFS shows one
directory with a different FSID, but the local filesystem has two: the
mountpoint directory and the root of the filesystem mounted upon it.

(3) STATX_INFO_REMOTE is set on files acquired over NFS.

(4) STATX_IOC_FLAGS is set and if the atime is unavailable on a file,
st_ioc_flags will have FL_NOATIME_FL set in it.

Furthermore, what nfs_getattr() does can be controlled as follows:

(1) If AT_NO_ATTR_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_FORCE_ATTR_SYNC is indicated, or mtime, ctime or
data_version (NFSv4 only) 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_FORCE_ATTR_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 ~]# ./samples/statx/test-statx /warthog/
statx(/warthog/) = 0
results=37ef
Size: 4096 Blocks: 8 IO Block: 1048576 directory
Device: 00:26 Inode: 2 Links: 122
Access: (3777/drwxrwxrwx) Uid: 0 Gid: 4041
Access: 2015-10-30 16:15:41.730925545+0000
Modify: 2015-10-07 10:33:19.896108112+0100
Change: 2015-10-07 10:33:19.896108112+0100
Data version: 5614e6df35698650h
Inode flags: 00000000 (-------- -------- -------- --------)
Information: 00000010 (-------- -------- -------- ---r----)
IO-blocksize: blksize=1048576

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 IOC flags. There is also a backup time that could be
added.

Signed-off-by: David Howells <dhowells@redhat.com>
---

fs/nfs/inode.c | 41 ++++++++++++++++++++++++++++++++++-------
1 file changed, 34 insertions(+), 7 deletions(-)

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 738c84a42eb0..8637236bca0c 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -655,12 +655,23 @@ static bool nfs_need_revalidate_inode(struct inode *inode)
int nfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
{
struct inode *inode = d_inode(dentry);
- int need_atime = NFS_I(inode)->cache_validity & NFS_INO_INVALID_ATIME;
+ bool force_sync = stat->query_flags & AT_FORCE_ATTR_SYNC;
+ bool suppress_sync = stat->query_flags & AT_NO_ATTR_SYNC;
+ bool need_atime = NFS_I(inode)->cache_validity & NFS_INO_INVALID_ATIME;
int err = 0;

trace_nfs_getattr_enter(inode);
- /* Flush out writes to the server in order to update c/mtime. */
- if (S_ISREG(inode->i_mode)) {
+
+ if (NFS_SERVER(inode)->nfs_client->rpc_ops->version < 4)
+ stat->request_mask &= ~STATX_VERSION;
+
+ /* Flush out writes to the server in order to update c/mtime or data
+ * version if the user wants them.
+ */
+ if (S_ISREG(inode->i_mode) && !suppress_sync &&
+ (force_sync || (stat->request_mask &
+ (STATX_MTIME | STATX_CTIME | STATX_VERSION)))
+ ) {
inode_lock(inode);
err = nfs_sync_inode(inode);
inode_unlock(inode);
@@ -677,11 +688,13 @@ int nfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
* - NFS never sets MS_NOATIME or MS_NODIRATIME so there is
* no point in checking those.
*/
- if ((mnt->mnt_flags & MNT_NOATIME) ||
- ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode)))
- need_atime = 0;
+ if (!(stat->request_mask & STATX_ATIME) ||
+ (mnt->mnt_flags & MNT_NOATIME) ||
+ ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode)))
+ need_atime = false;

- if (need_atime || nfs_need_revalidate_inode(inode)) {
+ if (!suppress_sync &&
+ (force_sync || need_atime || nfs_need_revalidate_inode(inode))) {
struct nfs_server *server = NFS_SERVER(inode);

if (server->caps & NFS_CAP_READDIRPLUS)
@@ -694,6 +707,20 @@ int nfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
if (S_ISDIR(inode->i_mode))
stat->blksize = NFS_SERVER(inode)->dtsize;
}
+
+ generic_fillattr(inode, stat);
+ stat->ino = nfs_compat_user_ino64(NFS_FILEID(inode));
+
+ if (stat->request_mask & STATX_VERSION) {
+ stat->version = inode->i_version;
+ stat->result_mask |= STATX_VERSION;
+ }
+
+ if (IS_AUTOMOUNT(inode))
+ stat->information |= STATX_INFO_FABRICATED;
+
+ stat->information |= STATX_INFO_REMOTE;
+
out:
trace_nfs_getattr_exit(inode, err);
return err;