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

[Andreas Dilger]

On Apr 29, 2016, at 6:58 AM, David Howells <dhowells@xxxxxxxxxx> wrote:
> 
> 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.

This is not implemented in this patch, and should removed from the commit
message.  The generic_fillattr() change in [1/6] will clear the STATX_ATIME
flag if IS_NOATIME() is true, so maybe that is enough for what you intended?

Cheers, Andreas

> 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@xxxxxxxxxx>
> ---
> 
> 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;
> 
> --
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Cheers, Andreas

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