Re: [PATCH 4/6] xstat: NFS: Return extended attributes

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On Thu, 2012-04-19 at 15:06 +0100, David Howells wrote:
> Return extended attributes from the NFS filesystem.  This includes the
> following:
> 
>  (1) The change attribute as st_data_version if NFSv4.
> 
>  (2) XSTAT_INFO_AUTOMOUNT and XSTAT_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) XSTAT_INFO_REMOTE is set on files acquired over NFS.
> 
> Furthermore, what nfs_getattr() does can be controlled as follows:
> 
>  (1) 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.
> 
>  (2) The inode's attributes may be synchronised with the server:
> 
>      (a) If AT_FORCE_ATTR_SYNC is indicated or if atime is requested (and atime
>      	 updating is not suppressed by a mount flag) then the attributes will
>      	 be reread unconditionally.
> 
>      (b) If the data version or any of basic stats are requested then the
>      	 attributes will be reread if the cached attributes have expired.
> 
>      (c) Otherwise the cached attributes will be used - even if expired -
>      	 without reference to the server.

Hmm... As far as I can see you are still doing an nfs_revalidate_inode()
in the non-forced case. That will cause expired attributes to be
retrieved from the server.

> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> ---
> 
>  fs/nfs/inode.c |   49 +++++++++++++++++++++++++++++++++++++------------
>  fs/nfs/super.c |    1 +
>  2 files changed, 38 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
> index e8bbfa5..460fcf3 100644
> --- a/fs/nfs/inode.c
> +++ b/fs/nfs/inode.c
> @@ -509,11 +509,18 @@ void nfs_setattr_update_inode(struct inode *inode, struct iattr *attr)
>  int nfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
>  {
>  	struct inode *inode = dentry->d_inode;
> +	unsigned force = stat->query_flags & AT_FORCE_ATTR_SYNC;
>  	int need_atime = NFS_I(inode)->cache_validity & NFS_INO_INVALID_ATIME;
>  	int err;
>  
> -	/* 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 &= ~XSTAT_VERSION;
> +
> +	/* Flush out writes to the server in order to update c/mtime
> +	 * or data version if the user wants them */
> +	if ((force || (stat->request_mask &
> +		       (XSTAT_MTIME | XSTAT_CTIME | XSTAT_VERSION))) &&
> +	    S_ISREG(inode->i_mode)) {
>  		err = filemap_write_and_wait(inode->i_mapping);

We can get rid of the filemap_write_and_wait() if the caller allows us
to approximate m/ctime values. That would give a major speed-up for most
stat() workloads.

>  		if (err)
>  			goto out;
> @@ -528,18 +535,36 @@ 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)))
> +	if (mnt->mnt_flags & MNT_NOATIME ||
> +	    (mnt->mnt_flags & MNT_NODIRATIME && S_ISDIR(inode->i_mode))) {
> +		stat->ioc_flags |= FS_NOATIME_FL;
> +		need_atime = 0;
> +	} else if (!(stat->request_mask & XSTAT_ATIME)) {
>  		need_atime = 0;
> +	}
>  
> -	if (need_atime)
> -		err = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
> -	else
> -		err = nfs_revalidate_inode(NFS_SERVER(inode), inode);
> -	if (!err) {
> -		generic_fillattr(inode, stat);
> -		stat->ino = nfs_compat_user_ino64(NFS_FILEID(inode));
> +	if (force || stat->request_mask & (XSTAT_BASIC_STATS | XSTAT_VERSION)) {
> +		if (force || need_atime)
> +			err = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
> +		else
> +			err = nfs_revalidate_inode(NFS_SERVER(inode), inode);
> +		if (err)
> +			goto out;
>  	}
> +
> +	generic_fillattr(inode, stat);
> +	stat->ino = nfs_compat_user_ino64(NFS_FILEID(inode));
> +
> +	if (stat->request_mask & XSTAT_VERSION) {
> +		stat->version = inode->i_version;
> +		stat->result_mask |= XSTAT_VERSION;
> +	}
> +
> +	if (IS_AUTOMOUNT(inode))
> +		stat->information |= XSTAT_INFO_FABRICATED;
> +
> +	stat->information |= XSTAT_INFO_REMOTE;
> +
>  out:
>  	return err;
>  }
> @@ -852,7 +877,7 @@ int nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
>  static int nfs_invalidate_mapping(struct inode *inode, struct address_space *mapping)
>  {
>  	struct nfs_inode *nfsi = NFS_I(inode);
> -	
> +
>  	if (mapping->nrpages != 0) {
>  		int ret = invalidate_inode_pages2(mapping);
>  		if (ret < 0)
> diff --git a/fs/nfs/super.c b/fs/nfs/super.c
> index 37412f7..faa652c 100644
> --- a/fs/nfs/super.c
> +++ b/fs/nfs/super.c
> @@ -2222,6 +2222,7 @@ static int nfs_set_super(struct super_block *s, void *data)
>  	ret = set_anon_super(s, server);
>  	if (ret == 0)
>  		server->s_dev = s->s_dev;
> +	memcpy(&s->s_volume_id, &server->fsid, sizeof(s->s_volume_id));
>  	return ret;
>  }
>  
> 
> --
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-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com

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