Re: [PATCH 3/2] [RFC] NFS: Support the AT_NO_TIMES and AT_STRICT fstatat flags

[Trond Myklebust <Trond.Myklebust@netapp.com>]

If the kernel knows that the application doesn't care about the time
information, then we can avoid having to flush out writes, and we can avoid
revalidating the atime information.

OTOH, if the app sets AT_STRICT then we must force a revalidation of the
attribute metadata.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
---
 fs/nfs/inode.c |   16 +++++++++++-----
 1 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 67db3a9..76bd229 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -506,9 +506,14 @@ int nfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat,
 		int flags)
 {
 	struct inode *inode = dentry->d_inode;
-	int need_atime = NFS_I(inode)->cache_validity & NFS_INO_INVALID_ATIME;
+	int force_reval = 0;
 	int err;
 
+	force_reval |= (flags & AT_STRICT) != 0;
+
+	if (!(flags & AT_NO_TIMES))
+		goto do_revalidate;
+
 	/*
 	 * Flush out writes to the server in order to update c/mtime.
 	 *
@@ -531,11 +536,12 @@ 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 (!((mnt->mnt_flags & MNT_NOATIME) ||
+ 	    ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode))))
+		force_reval |= (NFS_I(inode)->cache_validity & NFS_INO_INVALID_ATIME) != 0;
 
-	if (need_atime)
+do_revalidate:
+	if (force_reval)
 		err = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
 	else
 		err = nfs_revalidate_inode(NFS_SERVER(inode), inode);
-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com