NFS: Fix inode fileid checks in attribute revalidation code

We want to throw out the attrbute if it refers to the mounted on fileid,
and not the real fileid. However we do not want to block cache consistency
updates from NFSv4 writes.

Reported-by: Murphy Zhou <jencce.kernel@gmail.com>
Fixes: 7e10cc2 ("NFS: Don't refresh attributes with mounted-on-file...")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/inode.c

@@ -1403,11 +1403,12 @@ static int nfs_check_inode_attributes(struct inode *inode, struct nfs_fattr *fat
 	if (NFS_PROTO(inode)->have_delegation(inode, FMODE_READ))
 		return 0;
 
-	/* No fileid? Just exit */
-	if (!(fattr->valid & NFS_ATTR_FATTR_FILEID))
-		return 0;
+	if (!(fattr->valid & NFS_ATTR_FATTR_FILEID)) {
+		/* Only a mounted-on-fileid? Just exit */
+		if (fattr->valid & NFS_ATTR_FATTR_MOUNTED_ON_FILEID)
+			return 0;
 	/* Has the inode gone and changed behind our back? */
-	if (nfsi->fileid != fattr->fileid) {
+	} else if (nfsi->fileid != fattr->fileid) {
 		/* Is this perhaps the mounted-on fileid? */
 		if ((fattr->valid & NFS_ATTR_FATTR_MOUNTED_ON_FILEID) &&
 		    nfsi->fileid == fattr->mounted_on_fileid)
@@ -1807,11 +1808,12 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
 			nfs_display_fhandle_hash(NFS_FH(inode)),
 			atomic_read(&inode->i_count), fattr->valid);
 
-	/* No fileid? Just exit */
-	if (!(fattr->valid & NFS_ATTR_FATTR_FILEID))
-		return 0;
+	if (!(fattr->valid & NFS_ATTR_FATTR_FILEID)) {
+		/* Only a mounted-on-fileid? Just exit */
+		if (fattr->valid & NFS_ATTR_FATTR_MOUNTED_ON_FILEID)
+			return 0;
 	/* Has the inode gone and changed behind our back? */
-	if (nfsi->fileid != fattr->fileid) {
+	} else if (nfsi->fileid != fattr->fileid) {
 		/* Is this perhaps the mounted-on fileid? */
 		if ((fattr->valid & NFS_ATTR_FATTR_MOUNTED_ON_FILEID) &&
 		    nfsi->fileid == fattr->mounted_on_fileid)