NFS: Fix the fsid revalidation in nfs_update_inode()

When we detect that we've crossed a mountpoint on the remote server, we
must take care not to use that inode to revalidate the fsid on our
current superblock. To do so, we label the inode as a remote mountpoint,
and check for that in nfs_update_inode().

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 5 insertions, 2 deletions

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 966a8850aa30..a4c7cf2bff3a 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -299,6 +299,7 @@ nfs_fhget(struct super_block *sb, struct nfs_fh *fh, struct nfs_fattr *fattr)
                                 else
                                         inode->i_op = &nfs_mountpoint_inode_operations;
                                 inode->i_fop = NULL;
+                                set_bit(NFS_INO_MOUNTPOINT, &nfsi->flags);
                         }
                 } else if (S_ISLNK(inode->i_mode))
                         inode->i_op = &nfs_symlink_inode_operations;
@@ -1003,8 +1004,9 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
 
         server = NFS_SERVER(inode);
         /* Update the fsid? */
-        if (S_ISDIR(inode->i_mode)
-                        && !nfs_fsid_equal(&server->fsid, &fattr->fsid))
+        if (S_ISDIR(inode->i_mode) &&
+                        !nfs_fsid_equal(&server->fsid, &fattr->fsid) &&
+                        !test_bit(NFS_INO_MOUNTPOINT, &nfsi->flags))
                 server->fsid = fattr->fsid;
 
         /*
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index a69ba80f2dfe..f4a0e4c218df 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -195,6 +195,7 @@ struct nfs_inode {
 #define NFS_INO_ADVISE_RDPLUS   (1)             /* advise readdirplus */
 #define NFS_INO_STALE           (2)             /* possible stale inode */
 #define NFS_INO_ACL_LRU_SET     (3)             /* Inode is on the LRU list */
+#define NFS_INO_MOUNTPOINT      (4)             /* inode is remote mountpoint */
 
 static inline struct nfs_inode *NFS_I(const struct inode *inode)
 {