5 files changed, 60 insertions, 2 deletions

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 0d8302e59d69..ee13cb01b56e 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -888,7 +888,10 @@ nfs_fhget(struct super_block *sb, struct nfs_fh *fh, struct nfs_fattr *fattr)
                                 set_bit(NFS_INO_ADVISE_RDPLUS, &NFS_FLAGS(inode));
                         /* Deal with crossing mountpoints */
                         if (!nfs_fsid_equal(&NFS_SB(sb)->fsid, &fattr->fsid)) {
-                                inode->i_op = &nfs_mountpoint_inode_operations;
+                                if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
+                                        inode->i_op = &nfs_referral_inode_operations;
+                                else
+                                        inode->i_op = &nfs_mountpoint_inode_operations;
                                 inode->i_fop = NULL;
                         }
                 } else if (S_ISLNK(inode->i_mode))
diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index e426516c1116..8ca44b7b25c3 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -58,7 +58,10 @@ static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
         if (err != 0)
                 goto out_err;
 
-        mnt = nfs_do_submount(nd->mnt, nd->dentry, &fh, &fattr);
+        if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL)
+                mnt = nfs_do_refmount(nd->mnt, nd->dentry);
+        else
+                mnt = nfs_do_submount(nd->mnt, nd->dentry, &fh, &fattr);
         err = PTR_ERR(mnt);
         if (IS_ERR(mnt))
                 goto out_err;
@@ -94,6 +97,10 @@ struct inode_operations nfs_mountpoint_inode_operations = {
         .getattr        = nfs_getattr,
 };
 
+struct inode_operations nfs_referral_inode_operations = {
+        .follow_link    = nfs_follow_mountpoint,
+};
+
 static void nfs_expire_automounts(void *data)
 {
         struct list_head *list = (struct list_head *)data;
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 90ee21a07b3e..3300e35d74ad 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1462,6 +1462,50 @@ out:
         return nfs4_map_errors(status);
 }
 
+/*
+ * Get locations and (maybe) other attributes of a referral.
+ * Note that we'll actually follow the referral later when
+ * we detect fsid mismatch in inode revalidation
+ */
+static int nfs4_get_referral(struct inode *dir, struct qstr *name, struct nfs_fattr *fattr, struct nfs_fh *fhandle)
+{
+        int status = -ENOMEM;
+        struct page *page = NULL;
+        struct nfs4_fs_locations *locations = NULL;
+        struct dentry dentry = {};
+
+        page = alloc_page(GFP_KERNEL);
+        if (page == NULL)
+                goto out;
+        locations = kmalloc(sizeof(struct nfs4_fs_locations), GFP_KERNEL);
+        if (locations == NULL)
+                goto out;
+
+        dentry.d_name.name = name->name;
+        dentry.d_name.len = name->len;
+        status = nfs4_proc_fs_locations(dir, &dentry, locations, page);
+        if (status != 0)
+                goto out;
+        /* Make sure server returned a different fsid for the referral */
+        if (nfs_fsid_equal(&NFS_SERVER(dir)->fsid, &locations->fattr.fsid)) {
+                dprintk("%s: server did not return a different fsid for a referral at %s\n", __FUNCTION__, name->name);
+                status = -EIO;
+                goto out;
+        }
+
+        memcpy(fattr, &locations->fattr, sizeof(struct nfs_fattr));
+        fattr->valid |= NFS_ATTR_FATTR_V4_REFERRAL;
+        if (!fattr->mode)
+                fattr->mode = S_IFDIR;
+        memset(fhandle, 0, sizeof(struct nfs_fh));
+out:
+        if (page)
+                __free_page(page);
+        if (locations)
+                kfree(locations);
+        return status;
+}
+
 static int _nfs4_proc_getattr(struct nfs_server *server, struct nfs_fh *fhandle, struct nfs_fattr *fattr)
 {
         struct nfs4_getattr_arg args = {
@@ -1566,6 +1610,8 @@ static int _nfs4_proc_lookup(struct inode *dir, struct qstr *name,
         
         dprintk("NFS call  lookup %s\n", name->name);
         status = rpc_call_sync(NFS_CLIENT(dir), &msg, 0);
+        if (status == -NFS4ERR_MOVED)
+                status = nfs4_get_referral(dir, name, fattr, fhandle);
         dprintk("NFS reply lookup: %d\n", status);
         return status;
 }
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 09271b10f9a8..152798949113 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -409,6 +409,7 @@ extern void nfs_unregister_sysctl(void);
  */
 extern struct list_head nfs_automount_list;
 extern struct inode_operations nfs_mountpoint_inode_operations;
+extern struct inode_operations nfs_referral_inode_operations;
 extern int nfs_mountpoint_expiry_timeout;
 extern void nfs_release_automount_timer(void);
 
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index d6eea8348728..7c7320fa51aa 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -63,6 +63,7 @@ struct nfs_fattr {
 #define NFS_ATTR_FATTR          0x0002          /* post-op attributes */
 #define NFS_ATTR_FATTR_V3       0x0004          /* NFSv3 attributes */
 #define NFS_ATTR_FATTR_V4       0x0008          /* NFSv4 change attribute */
+#define NFS_ATTR_FATTR_V4_REFERRAL      0x0010          /* NFSv4 referral */
 
 /*
  * Info on the file system