NFS: Use d_automount() rather than abusing follow_link()

Make NFS use the new d_automount() dentry operation rather than abusing
follow_link() on directories.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

4 files changed, 46 insertions, 47 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index df8c03a02161..2c3eb33b904d 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -970,7 +970,7 @@ int nfs_lookup_verify_inode(struct inode *inode, struct nameidata *nd)
 {
         struct nfs_server *server = NFS_SERVER(inode);
 
-        if (test_bit(NFS_INO_MOUNTPOINT, &NFS_I(inode)->flags))
+        if (IS_AUTOMOUNT(inode))
                 return 0;
         if (nd != NULL) {
                 /* VFS wants an on-the-wire revalidation */
@@ -1173,6 +1173,7 @@ const struct dentry_operations nfs_dentry_operations = {
         .d_revalidate   = nfs_lookup_revalidate,
         .d_delete       = nfs_dentry_delete,
         .d_iput         = nfs_dentry_iput,
+        .d_automount    = nfs_d_automount,
 };
 
 static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, struct nameidata *nd)
@@ -1246,6 +1247,7 @@ const struct dentry_operations nfs4_dentry_operations = {
         .d_revalidate   = nfs_open_revalidate,
         .d_delete       = nfs_dentry_delete,
         .d_iput         = nfs_dentry_iput,
+        .d_automount    = nfs_d_automount,
 };
 
 /*
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index ce00b704452c..d8512423ba72 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -300,7 +300,7 @@ 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);
+                                inode->i_flags |= S_AUTOMOUNT;
                         }
                 } else if (S_ISLNK(inode->i_mode))
                         inode->i_op = &nfs_symlink_inode_operations;
@@ -1208,7 +1208,7 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
         /* Update the fsid? */
         if (S_ISDIR(inode->i_mode) && (fattr->valid & NFS_ATTR_FATTR_FSID) &&
                         !nfs_fsid_equal(&server->fsid, &fattr->fsid) &&
-                        !test_bit(NFS_INO_MOUNTPOINT, &nfsi->flags))
+                        !IS_AUTOMOUNT(inode))
                 server->fsid = fattr->fsid;
 
         /*
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index bfa3a34af801..4644f04b4b46 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -252,6 +252,7 @@ extern char *nfs_path(const char *base,
                       const struct dentry *droot,
                       const struct dentry *dentry,
                       char *buffer, ssize_t buflen);
+extern struct vfsmount *nfs_d_automount(struct path *path);
 
 /* getroot.c */
 extern struct dentry *nfs_get_root(struct super_block *, struct nfs_fh *);
diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index bfcb933e5755..f3fbb1bf3f18 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -97,9 +97,8 @@ Elong:
 }
 
 /*
- * nfs_follow_mountpoint - handle crossing a mountpoint on the server
- * @dentry - dentry of mountpoint
- * @nd - nameidata info
+ * nfs_d_automount - Handle crossing a mountpoint on the server
+ * @path - The mountpoint
  *
  * When we encounter a mountpoint on the server, we want to set up
  * a mountpoint on the client too, to prevent inode numbers from
@@ -109,84 +108,81 @@ Elong:
  * situation, and that different filesystems may want to use
  * different security flavours.
  */
-static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
+struct vfsmount *nfs_d_automount(struct path *path)
 {
         struct vfsmount *mnt;
-        struct nfs_server *server = NFS_SERVER(dentry->d_inode);
+        struct nfs_server *server = NFS_SERVER(path->dentry->d_inode);
         struct dentry *parent;
         struct nfs_fh *fh = NULL;
         struct nfs_fattr *fattr = NULL;
         int err;
 
-        dprintk("--> nfs_follow_mountpoint()\n");
+        dprintk("--> nfs_d_automount()\n");
 
-        err = -ESTALE;
-        if (IS_ROOT(dentry))
-                goto out_err;
+        mnt = ERR_PTR(-ESTALE);
+        if (IS_ROOT(path->dentry))
+                goto out_nofree;
 
-        err = -ENOMEM;
+        mnt = ERR_PTR(-ENOMEM);
         fh = nfs_alloc_fhandle();
         fattr = nfs_alloc_fattr();
         if (fh == NULL || fattr == NULL)
-                goto out_err;
+                goto out;
 
         dprintk("%s: enter\n", __func__);
-        dput(nd->path.dentry);
-        nd->path.dentry = dget(dentry);
 
-        /* Look it up again */
-        parent = dget_parent(nd->path.dentry);
+        /* Look it up again to get its attributes */
+        parent = dget_parent(path->dentry);
         err = server->nfs_client->rpc_ops->lookup(parent->d_inode,
-                                                  &nd->path.dentry->d_name,
+                                                  &path->dentry->d_name,
                                                   fh, fattr);
         dput(parent);
-        if (err != 0)
-                goto out_err;
+        if (err != 0) {
+                mnt = ERR_PTR(err);
+                goto out;
+        }
 
         if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
-                mnt = nfs_do_refmount(nd->path.mnt, nd->path.dentry);
+                mnt = nfs_do_refmount(path->mnt, path->dentry);
         else
-                mnt = nfs_do_submount(nd->path.mnt, nd->path.dentry, fh,
-                                      fattr);
-        err = PTR_ERR(mnt);
+                mnt = nfs_do_submount(path->mnt, path->dentry, fh, fattr);
         if (IS_ERR(mnt))
-                goto out_err;
+                goto out;
 
         mntget(mnt);
-        err = do_add_mount(mnt, &nd->path, nd->path.mnt->mnt_flags|MNT_SHRINKABLE,
+        err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE,
                            &nfs_automount_list);
-        if (err < 0) {
+        switch (err) {
+        case 0:
+                dprintk("%s: done, success\n", __func__);
+                schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
+                break;
+        case -EBUSY:
+                /* someone else made a mount here whilst we were busy */
                 mntput(mnt);
-                if (err == -EBUSY)
-                        goto out_follow;
-                goto out_err;
+                dprintk("%s: done, collision\n", __func__);
+                mnt = NULL;
+                break;
+        default:
+                mntput(mnt);
+                dprintk("%s: done, error %d\n", __func__, err);
+                mnt = ERR_PTR(err);
+                break;
         }
-        path_put(&nd->path);
-        nd->path.mnt = mnt;
-        nd->path.dentry = dget(mnt->mnt_root);
-        schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
+
 out:
         nfs_free_fattr(fattr);
         nfs_free_fhandle(fh);
-        dprintk("%s: done, returned %d\n", __func__, err);
-
-        dprintk("<-- nfs_follow_mountpoint() = %d\n", err);
-        return ERR_PTR(err);
-out_err:
-        path_put(&nd->path);
-        goto out;
-out_follow:
-        err = follow_down(&nd->path, false);
-        goto out;
+out_nofree:
+        dprintk("<-- nfs_follow_mountpoint() = %p\n", mnt);
+        return mnt;
 }
 
 const struct inode_operations nfs_mountpoint_inode_operations = {
-        .follow_link    = nfs_follow_mountpoint,
         .getattr        = nfs_getattr,
 };
 
 const struct inode_operations nfs_referral_inode_operations = {
-        .follow_link    = nfs_follow_mountpoint,
 };
 
 static void nfs_expire_automounts(struct work_struct *work)