[GFS2] Fix recursive locking attempt with NFS

In certain cases, its possible for NFS to call the lookup code while
holding the glock (when doing a readdirplus operation) so we need to
check for that and not try and lock the glock twice. This also fixes a
typo in a previous NFS related GFS2 patch.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 15 insertions, 8 deletions

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index f7c8d31ce41a..88fcfb4f5c4d 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -395,8 +395,10 @@ struct inode *gfs2_lookup_simple(struct inode *dip, const char *name)
  * @is_root: If 1, ignore the caller's permissions
  * @i_gh: An uninitialized holder for the new inode glock
  *
- * There will always be a vnode (Linux VFS inode) for the d_gh inode unless
- * @is_root is true.
+ * This can be called via the VFS filldir function when NFS is doing
+ * a readdirplus and the inode which its intending to stat isn't
+ * already in cache. In this case we must not take the directory glock
+ * again, since the readdir call will have already taken that lock.
  *
  * Returns: errno
  */
@@ -409,8 +411,9 @@ struct inode *gfs2_lookupi(struct inode *dir, const struct qstr *name,
         struct gfs2_holder d_gh;
         struct gfs2_inum_host inum;
         unsigned int type;
-        int error = 0;
+        int error;
         struct inode *inode = NULL;
+        int unlock = 0;
 
         if (!name->len || name->len > GFS2_FNAMESIZE)
                 return ERR_PTR(-ENAMETOOLONG);
@@ -422,9 +425,12 @@ struct inode *gfs2_lookupi(struct inode *dir, const struct qstr *name,
                 return dir;
         }
 
-        error = gfs2_glock_nq_init(dip->i_gl, LM_ST_SHARED, 0, &d_gh);
-        if (error)
-                return ERR_PTR(error);
+        if (gfs2_glock_is_locked_by_me(dip->i_gl) == 0) {
+                error = gfs2_glock_nq_init(dip->i_gl, LM_ST_SHARED, 0, &d_gh);
+                if (error)
+                        return ERR_PTR(error);
+                unlock = 1;
+        }
 
         if (!is_root) {
                 error = permission(dir, MAY_EXEC, NULL);
@@ -439,10 +445,11 @@ struct inode *gfs2_lookupi(struct inode *dir, const struct qstr *name,
         inode = gfs2_inode_lookup(sb, &inum, type);
 
 out:
-        gfs2_glock_dq_uninit(&d_gh);
+        if (unlock)
+                gfs2_glock_dq_uninit(&d_gh);
         if (error == -ENOENT)
                 return NULL;
-        return inode;
+        return inode ? inode : ERR_PTR(error);
 }
 
 static int pick_formal_ino_1(struct gfs2_sbd *sdp, u64 *formal_ino)