vfs: split do_lookup()

Split do_lookup() into two functions:

  lookup_fast() - does cached lookup without i_mutex
  lookup_slow() - does lookup with i_mutex

Both follow managed dentries.

The new functions are needed by atomic_open.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 45 insertions, 14 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 93ac9323b1f7..7f4ab820811a 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1125,8 +1125,8 @@ static struct dentry *__lookup_hash(struct qstr *name,
  *  small and for now I'd prefer to have fast path as straight as possible.
  *  It _is_ time-critical.
  */
-static int do_lookup(struct nameidata *nd, struct qstr *name,
-                        struct path *path, struct inode **inode)
+static int lookup_fast(struct nameidata *nd, struct qstr *name,
+                       struct path *path, struct inode **inode)
 {
         struct vfsmount *mnt = nd->path.mnt;
         struct dentry *dentry, *parent = nd->path.dentry;
@@ -1208,7 +1208,7 @@ unlazy:
                         goto need_lookup;
                 }
         }
-done:
+
         path->mnt = mnt;
         path->dentry = dentry;
         err = follow_managed(path, nd->flags);
@@ -1222,6 +1222,17 @@ done:
         return 0;
 
 need_lookup:
+        return 1;
+}
+
+/* Fast lookup failed, do it the slow way */
+static int lookup_slow(struct nameidata *nd, struct qstr *name,
+                       struct path *path)
+{
+        struct dentry *dentry, *parent;
+        int err;
+
+        parent = nd->path.dentry;
         BUG_ON(nd->inode != parent->d_inode);
 
         mutex_lock(&parent->d_inode->i_mutex);
@@ -1229,7 +1240,16 @@ need_lookup:
         mutex_unlock(&parent->d_inode->i_mutex);
         if (IS_ERR(dentry))
                 return PTR_ERR(dentry);
-        goto done;
+        path->mnt = nd->path.mnt;
+        path->dentry = dentry;
+        err = follow_managed(path, nd->flags);
+        if (unlikely(err < 0)) {
+                path_put_conditional(path, nd);
+                return err;
+        }
+        if (err)
+                nd->flags |= LOOKUP_JUMPED;
+        return 0;
 }
 
 static inline int may_lookup(struct nameidata *nd)
@@ -1301,21 +1321,26 @@ static inline int walk_component(struct nameidata *nd, struct path *path,
          */
         if (unlikely(type != LAST_NORM))
                 return handle_dots(nd, type);
-        err = do_lookup(nd, name, path, &inode);
+        err = lookup_fast(nd, name, path, &inode);
         if (unlikely(err)) {
-                terminate_walk(nd);
-                return err;
-        }
-        if (!inode) {
-                path_to_nameidata(path, nd);
-                terminate_walk(nd);
-                return -ENOENT;
+                if (err < 0)
+                        goto out_err;
+
+                err = lookup_slow(nd, name, path);
+                if (err < 0)
+                        goto out_err;
+
+                inode = path->dentry->d_inode;
         }
+        err = -ENOENT;
+        if (!inode)
+                goto out_path_put;
+
         if (should_follow_link(inode, follow)) {
                 if (nd->flags & LOOKUP_RCU) {
                         if (unlikely(unlazy_walk(nd, path->dentry))) {
-                                terminate_walk(nd);
-                                return -ECHILD;
+                                err = -ECHILD;
+                                goto out_err;
                         }
                 }
                 BUG_ON(inode != path->dentry->d_inode);
@@ -1324,6 +1349,12 @@ static inline int walk_component(struct nameidata *nd, struct path *path,
         path_to_nameidata(path, nd);
         nd->inode = inode;
         return 0;
+
+out_path_put:
+        path_to_nameidata(path, nd);
+out_err:
+        terminate_walk(nd);
+        return err;
 }
 
 /*