1 files changed, 49 insertions, 0 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 14ab8d3f2f0c..5ba42c453e31 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1134,6 +1134,30 @@ static struct dentry *d_alloc_and_lookup(struct dentry *parent,
 }
 
 /*
+ * We already have a dentry, but require a lookup to be performed on the parent
+ * directory to fill in d_inode. Returns the new dentry, or ERR_PTR on error.
+ * parent->d_inode->i_mutex must be held. d_lookup must have verified that no
+ * child exists while under i_mutex.
+ */
+static struct dentry *d_inode_lookup(struct dentry *parent, struct dentry *dentry,
+                                     struct nameidata *nd)
+{
+        struct inode *inode = parent->d_inode;
+        struct dentry *old;
+
+        /* Don't create child dentry for a dead directory. */
+        if (unlikely(IS_DEADDIR(inode)))
+                return ERR_PTR(-ENOENT);
+
+        old = inode->i_op->lookup(inode, dentry, nd);
+        if (unlikely(old)) {
+                dput(dentry);
+                dentry = old;
+        }
+        return dentry;
+}
+
+/*
  *  It's more convoluted than I'd like it to be, but... it's still fairly
  *  small and for now I'd prefer to have fast path as straight as possible.
  *  It _is_ time-critical.
@@ -1172,6 +1196,8 @@ static int do_lookup(struct nameidata *nd, struct qstr *name,
                                 goto unlazy;
                         }
                 }
+                if (unlikely(d_need_lookup(dentry)))
+                        goto unlazy;
                 path->mnt = mnt;
                 path->dentry = dentry;
                 if (unlikely(!__follow_mount_rcu(nd, path, inode)))
@@ -1186,6 +1212,10 @@ unlazy:
                 dentry = __d_lookup(parent, name);
         }
 
+        if (dentry && unlikely(d_need_lookup(dentry))) {
+                dput(dentry);
+                dentry = NULL;
+        }
 retry:
         if (unlikely(!dentry)) {
                 struct inode *dir = parent->d_inode;
@@ -1202,6 +1232,15 @@ retry:
                         /* known good */
                         need_reval = 0;
                         status = 1;
+                } else if (unlikely(d_need_lookup(dentry))) {
+                        dentry = d_inode_lookup(parent, dentry, nd);
+                        if (IS_ERR(dentry)) {
+                                mutex_unlock(&dir->i_mutex);
+                                return PTR_ERR(dentry);
+                        }
+                        /* known good */
+                        need_reval = 0;
+                        status = 1;
                 }
                 mutex_unlock(&dir->i_mutex);
         }
@@ -1683,6 +1722,16 @@ static struct dentry *__lookup_hash(struct qstr *name,
          */
         dentry = d_lookup(base, name);
 
+        if (dentry && d_need_lookup(dentry)) {
+                /*
+                 * __lookup_hash is called with the parent dir's i_mutex already
+                 * held, so we are good to go here.
+                 */
+                dentry = d_inode_lookup(base, dentry, nd);
+                if (IS_ERR(dentry))
+                        return dentry;
+        }
+
         if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE))
                 dentry = do_revalidate(dentry, nd);