Merge remote-tracking branch 'xfs/for-next'

[karo-tx-linux.git] / fs / namei.c

diff --git a/fs/namei.c b/fs/namei.c
index 33e9495a31293e2c080b5b0bd2e50523a460ceee..5d4645e6537691677ba91a488bfb149c24fa0b08 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2282,6 +2282,8 @@ EXPORT_SYMBOL(vfs_path_lookup);
  *
  * Note that this routine is purely a helper for filesystem usage and should
  * not be called by generic code.
+ *
+ * The caller must hold base->i_mutex.
  */
 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
 {
@@ -2325,6 +2327,78 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
 }
 EXPORT_SYMBOL(lookup_one_len);
 
+/**
+ * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
+ * @name:      pathname component to lookup
+ * @base:      base directory to lookup from
+ * @len:       maximum length @len should be interpreted to
+ *
+ * Note that this routine is purely a helper for filesystem usage and should
+ * not be called by generic code.
+ *
+ * Unlike lookup_one_len, it should be called without the parent
+ * i_mutex held, and will take the i_mutex itself if necessary.
+ */
+struct dentry *lookup_one_len_unlocked(const char *name,
+                                      struct dentry *base, int len)
+{
+       struct qstr this;
+       unsigned int c;
+       int err;
+       struct dentry *ret;
+
+       this.name = name;
+       this.len = len;
+       this.hash = full_name_hash(name, len);
+       if (!len)
+               return ERR_PTR(-EACCES);
+
+       if (unlikely(name[0] == '.')) {
+               if (len < 2 || (len == 2 && name[1] == '.'))
+                       return ERR_PTR(-EACCES);
+       }
+
+       while (len--) {
+               c = *(const unsigned char *)name++;
+               if (c == '/' || c == '\0')
+                       return ERR_PTR(-EACCES);
+       }
+       /*
+        * See if the low-level filesystem might want
+        * to use its own hash..
+        */
+       if (base->d_flags & DCACHE_OP_HASH) {
+               int err = base->d_op->d_hash(base, &this);
+               if (err < 0)
+                       return ERR_PTR(err);
+       }
+
+       err = inode_permission(base->d_inode, MAY_EXEC);
+       if (err)
+               return ERR_PTR(err);
+
+       ret = __d_lookup(base, &this);
+       if (ret)
+               return ret;
+       /*
+        * __d_lookup() is used to try to get a quick answer and avoid the
+        * mutex.  A false-negative does no harm.
+        */
+       ret = __d_lookup(base, &this);
+       if (ret && ret->d_flags & DCACHE_OP_REVALIDATE) {
+               dput(ret);
+               ret = NULL;
+       }
+       if (ret)
+               return ret;
+
+       mutex_lock(&base->d_inode->i_mutex);
+       ret =  __lookup_hash(&this, base, 0);
+       mutex_unlock(&base->d_inode->i_mutex);
+       return ret;
+}
+EXPORT_SYMBOL(lookup_one_len_unlocked);
+
 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
                 struct path *path, int *empty)
 {