vfs: document locking requirements for d_move, __d_move and d_materia…

…lise_unique Adding a comment to d_materialise_unique per Al's request... d_move and __d_move have some pretty substantial locking requirements, but they are not clearly documented. Add some comments spelling them out. Also, document the requirement for the i_mutex of the parent in d_materialise_unique. Cc: Al Viro <[email protected]> Signed-off-by: Jeff Layton <[email protected]> Signed-off-by: Al Viro <[email protected]>
kev009 · Jul 26, 2011 · c46c887 · c46c887
1 parent 41c9648
commit c46c887
Showing 1 changed file with 7 additions and 4 deletions.
diff --git a/fs/dcache.c b/fs/dcache.c
@@ -2138,8 +2138,9 @@ static void dentry_unlock_parents_for_move(struct dentry *dentry,
  * @target: new dentry
  *
  * Update the dcache to reflect the move of a file name. Negative
- * dcache entries should not be moved in this way.  Caller hold
- * rename_lock.
+ * dcache entries should not be moved in this way. Caller must hold
+ * rename_lock, the i_mutex of the source and target directories,
+ * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
  */
 static void __d_move(struct dentry * dentry, struct dentry * target)
 {
@@ -2202,7 +2203,8 @@ static void __d_move(struct dentry * dentry, struct dentry * target)
  * @target: new dentry
  *
  * Update the dcache to reflect the move of a file name. Negative
- * dcache entries should not be moved in this way.
+ * dcache entries should not be moved in this way. See the locking
+ * requirements for __d_move.
  */
 void d_move(struct dentry *dentry, struct dentry *target)
 {
@@ -2320,7 +2322,8 @@ static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
  * @inode: inode to bind to the dentry, to which aliases may be attached
  *
  * Introduces an dentry into the tree, substituting an extant disconnected
- * root directory alias in its place if there is one
+ * root directory alias in its place if there is one. Caller must hold the
+ * i_mutex of the parent directory.
  */
 struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
 {