Merge branch 'd_real' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs into work.misc

1 files changed, 26 insertions, 14 deletions

diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index d4e07c00e18e..70a056fe51a3 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -364,7 +364,6 @@ struct inode_operations {
 	int (*atomic_open)(struct inode *, struct dentry *, struct file *,
 			unsigned open_flag, umode_t create_mode, int *opened);
 	int (*tmpfile) (struct inode *, struct dentry *, umode_t);
-	int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
 };
 
 Again, all methods are called without any locks being held, unless
@@ -694,13 +693,6 @@ struct address_space_operations {
   	but instead uses bmap to find out where the blocks in the file
   	are and uses those addresses directly.
 
-  dentry_open: *WARNING: probably going away soon, do not use!* This is an
-	alternative to f_op->open(), the difference is that this method may open
-	a file not necessarily originating from the same filesystem as the one
-	i_op->open() was called on.  It may be useful for stacking filesystems
-	which want to allow native I/O directly on underlying files.
-
-
   invalidatepage: If a page has PagePrivate set, then invalidatepage
         will be called when part or all of the page is to be removed
 	from the address space.  This generally corresponds to either a
@@ -936,6 +928,8 @@ struct dentry_operations {
 	char *(*d_dname)(struct dentry *, char *, int);
 	struct vfsmount *(*d_automount)(struct path *);
 	int (*d_manage)(struct dentry *, bool);
+	struct dentry *(*d_real)(struct dentry *, const struct inode *,
+				 unsigned int);
 };
 
   d_revalidate: called when the VFS needs to revalidate a dentry. This
@@ -1020,6 +1014,14 @@ struct dentry_operations {
 	at the end of the buffer, and returns a pointer to the first char.
 	dynamic_dname() helper function is provided to take care of this.
 
+	Example :
+
+	static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen)
+	{
+		return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
+				dentry->d_inode->i_ino);
+	}
+
   d_automount: called when an automount dentry is to be traversed (optional).
 	This should create a new VFS mount record and return the record to the
 	caller.  The caller is supplied with a path parameter giving the
@@ -1058,13 +1060,23 @@ struct dentry_operations {
 	This function is only used if DCACHE_MANAGE_TRANSIT is set on the
 	dentry being transited from.
 
-Example :
+  d_real: overlay/union type filesystems implement this method to return one of
+	the underlying dentries hidden by the overlay.  It is used in three
+	different modes:
 
-static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen)
-{
-	return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
-				dentry->d_inode->i_ino);
-}
+	Called from open it may need to copy-up the file depending on the
+	supplied open flags.  This mode is selected with a non-zero flags
+	argument.  In this mode the d_real method can return an error.
+
+	Called from file_dentry() it returns the real dentry matching the inode
+	argument.  The real dentry may be from a lower layer already copied up,
+	but still referenced from the file.  This mode is selected with a
+	non-NULL inode argument.  This will always succeed.
+
+	With NULL inode and zero flags the topmost real underlying dentry is
+	returned.  This will always succeed.
+
+	This method is never called with both non-NULL inode and non-zero flags.
 
 Each dentry has a pointer to its parent dentry, as well as a hash list
 of child dentries. Child dentries are basically like files in a