Document ->tmpfile()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Documentation/filesystems/Locking

@@ -64,6 +64,7 @@ prototypes:
 	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);
 
 locking rules:
 	all may block
@@ -91,6 +92,7 @@ removexattr:	yes
 fiemap:		no
 update_time:	no
 atomic_open:	yes
+tmpfile:	no
 
 	Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on
 victim.

Documentation/filesystems/vfs.txt

@@ -360,6 +360,8 @@ struct inode_operations {
 	int (*removexattr) (struct dentry *, const char *);
 	void (*update_time)(struct inode *, struct timespec *, int);
 	int (*atomic_open)(struct inode *, struct dentry *,
+	int (*tmpfile) (struct inode *, struct dentry *, umode_t);
+} ____cacheline_aligned;
 				struct file *, unsigned open_flag,
 				umode_t create_mode, int *opened);
 };
@@ -472,6 +474,9 @@ otherwise noted.
   	component is negative or needs lookup.  Cached positive dentries are
   	still handled by f_op->open().
 
+  tmpfile: called in the end of O_TMPFILE open().  Optional, equivalent to
+	atomically creating, opening and unlinking a file in given directory.
+
 The Address Space Object
 ========================