Export 'get_pipe_info()' to other users

And in particular, use it in 'pipe_fcntl()'.

The other pipe functions do not need to use the 'careful' version, since
they are only ever called for things that are already known to be pipes.

The normal read/write/ioctl functions are called through the file
operations structures, so if a file isn't a pipe, they'd never get
called.  But pipe_fcntl() is special, and called directly from the
generic fcntl code, and needs to use the same careful function that the
splice code is using.

Cc: Jens Axboe <jaxboe@fusionio.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Jones <davej@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/pipe.c

@@ -1204,7 +1204,7 @@ long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
 	struct pipe_inode_info *pipe;
 	long ret;
 
-	pipe = file->f_path.dentry->d_inode->i_pipe;
+	pipe = get_pipe_info(file);
 	if (!pipe)
 		return -EBADF;
 

fs/splice.c

@@ -1311,17 +1311,6 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
 			       struct pipe_inode_info *opipe,
 			       size_t len, unsigned int flags);
-/*
- * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
- * location, so checking ->i_pipe is not enough to verify that this is a
- * pipe.
- */
-static inline struct pipe_inode_info *get_pipe_info(struct file *file)
-{
-	struct inode *i = file->f_path.dentry->d_inode;
-
-	return S_ISFIFO(i->i_mode) ? i->i_pipe : NULL;
-}
 
 /*
  * Determine where to splice to/from.

include/linux/pipe_fs_i.h

@@ -161,4 +161,16 @@ void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
 long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
 
+/*
+ * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
+ * location, so checking ->i_pipe is not enough to verify that this is a
+ * pipe.
+ */
+static inline struct pipe_inode_info *get_pipe_info(struct file *file)
+{
+	struct inode *i = file->f_path.dentry->d_inode;
+
+	return S_ISFIFO(i->i_mode) ? i->i_pipe : NULL;
+}
+
 #endif