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>
diff --git a/fs/pipe.c b/fs/pipe.c
index a8012a9..b8997f8 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -1204,7 +1204,7 @@
 	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;