Commit 6965031d authored Aug 03, 2010 by Miklos Szeredi Committed by Jens Axboe Aug 07, 2010

splice: fix misuse of SPLICE_F_NONBLOCK



SPLICE_F_NONBLOCK is clearly documented to only affect blocking on the
pipe.  In __generic_file_splice_read(), however, it causes an EAGAIN
if the page is currently being read.

This makes it impossible to write an application that only wants
failure if the pipe is full.  For example if the same process is
handling both ends of a pipe and isn't otherwise able to determine
whether a splice to the pipe will fill it or not.

We could make the read non-blocking on O_NONBLOCK or some other splice
flag, but for now this is the simplest fix.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: stable@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

parent 7901d141

fs/splice.c

+1 −11

Original line number	Diff line number	Diff line
		@@ -399,16 +399,6 @@ __generic_file_splice_read(struct file in, loff_t ppos,
		* If the page isn't uptodate, we may need to start io on it
		*/
		if (!PageUptodate(page)) {
		/*
		* If in nonblock mode then dont block on waiting
		* for an in-flight io page
		*/
		if (flags & SPLICE_F_NONBLOCK) {
		if (!trylock_page(page)) {
		error = -EAGAIN;
		break;
		}
		} else
		lock_page(page);

		/*