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Commit d88992f6 authored by David Chinner's avatar David Chinner Committed by Nathan Scott
Browse files

[XFS] Fix a race in xfs_submit_ioend() where we can be completing I/O for 


a page while we are still submitting other buffers on the same page for
I/O.

SGI-PV: 948197
SGI-Modid: xfs-linux-melb:xfs-kern:25004a

Signed-off-by: default avatarDavid Chinner <dgc@sgi.com>
Signed-off-by: default avatarNathan Scott <nathans@sgi.com>
parent 2664b250

fs/xfs/linux-2.6/xfs_aops.c

+26 −3
Original line number Diff line number Diff line
@@ -336,24 +336,47 @@ static inline int bio_add_buffer(struct bio *bio, struct buffer_head *bh) 
}



/*

 * Submit all of the bios for all of the ioends we have saved up,

 * covering the initial writepage page and also any probed pages.

 * Submit all of the bios for all of the ioends we have saved up, covering the

 * initial writepage page and also any probed pages.

 *

 * Because we may have multiple ioends spanning a page, we need to start

 * writeback on all the buffers before we submit them for I/O. If we mark the

 * buffers as we got, then we can end up with a page that only has buffers

 * marked async write and I/O complete on can occur before we mark the other

 * buffers async write.

 *

 * The end result of this is that we trip a bug in end_page_writeback() because

 * we call it twice for the one page as the code in end_buffer_async_write()

 * assumes that all buffers on the page are started at the same time.

 *

 * The fix is two passes across the ioend list - one to start writeback on the

 * bufferheads, and then the second one submit them for I/O.

 */

STATIC void

xfs_submit_ioend(

	xfs_ioend_t		*ioend)

{

	xfs_ioend_t		*head = ioend;

	xfs_ioend_t		*next;

	struct buffer_head	*bh;

	struct bio		*bio;

	sector_t		lastblock = 0;



	/* Pass 1 - start writeback */

	do {

		next = ioend->io_list;

		for (bh = ioend->io_buffer_head; bh; bh = bh->b_private) {

			xfs_start_buffer_writeback(bh);

		}

	} while ((ioend = next) != NULL);



	/* Pass 2 - submit I/O */

	ioend = head;

	do {

		next = ioend->io_list;

		bio = NULL;



		for (bh = ioend->io_buffer_head; bh; bh = bh->b_private) {

			xfs_start_buffer_writeback(bh);



			if (!bio) {

 retry: