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Commit e927af90 authored by David Chinner's avatar David Chinner Committed by Tim Shimmin
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[XFS] Block on unwritten extent conversion during synchronous direct I/O. 



Currently we do not wait on extent conversion to occur, and hence we can
return to userspace from a synchronous direct I/O write without having
completed all the actions in the write. Hence a read after the write may
see zeroes (unwritten extent) rather than the data that was written.

Block the I/O completion by triggering a synchronous workqueue flush to
ensure that the conversion has occurred before we return to userspace.

SGI-PV: 964092
SGI-Modid: xfs-linux-melb:xfs-kern:28775a

Signed-off-by: default avatarDavid Chinner <dgc@sgi.com>
Signed-off-by: default avatarTim Shimmin <tes@sgi.com>
parent f4a9f28a

fs/xfs/linux-2.6/xfs_aops.c

+20 −8
Original line number Diff line number Diff line
@@ -108,14 +108,19 @@ xfs_page_trace( 


/*

 * Schedule IO completion handling on a xfsdatad if this was

 * the final hold on this ioend.

 * the final hold on this ioend. If we are asked to wait,

 * flush the workqueue.

 */

STATIC void

xfs_finish_ioend(

	xfs_ioend_t		*ioend)

	xfs_ioend_t	*ioend,

	int		wait)

{

	if (atomic_dec_and_test(&ioend->io_remaining))

	if (atomic_dec_and_test(&ioend->io_remaining)) {

		queue_work(xfsdatad_workqueue, &ioend->io_work);

		if (wait)

			flush_workqueue(xfsdatad_workqueue);

	}

}



/*
@@ -334,7 +339,7 @@ xfs_end_bio( 
	bio->bi_end_io = NULL;

	bio_put(bio);



	xfs_finish_ioend(ioend);

	xfs_finish_ioend(ioend, 0);

	return 0;

}
@@ -470,7 +475,7 @@ xfs_submit_ioend( 
		}

		if (bio)

			xfs_submit_ioend_bio(ioend, bio);

		xfs_finish_ioend(ioend);

		xfs_finish_ioend(ioend, 0);

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

}
@@ -1416,6 +1421,13 @@ xfs_end_io_direct( 
	 * This is not necessary for synchronous direct I/O, but we do

	 * it anyway to keep the code uniform and simpler.

	 *

	 * Well, if only it were that simple. Because synchronous direct I/O

	 * requires extent conversion to occur *before* we return to userspace,

	 * we have to wait for extent conversion to complete. Look at the

	 * iocb that has been passed to us to determine if this is AIO or

	 * not. If it is synchronous, tell xfs_finish_ioend() to kick the

	 * workqueue and wait for it to complete.

	 *

	 * The core direct I/O code might be changed to always call the

	 * completion handler in the future, in which case all this can

	 * go away.
@@ -1423,9 +1435,9 @@ xfs_end_io_direct( 
	ioend->io_offset = offset;

	ioend->io_size = size;

	if (ioend->io_type == IOMAP_READ) {

		xfs_finish_ioend(ioend);

		xfs_finish_ioend(ioend, 0);

	} else if (private && size > 0) {

		xfs_finish_ioend(ioend);

		xfs_finish_ioend(ioend, is_sync_kiocb(iocb));

	} else {

		/*

		 * A direct I/O write ioend starts it's life in unwritten
@@ -1434,7 +1446,7 @@ xfs_end_io_direct( 
		 * handler.

		 */

		INIT_WORK(&ioend->io_work, xfs_end_bio_written);

		xfs_finish_ioend(ioend);

		xfs_finish_ioend(ioend, 0);

	}



	/*