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Commit c626d174 authored by Dave Chinner's avatar Dave Chinner Committed by Christoph Hellwig
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xfs: prevent unwritten extent conversion from blocking I/O completion 



Unwritten extent conversion can recurse back into the filesystem due
to memory allocation. Memory reclaim requires I/O completions to be
processed to allow the callers to make progress. If the I/O
completion workqueue thread is doing the recursion, then we have a
deadlock situation.

Move unwritten extent completion into it's own workqueue so it
doesn't block I/O completions for normal delayed allocation or
overwrite data.

Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
parent 705db3fd

fs/xfs/linux-2.6/xfs_aops.c

+21 −17
Original line number Diff line number Diff line
@@ -152,23 +152,6 @@ xfs_find_bdev_for_inode( 
		return mp->m_ddev_targp->bt_bdev;

}



/*

 * Schedule IO completion handling on a xfsdatad if this was

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

 * flush the workqueue.

 */

STATIC void

xfs_finish_ioend(

	xfs_ioend_t	*ioend,

	int		wait)

{

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

		queue_work(xfsdatad_workqueue, &ioend->io_work);

		if (wait)

			flush_workqueue(xfsdatad_workqueue);

	}

}



/*

 * We're now finished for good with this ioend structure.

 * Update the page state via the associated buffer_heads,
@@ -309,6 +292,27 @@ xfs_end_bio_read( 
	xfs_destroy_ioend(ioend);

}



/*

 * Schedule IO completion handling on a xfsdatad if this was

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

 * flush the workqueue.

 */

STATIC void

xfs_finish_ioend(

	xfs_ioend_t	*ioend,

	int		wait)

{

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

		struct workqueue_struct *wq = xfsdatad_workqueue;

		if (ioend->io_work.func == xfs_end_bio_unwritten)

			wq = xfsconvertd_workqueue;



		queue_work(wq, &ioend->io_work);

		if (wait)

			flush_workqueue(wq);

	}

}



/*

 * Allocate and initialise an IO completion structure.

 * We need to track unwritten extent write completion here initially.

fs/xfs/linux-2.6/xfs_aops.h

+1 −0
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#define __XFS_AOPS_H__



extern struct workqueue_struct *xfsdatad_workqueue;

extern struct workqueue_struct *xfsconvertd_workqueue;

extern mempool_t *xfs_ioend_pool;



/*

fs/xfs/linux-2.6/xfs_buf.c

+9 −0
Original line number Diff line number Diff line
@@ -51,6 +51,7 @@ static struct shrinker xfs_buf_shake = { 


static struct workqueue_struct *xfslogd_workqueue;

struct workqueue_struct *xfsdatad_workqueue;

struct workqueue_struct *xfsconvertd_workqueue;



#ifdef XFS_BUF_TRACE

void
@@ -1775,6 +1776,7 @@ xfs_flush_buftarg( 
	xfs_buf_t	*bp, *n;

	int		pincount = 0;



	xfs_buf_runall_queues(xfsconvertd_workqueue);

	xfs_buf_runall_queues(xfsdatad_workqueue);

	xfs_buf_runall_queues(xfslogd_workqueue);
@@ -1831,9 +1833,15 @@ xfs_buf_init(void) 
	if (!xfsdatad_workqueue)

		goto out_destroy_xfslogd_workqueue;



	xfsconvertd_workqueue = create_workqueue("xfsconvertd");

	if (!xfsconvertd_workqueue)

		goto out_destroy_xfsdatad_workqueue;



	register_shrinker(&xfs_buf_shake);

	return 0;



 out_destroy_xfsdatad_workqueue:

	destroy_workqueue(xfsdatad_workqueue);

 out_destroy_xfslogd_workqueue:

	destroy_workqueue(xfslogd_workqueue);

 out_free_buf_zone:
@@ -1849,6 +1857,7 @@ void 
xfs_buf_terminate(void)

{

	unregister_shrinker(&xfs_buf_shake);

	destroy_workqueue(xfsconvertd_workqueue);

	destroy_workqueue(xfsdatad_workqueue);

	destroy_workqueue(xfslogd_workqueue);

	kmem_zone_destroy(xfs_buf_zone);