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: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/xfs/linux-2.6/xfs_aops.h b/fs/xfs/linux-2.6/xfs_aops.h
index 1dd528849755..221b3e66ceef 100644
--- a/fs/xfs/linux-2.6/xfs_aops.h
+++ b/fs/xfs/linux-2.6/xfs_aops.h
@@ -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;
 
 /*