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>

diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index c13f673..7ec89fc 100644 (file)
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -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.

diff --cc fs/xfs/linux-2.6/xfs_aops.h
Simple merge

diff --cc fs/xfs/linux-2.6/xfs_buf.c
Simple merge