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[PATCH] xfs: Fix WARN_ON(delalloc) in xfs_vm_releasepage()

To: xfs@xxxxxxxxxxx
Subject: [PATCH] xfs: Fix WARN_ON(delalloc) in xfs_vm_releasepage()
From: Jan Kara <jack@xxxxxxx>
Date: Thu, 14 Mar 2013 14:30:54 +0100
Cc: Jan Kara <jack@xxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
When a dirty page is truncated from a file but reclaim gets to it before
truncate_inode_pages(), we hit WARN_ON(delalloc) in
xfs_vm_releasepage(). This is because reclaim tries to write the page,
xfs_vm_writepage() just bails out (leaving page clean) and thus reclaim
thinks it can continue and calls xfs_vm_releasepage() on page with dirty
buffers.

Fix the issue by redirtying the page in xfs_vm_writepage(). This makes
reclaim stop reclaiming the page and also logically it keeps page in a
more consistent state where page with dirty buffers has PageDirty set.

Signed-off-by: Jan Kara <jack@xxxxxxx>
---
 fs/xfs/xfs_aops.c |   12 ++++++------
 1 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 5f707e5..3244c98 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -953,13 +953,13 @@ xfs_vm_writepage(
                unsigned offset_into_page = offset & (PAGE_CACHE_SIZE - 1);
 
                /*
-                * Just skip the page if it is fully outside i_size, e.g. due
-                * to a truncate operation that is in progress.
+                * Skip the page if it is fully outside i_size, e.g. due to a
+                * truncate operation that is in progress. We must redirty the
+                * page so that reclaim stops reclaiming it. Otherwise
+                * xfs_vm_releasepage() is called on it and gets confused.
                 */
-               if (page->index >= end_index + 1 || offset_into_page == 0) {
-                       unlock_page(page);
-                       return 0;
-               }
+               if (page->index >= end_index + 1 || offset_into_page == 0)
+                       goto redirty;
 
                /*
                 * The page straddles i_size.  It must be zeroed out on each
-- 
1.7.1

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