Re: Crash...

[Ryusuke Konishi <ryusuke-sG5X7nlA6pw@public.gmane.org>]

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Hi Andrea,
On Thu, 23 Jul 2009 23:02:47 +0200, Andrea Gelmini wrote:
> 2009/7/23 Ryusuke Konishi <ryusuke-sG5X7nlA6pw@public.gmane.org>:
> > It also suggests that an inconsistent state in page cache of B-tree
> > nodes hit the function; the function found a dirty page, but the page
> > didn't have buffer heads which was supposed to be impossible for the
> > b-tree of nilfs.
> 
> Well,
>    thanks for your quick reply.
>    Anyway, I can reproduce the same problem doing same things with
> stable kernel (2.6.29.6) and nilfs2-module from git repository.
>    I do this:
>    -> mkfs.nilfs2 -b 1024 /dev/mapper/VG-NilfHome (maybe the problem
> is the 1K block size?)
>    -> mount /dev/mapper/VG-NilfHome /tmp/test/
>    -> I run mirrordir (here's exactly as a "cp -a")
> 
>    It stucks at the same file as the crash before.
>    It's a 5G file, if it could help.

I found a bug which may cause the kernel oops you reported.
The bug can arise only if buffer size is smaller than page size.

Here I attach the patch that will hopefully fix this problem.

Could you test if the patch makes a difference for the same file ?

Regards,
Ryusuke Konishi
---
 fs/nilfs2/segment.c |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index 8b5e477..51ff3d0 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -1859,12 +1859,26 @@ static void nilfs_end_page_io(struct page *page, int err)
 	if (!page)
 		return;
 
-	if (buffer_nilfs_node(page_buffers(page)) && !PageWriteback(page))
+	if (buffer_nilfs_node(page_buffers(page)) && !PageWriteback(page)) {
 		/*
 		 * For b-tree node pages, this function may be called twice
 		 * or more because they might be split in a segment.
 		 */
+		if (PageDirty(page)) {
+			/*
+			 * For pages holding split b-tree node buffers, dirty
+			 * flag on the buffers may be cleared discretely.
+			 * In that case, the page is once redirtied for
+			 * remaining buffers, and it must be cancelled if
+			 * all the buffers get cleaned later.
+			 */
+			lock_page(page);
+			if (nilfs_page_buffers_clean(page))
+				__nilfs_clear_page_dirty(page);
+			unlock_page(page);
+		}
 		return;
+	}
 
 	__nilfs_end_page_io(page, err);
 }
-- 
1.6.3.3


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