This is actually inspired by Filipe's patch(55e3bd2e0c2e1).
When submit_extent_page() in __extent_writepage_io() fails,
Btrfs misses clearing a writeback bit of the failed page.
This causes the false under-writeback page.
Then, another sync task hangs in filemap_fdatawait_range(),
because it waits the false under-writeback page.
CPU0 CPU1
__extent_writepage_io()
ret = submit_extent_page() // fail
if (ret)
SetPageError(page)
// miss clearing the writeback bit
sync()
...
filemap_fdatawait_range()
wait_on_page_writeback(page);
// wait the false under-writeback page
Signed-off-by: Takafumi Kubota <takafumi.kubota1012@xxxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/extent_io.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 1e67723..ef9793b 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3443,8 +3443,10 @@ static noinline_for_stack int __extent_writepage_io(struct inode *inode,
bdev, &epd->bio, max_nr,
end_bio_extent_writepage,
0, 0, 0, false);
- if (ret)
+ if (ret) {
SetPageError(page);
+ end_page_writeback(page);
+ }
cur = cur + iosize;
pg_offset += iosize;
--
1.9.3
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