If btrfs_bio_alloc fails in submit_extent_page, submit_extent_page returns
without clearing the writeback bit of the failed page.
__extent_writepage_io, that is a caller of submit_extent_page,
does not clear the remaining writeback bit anywhere.
As a result, this will cause the hang at filemap_fdatawait_range,
because it waits the writeback bit to be cleared from the failed page.
So, we have to call end_page_writeback to clear the writeback bit.
For reproducing the hang, we inject a fault like
if (should_failtest()) { // I define should_failtest()
bio = NULL;
}
else {
bio = btrfs_bio_alloc(...);
}
in submit_extent_page.
We should also check whether page has the bit before end_page_writeback,
to avoid the conflict against the other end_page_writeback in bio_endio.
Thus, we add PageWriteback checks not only in __extent_writepage_io,
but also in write_one_eb too, because it misses the check.
Signed-off-by: Takafumi Kubota <takafumi.kubota1...@sslab.ics.keio.ac.jp>
Reviewed-by: Liu Bo <bo.li....@oracle.com>
Cc: David Sterba <dste...@suse.cz>
---
fs/btrfs/extent_io.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 4ac383a..aa1908a 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3445,8 +3445,11 @@ 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);
+ if (PageWriteback(page))
+ end_page_writeback(page);
+ }
cur = cur + iosize;
pg_offset += iosize;
@@ -3767,7 +3770,8 @@ static noinline_for_stack int write_one_eb(struct
extent_buffer *eb,
epd->bio_flags = bio_flags;
if (ret) {
set_btree_ioerr(p);
- end_page_writeback(p);
+ if (PageWriteback(p))
+ end_page_writeback(p);
if (atomic_sub_and_test(num_pages - i, &eb->io_pages))
end_extent_buffer_writeback(eb);
ret = -EIO;
--
1.9.3
