| Message ID | 1486628673-30631-1-git-send-email-takafumi.kubota1012@sslab.ics.keio.ac.jp (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
On Thu, Feb 09, 2017 at 05:24:33PM +0900, Takafumi Kubota wrote: > 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.kubota1012@sslab.ics.keio.ac.jp> > Reviewed-by: Liu Bo <bo.li.liu@oracle.com> > Cc: David Sterba <dsterba@suse.cz> Added to 4.11 queue, thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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;
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.kubota1012@sslab.ics.keio.ac.jp> Reviewed-by: Liu Bo <bo.li.liu@oracle.com> Cc: David Sterba <dsterba@suse.cz> --- fs/btrfs/extent_io.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)