From: Christoph Hellwig hch@lst.de
commit effa24f689ce0948f68c754991a445a8d697d3a8 upstream.
extent_write_cache_pages stops writing pages as soon as nr_to_write hits zero. That is the right thing for opportunistic writeback, but incorrect for data integrity writeback, which needs to ensure that no dirty pages are left in the range. Thus only stop the writeback for WB_SYNC_NONE if nr_to_write hits 0.
This is a port of write_cache_pages changes in commit 05fe478dd04e ("mm: write_cache_pages integrity fix").
Note that I've only trigger the problem with other changes to the btrfs writeback code, but this condition seems worthwhile fixing anyway.
CC: stable@vger.kernel.org # 4.14+ Reviewed-by: Josef Bacik josef@toxicpanda.com Signed-off-by: Christoph Hellwig hch@lst.de Reviewed-by: David Sterba dsterba@suse.com [ updated comment ] Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/extent_io.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
--- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4844,11 +4844,12 @@ retry: }
/* - * the filesystem may choose to bump up nr_to_write. + * The filesystem may choose to bump up nr_to_write. * We have to make sure to honor the new nr_to_write - * at any time + * at any time. */ - nr_to_write_done = wbc->nr_to_write <= 0; + nr_to_write_done = (wbc->sync_mode == WB_SYNC_NONE && + wbc->nr_to_write <= 0); } pagevec_release(&pvec); cond_resched();