[PATCH 4.9 17/78] Btrfs: fix missing error return if writeback for extent buffer never started

Greg Kroah-Hartman
2020-11-17T13:10:29Z

From: Filipe Manana <fdmanana@suse.com>

[ Upstream commit 0607eb1d452d45c5ac4c745a9e9e0d95152ea9d0 ]

If lock_extent_buffer_for_io() fails, it returns a negative value, but its
caller btree_write_cache_pages() ignores such error. This means that a
call to flush_write_bio(), from lock_extent_buffer_for_io(), might have
failed. We should make btree_write_cache_pages() notice such error values
and stop immediatelly, making sure filemap_fdatawrite_range() returns an
error to the transaction commit path. A failure from flush_write_bio()
should also result in the endio callback end_bio_extent_buffer_writepage()
being invoked, which sets the BTRFS_FS_*_ERR bits appropriately, so that
there's no risk a transaction or log commit doesn't catch a writeback
failure.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/btrfs/extent_io.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index d6c827a9ebc56..5c2f4f58da8ff 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3879,6 +3879,10 @@ int btree_write_cache_pages(struct address_space *mapping,
if (!ret) {
free_extent_buffer(eb);
continue;
+ } else if (ret < 0) {
+ done = 1;
+ free_extent_buffer(eb);
+ break;
}

ret = write_one_eb(eb, fs_info, wbc, &epd);
--
2.27.0