btrfs: extent_io: Handle errors better in btree_write_cache_pages()

In btree_write_cache_pages(), we can only get @ret <= 0.
Add an ASSERT() for it just in case.

Then instead of submitting the write bio even we got some error, check
the return value first.
If we have already hit some error, just clean up the corrupted or
half-baked bio, and return error.

If there is no error so far, then call flush_write_bio() and return the
result.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 9d52f3b78732..8399fc4b27ae 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3748,7 +3748,6 @@ int btree_write_cache_pages(struct address_space *mapping,
 		.sync_io = wbc->sync_mode == WB_SYNC_ALL,
 	};
 	int ret = 0;
-	int flush_ret;
 	int done = 0;
 	int nr_to_write_done = 0;
 	struct pagevec pvec;
@@ -3848,8 +3847,12 @@ retry:
 		index = 0;
 		goto retry;
 	}
-	flush_ret = flush_write_bio(&epd);
-	BUG_ON(flush_ret < 0);
+	ASSERT(ret <= 0);
+	if (ret < 0) {
+		end_write_bio(&epd, ret);
+		return ret;
+	}
+	ret = flush_write_bio(&epd);
 	return ret;
 }