[PATCH v5.2 10/12] btrfs: extent_io: Kill the BUG_ON() in extent_write_cache_pages()

[Qu Wenruo <wqu@suse.com>]

In extent_write_cache_pages() since flush_write_bio() can return error,
we need some extra error handling.

For the first flush_write_bio() since we haven't locked the page, we
only need to exit the loop.

For the seconds flush_write_bio() call, we have the page locked, despite
that there is nothing special need to handle.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
---
changelog:
v5.2:
- Update commit message to explain why the error out behavior is
  correct.
- Add a missing unlock_page() for the 2nd error out case.
---
 fs/btrfs/extent_io.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 1572e892ec7b..477d7f19a34a 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3998,7 +3998,10 @@ static int extent_write_cache_pages(struct address_space *mapping,
 			 */
 			if (!trylock_page(page)) {
 				ret = flush_write_bio(epd);
-				BUG_ON(ret < 0);
+				if (ret < 0) {
+					done = 1;
+					break;
+				}
 				lock_page(page);
 			}
 
@@ -4010,7 +4013,11 @@ static int extent_write_cache_pages(struct address_space *mapping,
 			if (wbc->sync_mode != WB_SYNC_NONE) {
 				if (PageWriteback(page)) {
 					ret = flush_write_bio(epd);
-					BUG_ON(ret < 0);
+					if (ret < 0) {
+						unlock_page(page);
+						done = 1;
+						break;
+					}
 				}
 				wait_on_page_writeback(page);
 			}
-- 
2.21.0