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

[Qu Wenruo]

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 <w...@suse.com>
Reviewed-by: Johannes Thumshirn <jthumsh...@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