btrfs: extent_io: Handle errors better in extent_writepages()

We can only get <=0 from extent_write_cache_pages, add an ASSERT() for
it just in case.

Then instead of submitting the write bio even if 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>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 38dcac0a152e499e707a29b77e498d628a39a24a..e304d5f50c5a0ec1db71aabde6fc3518ad577b08 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4104,7 +4104,6 @@ int extent_writepages(struct address_space *mapping,
                      struct writeback_control *wbc)
 {
        int ret = 0;
-       int flush_ret;
        struct extent_page_data epd = {
                .bio = NULL,
                .tree = &BTRFS_I(mapping->host)->io_tree,
@@ -4113,8 +4112,12 @@ int extent_writepages(struct address_space *mapping,
        };
 
        ret = extent_write_cache_pages(mapping, wbc, &epd);
-       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;
 }