bcache: don't write back data if reading it failed

If an IO operation fails, and we didn't successfully read data from the
cache, don't writeback invalid/partial data to the backing disk.

Signed-off-by: Michael Lyle <mlyle@lyle.org>
Reviewed-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index e663ca082183e6a126305fd62757ad538111cd9f..5e65a392287d083a5030bd804bde46589ae98ca2 100644 (file)
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -179,13 +179,21 @@ static void write_dirty(struct closure *cl)
        struct dirty_io *io = container_of(cl, struct dirty_io, cl);
        struct keybuf_key *w = io->bio.bi_private;
 
-       dirty_init(w);
-       bio_set_op_attrs(&io->bio, REQ_OP_WRITE, 0);
-       io->bio.bi_iter.bi_sector = KEY_START(&w->key);
-       bio_set_dev(&io->bio, io->dc->bdev);
-       io->bio.bi_end_io       = dirty_endio;
+       /*
+        * IO errors are signalled using the dirty bit on the key.
+        * If we failed to read, we should not attempt to write to the
+        * backing device.  Instead, immediately go to write_dirty_finish
+        * to clean up.
+        */
+       if (KEY_DIRTY(&w->key)) {
+               dirty_init(w);
+               bio_set_op_attrs(&io->bio, REQ_OP_WRITE, 0);
+               io->bio.bi_iter.bi_sector = KEY_START(&w->key);
+               bio_set_dev(&io->bio, io->dc->bdev);
+               io->bio.bi_end_io       = dirty_endio;
 
-       closure_bio_submit(&io->bio, cl);
+               closure_bio_submit(&io->bio, cl);
+       }
 
        continue_at(cl, write_dirty_finish, io->dc->writeback_write_wq);
 }