Rui Hua-- Thank you for fixing this. On 11/21/2017 05:58 AM, Rui Hua wrote: > The read request might meet error when searching the btree, but the error was > not handled in cache_lookup(), and this kind of metadata failure will not go > into cached_dev_read_error(), finally, the upper layer will receive bi_status=0. > In this patch we judge the metadata error by the return value of > bch_btree_map_keys(), there are two potential paths give rise to the error: > 1.Because the btree is not totally cached in memery, we maybe get error when > read btree node from cache device (see bch_btree_node_get()), the likely > errno is -EIO, -ENOMEM > 2.When read miss happend, bch_btree_insert_check_key() will be called to > insert a "replace_key" to btree(see cached_dev_cache_miss(), just for doing > preparatory work before insert the missed data to cache device), a failure > can also happen in this situation, the likely errno is -ENOMEM > bch_btree_map_keys() will return MAP_DONE in normal scenario, but we will > get either -EIO or -ENOMEM in above two cases. if these happend, we should > NOT recover data from backing device (when cache device is dirty) because > we don't know whether bkeys the read request covered are all clean. > And after that happend, s->iop.status is still its initially value(0) > before we submit s->bio.bio, we set it to BLK_STS_IOERR, so it can go into > cached_dev_read_error(), and finally it can be passed to upper layer, > or recovered by reread from backing device. > > Signed-off-by: Hua Rui <huarui.dev@xxxxxxxxx> This preliminarily LGTM-- I have added it to my tree, though I plan to make another review pass through all of the error path here. Reviewed-by: Michael Lyle <mlyle@xxxxxxxx> Mike
