From: Rui Hua huarui.dev@gmail.com
[ Upstream commit b221fc130c49c50f4c2250d22e873420765a9fa2 ]
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 happens, 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 this happened, 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 happened, 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.
[edit by mlyle: patch formatting, word-wrap, comment spelling, commit log format]
Signed-off-by: Hua Rui huarui.dev@gmail.com Reviewed-by: Michael Lyle mlyle@lyle.org Signed-off-by: Michael Lyle mlyle@lyle.org Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- drivers/md/bcache/request.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+)
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c index e9fbf2bcd122..f34ad8720756 100644 --- a/drivers/md/bcache/request.c +++ b/drivers/md/bcache/request.c @@ -568,6 +568,7 @@ static void cache_lookup(struct closure *cl) { struct search *s = container_of(cl, struct search, iop.cl); struct bio *bio = &s->bio.bio; + struct cached_dev *dc; int ret;
bch_btree_op_init(&s->op, -1); @@ -580,6 +581,27 @@ static void cache_lookup(struct closure *cl) return; }
+ /* + * We might meet err when searching the btree, If that happens, we will + * get negative ret, in this scenario 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 happened, s->iop.status is still its initial value + * before we submit s->bio.bio + */ + if (ret < 0) { + BUG_ON(ret == -EINTR); + if (s->d && s->d->c && + !UUID_FLASH_ONLY(&s->d->c->uuids[s->d->id])) { + dc = container_of(s->d, struct cached_dev, disk); + if (dc && atomic_read(&dc->has_dirty)) + s->recoverable = false; + } + if (!s->iop.status) + s->iop.status = BLK_STS_IOERR; + } + closure_return(cl); }