From: Khazhismel Kumykov khazhy@chromium.org
[ Upstream commit a1795c2ccb1e4c49220d2a0d381540024d71647c ]
This fixes crashes in bfq_add_bfqq_busy due to waker_bfqq being NULL, but woken_list_node still being hashed. This would happen when bfq_init_rq() expects a brand new allocated queue to be returned from bfq_get_bfqq_handle_split() and unconditionally updates waker_bfqq without resetting woken_list_node. Since we can always return oom_bfqq when attempting to allocate, we cannot assume waker_bfqq starts as NULL.
Avoid setting woken_bfqq for oom_bfqq entirely, as it's not useful.
Crashes would have a stacktrace like: [160595.656560] bfq_add_bfqq_busy+0x110/0x1ec [160595.661142] bfq_add_request+0x6bc/0x980 [160595.666602] bfq_insert_request+0x8ec/0x1240 [160595.671762] bfq_insert_requests+0x58/0x9c [160595.676420] blk_mq_sched_insert_request+0x11c/0x198 [160595.682107] blk_mq_submit_bio+0x270/0x62c [160595.686759] __submit_bio_noacct_mq+0xec/0x178 [160595.691926] submit_bio+0x120/0x184 [160595.695990] ext4_mpage_readpages+0x77c/0x7c8 [160595.701026] ext4_readpage+0x60/0xb0 [160595.705158] filemap_read_page+0x54/0x114 [160595.711961] filemap_fault+0x228/0x5f4 [160595.716272] do_read_fault+0xe0/0x1f0 [160595.720487] do_fault+0x40/0x1c8
Tested by injecting random failures into bfq_get_queue, crashes go away completely.
Fixes: 8ef3fc3a043c ("block, bfq: make shared queues inherit wakers") Signed-off-by: Khazhismel Kumykov khazhy@google.com Reviewed-by: Jan Kara jack@suse.cz Link: https://lore.kernel.org/r/20221108181030.1611703-1-khazhy@google.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- block/bfq-iosched.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 7ea427817f7f..ca04ec868c40 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -6784,6 +6784,12 @@ static struct bfq_queue *bfq_init_rq(struct request *rq) bfqq = bfq_get_bfqq_handle_split(bfqd, bic, bio, true, is_sync, NULL); + if (unlikely(bfqq == &bfqd->oom_bfqq)) + bfqq_already_existing = true; + } else + bfqq_already_existing = true; + + if (!bfqq_already_existing) { bfqq->waker_bfqq = old_bfqq->waker_bfqq; bfqq->tentative_waker_bfqq = NULL;
@@ -6797,8 +6803,7 @@ static struct bfq_queue *bfq_init_rq(struct request *rq) if (bfqq->waker_bfqq) hlist_add_head(&bfqq->woken_list_node, &bfqq->waker_bfqq->woken_list); - } else - bfqq_already_existing = true; + } } }