The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 73aeab373557fa6ee4ae0b742c6211ccd9859280 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024100230-epilogue-hush-6a49@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

73aeab373557 ("block, bfq: fix procress reference leakage for bfqq in merge chain") 9778369a2d6c ("block, bfq: split sync bfq_queues on a per-actuator basis") 246cf66e300b ("block, bfq: fix uaf for bfqq in bfq_exit_icq_bfqq") 337366e02b37 ("block, bfq: replace 0/1 with false/true in bic apis") 64dc8c732f5c ("block, bfq: fix possible uaf for 'bfqq->bic'") dc469ba2e790 ("block/bfq: Use the new blk_opf_t type") 4e54a2493e58 ("bfq: Get rid of __bio_blkcg() usage") 09f871868080 ("bfq: Track whether bfq_group is still online") ea591cd4eb27 ("bfq: Update cgroup information before merging bio") 3bc5e683c67d ("bfq: Split shared queues on move between cgroups") f6bad159f5d5 ("block/bfq-iosched.c: use "false" rather than "BLK_RW_ASYNC"") a0725c22cd84 ("bfq: use bfq_bic_lookup in bfq_limit_depth") 1f18b7005b49 ("bfq: Limit waker detection in time") 76f1df88bbc2 ("bfq: Limit number of requests consumed by each cgroup") 44dfa279f117 ("bfq: Store full bitmap depth in bfq_data") ae0f1a732f4a ("blk-mq: Stop using pointers for blk_mq_tags bitmap tags") e155b0c238b2 ("blk-mq: Use shared tags for shared sbitmap support") 645db34e5050 ("blk-mq: Refactor and rename blk_mq_free_map_and_{requests->rqs}()") 63064be150e4 ("blk-mq: Add blk_mq_alloc_map_and_rqs()") a7e7388dced4 ("blk-mq: Add blk_mq_tag_update_sched_shared_sbitmap()")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 73aeab373557fa6ee4ae0b742c6211ccd9859280 Mon Sep 17 00:00:00 2001 From: Yu Kuai yukuai3@huawei.com Date: Mon, 9 Sep 2024 21:41:49 +0800 Subject: [PATCH] block, bfq: fix procress reference leakage for bfqq in merge chain MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

Original state:

Process 1 Process 2 Process 3 Process 4 (BIC1) (BIC2) (BIC3) (BIC4) Λ | | | --------------\ -------------\ -------------| V V V bfqq1--------->bfqq2---------->bfqq3----------->bfqq4 ref 0 1 2 4

After commit 0e456dba86c7 ("block, bfq: choose the last bfqq from merge chain in bfq_setup_cooperator()"), if P1 issues a new IO:

Without the patch:

Process 1 Process 2 Process 3 Process 4 (BIC1) (BIC2) (BIC3) (BIC4) Λ | | | ------------------------------\ -------------| V V bfqq1--------->bfqq2---------->bfqq3----------->bfqq4 ref 0 0 2 4

bfqq3 will be used to handle IO from P1, this is not expected, IO should be redirected to bfqq4;

With the patch:

------------------------------------------- | | Process 1 Process 2 Process 3 | Process 4 (BIC1) (BIC2) (BIC3) | (BIC4) | | | | -------------\ -------------| V V bfqq1--------->bfqq2---------->bfqq3----------->bfqq4 ref 0 0 2 4

IO is redirected to bfqq4, however, procress reference of bfqq3 is still 2, while there is only P2 using it.

Fix the problem by calling bfq_merge_bfqqs() for each bfqq in the merge chain. Also change bfqq_merge_bfqqs() to return new_bfqq to simplify code.

Fixes: 0e456dba86c7 ("block, bfq: choose the last bfqq from merge chain in bfq_setup_cooperator()") Signed-off-by: Yu Kuai yukuai3@huawei.com Link: https://lore.kernel.org/r/20240909134154.954924-3-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe axboe@kernel.dk

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index d5d39974c674..f4192d5411d2 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -3129,10 +3129,12 @@ void bfq_release_process_ref(struct bfq_data *bfqd, struct bfq_queue *bfqq) bfq_put_queue(bfqq); }

-static void -bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic, - struct bfq_queue *bfqq, struct bfq_queue *new_bfqq) +static struct bfq_queue *bfq_merge_bfqqs(struct bfq_data *bfqd, + struct bfq_io_cq *bic, + struct bfq_queue *bfqq) { + struct bfq_queue *new_bfqq = bfqq->new_bfqq; + bfq_log_bfqq(bfqd, bfqq, "merging with queue %lu", (unsigned long)new_bfqq->pid); /* Save weight raising and idle window of the merged queues */ @@ -3226,6 +3228,8 @@ bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic, bfq_reassign_last_bfqq(bfqq, new_bfqq);

bfq_release_process_ref(bfqd, bfqq); + + return new_bfqq; }

static bool bfq_allow_bio_merge(struct request_queue *q, struct request *rq, @@ -3261,14 +3265,8 @@ static bool bfq_allow_bio_merge(struct request_queue *q, struct request *rq, * fulfilled, i.e., bic can be redirected to new_bfqq * and bfqq can be put. */ - bfq_merge_bfqqs(bfqd, bfqd->bio_bic, bfqq, - new_bfqq); - /* - * If we get here, bio will be queued into new_queue, - * so use new_bfqq to decide whether bio and rq can be - * merged. - */ - bfqq = new_bfqq; + while (bfqq != new_bfqq) + bfqq = bfq_merge_bfqqs(bfqd, bfqd->bio_bic, bfqq);

/* * Change also bqfd->bio_bfqq, as @@ -5705,9 +5703,7 @@ bfq_do_early_stable_merge(struct bfq_data *bfqd, struct bfq_queue *bfqq, * state before killing it. */ bfqq->bic = bic; - bfq_merge_bfqqs(bfqd, bic, bfqq, new_bfqq); - - return new_bfqq; + return bfq_merge_bfqqs(bfqd, bic, bfqq); }

/* @@ -6162,6 +6158,7 @@ static bool __bfq_insert_request(struct bfq_data *bfqd, struct request *rq) bool waiting, idle_timer_disabled = false;

if (new_bfqq) { + struct bfq_queue *old_bfqq = bfqq; /* * Release the request's reference to the old bfqq * and make sure one is taken to the shared queue. @@ -6178,18 +6175,18 @@ static bool __bfq_insert_request(struct bfq_data *bfqd, struct request *rq) * new_bfqq. */ if (bic_to_bfqq(RQ_BIC(rq), true, - bfq_actuator_index(bfqd, rq->bio)) == bfqq) - bfq_merge_bfqqs(bfqd, RQ_BIC(rq), - bfqq, new_bfqq); + bfq_actuator_index(bfqd, rq->bio)) == bfqq) { + while (bfqq != new_bfqq) + bfqq = bfq_merge_bfqqs(bfqd, RQ_BIC(rq), bfqq); + }

- bfq_clear_bfqq_just_created(bfqq); + bfq_clear_bfqq_just_created(old_bfqq); /* * rq is about to be enqueued into new_bfqq, * release rq reference on bfqq */ - bfq_put_queue(bfqq); + bfq_put_queue(old_bfqq); rq->elv.priv[1] = new_bfqq; - bfqq = new_bfqq; }

bfq_update_io_thinktime(bfqd, bfqq);