[Crash-utility] Re: [PATCH] Add blk_mq_tag_set shared_tags check

Date: Wed, 19 Nov 2025 15:36:29 +1300 From: Tao Liu <ltao(a)redhat.com&gt; Subject: [Crash-utility] [PATCH] Add blk_mq_tag_set shared_tags check To: devel(a)lists.crash-utility.osci.io Cc: Tao Liu <ltao(a)redhat.com&gt; Message-ID: <20251119023628.15998-2-ltao(a)redhat.com&gt; Content-Type: text/plain; charset="US-ASCII"; x-default=true A regression of cmd dev -d/-D noticed on some vmcores as: dev: invalid structure member offset: blk_mq_tag_set_shared_tags FILE: dev.c LINE: 4468 FUNCTION: blk_mq_queue_tag_busy_iter() MAJOR GENDISK NAME REQUEST_QUEUE TOTAL ASYNC SYNC [crash] error trace: 91aa85 => 91a552 => 94d6ba => 94d647 94d647: OFFSET_verify.part.0+55 94d6ba: OFFSET_verify+42 91a552: get_diskio_1+2194 91aa85: display_all_diskio+1253 The root cause is, though upstream kernel have defined BLK_MQ_F_TAG_HCTX_SHARED as (1 << 3), the value might be set different, e.g. [1]. So a single

shared_tagsblk_mq_is_shared_tags() check is not sufficient. This patch will add shared_tags member check within blk_mq_tag_set struct as an enhancment.

https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-8/-/blob... Fixes: 62486400d35b ("Add blk_mq shared tags support for dev -d/-D") Signed-off-by: Tao Liu <ltao(a)redhat.com&gt; --- dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/dev.c b/dev.c index 8391d71..27318e8 100644 --- a/dev.c +++ b/dev.c @@ -4464,7 +4464,7 @@ static void blk_mq_queue_tag_busy_iter(ulong q, ulong *hctx, uint cnt, readmem(addr + OFFSET(blk_mq_tag_set_flags), KVADDR, &flags, sizeof(uint), "blk_mq_tag_set.flags", RETURN_ON_ERROR); - if (blk_mq_is_shared_tags(flags)) { + if (blk_mq_is_shared_tags(flags) && VALID_MEMBER(blk_mq_tag_set_shared_tags)) { addr = addr + OFFSET(blk_mq_tag_set_shared_tags); queue_for_each_hw_ctx(q, addr, bitmap_tags_is_ptr, dio); return; -- 2.47.0