I will apply the v1, aka "Add blk_mq_tag_set shared_tags check", and fix the "runtime get BLK_MQ_F_TAG_HCTX_SHARED" later, since v3 has some problems and we are running out of time before release.
On Thu, Nov 20, 2025 at 4:25 PM Tao Liu <[email protected]> wrote: > > On Thu, Nov 20, 2025 at 3:56 PM lijiang <[email protected]> wrote: > > > > On Thu, Nov 20, 2025 at 4:37 AM Tao Liu <[email protected]> wrote: > >> > >> Hi lianbo, > >> > >> On Wed, Nov 19, 2025 at 10:31 PM lijiang <[email protected]> wrote: > >> > > >> > On Wed, Nov 19, 2025 at 12:51 PM > >> > <[email protected]> wrote: > >> >> > >> >> Date: Wed, 19 Nov 2025 15:36:29 +1300 > >> >> From: Tao Liu <[email protected]> > >> >> Subject: [Crash-utility] [PATCH] Add blk_mq_tag_set shared_tags check > >> >> To: [email protected] > >> >> Cc: Tao Liu <[email protected]> > >> >> Message-ID: <[email protected]> > >> >> 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 > >> > > >> > > >> > We should be able to get the value of BLK_MQ_F_TAG_HCTX_SHARED via the > >> > dump_enumerator_list(), and then test it in the following function: > >> > >> Please see [1], I removed (1<<3) and resolved it at runtime. > >> dump_enumerator_list() is not appropriate, but I used > >> arg_to_datatype(). > > > > > > Can you try the enumerator_value()? Looks more appropriate. E.g: > > > > enumerator_value("BLK_MQ_F_TAG_HCTX_SHARED", &value); > > Sure, looks better. > > Please see v3: > https://www.mail-archive.com/[email protected]/msg01845.html > > Thanks, > Tao Liu > > > > > > > Thanks > > Lianbo > > > >> In dump_enumerator_list("BLK_MQ_F_TAG_HCTX_SHARED"), > >> > >> if (!arg_to_datatype(e, dm, RETURN_ON_ERROR) || > >> (dm->size < 0) || (dm->type != ENUM) || dm->tagname) > >> > >> dm->tagname is not NULL and will make dump_enumerator_list return false: > >> > >> (gdb) p dm > >> $1 = {name = 0xe4911b "BLK_MQ_F_TAG_HCTX_SHARED", member = 0x0, type = > >> 8192, size = 0, member_offset = 0, member_size = 0, > >> member_typecode = 0, flags = 0, tagname = 0xd41dfd "(unknown)", > >> value = 8, vaddr = 0} > >> > >> [1]: > >> https://www.mail-archive.com/[email protected]/msg01841.html > >> > >> > > >> > static bool blk_mq_is_shared_tags(unsigned int flags) > >> > { > >> > return flags & BLK_MQ_F_TAG_HCTX_SHARED; > >> > } > >> > > >> > That can follow the changes once the upstream kernel modifies the value. > >> > > >> >> blk_mq_is_shared_tags() check is not sufficient. This patch will add > >> >> 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. > >> > > >> > > >> > Anyway, this change looks good, so: Ack > >> > > >> > Lianbo > >> > > >> >> [1]: > >> >> https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-8/-/blob/c8s/include/linux/blk-mq.h?ref_type=heads#L321 > >> >> > >> >> Fixes: 62486400d35b ("Add blk_mq shared tags support for dev -d/-D") > >> >> Signed-off-by: Tao Liu <[email protected]> > >> >> --- > >> >> 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 > >> -- Crash-utility mailing list -- [email protected] To unsubscribe send an email to [email protected] https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ Contribution Guidelines: https://github.com/crash-utility/crash/wiki
