Hi lianbo,
Kindly ping for this patch...
Thanks,
Tao Liu
On Fri, Jun 27, 2025 at 11:33 PM Tao Liu <l...@redhat.com> wrote:
>
> When blk_mq shared tags enabled for devices like scsi, the IO status is
> incorrect, e.g:
>
> crash> dev -d
> MAJOR GENDISK NAME REQUEST_QUEUE TOTAL ASYNC SYNC
> 8 ffff90528df86000 sda ffff9052a3d61800 144 144 0
> 8 ffff905280718c00 sdb ffff9052a3d63c00 48 48 0
>
> crash> epython rqlist
> ffff90528e94a5c0 sda is unknown, deadline: 89.992 (90) rq_alloc:
> 0.196
> ffff90528e92f700 sda is unknown, deadline: 89.998 (90) rq_alloc:
> 0.202
> ffff90528e95ccc0 sda is unknown, deadline: 89.999 (90) rq_alloc:
> 0.203
> ffff90528e968bc0 sdb is unknown, deadline: 89.997 (90) rq_alloc:
> 0.201
>
> The root cause is: for shared tags case, only the shared tags are put
> into count. Without this patch, tags of all the hw_ctx are counted,
> which is incorrect.
>
> After apply the patch:
>
> crash> dev -d
> MAJOR GENDISK NAME REQUEST_QUEUE TOTAL READ WRITE
> 8 ffff90528df86000 sda ffff9052a3d61800 3 3 0
> 8 ffff905280718c00 sdb ffff9052a3d63c00 1 1 0
>
> This patch makes the following modification:
> 1) blk_mq shared tag support.
> 2) Function renaming: queue_for_each_hw_ctx -> blk_mq_queue_tag_busy_iter,
> because the latter is more close to the corresponding kernel function.
> 3) Extract a new queue_for_each_hw_ctx() function to be called for both
> shared-tags case and the hw_ctx case.
>
> Note:
> The patch is safe for earlier kernels which have no blk_mq shared tags
> implemented, because the blk_mq_is_shared_tags() check will exit safely.
>
> Signed-off-by: Tao Liu <l...@redhat.com>
> ---
>
> Please discard the previous patch "Filter repeated rq for cmd dev -d/-D",
> because filtering is an incorrect fix.
>
> ---
> defs.h | 3 ++
> dev.c | 96 ++++++++++++++++++++++++++++++++++++++-----------------
> symbols.c | 6 ++++
> 3 files changed, 76 insertions(+), 29 deletions(-)
>
> diff --git a/defs.h b/defs.h
> index bbd6d4b..4fecb83 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -2271,6 +2271,9 @@ struct offset_table { /* stash of
> commonly-used offsets */
> long task_struct_thread_context_x28;
> long neigh_table_hash_heads;
> long neighbour_hash;
> + long request_queue_tag_set;
> + long blk_mq_tag_set_flags;
> + long blk_mq_tag_set_shared_tags;
> };
>
> struct size_table { /* stash of commonly-used sizes */
> diff --git a/dev.c b/dev.c
> index 9d38aef..0a4d5c9 100644
> --- a/dev.c
> +++ b/dev.c
> @@ -4326,6 +4326,12 @@ struct bt_iter_data {
> #define MQ_RQ_IN_FLIGHT 1
> #define REQ_OP_BITS 8
> #define REQ_OP_MASK ((1 << REQ_OP_BITS) - 1)
> +#define BLK_MQ_F_TAG_HCTX_SHARED (1 << 3)
> +
> +static bool blk_mq_is_shared_tags(unsigned int flags)
> +{
> + return flags & BLK_MQ_F_TAG_HCTX_SHARED;
> +}
>
> static uint op_is_write(uint op)
> {
> @@ -4403,43 +4409,72 @@ static void bt_for_each(ulong q, ulong tags, ulong
> sbq, uint reserved, uint nr_r
> sbitmap_for_each_set(&sc, bt_iter, &iter_data);
> }
>
> -static void queue_for_each_hw_ctx(ulong q, ulong *hctx, uint cnt, struct
> diskio *dio)
> +static bool queue_for_each_hw_ctx(ulong q, ulong blk_mq_tags_ptr,
> + bool bitmap_tags_is_ptr, struct diskio *dio)
> {
> - uint i;
> + uint i, nr_reserved_tags = 0;
> + ulong tags = 0, addr = 0;
> + bool ret = FALSE;
> +
> + if (!readmem(blk_mq_tags_ptr, KVADDR, &tags, sizeof(ulong),
> + "blk_mq_hw_ctx.tags", RETURN_ON_ERROR))
> + goto out;
> +
> + addr = tags + OFFSET(blk_mq_tags_nr_reserved_tags);
> + if (!readmem(addr, KVADDR, &nr_reserved_tags, sizeof(uint),
> + "blk_mq_tags_nr_reserved_tags", RETURN_ON_ERROR))
> + goto out;
> +
> + if (nr_reserved_tags) {
> + addr = tags + OFFSET(blk_mq_tags_breserved_tags);
> + if (bitmap_tags_is_ptr &&
> + !readmem(addr, KVADDR, &addr, sizeof(ulong),
> + "blk_mq_tags.bitmap_tags", RETURN_ON_ERROR))
> + goto out;
> + bt_for_each(q, tags, addr, 1, nr_reserved_tags, dio);
> + }
> + addr = tags + OFFSET(blk_mq_tags_bitmap_tags);
> + if (bitmap_tags_is_ptr &&
> + !readmem(addr, KVADDR, &addr, sizeof(ulong),
> + "blk_mq_tags.bitmap_tags", RETURN_ON_ERROR))
> + goto out;
> + bt_for_each(q, tags, addr, 0, nr_reserved_tags, dio);
> +
> + ret = TRUE;
> +out:
> + return ret;
> +}
> +
> +/*
> + * Replica of kernel block/blk-mq-tag.c:blk_mq_queue_tag_busy_iter()
> +*/
> +static void blk_mq_queue_tag_busy_iter(ulong q, ulong *hctx, uint cnt,
> + struct diskio *dio)
> +{
> + uint i, flags;
> int bitmap_tags_is_ptr = 0;
> + ulong addr = 0;
>
> if (MEMBER_TYPE("blk_mq_tags", "bitmap_tags") == TYPE_CODE_PTR)
> bitmap_tags_is_ptr = 1;
>
> - for (i = 0; i < cnt; i++) {
> - ulong addr = 0, tags = 0;
> - uint nr_reserved_tags = 0;
> + readmem(q + OFFSET(request_queue_tag_set), KVADDR, &addr,
> + sizeof(ulong), "request_queue.tag_set", RETURN_ON_ERROR);
>
> - /* Tags owned by the block driver */
> - addr = hctx[i] + OFFSET(blk_mq_hw_ctx_tags);
> - if (!readmem(addr, KVADDR, &tags, sizeof(ulong),
> - "blk_mq_hw_ctx.tags", RETURN_ON_ERROR))
> - break;
> + readmem(addr + OFFSET(blk_mq_tag_set_flags), KVADDR,
> + &flags, sizeof(uint), "blk_mq_tag_set.flags",
> RETURN_ON_ERROR);
>
> - addr = tags + OFFSET(blk_mq_tags_nr_reserved_tags);
> - if (!readmem(addr, KVADDR, &nr_reserved_tags, sizeof(uint),
> - "blk_mq_tags_nr_reserved_tags",
> RETURN_ON_ERROR))
> - break;
> + if (blk_mq_is_shared_tags(flags)) {
> + addr = addr + OFFSET(blk_mq_tag_set_shared_tags);
> + queue_for_each_hw_ctx(q, addr, bitmap_tags_is_ptr, dio);
> + return;
> + }
>
> - if (nr_reserved_tags) {
> - addr = tags + OFFSET(blk_mq_tags_breserved_tags);
> - if (bitmap_tags_is_ptr &&
> - !readmem(addr, KVADDR, &addr, sizeof(ulong),
> - "blk_mq_tags.bitmap_tags",
> RETURN_ON_ERROR))
> - break;
> - bt_for_each(q, tags, addr, 1, nr_reserved_tags, dio);
> - }
> - addr = tags + OFFSET(blk_mq_tags_bitmap_tags);
> - if (bitmap_tags_is_ptr &&
> - !readmem(addr, KVADDR, &addr, sizeof(ulong),
> - "blk_mq_tags.bitmap_tags", RETURN_ON_ERROR))
> - break;
> - bt_for_each(q, tags, addr, 0, nr_reserved_tags, dio);
> + for (i = 0; i < cnt; i++) {
> + /* Tags owned by the block driver */
> + addr = hctx[i] + OFFSET(blk_mq_hw_ctx_tags);
> + if (queue_for_each_hw_ctx(q, addr, bitmap_tags_is_ptr, dio)
> == FALSE)
> + return;
> }
> }
>
> @@ -4489,7 +4524,7 @@ static void get_mq_diskio_from_hw_queues(ulong q,
> struct diskio *dio)
> return;
> }
>
> - queue_for_each_hw_ctx(q, hctx_array, cnt, dio);
> + blk_mq_queue_tag_busy_iter(q, hctx_array, cnt, dio);
>
> FREEBUF(hctx_array);
> }
> @@ -4914,6 +4949,9 @@ void diskio_init(void)
> MEMBER_SIZE_INIT(class_private_devices, "class_private",
> "class_devices");
> MEMBER_OFFSET_INIT(disk_stats_in_flight, "disk_stats", "in_flight");
> + MEMBER_OFFSET_INIT(request_queue_tag_set, "request_queue", "tag_set");
> + MEMBER_OFFSET_INIT(blk_mq_tag_set_flags, "blk_mq_tag_set", "flags");
> + MEMBER_OFFSET_INIT(blk_mq_tag_set_shared_tags, "blk_mq_tag_set",
> "shared_tags");
>
> dt->flags |= DISKIO_INIT;
> }
> diff --git a/symbols.c b/symbols.c
> index e30fafe..794519a 100644
> --- a/symbols.c
> +++ b/symbols.c
> @@ -11487,6 +11487,12 @@ dump_offset_table(char *spec, ulong makestruct)
> OFFSET(blk_mq_tags_nr_reserved_tags));
> fprintf(fp, " blk_mq_tags_rqs: %ld\n",
> OFFSET(blk_mq_tags_rqs));
> + fprintf(fp, " request_queue_tag_set: %ld\n",
> + OFFSET(request_queue_tag_set));
> + fprintf(fp, " blk_mq_tag_set_flags: %ld\n",
> + OFFSET(blk_mq_tag_set_flags));
> + fprintf(fp, " blk_mq_tag_set_shared_tags: %ld\n",
> + OFFSET(blk_mq_tag_set_shared_tags));
>
> fprintf(fp, " subsys_private_subsys: %ld\n",
> OFFSET(subsys_private_subsys));
> fprintf(fp, " subsys_private_klist_devices: %ld\n",
> --
> 2.47.0
>
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