Please ignore the patch, filtering is incorrect. See "Add blk_mq
shared tags support for dev -d/-D" patch for the fix.
On Thu, Jun 26, 2025 at 12:16 PM Tao Liu <l...@redhat.com> wrote:
>
> CEE reported an issue that "dev -d/-D" reports incorrect value
> of read/write:
>
> 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 value of 144 ASYNC is incorrect and epython rqlist only show 3 items for
> sda.
> The reason is, mq_check_inflight() may get the same rq multiple times during
> iteration, so they are counted repeatly.
>
> This patch will add a rq repetition check. 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
>
> Signed-off-by: Tao Liu <l...@redhat.com>
> ---
> dev.c | 43 ++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 40 insertions(+), 3 deletions(-)
>
> diff --git a/dev.c b/dev.c
> index 9d38aef..b0434cf 100644
> --- a/dev.c
> +++ b/dev.c
> @@ -4316,6 +4316,9 @@ struct bt_iter_data {
> ulong tags;
> uint reserved;
> uint nr_reserved_tags;
> + ulong **rq_list;
> + int *rq_list_len;
> + int *rq_list_cap;
> busy_tag_iter_fn *fn;
> void *data;
> };
> @@ -4381,10 +4384,30 @@ static bool bt_iter(uint bitnr, void *data)
> if (!readmem(addr, KVADDR, &rq, sizeof(ulong), "blk_mq_tags.rqs[]",
> RETURN_ON_ERROR))
> return FALSE;
>
> + for (int i = 0; i < *iter_data->rq_list_len; i++) {
> + /* Skip the handled rq */
> + if ((*iter_data->rq_list)[i] == rq)
> + return TRUE;
> + }
> + /* Mark the rq is handled */
> + (*iter_data->rq_list)[(*iter_data->rq_list_len)++] = rq;
> + if (*iter_data->rq_list_len > *iter_data->rq_list_cap / 2) {
> + *iter_data->rq_list_cap <<= 1;
> + ulong *tmp = reallocarray(*iter_data->rq_list,
> + *iter_data->rq_list_cap,
> sizeof(ulong));
> + if (!tmp) {
> + free(*iter_data->rq_list);
> + error(FATAL, "cannot reallocarray rq_list array");
> + }
> + *iter_data->rq_list = tmp;
> + }
> +
> return iter_data->fn(rq, iter_data->data);
> }
>
> -static void bt_for_each(ulong q, ulong tags, ulong sbq, uint reserved, uint
> nr_resvd_tags, struct diskio *dio)
> +static void bt_for_each(ulong q, ulong tags, ulong sbq, uint reserved,
> + uint nr_resvd_tags, ulong **rq_list, int *rq_list_len,
> + int *rq_list_cap, struct diskio *dio)
> {
> struct sbitmap_context sc = {0};
> struct mq_inflight mi = {
> @@ -4395,6 +4418,9 @@ static void bt_for_each(ulong q, ulong tags, ulong sbq,
> uint reserved, uint nr_r
> .tags = tags,
> .reserved = reserved,
> .nr_reserved_tags = nr_resvd_tags,
> + .rq_list = rq_list,
> + .rq_list_len = rq_list_len,
> + .rq_list_cap = rq_list_cap,
> .fn = mq_check_inflight,
> .data = &mi,
> };
> @@ -4407,10 +4433,18 @@ static void queue_for_each_hw_ctx(ulong q, ulong
> *hctx, uint cnt, struct diskio
> {
> uint i;
> int bitmap_tags_is_ptr = 0;
> + ulong *rq_list;
> + int rq_list_len = 0;
> + int rq_list_cap = 1;
>
> if (MEMBER_TYPE("blk_mq_tags", "bitmap_tags") == TYPE_CODE_PTR)
> bitmap_tags_is_ptr = 1;
>
> + rq_list = calloc(rq_list_cap, sizeof(ulong));
> + if (!rq_list) {
> + error(FATAL, "cannot malloc rq_list array");
> + }
> +
> for (i = 0; i < cnt; i++) {
> ulong addr = 0, tags = 0;
> uint nr_reserved_tags = 0;
> @@ -4432,15 +4466,18 @@ static void queue_for_each_hw_ctx(ulong q, ulong
> *hctx, uint cnt, struct diskio
> !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);
> + bt_for_each(q, tags, addr, 1, nr_reserved_tags,
> &rq_list,
> + &rq_list_len, &rq_list_cap, 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);
> + bt_for_each(q, tags, addr, 1, nr_reserved_tags, &rq_list,
> + &rq_list_len, &rq_list_cap, dio);
> }
> + free(rq_list);
> }
>
> static void get_mq_diskio_from_hw_queues(ulong q, struct diskio *dio)
> --
> 2.47.0
>
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