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SubjectRe: [PATCH 2/2] block: hold queue lock while iterating in diskstats_show
On Thu, Jan 20, 2022 at 03:01:26PM +0100, Daniel Wagner wrote:
> On Thu, Jan 20, 2022 at 09:51:18PM +0800, Ming Lei wrote:
> > Then Can you figure out where blk_mq_queue_tag_busy_iter+0x1e4 points to
> > in source code? And what is NULL pointer?
>
> Here we go:
>
> /usr/src/debug/kernel-default-5.3.18-59.27.1.x86_64/linux-5.3/linux-obj/../include/linux/sbitmap.h: 249
> 0xffffffffb244a254 <blk_mq_queue_tag_busy_iter+484>: mov (%rax),%rdx
>
> 234static inline void __sbitmap_for_each_set(struct sbitmap *sb,
> 235 unsigned int start,
> 236 sb_for_each_fn fn, void *data)
> 237{
> 238 unsigned int index;
> 239 unsigned int nr;
> 240 unsigned int scanned = 0;
> 241
> 242 if (start >= sb->depth)
> 243 start = 0;
> 244 index = SB_NR_TO_INDEX(sb, start);
> 245 nr = SB_NR_TO_BIT(sb, start);
> 246
> 247 while (scanned < sb->depth) {
> 248 unsigned long word;
> 249 unsigned int depth = min_t(unsigned int,
> 250 sb->map[index].depth - nr,
> 251 sb->depth - scanned);
>

Seems more likely nvme recovery issue, tags is changed even though
->q_usage_counter is grabbed in blk_mq_queue_tag_busy_iter(), which is
added in v4.19.

You may check dmesg log and see if there is any nvme error recovery info.

Thanks,
Ming

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