On 19/02/2021 06:22, pragalla@codeaurora.org wrote:

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Hi John,

we ran the stability with the above patch
(https://lore.kernel.org/linux-block/1608203273-170555-2-git-send-email-john.garry@huawei.com/ (local)) 

with switching the io-schedulers in b/w for ~88hrs on 2 devices, we 
didn't notice any crash/issue.

Oh, good. I assume that this is same test which you were reporting 
crashes on previously.

So we still have the issue of changing IO scheduler and the tagset iters 
holding old references to tags. I tried Bart's idea to deal with the 
request queue tagset iter, and it seems to work, but not sure if 
acceptable. And also I might have a solution for blk_mq_tagset_busy_iter().

However I am not sure if these are seen in real-life, and whether the 
patch you tested is good enough for now.

Let me look at this again and I will report back.

Thanks very much,
John

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Do you have a full kernel log for your crash?