* Ocassional dropping of uevent of loop device (possible race)
@ 2020-10-27 18:49 Petr Vorel
2020-10-27 19:25 ` Cyril Hrubis
0 siblings, 1 reply; 2+ messages in thread
From: Petr Vorel @ 2020-10-27 18:49 UTC (permalink / raw)
To: linux-block
Cc: Martijn Coenen, Christoph Hellwig, Jens Axboe, ltp, Cyril Hrubis
Hi
commit 716ad0986cbd ("loop: Switch to set_capacity_revalidate_and_notify()")
from v5.8-rc1 caused occasional dropping of uevent of attached or detached loop
device (not sure which one). The only difference is that
set_capacity_revalidate_and_notify() has condition:
if (capacity != size && capacity != 0 && size != 0)
thus notification is not triggered here but in a different part of code.
It was found with LTP test uevent01 [1]:
# i=0; while true; do i=$((i+1)); echo "== $i =="; rmmod -f loop; ./uevent01 || break; done
It looks to be a race. Usually ~ 10 loops is enough.
Kind regards,
Petr
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* Re: Ocassional dropping of uevent of loop device (possible race)
2020-10-27 18:49 Ocassional dropping of uevent of loop device (possible race) Petr Vorel
@ 2020-10-27 19:25 ` Cyril Hrubis
0 siblings, 0 replies; 2+ messages in thread
From: Cyril Hrubis @ 2020-10-27 19:25 UTC (permalink / raw)
To: Petr Vorel
Cc: linux-block, Martijn Coenen, Christoph Hellwig, Jens Axboe, ltp
Hi!
> commit 716ad0986cbd ("loop: Switch to set_capacity_revalidate_and_notify()")
> from v5.8-rc1 caused occasional dropping of uevent of attached or detached loop
> device (not sure which one). The only difference is that
> set_capacity_revalidate_and_notify() has condition:
> if (capacity != size && capacity != 0 && size != 0)
> thus notification is not triggered here but in a different part of code.
>
> It was found with LTP test uevent01 [1]:
>
> # i=0; while true; do i=$((i+1)); echo "== $i =="; rmmod -f loop; ./uevent01 || break; done
>
> It looks to be a race. Usually ~ 10 loops is enough.
Looks like the link to test source is missing and should have been:
[1] https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/uevents/uevent01.c
--
Cyril Hrubis
chrubis@suse.cz
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2020-10-27 18:49 Ocassional dropping of uevent of loop device (possible race) Petr Vorel
2020-10-27 19:25 ` Cyril Hrubis
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