Messages in this thread | | | Date | Fri, 9 Aug 2019 07:30:00 -0400 (EDT) | From | Mikulas Patocka <> | Subject | Re: [PATCH] direct-io: use GFP_NOIO to avoid deadlock |
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On Fri, 9 Aug 2019, Dave Chinner wrote:
> And, FWIW, there's an argument to be made here that the underlying > bug is dm_bufio_shrink_scan() blocking kswapd by waiting on IO > completions while holding a mutex that other IO-level reclaim > contexts require to make progress. > > Cheers, > > Dave.
The IO-level reclaim contexts should use GFP_NOIO. If the dm-bufio shrinker is called with GFP_NOIO, it cannot be blocked by kswapd, because: * it uses trylock to acquire the mutex * it doesn't attempt to free buffers that are dirty or under I/O (see __try_evict_buffer)
I think that this logic is sufficient to prevent the deadlock.
Mikulas
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