Re: [PATCH RFC] btrfs: get rid of btrfs_(alloc|free)_compr_folio()

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

在 2026/3/6 04:16, Boris Burkov 写道:
[...]
>> So I stand by the reason of the pool but with the evolution of folios
>> and bs < ps the cost could be too high. I can still see the pool for a
>> subset of the combinations for some common scenario like 4K block size
>> on 64K page host (e.g. ARM).
>>
> 
> FWIW, we do already see issues with allocation in compressed IO in
> production, so I am hesitant to support this change.

May I ask how frequent the problem is, and what's the CPU arch?
Finally is it only happening after commit 6f706f34fc4c ("btrfs: switch 
to btrfs_compress_bio() interface for compressed writes"), aka v7.0 kernel.

I tried my best locally to introduce extra ASSERT()s to make sure every 
folio inside a compressed bio has a ref of 1, but it hasn't yet 
triggered inside zlib_compress_bio().

Thanks,
Qu

> 
> On the one hand, we have the issues so the pool is not completely saving
> us anyway. On the other hand, removing it seems likely to make this worse
> in the way that you predict, Dave.
> 
> If we do move forward with this, I will try to watch such errors closely
> on the first release of a kernel without the pool.
> 
> Thanks,
> Boris
> 
>>> And hopefully this will address David's recent crash (as usual I'm not
>>> able to reproduce locally).
>>
>> I'll run the test with this patch.
>