linux-kernel - Re: [PATCH] erofs: fix missing xas

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Message-ID: <55b07140-f7b9-6c25-acf0-93e9fbce0828@linux.alibaba.com>
Date:   Mon, 14 Nov 2022 20:11:39 +0800
From:   Jingbo Xu <jefflexu@...ux.alibaba.com>
To:     David Howells <dhowells@...hat.com>
Cc:     xiang@...nel.org, chao@...nel.org, yinxin.x@...edance.com,
        linux-erofs@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] erofs: fix missing xas_retry() in fscache mode

Hi David,

Thanks for the comment.

On 11/14/22 7:44 PM, David Howells wrote:
> Jingbo Xu <jefflexu@...ux.alibaba.com> wrote:
> 
>> The xarray iteration only holds RCU
> 
> I would say "the RCU read lock".

Yeah, this looks clearer. I will update the commit message in v2 later.

> 
> Also, I think you've copied the code to which my dodgy-maths fix applies:
> 
> 	https://lore.kernel.org/linux-fsdevel/166757988611.950645.7626959069846893164.stgit@warthog.procyon.org.uk/
> 

Thanks for the kindly reminder. Yeah this code was ever copied from
libnetfs. In the scenario of erofs, currently req->start is always
aligned with folio size and erofs doesn't support large folio yet. Thus
req->start won't be inside the folio so far, and I think the current
code works well in the scenario of erofs, though the issue indeed exist
mathematically.

Actually I'm working on the support for large folio now, and the
completion routine of erofs in fscache mode will be refactored quite a
lot. I think this issue will be fixed along with the refactoring.

Thanks again for the suggestion :)

-- 
Thanks,
Jingbo