linux-kernel - Re: Re: [RFC PATCH] fuse: support cache revalidation in writeback

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Message-ID: <CAFQAk7ibzCn8OD84-nfg6_AePsKFTu9m7pXuQwcQP5OBp7ZCag@mail.gmail.com>
Date:   Mon, 25 Apr 2022 21:32:57 +0800
From:   Jiachen Zhang <zhangjiachen.jaycee@...edance.com>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xie Yongji <xieyongji@...edance.com>
Subject: Re: Re: [RFC PATCH] fuse: support cache revalidation in
 writeback_cache mode

On Mon, Apr 25, 2022 at 8:41 PM Miklos Szeredi <miklos@...redi.hu> wrote:
>
> On Fri, 25 Mar 2022 at 14:23, Jiachen Zhang
> <zhangjiachen.jaycee@...edance.com> wrote:
> >
> > Hi all,
> >
> > This RFC patch implements attr cache and data cache revalidation for
> > fuse writeback_cache mode in kernel. Looking forward to any suggestions
> > or comments on this feature.
>
> Quick question before going into the details:  could the cache
> revalidation be done in the userspace filesystem instead, which would
> set/clear FOPEN_KEEP_CACHE based on the result of the revalidation?
>
> Thanks,
> Miklos

Hi, Miklos,

Thanks for replying. Yes, I believe we can also perform the
revalidation in userspace, and we can invalidate the data cache with
FOPEN_KEEP_CACHE cleared. But for now, there is no way we can
invalidate attr cache (c/mtime and size)  in writeback mode.

If it is more concise to implement most of the logic in userspace, do
you think we should add a flag for attr cache just like what
FOPEN_KEEP_CACHE does for data cache?

Thanks,
Jiachen