linux-kernel - Re: [PATCH] erofs: leave compressed inodes unsupported in fscache mode for now

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Message-ID: <Yo332UXnrZ+HVQZ7@B-P7TQMD6M-0146.local>
Date:   Wed, 25 May 2022 17:33:13 +0800
From:   Gao Xiang <hsiangkao@...ux.alibaba.com>
To:     Jeffle Xu <jefflexu@...ux.alibaba.com>
Cc:     xiang@...nel.org, chao@...nel.org, linux-erofs@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] erofs: leave compressed inodes unsupported in fscache
 mode for now

Hi Jeffle,

On Wed, May 25, 2022 at 03:59:50PM +0800, Jeffle Xu wrote:
> erofs over fscache doesn't support the compressed layout yet. It will
> cause NULL crash if there are compressed inodes contained when working
> in fscache mode.
> 
> So far in the erofs based container image distribution scenarios
> (RAFS v6), the compressed images are downloaded to local and then

... the compressed RAFS v6 images are downloaded and then decompressed
on demand as an uncompressed erofs image.

> decompressed as a erofs image of uncompressed layout. Then the erofs
> image is mounted in fscache mode and serves as the container image. Thus

... in fscache mode for containers to use. IOWs

> the current implementation won't break the container image distribution
> scenarios.

IOWs, currently compressed data is decompressed on the userspace side
instead and uncompressed erofs images will be finally cached.

> 
> The fscache support for the compressed layout is still under
> development. Anyway, to avoid the potential crash, let's leave the

The fscache support for the compressed layout is still under
development and it will be used for runtime decompression feature.
Anyway..

> compressed inodes unsupported in fscache mode until we support it later.
> 
> Fixes: 1442b02b66ad ("erofs: implement fscache-based data read for non-inline layout")

Otherwise looks good to me,

Reviewed-by: Gao Xiang <hsiangkao@...ux.alibaba.com>

Thanks,
Gao Xiang