linux-kernel - Re: [RFC 0/2] erofs: introduce bloom filter for xattr

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Message-ID: <c630bb18-2a50-13ed-f100-c4e40860e04b@linux.alibaba.com>
Date:   Tue, 4 Jul 2023 17:15:14 +0800
From:   Gao Xiang <hsiangkao@...ux.alibaba.com>
To:     Alexander Larsson <alexl@...hat.com>,
        Jingbo Xu <jefflexu@...ux.alibaba.com>
Cc:     chao@...nel.org, huyue2@...lpad.com, linux-erofs@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC 0/2] erofs: introduce bloom filter for xattr



On 2023/7/4 16:05, Alexander Larsson wrote:
> On Tue, Jul 4, 2023 at 7:56 AM Jingbo Xu <jefflexu@...ux.alibaba.com> wrote:
>>
>>

...

>> ```
>> seed: 25bbe08f
>> bit 31: trusted.overlay.metacopy, user.overlay.metacopy,
>>
>> seed: cc922efd
>> bit  3: trusted.overlay.opaque, user.overlay.opaque,
>>
>> seed: cd478c17
>> bit  6: trusted.overlay.metacopy, user.overlay.metacopy,
>> ```
>>
>>
>> Any other idea?
> 
> Any of these three is good to me. I don't have any ideas directly
> related to this. However,  semi-related, it would be really cool if
> fuse supported the same approach for xattr lookup. I.e. if lookup
> could add a bloom filter value as part of the inode data, then we
> could avoid a kernel<->fusefs-d transition for negative xattrs
> lookups.

I think we could just use a hardcoded magic number (e.g. 25bbe08f)
as a start first, since it seems already fulfill our requirement
and it's a compatible feature (and the implementation is also not
complex.)  So I'm not quite worried about this.

Thanks,
Gao Xiang

>