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Date: Mon, 19 Jan 2026 08:29:32 +0100
From: Christoph Hellwig <hch@lst.de>
To: Gao Xiang <hsiangkao@linux.alibaba.com>
Cc: Christoph Hellwig <hch@lst.de>, Hongbo Li <lihongbo22@huawei.com>,
	chao@kernel.org, brauner@kernel.org, djwong@kernel.org,
	amir73il@gmail.com, linux-fsdevel@vger.kernel.org,
	linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v15 5/9] erofs: introduce the page cache share feature
Message-ID: <20260119072932.GB2562@lst.de>
References: <20260116095550.627082-1-lihongbo22@huawei.com> <20260116095550.627082-6-lihongbo22@huawei.com> <20260116154623.GC21174@lst.de> <af1f3ff6-a163-4515-92bf-44c9cf6c92f3@linux.alibaba.com>
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On Sat, Jan 17, 2026 at 12:21:16AM +0800, Gao Xiang wrote:
> Hi Christoph,
>
> On 2026/1/16 23:46, Christoph Hellwig wrote:
>> I don't really understand the fingerprint idea.  Files with the
>> same content will point to the same physical disk blocks, so that
>> should be a much better indicator than a finger print?  Also how does
>
> Page cache sharing should apply to different EROFS
> filesystem images on the same machine too, so the
> physical disk block number idea cannot be applied
> to this.

Oh.  That's kinda unexpected and adds another twist to the whole scheme.
So in that case the on-disk data actually is duplicated in each image
and then de-duplicated in memory only?  Ewwww...