linux-kernel - Re: [RFC PATCHv5 0/6] zram: introduce writeback bio batching

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Message-ID: <d3c01e18-c556-4892-8283-08765c5e6cb9@linux.alibaba.com>
Date: Sun, 23 Nov 2025 09:23:31 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: Yuwen Chen <ywen.chen@...mail.com>, akpm@...ux-foundation.org,
 bgeffon@...gle.com, licayy@...look.com, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org, minchan@...nel.org,
 richardycc@...gle.com
Subject: Re: [RFC PATCHv5 0/6] zram: introduce writeback bio batching



On 2025/11/23 08:08, Sergey Senozhatsky wrote:
> On (25/11/22 22:09), Gao Xiang wrote:
>>> I thought you were talking about the backing device being
>>> ext4/btrfs.  Sorry, I don't have enough context/knowledge
>>> to understand what you're getting at.  zram has been doing
>>> writeback for ages, I really don't know what you mean by
>>> "to act like this".
>>
>> I mean, if zram is formatted as ext4, and then mount it;
>> and then there is a backing file which is also in another
>> ext4, you'd need a workqueue to do writeback I/Os (or needs
>> a loop device to transit), was that the original question
>> raised by Yuwen?
> 
> We take pages of data from zram0 and write them straight to
> the backing device.  Those writes don't go through vfs/fs so
> fs on the backing device will simply be corrupted, as far as
> I can tell.  This is not intendant use case for zram writeback.

I'm pretty sure you don't understand what I meant.

I won't reply this anymore, good luck.

Thanks,
Gao Xiang