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Message-ID: <701bee9a-a06d-8b1a-bf23-d893249c7764@samsung.com>
Date:   Mon, 13 Jun 2022 14:08:21 +0200
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Subject: Re: [PATCH v4 3/3] squashfs: implement readahead
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To:     Phillip Lougher <phillip@squashfs.org.uk>,
        Hsin-Yi Wang <hsinyi@chromium.org>,
        Matthew Wilcox <willy@infradead.org>,
        Xiongwei Song <Xiongwei.Song@windriver.com>
Cc:     Zheng Liang <zhengliang6@huawei.com>,
        Zhang Yi <yi.zhang@huawei.com>, Hou Tao <houtao1@huawei.com>,
        Miao Xie <miaoxie@huawei.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "linux-mm @ kvack . org" <linux-mm@kvack.org>,
        "squashfs-devel @ lists . sourceforge . net" 
        <squashfs-devel@lists.sourceforge.net>,
        linux-kernel@vger.kernel.org
From:   Marek Szyprowski <m.szyprowski@samsung.com>
In-Reply-To: <31ed17e7-29d1-55e8-cb09-a750ab80da15@squashfs.org.uk>
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References: <20220601103922.1338320-1-hsinyi@chromium.org>
        <20220601103922.1338320-4-hsinyi@chromium.org>
        <CGME20220603125421eucas1p17da286a3e7f2d4759aa4c7639dd62f75@eucas1p1.samsung.com>
        <c017d992-2746-045b-47c8-c5b9c3025f1a@samsung.com>
        <31ed17e7-29d1-55e8-cb09-a750ab80da15@squashfs.org.uk>
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Hi Phillip,

On 07.06.2022 09:35, Phillip Lougher wrote:
> On 03/06/2022 13:54, Marek Szyprowski wrote:
>> Hi,
>>
>> On 01.06.2022 12:39, Hsin-Yi Wang wrote:
>>> Implement readahead callback for squashfs. It will read datablocks
>>> which cover pages in readahead request. For a few cases it will
>>> not mark page as uptodate, including:
>>> - file end is 0.
>>> - zero filled blocks.
>>> - current batch of pages isn't in the same datablock or not enough in a
>>>     datablock.
>>> - decompressor error.
>>> Otherwise pages will be marked as uptodate. The unhandled pages will be
>>> updated by readpage later.
>>>
>>> Suggested-by: Matthew Wilcox <willy@infradead.org>
>>> Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
>>> Reported-by: Matthew Wilcox <willy@infradead.org>
>>> Reported-by: Phillip Lougher <phillip@squashfs.org.uk>
>>> Reported-by: Xiongwei Song <Xiongwei.Song@windriver.com>
>>> ---
>>
>> This patch landed recently in linux-next as commit 95f7a26191de
>> ("squashfs: implement readahead"). I've noticed that it causes serious
>> issues on my test systems (various ARM 32bit and 64bit based boards).
>> The easiest way to observe is udev timeout 'waiting for /dev to be fully
>> populated' and prolonged booting time. I'm using squashfs for deploying
>> kernel modules via initrd. Reverting aeefca9dfae7 & 95f7a26191deon on
>> top of the next-20220603 fixes the issue.
>>
>> Let me know how I can help debugging this issue. There is no hurry
>> though, because the next week I will be on holidays.
>
> Hi Marek,
>
> Can you supply an example Squashfs filesystem and script that
> reproduces the slow-down?  Failing that, can you supply a copy
> of your initrd/root-filesystem that can be run under emulation
> to reproduce the issue? (I don't have any modern ARM embedded
> systems).
>
> Again failing that, are you happy to test some debug code?
>
> Thanks
>
> Phillip (Squashfs maintainer and author).

I've just got back from my holidays.

Is this still relevant? I've noticed that v6 has been posted, but I 
failed to apply it on top of next-20220610 as mentioned in the 
cover-letter to test. I've also tried also to apply the mentioned 
'Squashfs: handle missing pages decompressing into page cache' patchset. 
On the other hand, next-20220610 seems to be working fine on my setup now.


Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland