linux-kernel - Re: [PATCH v4 3/3] squashfs: implement readahead

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Message-ID: <CAJMQK-hVT=TcVfsbhUiqxcTBz3ZrX=B7yBPbuc2=MD6i7iGkAw@mail.gmail.com>
Date:   Mon, 13 Jun 2022 21:45:34 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Phillip Lougher <phillip@...ashfs.org.uk>,
        Matthew Wilcox <willy@...radead.org>,
        Xiongwei Song <Xiongwei.Song@...driver.com>,
        Zheng Liang <zhengliang6@...wei.com>,
        Zhang Yi <yi.zhang@...wei.com>, Hou Tao <houtao1@...wei.com>,
        Miao Xie <miaoxie@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-mm @ kvack . org" <linux-mm@...ck.org>,
        "squashfs-devel @ lists . sourceforge . net" 
        <squashfs-devel@...ts.sourceforge.net>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/3] squashfs: implement readahead

On Mon, Jun 13, 2022 at 8:08 PM Marek Szyprowski
<m.szyprowski@...sung.com> wrote:
>
> 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@...radead.org>
> >>> Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> >>> Reported-by: Matthew Wilcox <willy@...radead.org>
> >>> Reported-by: Phillip Lougher <phillip@...ashfs.org.uk>
> >>> Reported-by: Xiongwei Song <Xiongwei.Song@...driver.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.
>

hi Marek,

next-20220610 contains v5 of the series. To apply v6, you need to
revert ca1505bf4805 ("squashfs: implement readahead") and 9d58b94aa73a
("squashfs: always build "file direct" version of page actor") first,
then apply  'Squashfs: handle missing pages decompressing into page
cache' patchset, then finally apply v6, since v6 is dependent on the
patchset.

Thanks.

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