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

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Date:   Fri, 3 Jun 2022 22:55:01 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Phillip Lougher <phillip@...ashfs.org.uk>,
        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 Fri, Jun 3, 2022 at 10:10 PM Marek Szyprowski
<m.szyprowski@...sung.com> wrote:
>
> Hi Matthew,
>
> On 03.06.2022 14:59, Matthew Wilcox wrote:
> > On Fri, Jun 03, 2022 at 02:54:21PM +0200, Marek Szyprowski wrote:
> >> 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.
> > How large are these files?  Just a few kilobytes?
>
> Yes, they are small, most of them are smaller than 16KB, some about
> 128KB and a few about 256KB. I've sent a detailed list in private mail.
>

Hi Marek,

Are there any obvious squashfs errors in dmesg? Did you enable
CONFIG_SQUASHFS_FILE_DIRECT or CONFIG_SQUASHFS_FILE_CACHE?

Thanks

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