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

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Message-ID: <YpoFnROxAwdSScuV@casper.infradead.org>
Date:   Fri, 3 Jun 2022 13:59:09 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Hsin-Yi Wang <hsinyi@...omium.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 03, 2022 at 02:54:21PM +0200, 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.

How large are these files?  Just a few kilobytes?