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Date:   Fri, 3 Jun 2022 13:59:09 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Marek Szyprowski <m.szyprowski@samsung.com>
Cc:     Hsin-Yi Wang <hsinyi@chromium.org>,
        Phillip Lougher <phillip@squashfs.org.uk>,
        Xiongwei Song <Xiongwei.Song@windriver.com>,
        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
Subject: Re: [PATCH v4 3/3] squashfs: implement readahead
Message-ID: <YpoFnROxAwdSScuV@casper.infradead.org>
References: <20220601103922.1338320-1-hsinyi@chromium.org>
 <20220601103922.1338320-4-hsinyi@chromium.org>
 <CGME20220603125421eucas1p17da286a3e7f2d4759aa4c7639dd62f75@eucas1p1.samsung.com>
 <c017d992-2746-045b-47c8-c5b9c3025f1a@samsung.com>
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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@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.

How large are these files?  Just a few kilobytes?