linux-kernel - Re: 4.14-rc2 on thinkpad x220: out of memory when inserting mmc card

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Date:   Tue, 3 Oct 2017 09:30:18 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Pavel Machek <pavel@....cz>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        linux-mm@...ck.org
Subject: Re: 4.14-rc2 on thinkpad x220: out of memory when inserting mmc card

On 02/10/17 17:09, Linus Walleij wrote:
> On Sun, Oct 1, 2017 at 12:57 PM, Tetsuo Handa
> <penguin-kernel@...ove.sakura.ne.jp> wrote:
> 
>>>> I inserted u-SD card, only to realize that it is not detected as it
>>>> should be. And dmesg indeed reveals:
>>>
>>> Tetsuo asked me to report this to linux-mm.
>>>
>>> But 2^4 is 16 pages, IIRC that can't be expected to work reliably, and
>>> thus this sounds like MMC bug, not mm bug.
> 
> 
> I'm not sure I fully understand this error message:
> "worker/2:1: page allocation failure: order:4"
> 
> What I guess from context is that the mmc_init_request()
> call is failing to allocate 16 pages, meaning for 4K pages
> 64KB which is the typical bounce buffer.
> 
> This is what the code has always allocated as bounce buffer,
> but it used to happen upfront, when probing the MMC block layer,
> rather than when allocating the requests.

That is not exactly right.  As I already wrote, the memory allocation used
to be optional but became mandatory with:

  commit 304419d8a7e9204c5d19b704467b814df8c8f5b1
  Author: Linus Walleij <linus.walleij@...aro.org>
  Date:   Thu May 18 11:29:32 2017 +0200

      mmc: core: Allocate per-request data using the block layer core