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

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Date:   Mon, 2 Oct 2017 23:55:23 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     mhocko@...nel.org, pavel@....cz
Cc:     linux-kernel@...r.kernel.org, adrian.hunter@...el.com,
        linux-mmc@...r.kernel.org, linux-mm@...ck.org
Subject: Re: 4.14-rc2 on thinkpad x220: out of memory when inserting mmc card

Michal Hocko wrote:
> On Sun 01-10-17 12:26:47, Pavel Machek wrote:
> > Hi!
> > 
> > > 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.
> 
> Well, I cannot comment on why MMC needs such a large allocation and
> whether it can safely fall back to vmalloc but __GFP_RETRY_MAYFAIL
> might help to try harder and require compaction to do more work.
> Relying on that for correctness is, of course, a different story and
> a very unreliable under memory pressure or long term fragmented memory.

Linus Walleij answered that kvmalloc() is against the design of the bounce buffer at
http://lkml.kernel.org/r/CACRpkdYirC+rh_KALgVqKZMjq2DgbW4oi9MJkmrzwn+1O+94-g@mail.gmail.com .