linux-kernel - Re: [PATCH] zram_drv: add __GFP_NOWARN flag on call to zs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YkQPefdRc+hxIXEV@dhcp22.suse.cz>
Date:   Wed, 30 Mar 2022 10:06:17 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Jaewon Kim <jaewon31.kim@...sung.com>
Cc:     minchan@...nel.org, ngupta@...are.org, senozhatsky@...omium.org,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, s.suk@...sung.com,
        jaewon31.kim@...il.com
Subject: Re: [PATCH] zram_drv: add __GFP_NOWARN flag on call to zs_malloc

On Wed 30-03-22 14:25:02, Jaewon Kim wrote:
> The page allocation with GFP_NOIO may fail. And zram can handle this
> allocation failure. We do not need to print log for this.

GFP_NOIO doesn't have any special meaning wrt to failures. zram
allocates from the memory reclaim context which is a bad design IMHO.
The failure you are seeing indicates that PF_MEMALLOC context (memory
reclaim) which is allow to dip into memory reserves without any limit
cannot find any memory! This is really bad and it is good to learn about
that.

Your description doesn't really explain why we should be ignoring that
situation. Is the memory allocation failure gracefully recoverable?

-- 
Michal Hocko
SUSE Labs