linux-ext4 - Re: ext2/zram issue [was: Linux 5.19]

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Message-ID: <YvImxBsHJcpNzC+i@google.com>
Date:   Tue, 9 Aug 2022 18:20:04 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Jiri Slaby <jirislaby@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        minchan@...nel.org, ngupta@...are.org, Jan Kara <jack@...e.com>,
        Ted Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>,
        avromanov@...rdevices.ru, ddrokosov@...rdevices.ru,
        Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: ext2/zram issue [was: Linux 5.19]

On (22/08/09 18:11), Sergey Senozhatsky wrote:
> > > > /me needs to confirm.
> > > 
> > > With that commit reverted, I see no more I/O errors, only oom-killer
> > > messages (which is OK IMO, provided I write 1G of urandom on a machine w/
> > > 800M of RAM):
> > 
> > Hmm... So handle allocation always succeeds in the slow path? (when we
> > try to allocate it second time)
> 
> Yeah I can see how handle re-allocation with direct reclaim can make it more
> successful, but in exchange it oom-kills some user-space process, I suppose.
> Is oom-kill really a good alternative though?

We likely will need to revert e7be8d1dd983 given that it has some
user visible changes. But, honestly, failing zram write vs oom-kill
a user-space is a tough choice.