linux-kernel - Re: [PATCH] f2fs: set deadline to drop expired inmem pages

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Message-ID: <20180413010433.GB51348@jaegeuk-macbookpro.roam.corp.google.com>
Date:   Thu, 12 Apr 2018 18:04:33 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH] f2fs: set deadline to drop expired inmem pages

On 04/10, Chao Yu wrote:
> Hi Jaegeuk,
> 
> On 2018/4/8 16:13, Chao Yu wrote:
> > f2fs doesn't allow abuse on atomic write class interface, so except
> > limiting in-mem pages' total memory usage capacity, we need to limit
> > start-commit time as well, otherwise we may run into infinite loop
> > during foreground GC because target blocks in victim segment are
> > belong to atomic opened file for long time.
> > 
> > Now, we will check the condition with f2fs_balance_fs_bg in
> > background threads, once if user doesn't commit data exceeding 30
> > seconds, we will drop all cached data, so I expect it can keep our
> > system running safely to prevent Dos attack.
> 
> Is it worth to add this patch to avoid abuse on atomic write interface by user?

Hmm, hope to see a real problem first in this case.

> Thanks,