linux-kernel - Re: [PATCH] f2fs: limit # of inmemory pages

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Date:   Thu, 19 Oct 2017 00:28:04 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH] f2fs: limit # of inmemory pages

On Wed, Oct 18, 2017 at 07:15:16PM -0700, Jaegeuk Kim wrote:
> If some abnormal users try lots of atomic write operations, f2fs is able to
> produce pinned pages in the main memory which affects system performance.
> This patch limits that as 20% over total memory size, and if f2fs reaches
> to the limit, it will drop all the inmemory pages.

Can you please document your "atomic" writes and how they pin memory
in a mail to linux-abi?  And how they compare to my O_ATOMIC implement
as well as the papers it is based on?

I tried to take a quick look at the code and it looks very bogus to me
in addition to being sneaked in through fs-specific ioctls without any
review whatsoever.