linux-kernel - Re: [RFC PATCH v3 0/4] Support large folios for tmpfs

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Message-ID: <Zw_IT136rxW_KuhU@casper.infradead.org>
Date: Wed, 16 Oct 2024 15:06:07 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: akpm@...ux-foundation.org, hughd@...gle.com, david@...hat.com,
	wangkefeng.wang@...wei.com, 21cnbao@...il.com, ryan.roberts@....com,
	ioworker0@...il.com, da.gomez@...sung.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v3 0/4] Support large folios for tmpfs

On Thu, Oct 10, 2024 at 05:58:10PM +0800, Baolin Wang wrote:
> Considering that tmpfs already has the 'huge=' option to control the THP
> allocation, it is necessary to maintain compatibility with the 'huge='
> option, as well as considering the 'deny' and 'force' option controlled
> by '/sys/kernel/mm/transparent_hugepage/shmem_enabled'.

No, it's not.  No other filesystem honours these settings.  tmpfs would
not have had these settings if it were written today.  It should simply
ignore them, the way that NFS ignores the "intr" mount option now that
we have a better solution to the original problem.

To reiterate my position:

 - When using tmpfs as a filesystem, it should behave like other
   filesystems.
 - When using tmpfs to implement MAP_ANONYMOUS | MAP_SHARED, it should
   behave like anonymous memory.

No more special mount options.