linux-kernel - Re: [PATCH] drop caches: skip tmpfs and ramfs

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Message-ID: <YrbTMJAuwY59CwRS@infradead.org>
Date:   Sat, 25 Jun 2022 02:19:44 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     cgel.zte@...il.com
Cc:     viro@...iv.linux.org.uk, hughd@...gle.com, ran.xiaokai@....com.cn,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH] drop caches: skip tmpfs and ramfs

On Fri, Jun 24, 2022 at 06:21:21PM +0000, cgel.zte@...il.com wrote:
> From: Ran Xiaokai <ran.xiaokai@....com.cn>
> 
> All tmpfs and ramfs pages have PG_dirty bit set
> once they are allocated and added to the pagecache。So pages
> can not be freed from tmpfs or ramfs. So skip tmpfs and ramfs
> when drop caches.

Hard coding magic constants in VFS code is a bad idea.  If you have
numbers to justify this change (which should go into this commit log),
it can be properly solved by a flag on the super block,
file_system_type or even better bdi.