linux-kernel - Re: [PATCH 10/16] tmpfs: fcntl(fd, F_MEM

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Message-ID: <YQieHio1oUKCfgqq@casper.infradead.org>
Date:   Tue, 3 Aug 2021 02:38:38 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Michal Hocko <mhocko@...e.com>,
        Rik van Riel <riel@...riel.com>,
        Christoph Hellwig <hch@...radead.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Alexey Gladkov <legion@...nel.org>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Matthew Auld <matthew.auld@...el.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 10/16] tmpfs: fcntl(fd, F_MEM_LOCK) to memlock a tmpfs
 file

On Fri, Jul 30, 2021 at 12:55:22AM -0700, Hugh Dickins wrote:
> A new uapi to lock the files on tmpfs in memory, to protect against swap
> without mapping the files. This commit introduces two new commands to
> fcntl and shmem: F_MEM_LOCK and F_MEM_UNLOCK. The locking will be
> charged against RLIMIT_MEMLOCK of uid in namespace of the caller.

It's not clear to me why this is limited to shmfs.  Would it not also
make sense for traditional filesystems, eg to force chrome's text pages
to stay in the page cache, no matter how much memory the tabs allocate?