linux-ext4 - Re: [PATCH] fs: i_version mntopt gets visible through /proc/mounts

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Date:   Tue, 14 Jul 2020 09:30:00 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Eric Sandeen <sandeen@...deen.net>
Cc:     Dave Chinner <david@...morbit.com>,
        Masayoshi Mizuma <msys.mizuma@...il.com>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Christoph Hellwig <hch@...radead.org>,
        Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Masayoshi Mizuma <m.mizuma@...fujitsu.com>,
        linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-xfs <linux-xfs@...r.kernel.org>
Subject: Re: [PATCH] fs: i_version mntopt gets visible through /proc/mounts

On Mon, Jul 13, 2020 at 04:45:19PM -0700, Eric Sandeen wrote:
> I wandered back into this thread for some reason ... ;)
> 
> Since iversion/noiversion is /already/ advertised as a vfs-level mount option,
> wouldn't exposing it in /proc/mounts solve the original problem here?
> 
> ("i_version" is wrong, because it's ext4-specific, but "iversion" is handled
> by the vfs, so it's meaningful for any filesystems, and it will also trivially
> allow mount(2) to preserve it across remounts for all filesystems that set it by
> default.)
> 
> Seems like that's the fastest path to fixing the current problems, even if a
> long-term goal may be to deprecate it altogether.

But they should not be exposed as a mount option.  E.g. for XFS we
decide internally if we have a useful i_version or not, totally
independent of the mount option that leaked into the VFS.  So we'll
need to fix how the flag is used before doing any new work in this area.