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From: David Howells <dhowells@redhat.com>
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To: Miklos Szeredi <miklos@szeredi.hu>
Cc: dhowells@redhat.com, "Theodore Y. Ts'o" <tytso@mit.edu>,
        Andy Lutomirski <luto@amacapital.net>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux FS Devel <linux-fsdevel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>
Subject: Re: [git pull] new mount API
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Date: Fri, 24 Aug 2018 15:26:44 +0100
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Miklos Szeredi <miklos@szeredi.hu> wrote:

> +/* Mount flags passed to fsmount(2) */
> +#define M_NOSUID	0x01
> +#define M_NODEV		0x02
> +#define M_NOEXEC	0x04
> +#define M_NOATIME	0x08
> +#define M_NODIRATIME	0x10
> +#define M_STRICTATIME	0x20
> +#define M_RDONLY	0x40

If we're going to do this, I would suggest a longer prefix than just 'M' and
renumber them to put *_RDONLY first.

> +	BUILD_BUG_ON(M_NOSUID != MNT_NOSUID || M_NODEV != MNT_NODEV ||
> +		     M_NOEXEC != MNT_NOEXEC || M_NOATIME != MNT_NOATIME ||
> +		     M_NODIRATIME != MNT_NODIRATIME ||
> +		     M_STRICTATIME != MNT_RELATIME || M_RDONLY != MNT_READONLY);

Please don't, please do:

	if (ms_flags & M_RDONLY)
		mnt_flags |= MNT_READONLY;

Yes, and at some point I'd also like to compress the numbering on the SB_*
constants and break the identity as Christoph suggested.

David