linux-kernel - Re: [PATCH 01/25] vfs: syscall: Add fsinfo() to query filesystem information [ver #13]

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Message-ID: <23583.1560896665@warthog.procyon.org.uk>
Date:   Tue, 18 Jun 2019 23:24:25 +0100
From:   David Howells <dhowells@...hat.com>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     dhowells@...hat.com, Al Viro <viro@...iv.linux.org.uk>,
        Ian Kent <raven@...maw.net>,
        Linux API <linux-api@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Miklos Szeredi <mszeredi@...hat.com>
Subject: Re: [PATCH 01/25] vfs: syscall: Add fsinfo() to query filesystem information [ver #13]

Miklos Szeredi <miklos@...redi.hu> wrote:

> Please don't resurrect MS_ flags.  They are from the old API and
> shouldn't be used in the new one.  Some of them (e.g. MS_POSIXACL,
> MS_I_VERSION) are actually internal flags despite being exported on
> the old API.

That makes it harder to emulate statfs() using this interface, but ok.

I wonder if I should split the standard parameters (rw/ro, posixacl, dirsync,
sync, lazytime, mand) out of FSINFO_ATTR_PARAMETERS and stick them in their
own attribute, say FSINFO_ATTR_STD_PARAMETERS.  That would make it easier for
a filesystem to only overload them if it wants to.

> And there's SB_SILENT which is simply not a superblock flag and we might be
> better getting rid of it entirely.

Yeah.  It's a parse-time flag.

> The proper way to query mount options should be analogous to the way
> they are set on the new API: list of {key, type, value, aux} tuples.

It's not quite that simple: "aux" might be a datum that you can't recover or
is meaningless to another process (an fd, for example).

David