linux-kernel - Re: [PATCH 03/19] fsinfo: Provide a bitmap of supported features [ver #16]

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Message-ID: <596567.1582201328@warthog.procyon.org.uk>
Date:   Thu, 20 Feb 2020 12:22:08 +0000
From:   David Howells <dhowells@...hat.com>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     dhowells@...hat.com, viro@...iv.linux.org.uk, raven@...maw.net,
        mszeredi@...hat.com, christian@...uner.io,
        linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/19] fsinfo: Provide a bitmap of supported features [ver #16]

Darrick J. Wong <darrick.wong@...cle.com> wrote:

> > +struct fsinfo_features {
> > +	__u8	features[(FSINFO_FEAT__NR + 7) / 8];
> 
> Hm...the structure size is pretty small (56 bytes) and will expand as we
> add new _FEAT flags.  Is this ok because the fsinfo code will truncate
> its response to userspace to whatever buffer size userspace tells it?

Yes.  Also, you can ask fsinfo how many feature bits it supports.

I should put this in the struct first rather than putting it elsewhere.

David