Re: [PATCH 05/11] quota: Allow to pass quotactl a mountpoint

From: Al Viro <viro@zeniv.linux.org.uk>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: linux-fsdevel@vger.kernel.org, linux-mtd@lists.infradead.org,
	Jan Kara <jack@suse.com>, Richard Weinberger <richard@nod.at>,
	kernel@pengutronix.de
Subject: Re: [PATCH 05/11] quota: Allow to pass quotactl a mountpoint
Date: Thu, 15 Aug 2019 00:51:24 +0100	[thread overview]
Message-ID: <20190814235124.GY1131@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20190814233946.GX1131@ZenIV.linux.org.uk>

On Thu, Aug 15, 2019 at 12:39:46AM +0100, Al Viro wrote:
> > 1) introduction of EXPORT_SYMBOL_GPL garbage
> > 2) aforementioned garbage on something that doesn't need to be exported
> > 3) *way* too easily abused - get_super() is, at least, not tempting to
> > play with in random code.  This one is, and it's too low-level to
> > allow.
> 
> ... and this is a crap userland API.
> 
> *IF* you want mountpoint-based variants of quotactl() commands, by all means,
> add those.  Do not overload the old ones.  And for path-based you don't
> need to mess with superblock references - just keep the struct path until
> the end.  That will keep the superblock alive and active just fine.

	To clarify: I suggest something like #define Q_PATH     0x400000
with users passing something like QCMD(Q_QUOTAON | Q_PATH, ...) instead
of QCMD(Q_QUOTAON, ...) to get a path-based behaviour.