linux-kernel - Re: [PATCH v3 0/2] quota: Add mountpath based quota support

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Message-ID: <20210524084912.GC32705@quack2.suse.cz>
Date:   Mon, 24 May 2021 10:49:12 +0200
From:   Jan Kara <jack@...e.cz>
To:     Sascha Hauer <s.hauer@...gutronix.de>
Cc:     Jan Kara <jack@...e.cz>, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>, kernel@...gutronix.de,
        Jan Kara <jack@...e.com>, Richard Weinberger <richard@....at>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <christian.brauner@...ntu.com>
Subject: Re: [PATCH v3 0/2] quota: Add mountpath based quota support

On Wed 12-05-21 17:03:46, Sascha Hauer wrote:
> On Wed, May 12, 2021 at 01:01:49PM +0200, Jan Kara wrote:
> > Added a few more CCs.
> > 
> > On Tue 16-03-21 12:29:16, Jan Kara wrote:
> > > On Thu 04-03-21 13:35:38, Sascha Hauer wrote:
> > > > Current quotactl syscall uses a path to a block device to specify the
> > > > filesystem to work on which makes it unsuitable for filesystems that
> > > > do not have a block device. This series adds a new syscall quotactl_path()
> > > > which replaces the path to the block device with a mountpath, but otherwise
> > > > behaves like original quotactl.
> > > > 
> > > > This is done to add quota support to UBIFS. UBIFS quota support has been
> > > > posted several times with different approaches to put the mountpath into
> > > > the existing quotactl() syscall until it has been suggested to make it a
> > > > new syscall instead, so here it is.
> > > > 
> > > > I'm not posting the full UBIFS quota series here as it remains unchanged
> > > > and I'd like to get feedback to the new syscall first. For those interested
> > > > the most recent series can be found here: https://lwn.net/Articles/810463/
> > > 
> > > Thanks. I've merged the two patches into my tree and will push them to
> > > Linus for the next merge window.
> > 
> > So there are some people at LWN whining that quotactl_path() has no dirfd
> > and flags arguments for specifying the target. Somewhat late in the game
> > but since there's no major release with the syscall and no userspace using
> > it, I think we could still change that. What do you think? What they
> > suggest does make some sense. But then, rather then supporting API for
> > million-and-one ways in which I may wish to lookup a fs object, won't it be
> > better to just pass 'fd' in the new syscall (it may well be just O_PATH fd
> > AFAICT) and be done with that?
> 
> This sounds like a much cleaner interface to me. If we agree on this I
> wouldn't mind spinning this patch for another few rounds.

So the syscall is currently disabled in Linus' tree. Will you send a patch
for new fd-based quotactl variant?

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR