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

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Message-ID: <20210512110149.GA31495@quack2.suse.cz>
Date:   Wed, 12 May 2021 13:01:49 +0200
From:   Jan Kara <jack@...e.cz>
To:     Sascha Hauer <s.hauer@...gutronix.de>
Cc:     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

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?

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