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From: Sascha Hauer <s.hauer@pengutronix.de>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org,
	Richard Weinberger <richard@nod.at>,
	linux-mtd@lists.infradead.org, kernel@pengutronix.de,
	Jan Kara <jack@suse.com>
Subject: Re: [PATCH 05/11] quota: Allow to pass quotactl a mountpoint
Date: Thu, 15 Aug 2019 09:46:51 +0200
Message-ID: <20190815074651.4wnzc2beh7tpcori@pengutronix.de> (raw)
In-Reply-To: <20190814233946.GX1131@ZenIV.linux.org.uk>

On Thu, Aug 15, 2019 at 12:39:46AM +0100, Al Viro wrote:
> On Thu, Aug 15, 2019 at 12:36:32AM +0100, Al Viro wrote:
> > On Wed, Aug 14, 2019 at 02:18:28PM +0200, Sascha Hauer wrote:
> > > +/**
> > > + * reference_super - get a reference to a given superblock
> > > + * @sb: superblock to get the reference from
> > > + *
> > > + * Takes a reference to a superblock. Can be used as when the superblock
> > > + * is known and leaves it in a state as if get_super had been called.
> > > + */
> > > +void reference_super(struct super_block *sb)
> > > +{
> > > +	spin_lock(&sb_lock);
> > > +	sb->s_count++;
> > > +	spin_unlock(&sb_lock);
> > > +
> > > +	down_read(&sb->s_umount);
> > > +}
> > > +EXPORT_SYMBOL_GPL(reference_super);
> > 
> > NAK, for a plenty of reasons
> > 
> > 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.

I'll happily drop these changes. To clarify, quota currently does:

	if (quotactl_cmd_onoff(cmd))
		sb = get_super_exclusive_thawed(bdev);
	else if (quotactl_cmd_write(cmd))
		sb = get_super_thawed(bdev);
	else
		sb = get_super(bdev);

You are saying that the struct super_block I get from a struct path pointer is
in a suitable state for all the cases above, right?

Sascha

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Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-14 12:18 [PATCH 00/11] Add quota support to UBIFS Sascha Hauer
2019-08-14 12:18 ` [PATCH 01/11] quota: Make inode optional Sascha Hauer
2019-08-14 12:18 ` [PATCH 02/11] quota: Only module_put the format when existing Sascha Hauer
2019-08-15 11:18   ` Jan Kara
2019-08-16 11:49     ` Sascha Hauer
2019-08-14 12:18 ` [PATCH 03/11] fs: move __get_super() out of loop Sascha Hauer
2019-08-14 23:32   ` Al Viro
2019-08-14 12:18 ` [PATCH 04/11] fs, quota: introduce wait_super_thawed() to wait until a superblock is thawed Sascha Hauer
2019-08-14 23:35   ` Al Viro
2019-08-14 12:18 ` [PATCH 05/11] quota: Allow to pass quotactl a mountpoint Sascha Hauer
2019-08-14 22:42   ` kbuild test robot
2019-08-14 23:33   ` kbuild test robot
2019-08-14 23:36   ` Al Viro
2019-08-14 23:39     ` Al Viro
2019-08-14 23:51       ` Al Viro
2019-08-15  9:53         ` Jan Kara
2019-08-15  7:46       ` Sascha Hauer [this message]
2019-08-14 12:18 ` [PATCH 06/11] ubifs: move checks and preparation into setflags() Sascha Hauer
2019-08-14 12:18 ` [PATCH 07/11] ubifs: Add support for FS_IOC_FS[SG]ETXATTR ioctls Sascha Hauer
2019-08-14 14:11   ` Mainz, Roland
2019-08-15  7:31     ` Sascha Hauer
2019-08-14 12:18 ` [PATCH 08/11] ubifs: do not ubifs_inode() on potentially NULL pointer Sascha Hauer
2019-08-14 12:18 ` [PATCH 09/11] ubifs: Add support for project id Sascha Hauer
2019-08-14 12:18 ` [PATCH 10/11] ubifs: export get_znode Sascha Hauer
2019-08-14 12:18 ` [PATCH 11/11] ubifs: Add quota support Sascha Hauer
2019-08-15 11:17   ` Jan Kara

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