From: Jan Kara <jack@suse.cz>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Jan Kara <jack@suse.cz>, Christoph Hellwig <hch@infradead.org>,
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 1/8] quota: Allow to pass mount path to quotactl
Date: Wed, 27 Jan 2021 15:19:52 +0100 [thread overview]
Message-ID: <20210127141952.GA13717@quack2.suse.cz> (raw)
In-Reply-To: <20210127140510.GI28722@pengutronix.de>
On Wed 27-01-21 15:05:10, Sascha Hauer wrote:
> On Tue, Jan 26, 2021 at 05:18:29PM +0100, Jan Kara wrote:
> > On Tue 26-01-21 13:34:06, Christoph Hellwig wrote:
> > > On Tue, Jan 26, 2021 at 02:17:52PM +0100, Jan Kara wrote:
> > > > Well, I don't think that "wait until unfrozen" is that strange e.g. for
> > > > Q_SETQUOTA - it behaves like setxattr() or any other filesystem
> > > > modification operation. And IMO it is desirable that filesystem freezing is
> > > > transparent for operations like these. For stuff like Q_QUOTAON, I agree
> > > > that returning EBUSY makes sense but then I'm not convinced it's really
> > > > simpler or more useful behavior...
> > >
> > > If we want it to behave like other syscalls we'll just need to throw in
> > > a mnt_want_write/mnt_drop_write pair. Than it behaves exactly like other
> > > syscalls.
> >
> > Right, we could do that. I'd just note that the "wait until unfrozen" and
> > holding of sb->s_umount semaphore is equivalent to
> > mnt_want_write/mnt_drop_write pair. But I agree
> > mnt_want_write/mnt_drop_write is easier to understand and there's no reason
> > not to use it. So I'm for that simplification in the new syscall.
>
> Due to the user_path_at() to the mountpoint the fs won't go away, so I
> guess for non-exclusive, non-write quota command I don't need any
> additional locking.
They still need s_umount in read mode - to serialize against quotaon /
quotaoff (happening either through quotactl or filesystem remount).
> For non-exclusive, write commands I'll need a
> mnt_want_write/mnt_drop_write pair. What about the exclusive, write
> commands (Q_QUOTAON/Q_QUOTAOFF)?
And these still need s_umount in write mode for similar reasons. So the
only thing you really save is the "wait-for-unfreeze" code.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2021-01-27 14:20 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-22 15:15 [PATCH v5 0/8] Add quota support to UBIFS Sascha Hauer
2021-01-22 15:15 ` [PATCH 1/8] quota: Allow to pass mount path to quotactl Sascha Hauer
2021-01-22 17:16 ` Christoph Hellwig
2021-01-25 8:38 ` Sascha Hauer
2021-01-25 15:45 ` Jan Kara
2021-01-25 20:42 ` Christoph Hellwig
2021-01-26 13:17 ` Jan Kara
2021-01-26 13:34 ` Christoph Hellwig
2021-01-26 16:18 ` Jan Kara
2021-01-27 14:05 ` Sascha Hauer
2021-01-27 14:19 ` Jan Kara [this message]
2021-01-26 10:45 ` Sascha Hauer
2021-01-27 14:46 ` Jan Kara
2021-01-27 16:25 ` Christoph Hellwig
2021-01-22 15:15 ` [PATCH 2/8] ubifs: move checks and preparation into setflags() Sascha Hauer
2021-01-22 15:15 ` [PATCH 3/8] ubifs: Add support for FS_IOC_FS[SG]ETXATTR ioctls Sascha Hauer
2021-01-22 17:18 ` Christoph Hellwig
2021-01-22 15:15 ` [PATCH 4/8] ubifs: do not ubifs_inode() on potentially NULL pointer Sascha Hauer
2021-01-22 15:15 ` [PATCH 5/8] ubifs: Factor out ubifs_set_feature_flag() Sascha Hauer
2021-01-22 15:15 ` [PATCH 6/8] ubifs: Add support for project id Sascha Hauer
2021-01-22 15:15 ` [PATCH 7/8] ubifs: export get_znode Sascha Hauer
2021-01-22 17:20 ` Christoph Hellwig
2021-01-22 15:15 ` [PATCH 8/8] ubifs: Add quota support Sascha Hauer
-- strict thread matches above, loose matches on Subject: below --
2020-01-24 13:13 [PATCH v4 0/8] Add quota support to UBIFS Sascha Hauer
2020-01-24 13:13 ` [PATCH 1/8] quota: Allow to pass mount path to quotactl Sascha Hauer
2020-01-27 10:45 ` Jan Kara
2020-01-28 10:06 ` Sascha Hauer
2020-01-28 11:41 ` Jan Kara
2020-01-29 1:29 ` Al Viro
2020-01-29 16:14 ` Jan Kara
2020-02-04 10:35 ` Sascha Hauer
2020-02-18 9:22 ` Jan Kara
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