[PATCH 1/8] quota: Allow to pass mount path to quotactl

[Sascha Hauer]

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. 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)?

Sascha

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