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 -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
