On Wed, Mar 02, 2016 at 11:22:54PM +0000, Al Viro wrote: > On Thu, Mar 03, 2016 at 09:47:30AM +1100, Dave Chinner wrote: > > > > So let's get it right. Preferably - without need for boot-to-shutdown > > > tracking just to mirror the state. What do we really want? > > > > > > * an ioctl to query the state (frozen/freezing/not frozen) for something in > > > util-linux to use? > > > > > > * /proc/fs/freezing and /proc/fs/frozen, with ->s_id of affected filesystems > > > or, pehaps, one file with (frozen|freezing) + ->s_id? > > > > > > * ability to audit on state changes? That'd need some thought re what to > > > do when some joker freezes the fs syslogd is logging to... > > > > > > * something else entirely? > > > > Such as: > > > > https://lkml.org/lkml/2015/6/16/456 > > IIRC, there had been a weird use of vfsmounts as proxies for superblocks and > even more strange requirements along the lines "you should just pick one and > use only it in case if there's more than one mountpoint for this fs". It's > been a while, though, so I might've forgotten if that stuff got resolved in > later thread... > > Lifetime rules are really odd there; the object is killed as we are about > to gut vfsmount for good, even though the code in there appears to assume > that it would stay connected to mount tree all the way until that point. > Again, that might have been resolved later; I really can't recall right now... Agreed, there were lots of unresolved problems with that patch set (e.g. the duplicate space accounting infrastructure, rather than just calling vfs_statfs() to grab the free/used space from the filesystems). I was just making the point that we really need a generic fs event mechanism, not just something specific to freeze/unfreeze. I've kind of been waiting for the kdbus stuff to work itself out, because if there's going to be a generic kernel-wide event mechanism added to the kernel, we should just be using that... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
