On Wed, 14 May 2014, Eric Sandeen wrote: > Date: Wed, 14 May 2014 17:40:22 -0500 > From: Eric Sandeen <esandeen@xxxxxxxxxx> > Reply-To: sandeen@xxxxxxxxxx > To: Dave Chinner <david@xxxxxxxxxxxxx>, Jan Kara <jack@xxxxxxx> > Cc: Mateusz Guzik <mguzik@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, > linux-fsdevel@xxxxxxxxxxxxxxx, Josef Bacik <jbacik@xxxxxx>, > Al Viro <viro@xxxxxxxxxxxxxxxxxx>, Joe Perches <joe@xxxxxxxxxxx> > Subject: Re: [PATCH V2 2/2] fs: print a message when freezing/unfreezing > filesystems > > On 5/14/14, 5:37 PM, Dave Chinner wrote: > > On Thu, May 15, 2014 at 08:00:52AM +1000, Dave Chinner wrote: > >> On Wed, May 14, 2014 at 01:39:45PM +0200, Jan Kara wrote: > >>> On Wed 14-05-14 13:26:21, Mateusz Guzik wrote: > >>>> On Wed, May 14, 2014 at 01:14:49PM +0200, Jan Kara wrote: > >>>>> On Wed 14-05-14 00:04:43, Mateusz Guzik wrote: > >>>>>> This helps hang troubleshooting efforts when only dmesg is available. > >>>>>> > >>>>>> While here remove code duplication with MS_RDONLY case and fix a > >>>>>> whitespace nit. > >>>>> I'm somewhat undecided here I have to say. On one hand I don't like > >>>>> printing to kernel log when everything is fine and kernel is operating > >>>>> normally. On the other hand I've seen quite a few cases where people have > >>>>> shot themselves in the foot with filesystem freezing so having some trace > >>>>> of this in the log doesn't seem like a completely bad thing either. What do > >>>>> other people think? > >>>>> > >>>> > >>>> I would like to note that the kernel already prints messages when e.g. > >>>> filesystems get mounted. > >>> Yeah, that's a fair point. > >> > >> But filesystems choose to output that info, not the VFS. When you do > >> a remount,ro there is no output in syslog, because filesystems don't > >> need to dump any output - the state change is reflected in > >> /proc/self/mounts. IMO frozen should state should be communicated > >> the same way so that it is silent when it just works, and the state > >> can easily be determined when something goes wrong. > > > > Say, like this: > > > > $ grep /mnt/test /proc/mounts > > /dev/vda /mnt/test xfs rw,relatime,attr2,inode64,noquota 0 0 > > $ sudo xfs_freeze -f /mnt/test > > $ grep /mnt/test /proc/mounts > > /dev/vda /mnt/test xfs rw,frozen,relatime,attr2,inode64,noquota 0 0 > > $ sudo xfs_freeze -u /mnt/test > > $ grep /mnt/test /proc/mounts > > /dev/vda /mnt/test xfs rw,relatime,attr2,inode64,noquota 0 0 > > $ > > I'm not totally convinced that including a non-mount option in what > has always (?) been a list of mount options is a great idea. I do not like it either. Mixing this together with other mount options does not seem like a great idea, however we really need a way to report this and I guess we can not just change the /proc/self/mounts, or /proc/self/mountinfo format. So what about crating a new file /proc/self/frozen with the list of frozen file systems in the same format what mounts, or mountinfo has ? > > (Granted, some options there are defaults, and weren't actually specified > as a mount option, but if they had been, they'd have been accepted). > > Maybe add a "mount -o remount,frozen" handler ? ;) That's the neat way to work around that :), but I would prefer a new procfs file rather than this. -Lukas > > -Eric > -- > 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 > -- 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
