Messages in this thread | | | From | Linus Torvalds <> | Date | Wed, 23 Aug 2017 17:42:05 -0700 | Subject | Re: [PATCH 0/1] devpts: use dynamic_dname() to generate proc name |
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On Wed, Aug 23, 2017 at 5:24 PM, Stefan Lippers-Hollmann <s.l-h@gmx.de> wrote: > > This patch[1] as part of 4.13-rc6 (up to, at least, > v4.13-rc6-45-g6470812e2226) introduces a regression for me when using > pbuilder 0.228.7[2] (a helper to build Debian packages in a chroot and > to create and update its chroots) when trying to umount /dev/ptmx (inside > the chroot) on Debian/ unstable (full log and pbuilder configuration > file[3] attached). > > [...] > Setting up build-essential (12.3) ... > Processing triggers for libc-bin (2.24-15) ... > I: unmounting dev/ptmx filesystem > W: Could not unmount dev/ptmx: umount: /var/cache/pbuilder/build/1340/dev/ptmx: target is busy
Yes, that patch definitely keeps a reference to the pts filesystem around while a pty is open.
We always used to do that, but we did it differently - we would keep the 's_active' count elevated so that the superblock never went away, even after it was unmounted.
Now it does an actual mntget(), and that makes umount _notice_ that the filesystem is still busy.
How annoying.
Because in a very real sehse the filesystem really is busy, but we used to hide it (perhaps on purpose - it's possible that people hit this problem before).
Let me try to think about alteratives. Clearly this is a regression and I need to fix it, I just need to figure out _how_.
Linus
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