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143c97cc65
This reverts commit c8c03f1858331e85d397bacccd34ef409aae993c.
It turns out that while fixing the ptmx file descriptor to have the
correct 'struct path' to the associated slave pty is a really good
thing, it breaks some user space tools for a very annoying reason.
The problem is that /dev/ptmx and its associated slave pty (/dev/pts/X)
are on different mounts. That was what caused us to have the wrong path
in the first place (we would mix up the vfsmount of the 'ptmx' node,
with the dentry of the pty slave node), but it also means that now while
we use the right vfsmount, having the pty master open also keeps the pts
mount busy.
And it turn sout that that makes 'pbuilder' very unhappy, as noted by
Stefan Lippers-Hollmann:
"This patch 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
(In some cases useful info about processes that
use the device is found by lsof(8) or fuser(1).)"
apparently pbuilder tries to unmount the /dev/pts filesystem while still
holding at least one master node open, which is arguably not very nice,
but we don't break user space even when fixing other bugs.
So this commit has to be reverted.
I'll try to figure out a way to avoid caching the path to the slave pty
in the master pty. The only thing that actually wants that slave pty
path is the "TIOCGPTPEER" ioctl, and I think we could just recreate the
path at that time.
Reported-by: Stefan Lippers-Hollmann <s.l-h@gmx.de>
Cc: Eric W Biederman <ebiederm@xmission.com>
Cc: Christian Brauner <christian.brauner@canonical.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.