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authorSeth Forshee <seth.forshee@canonical.com>2016-03-09 09:18:07 -0600
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-04-12 15:01:53 -0700
commit87243deb88671f70def4c52dfa7ca7830707bd31 (patch)
tree7364873c15017b4b33127d0d77d957c538861bc3 /lib
parentf55532a0c0b8bb6148f4e07853b876ef73bc69ca (diff)
downloadlinux-87243deb88671f70def4c52dfa7ca7830707bd31.tar.bz2
debugfs: Make automount point inodes permanently empty
Starting with 4.1 the tracing subsystem has its own filesystem which is automounted in the tracing subdirectory of debugfs. Prior to this debugfs could be bind mounted in a cloned mount namespace, but if tracefs has been mounted under debugfs this now fails because there is a locked child mount. This creates a regression for container software which bind mounts debugfs to satisfy the assumption of some userspace software. In other pseudo filesystems such as proc and sysfs we're already creating mountpoints like this in such a way that no dirents can be created in the directories, allowing them to be exceptions to some MNT_LOCKED tests. In fact we're already do this for the tracefs mountpoint in sysfs. Do the same in debugfs_create_automount(), since the intention here is clearly to create a mountpoint. This fixes the regression, as locked child mounts on permanently empty directories do not cause a bind mount to fail. Cc: stable@vger.kernel.org # v4.1+ Signed-off-by: Seth Forshee <seth.forshee@canonical.com> Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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