mount_namespaces.7: Clarify implications for other NS if mount point is removed in...

If a mount point is deleted or renamed or removed in one mount
namespace, this will cause an object that is mounted at that
location in another mount namespace to be unmounted (as verified
by experiment). This was implied by the existing text, but it is
better to make this detail explicit.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man7/mount_namespaces.7 b/man7/mount_namespaces.7
index 11d07bbcf5cd1d5840bac4312866b1c2cd14ecc0..a2e6a6bac1d6cdc56f0bf8c9cdcb429efe02fbae 100644 (file)
--- a/man7/mount_namespaces.7
+++ b/man7/mount_namespaces.7
@@ -1,4 +1,4 @@
-.\" Copyright (c) 2016 by Michael Kerrisk <mtk.manpages@gmail.com>
+.\" Copyright (c) 2016, 2019 by Michael Kerrisk <mtk.manpages@gmail.com>
 .\"
 .\" %%%LICENSE_START(VERBATIM)
 .\" Permission is granted to make and distribute verbatim copies of this
@@ -122,8 +122,17 @@ a mount point in another namespace, may be renamed, unlinked, or removed
 .RB ( rmdir (2))
 in the mount namespace in which it is not a mount point
 (subject to the usual permission checks).
+Consequently, the mount point is removed in the mount namespace
+where it was a mount point.
 .IP
-Previously, attempting to unlink, rename, or remove a file or directory
+Previously (before Linux 3.18),
+.\" mtk: The change was in Linux 3.18, I think, with this commit:
+.\"     commit 8ed936b5671bfb33d89bc60bdcc7cf0470ba52fe
+.\"     Author: Eric W. Biederman <ebiederman@twitter.com>
+.\"     Date:   Tue Oct 1 18:33:48 2013 -0700
+.\"
+.\"         vfs: Lazily remove mounts on unlinked files and directories.
+attempting to unlink, rename, or remove a file or directory
 that was a mount point in another mount namespace would result in the error
 .BR EBUSY .
 That behavior had technical problems of enforcement (e.g., for NFS)