[PATCH] umount.2: Correct the description of MNT_DETACH

From: Eric W. Biederman
Date: Mon Sep 29 2014 - 21:04:36 EST

I recently realized that I had been reasoning improperly about what
umount(MNT_DETACH) did based on an insufficient description in
the umount.2 man page, that matched my intuition but not the

When there are no submounts MNT_DETACH is essentially harmless to
applications. Where there are submounts MNT_DETACH changes what
is visible to applications using the detach directories.

Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
man2/umount.2 | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/man2/umount.2 b/man2/umount.2
index 5ff88152c738..aea39d8306fe 100644
--- a/man2/umount.2
+++ b/man2/umount.2
@@ -66,9 +66,10 @@ This can cause data loss.
(Only for NFS mounts.)
.BR MNT_DETACH " (since Linux 2.4.11)"
-Perform a lazy unmount: make the mount point unavailable for
-new accesses, and actually perform the unmount when the mount point
-ceases to be busy.
+Perform a lazy unmount: make the mount point unavailable for new
+accesses, immediately disconnect the filesystem and all filesystems
+mounted below it from each other and from the mount table, and
+actually perform the unmount when the mount point ceases to be busy.
.BR MNT_EXPIRE " (since Linux 2.6.8)"
Mark the mount point as expired.

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