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

[Eric W. Biederman]

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
implementation.

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.)
 .TP
 .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.
 .TP
 .BR MNT_EXPIRE " (since Linux 2.6.8)"
 Mark the mount point as expired.
-- 
1.9.1

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