[git commit] umount: always use umount2 syscall with specified flags

[Denys Vlasenko]

commit: http://git.busybox.net/busybox/commit/?id=c919d561adaf152d9b8834475539e2366c8aa484
branch: http://git.busybox.net/busybox/commit/?id=refs/heads/master

Make umount -f more compatible with util-linux 2.22.2.

Before:
  * 'umount -f': calls umount syscall,
        if it fails calls umount2 with 'MNT_FORCE'
  * 'mount -f -l': calls umount syscall,
        if it fails calls umount2 with 'MNT_LAZY'. 'MNT_FORCE' dropped
After:
  * 'umount -f': calls umount2 syscall with 'MNT_FORCE'
  * 'mount -f -l': calls umount2 syscall with 'MNT_LAZY' and 'MNT_FORCE'

function                                             old     new   delta
umount                                                45       -     -45
umount_main                                          610     555     -55

Signed-off-by: Anton Bondarenko <anton.bondarenko at axis.com>
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 util-linux/umount.c |   20 ++++++++++++++++----
 1 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/util-linux/umount.c b/util-linux/umount.c
index 4c2e882..c6c7441 100644
--- a/util-linux/umount.c
+++ b/util-linux/umount.c
@@ -81,8 +81,13 @@ int umount_main(int argc UNUSED_PARAM, char **argv)
 	argv += optind;
 
 	// MNT_FORCE and MNT_DETACH (from linux/fs.h) must match
-	// OPT_FORCE and OPT_LAZY, otherwise this trick won't work:
-	doForce = MAX((opt & OPT_FORCE), (opt & OPT_LAZY));
+	// OPT_FORCE and OPT_LAZY.
+	{
+		typedef char bug[
+			(OPT_FORCE != MNT_FORCE || OPT_LAZY != MNT_DETACH) ? -1 : 1
+		];
+	}
+	doForce = opt & (OPT_FORCE|OPT_LAZY);
 
 	/* Get a list of mount points from mtab.  We read them all in now mostly
 	 * for umount -a (so we don't have to worry about the list changing while
@@ -147,11 +152,18 @@ int umount_main(int argc UNUSED_PARAM, char **argv)
 		// umount the directory even if we were given the block device.
 		if (m) zapit = m->dir;
 
+// umount from util-linux 2.22.2 does not do this:
+// umount -f uses umount2(MNT_FORCE) immediately,
+// not trying umount() first.
+// (Strangely, umount -fl ignores -f: it is equivalent to umount -l.
+// We do pass both flags in this case)
+#if 0
 		// Let's ask the thing nicely to unmount.
 		curstat = umount(zapit);
 
-		// Force the unmount, if necessary.
+		// Unmount with force and/or lazy flags, if necessary.
 		if (curstat && doForce)
+#endif
 			curstat = umount2(zapit, doForce);
 
 		// If still can't umount, maybe remount read-only?
@@ -168,7 +180,7 @@ int umount_main(int argc UNUSED_PARAM, char **argv)
 				bb_error_msg(msg, m->device);
 			} else {
 				status = EXIT_FAILURE;
-				bb_perror_msg("can't %sumount %s", (doForce ? "forcibly " : ""), zapit);
+				bb_perror_msg("can't unmount %s", zapit);
 			}
 		} else {
 			// De-allocate the loop device.  This ioctl should be ignored on