From: Karel Zak <kzak@redhat.com>
Date: Mon, 22 Mar 2021 10:29:28 +0000 (+0100)
Subject: umount: support over-mounts for --recursive
X-Git-Tag: v2.37-rc1~52
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e2f6c9eaa2deb019ba2a9dad495881b20e797f91;p=thirdparty%2Futil-linux.git

umount: support over-mounts for --recursive

For example for hierarchy:

  $ findmnt -oTARGET,ID,PARENT
  TARGET                      ID PARENT
  /mnt/A                     802     62
  └─/mnt/A/B                 937    802
    ├─/mnt/A/B/C             964    937
    │ └─/mnt/A/B/C           991    964
    └─/mnt/A/B              1018    937
      └─/mnt/A/B            1045   1018

we need umount in order (id): 1045, 1018, 991, 964, 937, 802. The current
code first tries 991 in 937 branch.

Reported-by: Lennart Poettering <lennart@poettering.net>
Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/sys-utils/umount.8 b/sys-utils/umount.8
index a7f6b12e03..9f0c99777d 100644
--- a/sys-utils/umount.8
+++ b/sys-utils/umount.8
@@ -181,7 +181,8 @@ between mountpoints is determined by
 .I /proc/self/mountinfo
 entries.  The filesystem
 must be specified by mountpoint path; a recursive unmount by device name (or UUID)
-is unsupported.
+is unsupported.  Since version 2.37 it umounts also all over-mounted filesystems
+(more filesystems on the same mountpoint).
 .TP
 .BR \-r , " \-\-read\-only"
 When an unmount fails, try to remount the filesystem read-only.
diff --git a/sys-utils/umount.c b/sys-utils/umount.c
index 2f4742d13d..ec357d0dfe 100644
--- a/sys-utils/umount.c
+++ b/sys-utils/umount.c
@@ -299,13 +299,20 @@ static int umount_one_if_mounted(struct libmnt_context *cxt, const char *spec)
 static int umount_do_recurse(struct libmnt_context *cxt,
 		struct libmnt_table *tb, struct libmnt_fs *fs)
 {
-	struct libmnt_fs *child;
+	struct libmnt_fs *child, *over = NULL;
 	struct libmnt_iter *itr = mnt_new_iter(MNT_ITER_BACKWARD);
 	int rc;
 
 	if (!itr)
 		err(MNT_EX_SYSERR, _("libmount iterator allocation failed"));
 
+	/* first try overmount */
+	if (mnt_table_over_fs(tb, fs, &over) == 0 && over) {
+		rc = umount_do_recurse(cxt, tb, over);
+		if (rc != MNT_EX_SUCCESS)
+			goto done;
+	}
+
 	/* umount all children */
 	for (;;) {
 		rc = mnt_table_next_child_fs(tb, itr, fs, &child);
@@ -317,6 +324,9 @@ static int umount_do_recurse(struct libmnt_context *cxt,
 		} else if (rc == 1)
 			break;		/* no more children */
 
+		if (over && child == over)
+			continue;
+
 		rc = umount_do_recurse(cxt, tb, child);
 		if (rc != MNT_EX_SUCCESS)
 			goto done;