From f6c00320c13f58147ee9f1f2f952ca0c49117f95 Mon Sep 17 00:00:00 2001
From: Rob Wing <rob.wing@klarasystems.com>
Date: Fri, 6 Jan 2023 23:16:43 -0900
Subject: [PATCH] jectl: perform forced unmounts for a jail environment

When a jail is in a dying state it prevents the backing dataset from
being unmounted.

Workaround this for now by performing forced unmounts of jail
environment datasets.
---
 jectl.h         |  2 +-
 jectl_mount.c   | 30 ++++++++++++++++++++++++++----
 jectl_unmount.c | 36 +++++++++++++++++++++++++++++-------
 jectl_util.c    |  2 +-
 4 files changed, 57 insertions(+), 13 deletions(-)

diff --git a/jectl.h b/jectl.h
index ac0ac55..a956fdb 100644
--- a/jectl.h
+++ b/jectl.h
@@ -56,5 +56,5 @@ int je_activate(zfs_handle_t *, const char *);
 int je_destroy(zfs_handle_t *);
 int je_mount(zfs_handle_t *, const char *);
 int je_swapin(zfs_handle_t *, zfs_handle_t *);
-int je_unmount(zfs_handle_t *);
+int je_unmount(zfs_handle_t *, int);
 
diff --git a/jectl_mount.c b/jectl_mount.c
index 04b1fcf..22243af 100644
--- a/jectl_mount.c
+++ b/jectl_mount.c
@@ -60,14 +60,36 @@ je_mount(zfs_handle_t *jds, const char *mountpoint)
 	zfs_handle_t *je;
 	get_all_cb_t cb = { 0 };
 
-	if ((je = get_active_je(jds)) == NULL)
+	if ((je = get_active_je(jds)) == NULL) {
+		fprintf(stderr,
+		    "je_mount: cannot find active jail environment for '%s'\n",
+		    zfs_get_name(jds));
 		return (1);
+	}
 
-	if (zfs_prop_set(je, "mountpoint", mountpoint) != 0)
+	/*
+	 * XXX: work-around dying jails
+	 *
+	 * A dying jail can prevent the backing dataset from being unmounted.
+	 * Do a forced unmount until dying jails can be cleaned properly.
+	 */
+	if (je_unmount(je, MNT_FORCE) != 0) {
+		char mp[ZFS_MAXPROPLEN];
+
+		zfs_prop_get(je, ZFS_PROP_MOUNTPOINT, mp, sizeof(mp),
+		    NULL, NULL, 0, B_FALSE);
+		fprintf(stderr,
+		    "je_mount: cannot unmount '%s' from '%s'\n",
+		    zfs_get_name(je), mp);
 		return (1);
+	}
 
-	if (zfs_is_mounted(je, NULL))
-		return (0);
+	if (zfs_prop_set(je, "mountpoint", mountpoint) != 0) {
+		fprintf(stderr,
+		    "je_mount: cannot set mountpoint for '%s' at '%s'\n",
+		    zfs_get_name(je), mountpoint);
+		return (1);
+	}
 
 	libzfs_add_handle(&cb, je);
 	zfs_iter_dependents(je, B_TRUE, gather_cb, &cb);
diff --git a/jectl_unmount.c b/jectl_unmount.c
index 1d23b46..cfcd8d1 100644
--- a/jectl_unmount.c
+++ b/jectl_unmount.c
@@ -29,30 +29,52 @@
 
 #include "jectl.h"
 
+static void
+usage(void)
+{
+	fprintf(stderr, "usage: jectl umount [-f] <jailname>\n");
+	exit(1);
+}
+
 /*
  * unmount zhp and child datasets inheriting zhp's mountpoint
  */
 int
-je_unmount(zfs_handle_t *zhp)
+je_unmount(zfs_handle_t *zhp, int flags)
 {
 	if (!zfs_is_mounted(zhp, NULL))
 		return (0);
 
-	return (zfs_unmountall(zhp, 0));
+	return (zfs_unmountall(zhp, flags));
 }
 
 static int
 jectl_unmount(int argc, char **argv)
 {
+	int c;
 	int error;
+	int flags = 0;
 	zfs_handle_t *je, *jds;
 
-	if (argc != 2) {
-		fprintf(stderr, "usage: jectl umount <jailname>\n");
-		return (1);
+	while ((c = getopt(argc, argv, "f")) != -1) {
+		switch (c) {
+		case 'f':
+			flags |= MNT_FORCE;
+			break;
+		case '?':
+			usage();
+		}
+	}
+
+	argc -= optind;
+	argv += optind;
+
+	if (argc != 1) {
+		fprintf(stderr, "must provide jail name\n");
+		usage();
 	}
 
-	if ((jds = get_jail_dataset(argv[1])) == NULL)
+	if ((jds = get_jail_dataset(argv[0])) == NULL)
 		return (1);
 
 	if ((je = get_active_je(jds)) == NULL) {
@@ -60,7 +82,7 @@ jectl_unmount(int argc, char **argv)
 		return (1);
 	}
 
-	error = je_unmount(je);
+	error = je_unmount(je, flags);
 
 	zfs_close(je);
 	zfs_close(jds);
diff --git a/jectl_util.c b/jectl_util.c
index 9665339..6c9c1c5 100644
--- a/jectl_util.c
+++ b/jectl_util.c
@@ -240,7 +240,7 @@ je_swapin(zfs_handle_t *jds, zfs_handle_t *target)
 		return (0);
 	}
 
-	if (je_unmount(src) != 0 || je_unmount(target) != 0) {
+	if (je_unmount(src, 0) != 0 || je_unmount(target, 0) != 0) {
 		zfs_close(src);
 		return (1);
 	}