ANDROID: mnt: remount should propagate to slaves of slaves

propagate_remount was not accounting for the slave mounts
of other slave mounts, leading to some namespaces not
recieving the remount information.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Bug: 33731928
Change-Id: Idc9e8c2ed126a4143229fc23f10a959c2d0a3854

2 files changed, 22 insertions, 7 deletions

diff --git a/fs/pnode.c b/fs/pnode.c
index 2ef946f51a1..46a71f920a6 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -360,16 +360,31 @@ int propagate_umount(struct list_head *list)
 	return 0;
 }
 
-int propagate_remount(struct mount *mnt) {
-	struct mount *m;
+/*
+ *  Iterates over all slaves, and slaves of slaves.
+ */
+static struct mount *next_descendent(struct mount *root, struct mount *cur)
+{
+	if (!IS_MNT_NEW(cur) && !list_empty(&cur->mnt_slave_list))
+		return first_slave(cur);
+	do {
+		if (cur->mnt_slave.next != &cur->mnt_master->mnt_slave_list)
+			return next_slave(cur);
+		cur = cur->mnt_master;
+	} while (cur != root);
+	return NULL;
+}
+
+void propagate_remount(struct mount *mnt)
+{
+	struct mount *m = mnt;
 	struct super_block *sb = mnt->mnt.mnt_sb;
-	int ret = 0;
 
 	if (sb->s_op->copy_mnt_data) {
-		for (m = first_slave(mnt); m->mnt_slave.next != &mnt->mnt_slave_list; m = next_slave(m)) {
+		m = next_descendent(mnt, m);
+		while (m) {
 			sb->s_op->copy_mnt_data(m->mnt.data, mnt->mnt.data);
+			m = next_descendent(mnt, m);
 		}
 	}
-
-	return ret;
 }
diff --git a/fs/pnode.h b/fs/pnode.h
index ae8d67a9e96..b0709096de7 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -36,7 +36,7 @@ int propagate_mnt(struct mount *, struct mountpoint *, struct mount *,
 		struct list_head *);
 int propagate_umount(struct list_head *);
 int propagate_mount_busy(struct mount *, int);
-int propagate_remount(struct mount *);
+void propagate_remount(struct mount *);
 void mnt_release_group_id(struct mount *);
 int get_dominating_id(struct mount *mnt, const struct path *root);
 unsigned int mnt_get_count(struct mount *mnt);