From: Christian Brauner <christian.brauner@ubuntu.com>
Date: Wed, 17 Mar 2021 10:07:47 +0000 (+0100)
Subject: mount_utils: add helper to determine whether new mount api supports bind mounts
X-Git-Tag: lxc-5.0.0~197^2~9
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d4e07569bb5acafaaffa89ae7b713caa612518a0;p=thirdparty%2Flxc.git

mount_utils: add helper to determine whether new mount api supports bind mounts

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---

diff --git a/src/lxc/mount_utils.c b/src/lxc/mount_utils.c
index c0d5a4535..05d129ac1 100644
--- a/src/lxc/mount_utils.c
+++ b/src/lxc/mount_utils.c
@@ -488,3 +488,28 @@ bool can_use_mount_api(void)
 
 	return supported == 1;
 }
+
+bool can_use_bind_mounts(void)
+{
+	static int supported = -1;
+
+	if (supported == -1) {
+		int ret;
+
+		if (!can_use_mount_api()) {
+			supported = 0;
+			return false;
+		}
+
+		ret = mount_setattr(-EBADF, NULL, 0, NULL, 0);
+		if (!ret || errno == ENOSYS) {
+			supported = 0;
+			return false;
+		}
+
+		supported = 1;
+		TRACE("Kernel supports bind mounts in the new mount api");
+	}
+
+	return supported == 1;
+}
diff --git a/src/lxc/mount_utils.h b/src/lxc/mount_utils.h
index 5053ebfea..7edc15fd2 100644
--- a/src/lxc/mount_utils.h
+++ b/src/lxc/mount_utils.h
@@ -206,5 +206,6 @@ __hidden extern unsigned long add_required_remount_flags(const char *s,
 							 unsigned long flags);
 
 __hidden extern bool can_use_mount_api(void);
+__hidden extern bool can_use_bind_mounts(void);
 
 #endif /* __LXC_MOUNT_UTILS_H */