[PATCH 08/17] fsinfo: Allow mount topology and propagation info to be retrieved [ver #20]

@@ -291,9 +291,11 @@ static const struct fsinfo_attribute fsinfo_common_attributes[] = {
 	FSINFO_VSTRUCT_N(FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO, (void *)123UL),
 
 	FSINFO_VSTRUCT	(FSINFO_ATTR_MOUNT_INFO,	fsinfo_generic_mount_info),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_MOUNT_TOPOLOGY,	fsinfo_generic_mount_topology),
 	FSINFO_STRING	(FSINFO_ATTR_MOUNT_PATH,	fsinfo_generic_seq_read),
 	FSINFO_STRING	(FSINFO_ATTR_MOUNT_POINT,	fsinfo_generic_mount_point),
 	FSINFO_STRING	(FSINFO_ATTR_MOUNT_POINT_FULL,	fsinfo_generic_mount_point_full),
+	FSINFO_LIST	(FSINFO_ATTR_MOUNT_CHILDREN,	fsinfo_generic_mount_children),
 	{}
 };
 

@@ -98,8 +98,10 @@ extern void dissolve_on_fput(struct vfsmount *);
 extern int lookup_mount_object(struct path *, unsigned int, struct path *);
 extern int fsinfo_generic_mount_source(struct path *, struct fsinfo_context *);
 extern int fsinfo_generic_mount_info(struct path *, struct fsinfo_context *);
+extern int fsinfo_generic_mount_topology(struct path *, struct fsinfo_context *);
 extern int fsinfo_generic_mount_point(struct path *, struct fsinfo_context *);
 extern int fsinfo_generic_mount_point_full(struct path *, struct fsinfo_context *);
+extern int fsinfo_generic_mount_children(struct path *, struct fsinfo_context *);
 
 /*
  * fs_struct.c

@@ -4303,6 +4303,54 @@ int fsinfo_generic_mount_info(struct path *path, struct fsinfo_context *ctx)
 	return sizeof(*p);
 }
 
+/*
+ * Retrieve information about the topology at the nominated mount and
+ * its propogation attributes.
+ */
+int fsinfo_generic_mount_topology(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_mount_topology *p = ctx->buffer;
+	struct mount *m;
+	struct path root;
+
+	get_fs_root(current->fs, &root);
+
+	namespace_lock();
+
+	m = real_mount(path->mnt);
+
+	p->parent_id = m->mnt_parent->mnt_id;
+
+	if (path->mnt == root.mnt) {
+		p->parent_id = m->mnt_id;
+	} else {
+		rcu_read_lock();
+		if (!are_paths_connected(&root, path))
+			p->parent_id = m->mnt_id;
+		rcu_read_unlock();
+	}
+
+	if (IS_MNT_SHARED(m)) {
+		p->shared_group_id = m->mnt_group_id;
+		p->propagation_type |= MOUNT_PROPAGATION_SHARED;
+	} else if (IS_MNT_SLAVE(m)) {
+		int source = m->mnt_master->mnt_group_id;
+		int from = get_dominating_id(m, &root);
+		p->dependent_source_id = source;
+		if (from && from != source)
+			p->dependent_clone_of_id = from;
+		p->propagation_type |= MOUNT_PROPAGATION_DEPENDENT;
+	} else if (IS_MNT_UNBINDABLE(m)) {
+		p->propagation_type |= MOUNT_PROPAGATION_UNBINDABLE;
+	} else {
+		p->propagation_type |= MOUNT_PROPAGATION_PRIVATE;
+	}
+
+	namespace_unlock();
+	path_put(&root);
+	return sizeof(*p);
+}
+
 /*
  * Return the path of this mount relative to its parent and clipped to
  * the current chroot.

@@ -4379,4 +4427,50 @@ int fsinfo_generic_mount_point_full(struct path *path, struct fsinfo_context *ct
 	return (ctx->buffer + ctx->buf_size) - p;
 }
 
+/*
+ * Store a mount record into the fsinfo buffer.
+ */
+static void fsinfo_store_mount(struct fsinfo_context *ctx, const struct mount *p,
+			       bool is_root)
+{
+	struct fsinfo_mount_child record = {};
+	unsigned int usage = ctx->usage;
+
+	if (ctx->usage >= INT_MAX)
+		return;
+	ctx->usage = usage + sizeof(record);
+	if (!ctx->buffer || ctx->usage > ctx->buf_size)
+		return;
+
+	record.mnt_unique_id	= p->mnt_unique_id;
+	record.mnt_id		= p->mnt_id;
+	record.parent_id	= is_root ? p->mnt_id : p->mnt_parent->mnt_id;
+	memcpy(ctx->buffer + usage, &record, sizeof(record));
+}
+
+/*
+ * Return information about the submounts relative to path.
+ */
+int fsinfo_generic_mount_children(struct path *path, struct fsinfo_context *ctx)
+{
+	struct mount *m, *child;
+
+	m = real_mount(path->mnt);
+
+	read_seqlock_excl(&mount_lock);
+
+	list_for_each_entry_rcu(child, &m->mnt_mounts, mnt_child) {
+		if (child->mnt_parent != m)
+			continue;
+		fsinfo_store_mount(ctx, child, false);
+	}
+
+	/* End the list with a copy of the parameter mount's details so that
+	 * userspace can quickly check for changes.
+	 */
+	fsinfo_store_mount(ctx, m, true);
+	read_sequnlock_excl(&mount_lock);
+	return ctx->usage;
+}
+
 #endif /* CONFIG_FSINFO */

@@ -35,6 +35,8 @@
 #define FSINFO_ATTR_MOUNT_PATH		0x201	/* Bind mount/superblock path (string) */
 #define FSINFO_ATTR_MOUNT_POINT		0x202	/* Relative path of mount in parent (string) */
 #define FSINFO_ATTR_MOUNT_POINT_FULL	0x203	/* Absolute path of mount (string) */
+#define FSINFO_ATTR_MOUNT_TOPOLOGY	0x204	/* Mount object topology */
+#define FSINFO_ATTR_MOUNT_CHILDREN	0x205	/* Children of this mount (list) */
 
 /*
  * Optional fsinfo() parameter structure.

@@ -102,6 +104,31 @@ struct fsinfo_mount_info {
 
 #define FSINFO_ATTR_MOUNT_INFO__STRUCT struct fsinfo_mount_info
 
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_MOUNT_TOPOLOGY).
+ */
+struct fsinfo_mount_topology {
+	__u32	parent_id;		/* Parent mount identifier */
+	__u32	shared_group_id;	/* Shared: mount group ID */
+	__u32	dependent_source_id;	/* Dependent: source mount group ID */
+	__u32	dependent_clone_of_id;	/* Dependent: ID of mount this was cloned from */
+	__u32	propagation_type;	/* MOUNT_PROPAGATION_* type */
+};
+
+#define FSINFO_ATTR_MOUNT_TOPOLOGY__STRUCT struct fsinfo_mount_topology
+
+/*
+ * Information struct element for fsinfo(FSINFO_ATTR_MOUNT_CHILDREN).
+ * - An extra element is placed on the end representing the parent mount.
+ */
+struct fsinfo_mount_child {
+	__u64	mnt_unique_id;		/* Kernel-lifetime unique mount ID */
+	__u32	mnt_id;			/* Mount identifier (use with AT_FSINFO_MOUNTID_PATH) */
+	__u32	parent_id;		/* Parent mount identifier */
+};
+
+#define FSINFO_ATTR_MOUNT_CHILDREN__STRUCT struct fsinfo_mount_child
+
 /*
  * Information struct for fsinfo(FSINFO_ATTR_STATFS).
  * - This gives extended filesystem information.

@@ -105,7 +105,7 @@ enum fsconfig_command {
 #define FSMOUNT_CLOEXEC		0x00000001
 
 /*
- * Mount attributes.
+ * Mount object attributes (these are separate to filesystem attributes).
  */
 #define MOUNT_ATTR_RDONLY	0x00000001 /* Mount read-only */
 #define MOUNT_ATTR_NOSUID	0x00000002 /* Ignore suid and sgid bits */

@@ -117,4 +117,15 @@ enum fsconfig_command {
 #define MOUNT_ATTR_STRICTATIME	0x00000020 /* - Always perform atime updates */
 #define MOUNT_ATTR_NODIRATIME	0x00000080 /* Do not update directory access times */
 
+/*
+ * Mount object propagation type.
+ */
+enum propagation_type {
+	/* 0 is left unallocated to mean "no change" in mount_setattr()  */
+	MOUNT_PROPAGATION_UNBINDABLE	= 1, /* Make unbindable. */
+	MOUNT_PROPAGATION_PRIVATE	= 2, /* Do not receive or send mount events. */
+	MOUNT_PROPAGATION_DEPENDENT	= 3, /* Only receive mount events. */
+	MOUNT_PROPAGATION_SHARED	= 4, /* Send and receive mount events. */
+};
+
 #endif /* _UAPI_LINUX_MOUNT_H */

@@ -21,6 +21,7 @@
 #include <sys/syscall.h>
 #include <linux/fsinfo.h>
 #include <linux/socket.h>
+#include <linux/mount.h>
 #include <sys/stat.h>
 #include <arpa/inet.h>
 

@@ -305,6 +306,58 @@ static void dump_fsinfo_generic_mount_info(void *reply, unsigned int size)
 	printf("\tattr    : %x\n", r->attr);
 }
 
+static void dump_fsinfo_generic_mount_topology(void *reply, unsigned int size)
+{
+	struct fsinfo_mount_topology *r = reply;
+
+	printf("\n");
+	printf("\tparent  : %x\n", r->parent_id);
+
+	switch (r->propagation_type) {
+	case MOUNT_PROPAGATION_UNBINDABLE:
+		printf("\tpropag  : unbindable\n");
+		break;
+	case MOUNT_PROPAGATION_PRIVATE:
+		printf("\tpropag  : private\n");
+		break;
+	case MOUNT_PROPAGATION_DEPENDENT:
+		printf("\tpropag  : dependent source=%x clone_of=%x\n",
+		       r->dependent_source_id, r->dependent_clone_of_id);
+		break;
+	case MOUNT_PROPAGATION_SHARED:
+		printf("\tpropag  : shared group=%x\n", r->shared_group_id);
+		break;
+	default:
+		printf("\tpropag  : unknown type %x\n", r->propagation_type);
+		break;
+	}
+
+}
+
+static void dump_fsinfo_generic_mount_children(void *reply, unsigned int size)
+{
+	struct fsinfo_mount_child *r = reply;
+	ssize_t mplen;
+	char path[32], *mp;
+
+	struct fsinfo_params params = {
+		.flags		= FSINFO_FLAGS_QUERY_MOUNT,
+		.request	= FSINFO_ATTR_MOUNT_POINT,
+	};
+
+	if (!list_last) {
+		sprintf(path, "%u", r->mnt_id);
+		mplen = get_fsinfo(path, "FSINFO_ATTR_MOUNT_POINT", &params, (void **)&mp);
+		if (mplen < 0)
+			mp = "-";
+	} else {
+		mp = "<this>";
+	}
+
+	printf("%8x %16llx %s\n",
+	       r->mnt_id, (unsigned long long)r->mnt_unique_id, mp);
+}
+
 static void dump_string(void *reply, unsigned int size)
 {
 	char *s = reply, *p;

@@ -383,9 +436,11 @@ static const struct fsinfo_attribute fsinfo_attributes[] = {
 	FSINFO_LIST	(FSINFO_ATTR_FSINFO_ATTRIBUTES,	fsinfo_meta_attributes),
 
 	FSINFO_VSTRUCT	(FSINFO_ATTR_MOUNT_INFO,	fsinfo_generic_mount_info),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_MOUNT_TOPOLOGY,	fsinfo_generic_mount_topology),
 	FSINFO_STRING	(FSINFO_ATTR_MOUNT_PATH,	string),
 	FSINFO_STRING_N	(FSINFO_ATTR_MOUNT_POINT,	string),
 	FSINFO_STRING_N	(FSINFO_ATTR_MOUNT_POINT_FULL,	string),
+	FSINFO_LIST	(FSINFO_ATTR_MOUNT_CHILDREN,	fsinfo_generic_mount_children),
 	{}
 };