[15/18] fsinfo: Add an attribute that lists all the visible mounts in a namespace [ver #21]
diff mbox series

Message ID 159646191446.1784947.11228235431863356055.stgit@warthog.procyon.org.uk
State New
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Series
  • VFS: Filesystem information [ver #21]
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Commit Message

David Howells Aug. 3, 2020, 1:38 p.m. UTC
Add a filesystem attribute that exports a list of all the visible mounts in
a namespace, given the caller's chroot setting.  The returned list is an
array of:

	struct fsinfo_mount_child {
		__u64	mnt_unique_id;
		__u32	mnt_id;
		__u32	parent_id;
		__u32	mnt_notify_sum;
		__u32	sb_notify_sum;
	};

where each element contains a once-in-a-system-lifetime unique ID, the
mount ID (which may get reused), the parent mount ID and sums of the
notification/change counters for the mount and its superblock.

This works with a read lock on the namespace_sem, but ideally would do it
under the RCU read lock only.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/fsinfo.c                 |    1 +
 fs/internal.h               |    1 +
 fs/namespace.c              |   37 +++++++++++++++++++++++++++++++++++++
 include/uapi/linux/fsinfo.h |    4 ++++
 samples/vfs/test-fsinfo.c   |   22 ++++++++++++++++++++++
 5 files changed, 65 insertions(+)

Comments

Miklos Szeredi Aug. 4, 2020, 2:05 p.m. UTC | #1
On Mon, Aug 03, 2020 at 02:38:34PM +0100, David Howells wrote:
> Add a filesystem attribute that exports a list of all the visible mounts in
> a namespace, given the caller's chroot setting.  The returned list is an
> array of:
> 
> 	struct fsinfo_mount_child {
> 		__u64	mnt_unique_id;
> 		__u32	mnt_id;
> 		__u32	parent_id;
> 		__u32	mnt_notify_sum;
> 		__u32	sb_notify_sum;
> 	};
> 
> where each element contains a once-in-a-system-lifetime unique ID, the
> mount ID (which may get reused), the parent mount ID and sums of the
> notification/change counters for the mount and its superblock.

The change counters are currently conditional on CONFIG_MOUNT_NOTIFICATIONS.
Is this is intentional?

> 
> This works with a read lock on the namespace_sem, but ideally would do it
> under the RCU read lock only.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
> 
>  fs/fsinfo.c                 |    1 +
>  fs/internal.h               |    1 +
>  fs/namespace.c              |   37 +++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/fsinfo.h |    4 ++++
>  samples/vfs/test-fsinfo.c   |   22 ++++++++++++++++++++++
>  5 files changed, 65 insertions(+)
> 
> diff --git a/fs/fsinfo.c b/fs/fsinfo.c
> index 0540cce89555..f230124ffdf5 100644
> --- a/fs/fsinfo.c
> +++ b/fs/fsinfo.c
> @@ -296,6 +296,7 @@ static const struct fsinfo_attribute fsinfo_common_attributes[] = {
>  	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),
> +	FSINFO_LIST	(FSINFO_ATTR_MOUNT_ALL,		fsinfo_generic_mount_all),
>  	{}
>  };
>  
> diff --git a/fs/internal.h b/fs/internal.h
> index cb5edcc7125a..267b4aaf0271 100644
> --- a/fs/internal.h
> +++ b/fs/internal.h
> @@ -102,6 +102,7 @@ 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 *);
> +extern int fsinfo_generic_mount_all(struct path *, struct fsinfo_context *);
>  
>  /*
>   * fs_struct.c
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 122c12f9512b..1f2e06507244 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -4494,4 +4494,41 @@ int fsinfo_generic_mount_children(struct path *path, struct fsinfo_context *ctx)
>  	return ctx->usage;
>  }
>  
> +/*
> + * Return information about all the mounts in the namespace referenced by the
> + * path.
> + */
> +int fsinfo_generic_mount_all(struct path *path, struct fsinfo_context *ctx)
> +{
> +	struct mnt_namespace *ns;
> +	struct mount *m, *p;
> +	struct path chroot;
> +	bool allow;
> +
> +	m = real_mount(path->mnt);
> +	ns = m->mnt_ns;
> +
> +	get_fs_root(current->fs, &chroot);
> +	rcu_read_lock();
> +	allow = are_paths_connected(&chroot, path) || capable(CAP_SYS_ADMIN);
> +	rcu_read_unlock();
> +	path_put(&chroot);
> +	if (!allow)
> +		return -EPERM;
> +
> +	down_read(&namespace_sem);
> +
> +	list_for_each_entry(p, &ns->list, mnt_list) {

This is missing locking and check added by commit 9f6c61f96f2d ("proc/mounts:
add cursor").

> +		struct path mnt_root;
> +
> +		mnt_root.mnt	= &p->mnt;
> +		mnt_root.dentry	= p->mnt.mnt_root;
> +		if (are_paths_connected(path, &mnt_root))
> +			fsinfo_store_mount(ctx, p, p == m);
> +	}
> +
> +	up_read(&namespace_sem);
> +	return ctx->usage;
> +}
> +
>  #endif /* CONFIG_FSINFO */
> diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
> index 81329de6905e..e40192d98648 100644
> --- a/include/uapi/linux/fsinfo.h
> +++ b/include/uapi/linux/fsinfo.h
> @@ -37,6 +37,7 @@
>  #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) */
> +#define FSINFO_ATTR_MOUNT_ALL		0x206	/* List all mounts in a namespace (list) */
>  
>  #define FSINFO_ATTR_AFS_CELL_NAME	0x300	/* AFS cell name (string) */
>  #define FSINFO_ATTR_AFS_SERVER_NAME	0x301	/* Name of the Nth server (string) */
> @@ -128,6 +129,8 @@ 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.
> + *
> + * Information struct element for fsinfo(FSINFO_ATTR_MOUNT_ALL).
>   */
>  struct fsinfo_mount_child {
>  	__u64	mnt_unique_id;		/* Kernel-lifetime unique mount ID */
> @@ -139,6 +142,7 @@ struct fsinfo_mount_child {
>  };
>  
>  #define FSINFO_ATTR_MOUNT_CHILDREN__STRUCT struct fsinfo_mount_child
> +#define FSINFO_ATTR_MOUNT_ALL__STRUCT struct fsinfo_mount_child
>  
>  /*
>   * Information struct for fsinfo(FSINFO_ATTR_STATFS).
> diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
> index 374825ab85b0..596fa5e71762 100644
> --- a/samples/vfs/test-fsinfo.c
> +++ b/samples/vfs/test-fsinfo.c
> @@ -365,6 +365,27 @@ static void dump_fsinfo_generic_mount_children(void *reply, unsigned int size)
>  	       (unsigned long long)r->mnt_notify_sum, mp);
>  }
>  
> +static void dump_fsinfo_generic_mount_all(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_FULL,
> +	};
> +
> +	sprintf(path, "%u", r->mnt_id);
> +	mplen = get_fsinfo(path, "FSINFO_ATTR_MOUNT_POINT_FULL", &params, (void **)&mp);
> +	if (mplen < 0)
> +		mp = "-";
> +
> +	printf("%5x %5x %12llx %10llu %s\n",
> +	       r->mnt_id, r->parent_id, (unsigned long long)r->mnt_unique_id,
> +	       r->mnt_notify_sum, mp);
> +}
> +
>  static void dump_afs_fsinfo_server_address(void *reply, unsigned int size)
>  {
>  	struct fsinfo_afs_server_address *f = reply;
> @@ -492,6 +513,7 @@ static const struct fsinfo_attribute fsinfo_attributes[] = {
>  	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),
> +	FSINFO_LIST	(FSINFO_ATTR_MOUNT_ALL,		fsinfo_generic_mount_all),
>  
>  	FSINFO_STRING	(FSINFO_ATTR_AFS_CELL_NAME,	string),
>  	FSINFO_STRING	(FSINFO_ATTR_AFS_SERVER_NAME,	string),
> 
>
Ian Kent Aug. 5, 2020, 12:59 a.m. UTC | #2
On Tue, 2020-08-04 at 16:05 +0200, Miklos Szeredi wrote:
> On Mon, Aug 03, 2020 at 02:38:34PM +0100, David Howells wrote:
> > Add a filesystem attribute that exports a list of all the visible
> > mounts in
> > a namespace, given the caller's chroot setting.  The returned list
> > is an
> > array of:
> > 
> > 	struct fsinfo_mount_child {
> > 		__u64	mnt_unique_id;
> > 		__u32	mnt_id;
> > 		__u32	parent_id;
> > 		__u32	mnt_notify_sum;
> > 		__u32	sb_notify_sum;
> > 	};
> > 
> > where each element contains a once-in-a-system-lifetime unique ID,
> > the
> > mount ID (which may get reused), the parent mount ID and sums of
> > the
> > notification/change counters for the mount and its superblock.
> 
> The change counters are currently conditional on
> CONFIG_MOUNT_NOTIFICATIONS.
> Is this is intentional?
> 
> > This works with a read lock on the namespace_sem, but ideally would
> > do it
> > under the RCU read lock only.
> > 
> > Signed-off-by: David Howells <dhowells@redhat.com>
> > ---
> > 
> >  fs/fsinfo.c                 |    1 +
> >  fs/internal.h               |    1 +
> >  fs/namespace.c              |   37
> > +++++++++++++++++++++++++++++++++++++
> >  include/uapi/linux/fsinfo.h |    4 ++++
> >  samples/vfs/test-fsinfo.c   |   22 ++++++++++++++++++++++
> >  5 files changed, 65 insertions(+)
> > 
> > diff --git a/fs/fsinfo.c b/fs/fsinfo.c
> > index 0540cce89555..f230124ffdf5 100644
> > --- a/fs/fsinfo.c
> > +++ b/fs/fsinfo.c
> > @@ -296,6 +296,7 @@ static const struct fsinfo_attribute
> > fsinfo_common_attributes[] = {
> >  	FSINFO_STRING	(FSINFO_ATTR_MOUNT_POINT,	fsinfo_gene
> > ric_mount_point),
> >  	FSINFO_STRING	(FSINFO_ATTR_MOUNT_POINT_FULL,	fsinfo_gene
> > ric_mount_point_full),
> >  	FSINFO_LIST	(FSINFO_ATTR_MOUNT_CHILDREN,	fsinfo_generic_moun
> > t_children),
> > +	FSINFO_LIST	(FSINFO_ATTR_MOUNT_ALL,		fsinfo_generic_moun
> > t_all),
> >  	{}
> >  };
> >  
> > diff --git a/fs/internal.h b/fs/internal.h
> > index cb5edcc7125a..267b4aaf0271 100644
> > --- a/fs/internal.h
> > +++ b/fs/internal.h
> > @@ -102,6 +102,7 @@ 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 *);
> > +extern int fsinfo_generic_mount_all(struct path *, struct
> > fsinfo_context *);
> >  
> >  /*
> >   * fs_struct.c
> > diff --git a/fs/namespace.c b/fs/namespace.c
> > index 122c12f9512b..1f2e06507244 100644
> > --- a/fs/namespace.c
> > +++ b/fs/namespace.c
> > @@ -4494,4 +4494,41 @@ int fsinfo_generic_mount_children(struct
> > path *path, struct fsinfo_context *ctx)
> >  	return ctx->usage;
> >  }
> >  
> > +/*
> > + * Return information about all the mounts in the namespace
> > referenced by the
> > + * path.
> > + */
> > +int fsinfo_generic_mount_all(struct path *path, struct
> > fsinfo_context *ctx)
> > +{
> > +	struct mnt_namespace *ns;
> > +	struct mount *m, *p;
> > +	struct path chroot;
> > +	bool allow;
> > +
> > +	m = real_mount(path->mnt);
> > +	ns = m->mnt_ns;
> > +
> > +	get_fs_root(current->fs, &chroot);
> > +	rcu_read_lock();
> > +	allow = are_paths_connected(&chroot, path) ||
> > capable(CAP_SYS_ADMIN);
> > +	rcu_read_unlock();
> > +	path_put(&chroot);
> > +	if (!allow)
> > +		return -EPERM;
> > +
> > +	down_read(&namespace_sem);
> > +
> > +	list_for_each_entry(p, &ns->list, mnt_list) {
> 
> This is missing locking and check added by commit 9f6c61f96f2d
> ("proc/mounts:
> add cursor").

That's a good catch Miklos.

Yes, the extra lock and the cursor check that's now needed.

> 
> > +		struct path mnt_root;
> > +
> > +		mnt_root.mnt	= &p->mnt;
> > +		mnt_root.dentry	= p->mnt.mnt_root;
> > +		if (are_paths_connected(path, &mnt_root))
> > +			fsinfo_store_mount(ctx, p, p == m);
> > +	}
> > +
> > +	up_read(&namespace_sem);
> > +	return ctx->usage;
> > +}
> > +
> >  #endif /* CONFIG_FSINFO */
> > diff --git a/include/uapi/linux/fsinfo.h
> > b/include/uapi/linux/fsinfo.h
> > index 81329de6905e..e40192d98648 100644
> > --- a/include/uapi/linux/fsinfo.h
> > +++ b/include/uapi/linux/fsinfo.h
> > @@ -37,6 +37,7 @@
> >  #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) */
> > +#define FSINFO_ATTR_MOUNT_ALL		0x206	/* List all
> > mounts in a namespace (list) */
> >  
> >  #define FSINFO_ATTR_AFS_CELL_NAME	0x300	/* AFS cell name
> > (string) */
> >  #define FSINFO_ATTR_AFS_SERVER_NAME	0x301	/* Name of
> > the Nth server (string) */
> > @@ -128,6 +129,8 @@ 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.
> > + *
> > + * Information struct element for fsinfo(FSINFO_ATTR_MOUNT_ALL).
> >   */
> >  struct fsinfo_mount_child {
> >  	__u64	mnt_unique_id;		/* Kernel-lifetime unique
> > mount ID */
> > @@ -139,6 +142,7 @@ struct fsinfo_mount_child {
> >  };
> >  
> >  #define FSINFO_ATTR_MOUNT_CHILDREN__STRUCT struct
> > fsinfo_mount_child
> > +#define FSINFO_ATTR_MOUNT_ALL__STRUCT struct fsinfo_mount_child
> >  
> >  /*
> >   * Information struct for fsinfo(FSINFO_ATTR_STATFS).
> > diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
> > index 374825ab85b0..596fa5e71762 100644
> > --- a/samples/vfs/test-fsinfo.c
> > +++ b/samples/vfs/test-fsinfo.c
> > @@ -365,6 +365,27 @@ static void
> > dump_fsinfo_generic_mount_children(void *reply, unsigned int size)
> >  	       (unsigned long long)r->mnt_notify_sum, mp);
> >  }
> >  
> > +static void dump_fsinfo_generic_mount_all(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_FULL,
> > +	};
> > +
> > +	sprintf(path, "%u", r->mnt_id);
> > +	mplen = get_fsinfo(path, "FSINFO_ATTR_MOUNT_POINT_FULL",
> > &params, (void **)&mp);
> > +	if (mplen < 0)
> > +		mp = "-";
> > +
> > +	printf("%5x %5x %12llx %10llu %s\n",
> > +	       r->mnt_id, r->parent_id, (unsigned long long)r-
> > >mnt_unique_id,
> > +	       r->mnt_notify_sum, mp);
> > +}
> > +
> >  static void dump_afs_fsinfo_server_address(void *reply, unsigned
> > int size)
> >  {
> >  	struct fsinfo_afs_server_address *f = reply;
> > @@ -492,6 +513,7 @@ static const struct fsinfo_attribute
> > fsinfo_attributes[] = {
> >  	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_moun
> > t_children),
> > +	FSINFO_LIST	(FSINFO_ATTR_MOUNT_ALL,		fsinfo_generic_moun
> > t_all),
> >  
> >  	FSINFO_STRING	(FSINFO_ATTR_AFS_CELL_NAME,	string),
> >  	FSINFO_STRING	(FSINFO_ATTR_AFS_SERVER_NAME,	string),
> > 
> >
David Howells Aug. 5, 2020, 4:44 p.m. UTC | #3
Miklos Szeredi <miklos@szeredi.hu> wrote:

> > where each element contains a once-in-a-system-lifetime unique ID, the
> > mount ID (which may get reused), the parent mount ID and sums of the
> > notification/change counters for the mount and its superblock.
> 
> The change counters are currently conditional on CONFIG_MOUNT_NOTIFICATIONS.
> Is this is intentional?

Yeah - the counters aren't driven unless CONFIG_MOUNT_NOTIFICATIONS=y.

I could perhaps make it so they're driven in both cases, but driving the
in-subtree counter is somewhat tied up in the notification posting.

This is something that can be fixed after this patchset is taken - if it is
taken since that doesn't change the UAPI.

David

Patch
diff mbox series

diff --git a/fs/fsinfo.c b/fs/fsinfo.c
index 0540cce89555..f230124ffdf5 100644
--- a/fs/fsinfo.c
+++ b/fs/fsinfo.c
@@ -296,6 +296,7 @@  static const struct fsinfo_attribute fsinfo_common_attributes[] = {
 	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),
+	FSINFO_LIST	(FSINFO_ATTR_MOUNT_ALL,		fsinfo_generic_mount_all),
 	{}
 };
 
diff --git a/fs/internal.h b/fs/internal.h
index cb5edcc7125a..267b4aaf0271 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -102,6 +102,7 @@  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 *);
+extern int fsinfo_generic_mount_all(struct path *, struct fsinfo_context *);
 
 /*
  * fs_struct.c
diff --git a/fs/namespace.c b/fs/namespace.c
index 122c12f9512b..1f2e06507244 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4494,4 +4494,41 @@  int fsinfo_generic_mount_children(struct path *path, struct fsinfo_context *ctx)
 	return ctx->usage;
 }
 
+/*
+ * Return information about all the mounts in the namespace referenced by the
+ * path.
+ */
+int fsinfo_generic_mount_all(struct path *path, struct fsinfo_context *ctx)
+{
+	struct mnt_namespace *ns;
+	struct mount *m, *p;
+	struct path chroot;
+	bool allow;
+
+	m = real_mount(path->mnt);
+	ns = m->mnt_ns;
+
+	get_fs_root(current->fs, &chroot);
+	rcu_read_lock();
+	allow = are_paths_connected(&chroot, path) || capable(CAP_SYS_ADMIN);
+	rcu_read_unlock();
+	path_put(&chroot);
+	if (!allow)
+		return -EPERM;
+
+	down_read(&namespace_sem);
+
+	list_for_each_entry(p, &ns->list, mnt_list) {
+		struct path mnt_root;
+
+		mnt_root.mnt	= &p->mnt;
+		mnt_root.dentry	= p->mnt.mnt_root;
+		if (are_paths_connected(path, &mnt_root))
+			fsinfo_store_mount(ctx, p, p == m);
+	}
+
+	up_read(&namespace_sem);
+	return ctx->usage;
+}
+
 #endif /* CONFIG_FSINFO */
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index 81329de6905e..e40192d98648 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -37,6 +37,7 @@ 
 #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) */
+#define FSINFO_ATTR_MOUNT_ALL		0x206	/* List all mounts in a namespace (list) */
 
 #define FSINFO_ATTR_AFS_CELL_NAME	0x300	/* AFS cell name (string) */
 #define FSINFO_ATTR_AFS_SERVER_NAME	0x301	/* Name of the Nth server (string) */
@@ -128,6 +129,8 @@  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.
+ *
+ * Information struct element for fsinfo(FSINFO_ATTR_MOUNT_ALL).
  */
 struct fsinfo_mount_child {
 	__u64	mnt_unique_id;		/* Kernel-lifetime unique mount ID */
@@ -139,6 +142,7 @@  struct fsinfo_mount_child {
 };
 
 #define FSINFO_ATTR_MOUNT_CHILDREN__STRUCT struct fsinfo_mount_child
+#define FSINFO_ATTR_MOUNT_ALL__STRUCT struct fsinfo_mount_child
 
 /*
  * Information struct for fsinfo(FSINFO_ATTR_STATFS).
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index 374825ab85b0..596fa5e71762 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -365,6 +365,27 @@  static void dump_fsinfo_generic_mount_children(void *reply, unsigned int size)
 	       (unsigned long long)r->mnt_notify_sum, mp);
 }
 
+static void dump_fsinfo_generic_mount_all(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_FULL,
+	};
+
+	sprintf(path, "%u", r->mnt_id);
+	mplen = get_fsinfo(path, "FSINFO_ATTR_MOUNT_POINT_FULL", &params, (void **)&mp);
+	if (mplen < 0)
+		mp = "-";
+
+	printf("%5x %5x %12llx %10llu %s\n",
+	       r->mnt_id, r->parent_id, (unsigned long long)r->mnt_unique_id,
+	       r->mnt_notify_sum, mp);
+}
+
 static void dump_afs_fsinfo_server_address(void *reply, unsigned int size)
 {
 	struct fsinfo_afs_server_address *f = reply;
@@ -492,6 +513,7 @@  static const struct fsinfo_attribute fsinfo_attributes[] = {
 	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),
+	FSINFO_LIST	(FSINFO_ATTR_MOUNT_ALL,		fsinfo_generic_mount_all),
 
 	FSINFO_STRING	(FSINFO_ATTR_AFS_CELL_NAME,	string),
 	FSINFO_STRING	(FSINFO_ATTR_AFS_SERVER_NAME,	string),