linux-kernel - [PATCH 12/17] fsinfo: Allow the mount topology propogation flags to be retrieved [ver #17]

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Date:   Fri, 21 Feb 2020 18:03:24 +0000
From:   David Howells <dhowells@...hat.com>
To:     viro@...iv.linux.org.uk
Cc:     dhowells@...hat.com, raven@...maw.net, mszeredi@...hat.com,
        christian@...uner.io, jannh@...gle.com, darrick.wong@...cle.com,
        linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 12/17] fsinfo: Allow the mount topology propogation flags to
 be retrieved [ver #17]

Allow the mount topology propogation flags to be retrieved as part of the
FSINFO_ATTR_MOUNT_INFO attributes.

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

 fs/namespace.c              |    7 ++++++-
 include/uapi/linux/fsinfo.h |    2 +-
 include/uapi/linux/mount.h  |   10 +++++++++-
 samples/vfs/test-fsinfo.c   |    1 +
 samples/vfs/test-mntinfo.c  |    8 ++++----
 5 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index fc22aea18e2d..bbfd6cd5c501 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4142,15 +4142,20 @@ int fsinfo_generic_mount_info(struct path *path, struct fsinfo_context *ctx)
 			p->parent_id = p->mnt_id;
 		rcu_read_unlock();
 	}
-	if (IS_MNT_SHARED(m))
+	if (IS_MNT_SHARED(m)) {
 		p->group_id = m->mnt_group_id;
+		p->propagation |= MOUNT_PROPAGATION_SHARED;
+	}
 	if (IS_MNT_SLAVE(m)) {
 		int master = m->mnt_master->mnt_group_id;
 		int dom = get_dominating_id(m, &root);
 		p->master_id = master;
 		if (dom && dom != master)
 			p->from_id = dom;
+		p->propagation |= MOUNT_PROPAGATION_SLAVE;
 	}
+	if (IS_MNT_UNBINDABLE(m))
+		p->propagation |= MOUNT_PROPAGATION_UNBINDABLE;
 	path_put(&root);
 
 	flags = READ_ONCE(m->mnt.mnt_flags);
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index 29940d110ce3..119c371697be 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -100,7 +100,7 @@ struct fsinfo_mount_info {
 	__u32		from_id;	/* Slave propagated from ID */
 	__u32		attr;		/* MOUNT_ATTR_* flags */
 	__u32		change_counter;	/* Number of changes applied. */
-	__u32		__reserved[1];
+	__u32		propagation;	/* MOUNT_PROPAGATION_* flags */
 };
 
 #define FSINFO_ATTR_MOUNT_INFO__STRUCT struct fsinfo_mount_info
diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
index 96a0240f23fe..39e50fe9d8d9 100644
--- a/include/uapi/linux/mount.h
+++ b/include/uapi/linux/mount.h
@@ -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 +117,12 @@ 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 propogation attributes.
+ */
+#define MOUNT_PROPAGATION_UNBINDABLE	0x00000001 /* Mount is unbindable */
+#define MOUNT_PROPAGATION_SLAVE		0x00000002 /* Mount is slave */
+#define MOUNT_PROPAGATION_PRIVATE	0x00000000 /* Mount is private (ie. not shared) */
+#define MOUNT_PROPAGATION_SHARED	0x00000004 /* Mount is shared */
+
 #endif /* _UAPI_LINUX_MOUNT_H */
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index f761ded6a52c..6a61f3426982 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -291,6 +291,7 @@ static void dump_fsinfo_generic_mount_info(void *reply, unsigned int size)
 	printf("\tmnt_id  : %x\n", f->mnt_id);
 	printf("\tparent  : %x\n", f->parent_id);
 	printf("\tgroup   : %x\n", f->group_id);
+	printf("\tpropag  : %x\n", f->propagation);
 	printf("\tattr    : %x\n", f->attr);
 	printf("\tchanges : %x\n", f->change_counter);
 }
diff --git a/samples/vfs/test-mntinfo.c b/samples/vfs/test-mntinfo.c
index f4d90d0671c5..5a3d6b917447 100644
--- a/samples/vfs/test-mntinfo.c
+++ b/samples/vfs/test-mntinfo.c
@@ -135,9 +135,9 @@ static void display_mount(unsigned int mnt_id, unsigned int depth, char *path)
 	printf("%*.*s", s, s, "");
 
 	sprintf(dev, "%x:%x", ids.f_dev_major, ids.f_dev_minor);
-	printf("%10u %8x %2x %5s %s",
+	printf("%10u %8x %2x %x %5s %s",
 	       info.mnt_id, info.change_counter,
-	       info.attr,
+	       info.attr, info.propagation,
 	       dev, ids.f_fs_name);
 	putchar('\n');
 
@@ -236,8 +236,8 @@ int main(int argc, char **argv)
 		exit(2);
 	}
 
-	printf("MOUNT                                 MOUNT ID   CHANGE#  AT DEV   TYPE\n");
-	printf("------------------------------------- ---------- -------- -- ----- --------\n");
+	printf("MOUNT                                 MOUNT ID   CHANGE#  AT P DEV   TYPE\n");
+	printf("------------------------------------- ---------- -------- -- - ----- --------\n");
 	display_mount(mnt_id, 0, path);
 	return 0;
 }