[PATCH v4 7/9] ovl: opt-in for per-sb io stats

[Amir Goldstein <amir73il@gmail.com>]

Traditionally, system administrators have used the iostat utility
to track the amount of io performed to a local disk filesystem.

Similar functionality is provided for NFS mounts via the nfsstat
utility that reads the NFS client's stats from /proc/pid/mountstats.

There is currently no good way for a system administrator or a
monitoring application inside a container to track the amount of io
performed via overlayfs.

Opt-in for generic io stats via /proc/pid/mountstats to provide
that functionality.

This feature depends on CONFIG_FS_IOSTATS.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/overlayfs/super.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 7bb0a47cb615..4a5847bca1a6 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -6,6 +6,7 @@
 
 #include <uapi/linux/magic.h>
 #include <linux/fs.h>
+#include <linux/fs_iostats.h>
 #include <linux/namei.h>
 #include <linux/xattr.h>
 #include <linux/mount.h>
@@ -2165,7 +2166,7 @@ static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
 static struct file_system_type ovl_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "overlay",
-	.fs_flags	= FS_USERNS_MOUNT,
+	.fs_flags	= FS_USERNS_MOUNT | FS_SB_IOSTATS,
 	.mount		= ovl_mount,
 	.kill_sb	= kill_anon_super,
 };
-- 
2.25.1