[RFC PATCH] touch_mnt_namespace when the mount flags change

Daemons that need to be launched while the rootfs is read-only can now
poll /proc/mounts to be notified when their O_RDWR requests may no
longer end in EROFS.

Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/fs/namespace.c b/fs/namespace.c
index f527a0d..cce4670 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1550,8 +1550,13 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
        if (!err)
                path->mnt->mnt_flags = mnt_flags;
        up_write(&sb->s_umount);
-       if (!err)
+       if (!err) {
                security_sb_post_remount(path->mnt, flags, data);
+
+               spin_lock(&vfsmount_lock);
+               touch_mnt_namespace(path->mnt->mnt_ns);
+               spin_unlock(&vfsmount_lock);
+       }
        return err;
 }