From 0e55a7cca4b66f625d67b292f80b6a976e77c51b Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Fri, 26 Sep 2008 19:01:20 -0700
Subject: [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
--- 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;
 }
 
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