[PATCH 4.0 110/220] mnt: Add MNT_UMOUNT flag

[Greg Kroah-Hartman]

4.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>

commit 590ce4bcbfb4e0462a720a4ad901e84416080bba upstream.

In some instances it is necessary to know if the the unmounting
process has begun on a mount.  Add MNT_UMOUNT to make that reliably
testable.

This fix gets used in fixing locked mounts in MNT_DETACH

Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/namespace.c        |    4 +++-
 fs/pnode.c            |    1 +
 include/linux/mount.h |    1 +
 3 files changed, 5 insertions(+), 1 deletion(-)

--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1333,8 +1333,10 @@ static void umount_tree(struct mount *mn
 	struct mount *p;
 
 	/* Gather the mounts to umount */
-	for (p = mnt; p; p = next_mnt(p, mnt))
+	for (p = mnt; p; p = next_mnt(p, mnt)) {
+		p->mnt.mnt_flags |= MNT_UMOUNT;
 		list_move(&p->mnt_list, &tmp_list);
+	}
 
 	/* Hide the mounts from lookup_mnt and mnt_mounts */
 	list_for_each_entry(p, &tmp_list, mnt_list) {
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -384,6 +384,7 @@ static void __propagate_umount(struct mo
 		if (child && list_empty(&child->mnt_mounts)) {
 			list_del_init(&child->mnt_child);
 			hlist_del_init_rcu(&child->mnt_hash);
+			child->mnt.mnt_flags |= MNT_UMOUNT;
 			list_move_tail(&child->mnt_list, &mnt->mnt_list);
 		}
 	}
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -61,6 +61,7 @@ struct mnt_namespace;
 #define MNT_DOOMED		0x1000000
 #define MNT_SYNC_UMOUNT		0x2000000
 #define MNT_MARKED		0x4000000
+#define MNT_UMOUNT		0x8000000
 
 struct vfsmount {
 	struct dentry *mnt_root;	/* root of the mounted tree */


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