Patch "mnt: In umount_tree reuse mnt_list instead of mnt_hash" has been added to the 4.0-stable tree

Patch "mnt: In umount_tree reuse mnt_list instead of mnt_hash" has been added to the 4.0-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    mnt: In umount_tree reuse mnt_list instead of mnt_hash

to the 4.0-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mnt-in-umount_tree-reuse-mnt_list-instead-of-mnt_hash.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From c003b26ff98ca04a180ff34c38c007a3998d62f9 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Thu, 18 Dec 2014 13:10:48 -0600
Subject: mnt: In umount_tree reuse mnt_list instead of mnt_hash

From: "Eric W. Biederman" <ebiederm@xmission.com>

commit c003b26ff98ca04a180ff34c38c007a3998d62f9 upstream.

umount_tree builds a list of mounts that need to be unmounted.
Utilize mnt_list for this purpose instead of mnt_hash.  This begins to
allow keeping a mount on the mnt_hash after it is unmounted, which is
necessary for a properly functioning MNT_LOCKED implementation.

The fact that mnt_list is an ordinary list makding available list_move
is nice bonus.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/namespace.c |   20 +++++++++++---------
 fs/pnode.c     |    6 +++---
 fs/pnode.h     |    2 +-
 3 files changed, 15 insertions(+), 13 deletions(-)

--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1329,23 +1329,25 @@ enum umount_tree_flags {
  */
 static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
 {
-	HLIST_HEAD(tmp_list);
+	LIST_HEAD(tmp_list);
 	struct mount *p;
 
-	for (p = mnt; p; p = next_mnt(p, mnt)) {
-		hlist_del_init_rcu(&p->mnt_hash);
-		hlist_add_head(&p->mnt_hash, &tmp_list);
-	}
+	/* Gather the mounts to umount */
+	for (p = mnt; p; p = next_mnt(p, mnt))
+		list_move(&p->mnt_list, &tmp_list);
 
-	hlist_for_each_entry(p, &tmp_list, mnt_hash)
+	/* Hide the mounts from lookup_mnt and mnt_mounts */
+	list_for_each_entry(p, &tmp_list, mnt_list) {
+		hlist_del_init_rcu(&p->mnt_hash);
 		list_del_init(&p->mnt_child);
+	}
 
+	/* Add propogated mounts to the tmp_list */
 	if (how & UMOUNT_PROPAGATE)
 		propagate_umount(&tmp_list);
 
-	while (!hlist_empty(&tmp_list)) {
-		p = hlist_entry(tmp_list.first, struct mount, mnt_hash);
-		hlist_del_init_rcu(&p->mnt_hash);
+	while (!list_empty(&tmp_list)) {
+		p = list_first_entry(&tmp_list, struct mount, mnt_list);
 		list_del_init(&p->mnt_expire);
 		list_del_init(&p->mnt_list);
 		__touch_mnt_namespace(p->mnt_ns);
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -384,7 +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);
-			hlist_add_before_rcu(&child->mnt_hash, &mnt->mnt_hash);
+			list_move_tail(&child->mnt_list, &mnt->mnt_list);
 		}
 	}
 }
@@ -396,11 +396,11 @@ static void __propagate_umount(struct mo
  *
  * vfsmount lock must be held for write
  */
-int propagate_umount(struct hlist_head *list)
+int propagate_umount(struct list_head *list)
 {
 	struct mount *mnt;
 
-	hlist_for_each_entry(mnt, list, mnt_hash)
+	list_for_each_entry(mnt, list, mnt_list)
 		__propagate_umount(mnt);
 	return 0;
 }
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -40,7 +40,7 @@ static inline void set_mnt_shared(struct
 void change_mnt_propagation(struct mount *, int);
 int propagate_mnt(struct mount *, struct mountpoint *, struct mount *,
 		struct hlist_head *);
-int propagate_umount(struct hlist_head *);
+int propagate_umount(struct list_head *);
 int propagate_mount_busy(struct mount *, int);
 void mnt_release_group_id(struct mount *);
 int get_dominating_id(struct mount *mnt, const struct path *root);


Patches currently in stable-queue which might be from ebiederm@xmission.com are

queue-4.0/mnt-don-t-propagate-umounts-in-__detach_mounts.patch
queue-4.0/mnt-add-mnt_umount-flag.patch
queue-4.0/mnt-honor-mnt_locked-when-detaching-mounts.patch
queue-4.0/mnt-delay-removal-from-the-mount-hash.patch
queue-4.0/mnt-on-an-unmount-propagate-clearing-of-mnt_locked.patch
queue-4.0/mnt-don-t-propagate-unmounts-to-locked-mounts.patch
queue-4.0/mnt-factor-out-unhash_mnt-from-detach_mnt-and-umount_tree.patch
queue-4.0/mnt-factor-umount_mnt-from-umount_tree.patch
queue-4.0/mnt-fix-the-error-check-in-__detach_mounts.patch
queue-4.0/mnt-update-detach_mounts-to-leave-mounts-connected.patch
queue-4.0/mnt-improve-the-umount_tree-flags.patch
queue-4.0/mnt-in-umount_tree-reuse-mnt_list-instead-of-mnt_hash.patch