Patch "fs_pin: Allow for the possibility that m_list or s_list go unused." has been added to the 4.0-stable tree

Patch "fs_pin: Allow for the possibility that m_list or s_list go unused." 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

    fs_pin: Allow for the possibility that m_list or s_list go unused.

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:
     fs_pin-allow-for-the-possibility-that-m_list-or-s_list-go-unused.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 820f9f147dcce2602eefd9b575bbbd9ea14f0953 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Thu, 2 Apr 2015 16:35:48 -0500
Subject: fs_pin: Allow for the possibility that m_list or s_list go unused.

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

commit 820f9f147dcce2602eefd9b575bbbd9ea14f0953 upstream.

This is needed to support lazily umounting locked mounts.  Because the
entire unmounted subtree needs to stay together until there are no
users with references to any part of the subtree.

To support this guarantee that the fs_pin m_list and s_list nodes
are initialized by initializing them in init_fs_pin allowing
for the possibility that pin_insert_group does not touch them.

Further use hlist_del_init in pin_remove so that there is
a hlist_unhashed test before the list we attempt to update
the previous list item.

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

---
 fs/fs_pin.c            |    4 ++--
 include/linux/fs_pin.h |    2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

--- a/fs/fs_pin.c
+++ b/fs/fs_pin.c
@@ -9,8 +9,8 @@ static DEFINE_SPINLOCK(pin_lock);
 void pin_remove(struct fs_pin *pin)
 {
 	spin_lock(&pin_lock);
-	hlist_del(&pin->m_list);
-	hlist_del(&pin->s_list);
+	hlist_del_init(&pin->m_list);
+	hlist_del_init(&pin->s_list);
 	spin_unlock(&pin_lock);
 	spin_lock_irq(&pin->wait.lock);
 	pin->done = 1;
--- a/include/linux/fs_pin.h
+++ b/include/linux/fs_pin.h
@@ -13,6 +13,8 @@ struct vfsmount;
 static inline void init_fs_pin(struct fs_pin *p, void (*kill)(struct fs_pin *))
 {
 	init_waitqueue_head(&p->wait);
+	INIT_HLIST_NODE(&p->s_list);
+	INIT_HLIST_NODE(&p->m_list);
 	p->kill = kill;
 }
 


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

queue-4.0/mnt-fail-collect_mounts-when-applied-to-unmounted-mounts.patch
queue-4.0/fs_pin-allow-for-the-possibility-that-m_list-or-s_list-go-unused.patch