From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sat, 10 Jan 2015 22:53:21 +0000 (-0500)
Subject: new fs_pin killing logics
X-Git-Tag: fixes-v4.0-rc1~77^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=59eda0e07f43c950d31756213b607af673e551f0;p=pandora-kernel.git

new fs_pin killing logics

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/fs_pin.c b/fs/fs_pin.c
index 50ef7d2ef03c..0c77bdc238b2 100644
--- a/fs/fs_pin.c
+++ b/fs/fs_pin.c
@@ -1,4 +1,5 @@
 #include <linux/fs.h>
+#include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/fs_pin.h>
 #include "internal.h"
@@ -12,6 +13,10 @@ void pin_remove(struct fs_pin *pin)
 	hlist_del(&pin->m_list);
 	hlist_del(&pin->s_list);
 	spin_unlock(&pin_lock);
+	spin_lock_irq(&pin->wait.lock);
+	pin->done = 1;
+	wake_up_locked(&pin->wait);
+	spin_unlock_irq(&pin->wait.lock);
 }
 
 void pin_insert_group(struct fs_pin *pin, struct vfsmount *m, struct hlist_head *p)
@@ -28,19 +33,58 @@ void pin_insert(struct fs_pin *pin, struct vfsmount *m)
 	pin_insert_group(pin, m, &m->mnt_sb->s_pins);
 }
 
+void pin_kill(struct fs_pin *p)
+{
+	wait_queue_t wait;
+
+	if (!p) {
+		rcu_read_unlock();
+		return;
+	}
+	init_wait(&wait);
+	spin_lock_irq(&p->wait.lock);
+	if (likely(!p->done)) {
+		p->done = -1;
+		spin_unlock_irq(&p->wait.lock);
+		rcu_read_unlock();
+		p->kill(p);
+		return;
+	}
+	if (p->done > 0) {
+		spin_unlock_irq(&p->wait.lock);
+		rcu_read_unlock();
+		return;
+	}
+	__add_wait_queue(&p->wait, &wait);
+	while (1) {
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		spin_unlock_irq(&p->wait.lock);
+		rcu_read_unlock();
+		schedule();
+		rcu_read_lock();
+		if (likely(list_empty(&wait.task_list)))
+			break;
+		/* OK, we know p couldn't have been freed yet */
+		spin_lock_irq(&p->wait.lock);
+		if (p->done > 0) {
+			spin_unlock_irq(&p->wait.lock);
+			break;
+		}
+	}
+	rcu_read_unlock();
+}
+
 void mnt_pin_kill(struct mount *m)
 {
 	while (1) {
 		struct hlist_node *p;
-		struct fs_pin *pin;
 		rcu_read_lock();
 		p = ACCESS_ONCE(m->mnt_pins.first);
 		if (!p) {
 			rcu_read_unlock();
 			break;
 		}
-		pin = hlist_entry(p, struct fs_pin, m_list);
-		pin->kill(pin);
+		pin_kill(hlist_entry(p, struct fs_pin, m_list));
 	}
 }
 
@@ -48,14 +92,12 @@ void group_pin_kill(struct hlist_head *p)
 {
 	while (1) {
 		struct hlist_node *q;
-		struct fs_pin *pin;
 		rcu_read_lock();
 		q = ACCESS_ONCE(p->first);
 		if (!q) {
 			rcu_read_unlock();
 			break;
 		}
-		pin = hlist_entry(q, struct fs_pin, s_list);
-		pin->kill(pin);
+		pin_kill(hlist_entry(q, struct fs_pin, s_list));
 	}
 }
diff --git a/include/linux/fs_pin.h b/include/linux/fs_pin.h
index 2be38d1464ae..9dc4e0384bfb 100644
--- a/include/linux/fs_pin.h
+++ b/include/linux/fs_pin.h
@@ -1,11 +1,22 @@
-#include <linux/fs.h>
+#include <linux/wait.h>
 
 struct fs_pin {
+	wait_queue_head_t	wait;
+	int			done;
 	struct hlist_node	s_list;
 	struct hlist_node	m_list;
 	void (*kill)(struct fs_pin *);
 };
 
+struct vfsmount;
+
+static inline void init_fs_pin(struct fs_pin *p, void (*kill)(struct fs_pin *))
+{
+	init_waitqueue_head(&p->wait);
+	p->kill = kill;
+}
+
 void pin_remove(struct fs_pin *);
 void pin_insert_group(struct fs_pin *, struct vfsmount *, struct hlist_head *);
 void pin_insert(struct fs_pin *, struct vfsmount *);
+void pin_kill(struct fs_pin *);
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index b9cf6c51b181..918b117a7cd3 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -19,7 +19,7 @@ struct pidmap {
 #define BITS_PER_PAGE_MASK	(BITS_PER_PAGE-1)
 #define PIDMAP_ENTRIES		((PID_MAX_LIMIT+BITS_PER_PAGE-1)/BITS_PER_PAGE)
 
-struct bsd_acct_struct;
+struct fs_pin;
 
 struct pid_namespace {
 	struct kref kref;
@@ -37,7 +37,7 @@ struct pid_namespace {
 	struct dentry *proc_thread_self;
 #endif
 #ifdef CONFIG_BSD_PROCESS_ACCT
-	struct bsd_acct_struct *bacct;
+	struct fs_pin *bacct;
 #endif
 	struct user_namespace *user_ns;
 	struct work_struct proc_work;
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