bsdacct: turn acct off for all pidns-s on umount time

All the bsd_acct_strcts with opened accounting are linked into a global
list.  So, the acct_auto_close(_mnt) walks one and drops the accounting
for each.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/acct.c

@@ -89,9 +89,11 @@ struct bsd_acct_struct {
 	struct file		*file;
 	struct pid_namespace	*ns;
 	struct timer_list	timer;
+	struct list_head	list;
 };
 
 static DEFINE_SPINLOCK(acct_lock);
+static LIST_HEAD(acct_list);
 
 /*
  * Called whenever the timer says to check the free space.
@@ -188,12 +190,14 @@ static void acct_file_reopen(struct bsd_acct_struct *acct, struct file *file,
 		acct->needcheck = 0;
 		acct->file = NULL;
 		acct->ns = NULL;
+		list_del(&acct->list);
 	}
 	if (file) {
 		acct->file = file;
 		acct->ns = ns;
 		acct->needcheck = 0;
 		acct->active = 1;
+		list_add(&acct->list, &acct_list);
 		/* It's been deleted if it was used before so this is safe */
 		setup_timer(&acct->timer, acct_timeout, (unsigned long)acct);
 		acct->timer.expires = jiffies + ACCT_TIMEOUT*HZ;
@@ -314,13 +318,13 @@ void acct_auto_close_mnt(struct vfsmount *m)
 {
 	struct bsd_acct_struct *acct;
 
-	acct = init_pid_ns.bacct;
-	if (acct == NULL)
-		return;
-
 	spin_lock(&acct_lock);
-	if (acct->file && acct->file->f_path.mnt == m)
-		acct_file_reopen(acct, NULL, NULL);
+restart:
+	list_for_each_entry(acct, &acct_list, list)
+		if (acct->file && acct->file->f_path.mnt == m) {
+			acct_file_reopen(acct, NULL, NULL);
+			goto restart;
+		}
 	spin_unlock(&acct_lock);
 }
 
@@ -335,13 +339,13 @@ void acct_auto_close(struct super_block *sb)
 {
 	struct bsd_acct_struct *acct;
 
-	acct = init_pid_ns.bacct;
-	if (acct == NULL)
-		return;
-
 	spin_lock(&acct_lock);
-	if (acct->file && acct->file->f_path.mnt->mnt_sb == sb)
-		acct_file_reopen(acct, NULL, NULL);
+restart:
+	list_for_each_entry(acct, &acct_list, list)
+		if (acct->file && acct->file->f_path.mnt->mnt_sb == sb) {
+			acct_file_reopen(acct, NULL, NULL);
+			goto restart;
+		}
 	spin_unlock(&acct_lock);
 }