3 files changed, 50 insertions, 22 deletions

diff --git a/fs/file_table.c b/fs/file_table.c
index 9b70ed2bbc4e..0cc7bea6b51a 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -52,7 +52,8 @@ static void file_free_rcu(struct rcu_head *head)
 static inline void file_free(struct file *f)
 {
 	security_file_free(f);
-	percpu_counter_dec(&nr_files);
+	if (!(f->f_mode & FMODE_NOACCOUNT))
+		percpu_counter_dec(&nr_files);
 	call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
 }
 
@@ -91,6 +92,34 @@ int proc_nr_files(struct ctl_table *table, int write,
 }
 #endif
 
+static struct file *__alloc_file(int flags, const struct cred *cred)
+{
+	struct file *f;
+	int error;
+
+	f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
+	if (unlikely(!f))
+		return ERR_PTR(-ENOMEM);
+
+	f->f_cred = get_cred(cred);
+	error = security_file_alloc(f);
+	if (unlikely(error)) {
+		file_free_rcu(&f->f_u.fu_rcuhead);
+		return ERR_PTR(error);
+	}
+
+	atomic_long_set(&f->f_count, 1);
+	rwlock_init(&f->f_owner.lock);
+	spin_lock_init(&f->f_lock);
+	mutex_init(&f->f_pos_lock);
+	eventpoll_init_file(f);
+	f->f_flags = flags;
+	f->f_mode = OPEN_FMODE(flags);
+	/* f->f_version: 0 */
+
+	return f;
+}
+
 /* Find an unused file structure and return a pointer to it.
  * Returns an error pointer if some error happend e.g. we over file
  * structures limit, run out of memory or operation is not permitted.
@@ -105,7 +134,6 @@ struct file *alloc_empty_file(int flags, const struct cred *cred)
 {
 	static long old_max;
 	struct file *f;
-	int error;
 
 	/*
 	 * Privileged users can go above max_files
@@ -119,26 +147,10 @@ struct file *alloc_empty_file(int flags, const struct cred *cred)
 			goto over;
 	}
 
-	f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
-	if (unlikely(!f))
-		return ERR_PTR(-ENOMEM);
-
-	f->f_cred = get_cred(cred);
-	error = security_file_alloc(f);
-	if (unlikely(error)) {
-		file_free_rcu(&f->f_u.fu_rcuhead);
-		return ERR_PTR(error);
-	}
+	f = __alloc_file(flags, cred);
+	if (!IS_ERR(f))
+		percpu_counter_inc(&nr_files);
 
-	atomic_long_set(&f->f_count, 1);
-	rwlock_init(&f->f_owner.lock);
-	spin_lock_init(&f->f_lock);
-	mutex_init(&f->f_pos_lock);
-	eventpoll_init_file(f);
-	f->f_flags = flags;
-	f->f_mode = OPEN_FMODE(flags);
-	/* f->f_version: 0 */
-	percpu_counter_inc(&nr_files);
 	return f;
 
 over:
@@ -150,6 +162,21 @@ over:
 	return ERR_PTR(-ENFILE);
 }
 
+/*
+ * Variant of alloc_empty_file() that doesn't check and modify nr_files.
+ *
+ * Should not be used unless there's a very good reason to do so.
+ */
+struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred)
+{
+	struct file *f = __alloc_file(flags, cred);
+
+	if (!IS_ERR(f))
+		f->f_mode |= FMODE_NOACCOUNT;
+
+	return f;
+}
+
 /**
  * alloc_file - allocate and initialize a 'struct file'
  *
diff --git a/fs/internal.h b/fs/internal.h
index 52a346903748..442098fa0a84 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -94,6 +94,7 @@ extern void chroot_fs_refs(const struct path *, const struct path *);
  * file_table.c
  */
 extern struct file *alloc_empty_file(int, const struct cred *);
+extern struct file *alloc_empty_file_noaccount(int, const struct cred *);
 
 /*
  * super.c
diff --git a/fs/open.c b/fs/open.c
index dd15711eb658..9c6617dbb2c0 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -928,7 +928,7 @@ EXPORT_SYMBOL(dentry_open);
 struct file *open_with_fake_path(const struct path *path, int flags,
 				struct inode *inode, const struct cred *cred)
 {
-	struct file *f = alloc_empty_file(flags, cred);
+	struct file *f = alloc_empty_file_noaccount(flags, cred);
 	if (!IS_ERR(f)) {
 		int error;