propagate error from get_empty_filp() to its callers

Based on parts from Anatol's patch (the rest is the next commit).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/file_table.c

@@ -94,8 +94,8 @@ int proc_nr_files(ctl_table *table, int write,
 #endif
 
 /* Find an unused file structure and return a pointer to it.
- * Returns NULL, if there are no more free file structures or
- * we run out of memory.
+ * Returns an error pointer if some error happend e.g. we over file
+ * structures limit, run out of memory or operation is not permitted.
  *
  * Be very careful using this.  You are responsible for
  * getting write access to any mount that you might assign
@@ -107,7 +107,8 @@ struct file *get_empty_filp(void)
 {
 	const struct cred *cred = current_cred();
 	static long old_max;
-	struct file * f;
+	struct file *f;
+	int error;
 
 	/*
 	 * Privileged users can go above max_files
@@ -122,13 +123,16 @@ struct file *get_empty_filp(void)
 	}
 
 	f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
-	if (f == NULL)
-		goto fail;
+	if (unlikely(!f))
+		return ERR_PTR(-ENOMEM);
 
 	percpu_counter_inc(&nr_files);
 	f->f_cred = get_cred(cred);
-	if (security_file_alloc(f))
-		goto fail_sec;
+	error = security_file_alloc(f);
+	if (unlikely(error)) {
+		file_free(f);
+		return ERR_PTR(error);
+	}
 
 	INIT_LIST_HEAD(&f->f_u.fu_list);
 	atomic_long_set(&f->f_count, 1);
@@ -144,12 +148,7 @@ struct file *get_empty_filp(void)
 		pr_info("VFS: file-max limit %lu reached\n", get_max_files());
 		old_max = get_nr_files();
 	}
-	goto fail;
-
-fail_sec:
-	file_free(f);
-fail:
-	return NULL;
+	return ERR_PTR(-ENFILE);
 }
 
 /**
@@ -173,7 +172,7 @@ struct file *alloc_file(struct path *path, fmode_t mode,
 	struct file *file;
 
 	file = get_empty_filp();
-	if (!file)
+	if (IS_ERR(file))
 		return NULL;
 
 	file->f_path = *path;

fs/namei.c

@@ -2941,8 +2941,8 @@ static struct file *path_openat(int dfd, struct filename *pathname,
 	int error;
 
 	file = get_empty_filp();
-	if (!file)
-		return ERR_PTR(-ENFILE);
+	if (IS_ERR(file))
+		return file;
 
 	file->f_flags = op->open_flag;
 

fs/open.c

@@ -810,23 +810,22 @@ struct file *dentry_open(const struct path *path, int flags,
 	/* We must always pass in a valid mount pointer. */
 	BUG_ON(!path->mnt);
 
-	error = -ENFILE;
 	f = get_empty_filp();
-	if (f == NULL)
-		return ERR_PTR(error);
-
-	f->f_flags = flags;
-	f->f_path = *path;
-	error = do_dentry_open(f, NULL, cred);
-	if (!error) {
-		error = open_check_o_direct(f);
-		if (error) {
-			fput(f);
+	if (!IS_ERR(f)) {
+		f->f_flags = flags;
+		f->f_path = *path;
+		error = do_dentry_open(f, NULL, cred);
+		if (!error) {
+			/* from now on we need fput() to dispose of f */
+			error = open_check_o_direct(f);
+			if (error) {
+				fput(f);
+				f = ERR_PTR(error);
+			}
+		} else { 
+			put_filp(f);
 			f = ERR_PTR(error);
 		}
-	} else { 
-		put_filp(f);
-		f = ERR_PTR(error);
 	}
 	return f;
 }