fifo: Don't lookup reg path twice

Same for previous patch with vmas -- we do it on collect and
on real open. Just put the pointer on fifo_info structure.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

fifo.c

@@ -33,6 +33,7 @@ struct fifo_info {
 	struct file_desc	d;
 	FifoEntry		*fe;
 	bool			restore_data;
+	struct file_desc	*reg_d;
 };
 
 static LIST_HEAD(fifo_head);
@@ -109,7 +110,7 @@ static int open_fifo_fd(struct file_desc *d)
 {
 	struct fifo_info *info = container_of(d, struct fifo_info, d);
 
-	return open_path_by_id(info->fe->id, do_open_fifo, info);
+	return open_path(info->reg_d, do_open_fifo, info);
 }
 
 static void collect_fifo_fd(struct file_desc *d,
@@ -118,9 +119,8 @@ static void collect_fifo_fd(struct file_desc *d,
 	struct fifo_info *info;
 
 	info = container_of(d, struct fifo_info, d);
-	if (collect_special_file(info->fe->id) == NULL)
-		BUG();
-
+	info->reg_d = collect_special_file(info->fe->id);
+	BUG_ON(info->reg_d == NULL);
 	collect_gen_fd(fle, ri);
 }
 

files-reg.c

@@ -581,7 +581,7 @@ const struct fdtype_ops regfile_dump_ops = {
 	.dump		= dump_one_reg_file,
 };
 
-static int open_path(struct file_desc *d,
+int open_path(struct file_desc *d,
 		int(*open_cb)(struct reg_file_info *, void *), void *arg)
 {
 	struct reg_file_info *rfi;
@@ -620,7 +620,7 @@ static int open_path(struct file_desc *d,
 	return tmp;
 }
 
-int open_path_by_id(u32 id, int (*open_cb)(struct reg_file_info *, void *), void *arg)
+static int open_path_by_id(u32 id, int (*open_cb)(struct reg_file_info *, void *), void *arg)
 {
 	struct file_desc *fd;
 

include/files-reg.h

@@ -24,7 +24,7 @@ struct reg_file_info {
 };
 
 extern int open_reg_by_id(u32 id);
-extern int open_path_by_id(u32 id, int (*open_cb)(struct reg_file_info *, void *), void *arg);
+extern int open_path(struct file_desc *, int (*open_cb)(struct reg_file_info *, void *), void *arg);
 extern void clear_ghost_files(void);
 
 extern int prepare_shared_reg_files(void);