files: Keep single sorted list of fds

After fds restore set merge we no longer need two lists.

Don't BUG in eventpoll when the tfd is not on the list.
This situation means that it's restored, so it's safe
to report OK from this place.
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/eventpoll.c

@@ -153,7 +153,7 @@ static int epoll_not_ready_tfd(EventpollTfdEntry *tdefe)
 {
 	struct fdinfo_list_entry *fle;
 
-	list_for_each_entry(fle, &rsti(current)->used, used_list) {
+	list_for_each_entry(fle, &rsti(current)->fds, ps_list) {
 		if (tdefe->tfd != fle->fe->fd)
 			continue;
 
@@ -162,7 +162,11 @@ static int epoll_not_ready_tfd(EventpollTfdEntry *tdefe)
 		else
 			return (fle->stage != FLE_RESTORED);
 	}
-	BUG();
+
+	/*
+	 * If tgt fle is not on the fds list, it's already
+	 * restored (see open_fdinfos), so we're ready.
+	 */
 	return 0;
 }
 

criu/files.c

@@ -103,8 +103,8 @@ struct fdinfo_list_entry *find_used_fd(struct pstree_item *task, int fd)
 	struct list_head *head;
 	struct fdinfo_list_entry *fle;
 
-	head = &rsti(task)->used;
-	list_for_each_entry_reverse(fle, head, used_list) {
+	head = &rsti(task)->fds;
+	list_for_each_entry_reverse(fle, head, ps_list) {
 		if (fle->fe->fd == fd)
 			return fle;
 		/* List is ordered, so let's stop */
@@ -118,16 +118,13 @@ void collect_task_fd(struct fdinfo_list_entry *new_fle, struct rst_info *ri)
 {
 	struct fdinfo_list_entry *fle;
 
-	/* fles in fds list are disordered */
-	list_add_tail(&new_fle->ps_list, &ri->fds);
-
-	/* fles in used list are ordered by fd */
-	list_for_each_entry(fle, &ri->used, used_list) {
+	/* fles in fds list are ordered by fd */
+	list_for_each_entry(fle, &ri->fds, ps_list) {
 		if (new_fle->fe->fd < fle->fe->fd)
 			break;
 	}
 
-	list_add_tail(&new_fle->used_list, &fle->used_list);
+	list_add_tail(&new_fle->ps_list, &fle->ps_list);
 }
 
 unsigned int find_unused_fd(struct pstree_item *task, int hint_fd)
@@ -142,9 +139,9 @@ unsigned int find_unused_fd(struct pstree_item *task, int hint_fd)
 	}
 
 	prev_fd = service_fd_min_fd() - 1;
-	head = &rsti(task)->used;
+	head = &rsti(task)->fds;
 
-	list_for_each_entry_reverse(fle, head, used_list) {
+	list_for_each_entry_reverse(fle, head, ps_list) {
 		fd = fle->fe->fd;
 		if (prev_fd > fd) {
 			fd++;
@@ -788,7 +785,6 @@ int prepare_fd_pid(struct pstree_item *item)
 	pid_t pid = vpid(item);
 	struct rst_info *rst_info = rsti(item);
 
-	INIT_LIST_HEAD(&rst_info->used);
 	INIT_LIST_HEAD(&rst_info->fds);
 
 	if (item->ids == NULL) /* zombie */
@@ -876,7 +872,7 @@ static bool task_fle(struct pstree_item *task, struct fdinfo_list_entry *fle)
 {
 	struct fdinfo_list_entry *tmp;
 
-	list_for_each_entry(tmp, &rsti(task)->used, used_list)
+	list_for_each_entry(tmp, &rsti(task)->fds, ps_list)
 		if (fle == tmp)
 			return true;
 	return false;

criu/include/files.h

@@ -74,7 +74,6 @@ struct fdinfo_list_entry {
 	struct list_head	desc_list;	/* To chain on  @fd_info_head */
 	struct file_desc	*desc;		/* Associated file descriptor */
 	struct list_head	ps_list;	/* To chain  per-task files */
-	struct list_head	used_list;	/* To chain per-task used fds */
 	int			pid;
 	FdinfoEntry		*fe;
 	u8			received:1;

criu/include/rst_info.h

@@ -26,7 +26,6 @@ struct fdt {
 struct _MmEntry;
 
 struct rst_info {
-	struct list_head	used;
 	struct list_head	fds;
 
 	void			*premmapped_addr;