File locking fixes for v5.13

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Merge tag 'locks-v5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux

Pull file locking updates from Jeff Layton:
 "When we reworked the blocked locks into a tree structure instead of a
  flat list a few releases ago, we lost the ability to see all of the
  file locks in /proc/locks. Luo's patch fixes it to dump out all of the
  blocked locks instead, which restores the full output.

  This changes the format of /proc/locks as the blocked locks are shown
  at multiple levels of indentation now, but lslocks (the only common
  program I've ID'ed that scrapes this info) seems to be OK with that.

  Tian also contributed a small patch to remove a useless assignment"

* tag 'locks-v5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux:
  fs/locks: remove useless assignment in fcntl_getlk
  fs/locks: print full locks information

fs/locks.c

@@ -2369,7 +2369,6 @@ int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock *flock)
 		if (flock->l_pid != 0)
 			goto out;
 
-		cmd = F_GETLK;
 		fl->fl_flags |= FL_OFDLCK;
 		fl->fl_owner = filp;
 	}
@@ -2825,7 +2824,7 @@ struct locks_iterator {
 };
 
 static void lock_get_status(struct seq_file *f, struct file_lock *fl,
-			    loff_t id, char *pfx)
+			    loff_t id, char *pfx, int repeat)
 {
 	struct inode *inode = NULL;
 	unsigned int fl_pid;
@@ -2841,7 +2840,11 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
 	if (fl->fl_file != NULL)
 		inode = locks_inode(fl->fl_file);
 
-	seq_printf(f, "%lld:%s ", id, pfx);
+	seq_printf(f, "%lld: ", id);
+
+	if (repeat)
+		seq_printf(f, "%*s", repeat - 1 + (int)strlen(pfx), pfx);
+
 	if (IS_POSIX(fl)) {
 		if (fl->fl_flags & FL_ACCESS)
 			seq_puts(f, "ACCESS");
@@ -2903,21 +2906,64 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
 	}
 }
 
+static struct file_lock *get_next_blocked_member(struct file_lock *node)
+{
+	struct file_lock *tmp;
+
+	/* NULL node or root node */
+	if (node == NULL || node->fl_blocker == NULL)
+		return NULL;
+
+	/* Next member in the linked list could be itself */
+	tmp = list_next_entry(node, fl_blocked_member);
+	if (list_entry_is_head(tmp, &node->fl_blocker->fl_blocked_requests, fl_blocked_member)
+		|| tmp == node) {
+		return NULL;
+	}
+
+	return tmp;
+}
+
 static int locks_show(struct seq_file *f, void *v)
 {
 	struct locks_iterator *iter = f->private;
-	struct file_lock *fl, *bfl;
+	struct file_lock *cur, *tmp;
 	struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file)->i_sb);
+	int level = 0;
 
-	fl = hlist_entry(v, struct file_lock, fl_link);
+	cur = hlist_entry(v, struct file_lock, fl_link);
 
-	if (locks_translate_pid(fl, proc_pidns) == 0)
+	if (locks_translate_pid(cur, proc_pidns) == 0)
 		return 0;
 
-	lock_get_status(f, fl, iter->li_pos, "");
+	/* View this crossed linked list as a binary tree, the first member of fl_blocked_requests
+	 * is the left child of current node, the next silibing in fl_blocked_member is the
+	 * right child, we can alse get the parent of current node from fl_blocker, so this
+	 * question becomes traversal of a binary tree
+	 */
+	while (cur != NULL) {
+		if (level)
+			lock_get_status(f, cur, iter->li_pos, "-> ", level);
+		else
+			lock_get_status(f, cur, iter->li_pos, "", level);
 
-	list_for_each_entry(bfl, &fl->fl_blocked_requests, fl_blocked_member)
-		lock_get_status(f, bfl, iter->li_pos, " ->");
+		if (!list_empty(&cur->fl_blocked_requests)) {
+			/* Turn left */
+			cur = list_first_entry_or_null(&cur->fl_blocked_requests,
+				struct file_lock, fl_blocked_member);
+			level++;
+		} else {
+			/* Turn right */
+			tmp = get_next_blocked_member(cur);
+			/* Fall back to parent node */
+			while (tmp == NULL && cur->fl_blocker != NULL) {
+				cur = cur->fl_blocker;
+				level--;
+				tmp = get_next_blocked_member(cur);
+			}
+			cur = tmp;
+		}
+	}
 
 	return 0;
 }
@@ -2938,7 +2984,7 @@ static void __show_fd_locks(struct seq_file *f,
 
 		(*id)++;
 		seq_puts(f, "lock:\t");
-		lock_get_status(f, fl, *id, "");
+		lock_get_status(f, fl, *id, "", 0);
 	}
 }