btrfs: add enospc debug messages for ticket failure

When debugging weird enospc problems it's handy to be able to dump the
space info when we wake up all tickets, and see what the ticket values
are.  This helped me figure out cases where we were enospc'ing when we
shouldn't have been.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/space-info.c

@@ -258,14 +258,11 @@ do {									\
 	spin_unlock(&__rsv->lock);					\
 } while (0)
 
-void btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
-			   struct btrfs_space_info *info, u64 bytes,
-			   int dump_block_groups)
+static void __btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
+				    struct btrfs_space_info *info)
 {
-	struct btrfs_block_group_cache *cache;
-	int index = 0;
+	lockdep_assert_held(&info->lock);
 
-	spin_lock(&info->lock);
 	btrfs_info(fs_info, "space_info %llu has %llu free, is %sfull",
 		   info->flags,
 		   info->total_bytes - btrfs_space_info_used(info, true),
@@ -275,7 +272,6 @@ void btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
 		info->total_bytes, info->bytes_used, info->bytes_pinned,
 		info->bytes_reserved, info->bytes_may_use,
 		info->bytes_readonly);
-	spin_unlock(&info->lock);
 
 	DUMP_BLOCK_RSV(fs_info, global_block_rsv);
 	DUMP_BLOCK_RSV(fs_info, trans_block_rsv);
@@ -283,6 +279,19 @@ void btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
 	DUMP_BLOCK_RSV(fs_info, delayed_block_rsv);
 	DUMP_BLOCK_RSV(fs_info, delayed_refs_rsv);
 
+}
+
+void btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
+			   struct btrfs_space_info *info, u64 bytes,
+			   int dump_block_groups)
+{
+	struct btrfs_block_group_cache *cache;
+	int index = 0;
+
+	spin_lock(&info->lock);
+	__btrfs_dump_space_info(fs_info, info);
+	spin_unlock(&info->lock);
+
 	if (!dump_block_groups)
 		return;
 
@@ -696,6 +705,11 @@ static bool maybe_fail_all_tickets(struct btrfs_fs_info *fs_info,
 	u64 tickets_id = space_info->tickets_id;
 	u64 first_ticket_bytes = 0;
 
+	if (btrfs_test_opt(fs_info, ENOSPC_DEBUG)) {
+		btrfs_info(fs_info, "cannot satisfy tickets, dumping space info");
+		__btrfs_dump_space_info(fs_info, space_info);
+	}
+
 	while (!list_empty(&space_info->tickets) &&
 	       tickets_id == space_info->tickets_id) {
 		ticket = list_first_entry(&space_info->tickets,
@@ -716,6 +730,10 @@ static bool maybe_fail_all_tickets(struct btrfs_fs_info *fs_info,
 		else if (first_ticket_bytes > ticket->bytes)
 			return true;
 
+		if (btrfs_test_opt(fs_info, ENOSPC_DEBUG))
+			btrfs_info(fs_info, "failing ticket with %llu bytes",
+				   ticket->bytes);
+
 		list_del_init(&ticket->list);
 		ticket->error = -ENOSPC;
 		wake_up(&ticket->wait);