btrfs: zoned: add ASSERT and WARN for EXTENT_BUFFER_ZONED_ZEROOUT handling

Add an ASSERT to catch a faulty delayed reference item resulting from
prematurely cleared extent buffer.

Also, add a WARN to detect if we try to dirty a ZEROOUT buffer again, which
is suspicious as its update will be lost.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent-tree.c

@@ -3464,6 +3464,14 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
 	if (root_id != BTRFS_TREE_LOG_OBJECTID) {
 		struct btrfs_ref generic_ref = { 0 };
 
+		/*
+		 * Assert that the extent buffer is not cleared due to
+		 * EXTENT_BUFFER_ZONED_ZEROOUT. Please refer
+		 * btrfs_clear_buffer_dirty() and btree_csum_one_bio() for
+		 * detail.
+		 */
+		ASSERT(btrfs_header_bytenr(buf) != 0);
+
 		btrfs_init_generic_ref(&generic_ref, BTRFS_DROP_DELAYED_REF,
 				       buf->start, buf->len, parent,
 				       btrfs_header_owner(buf));

fs/btrfs/extent_io.c

@@ -4193,6 +4193,7 @@ void set_extent_buffer_dirty(struct extent_buffer *eb)
 	num_folios = num_extent_folios(eb);
 	WARN_ON(atomic_read(&eb->refs) == 0);
 	WARN_ON(!test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags));
+	WARN_ON(test_bit(EXTENT_BUFFER_ZONED_ZEROOUT, &eb->bflags));
 
 	if (!was_dirty) {
 		bool subpage = eb->fs_info->nodesize < PAGE_SIZE;