MDEV-22710 Assertion ...status != buf_page_t::FREED in ibuf_remove_free_page()

The buf_page_free() call that was introduced in MDEV-15528 was
performed too early in fseg_free_page(), tripping a debug check
in ibuf_remove_free_page(). In all other callers, we can (and will)
invoke buf_page_free() right after fseg_free_page(), but in
ibuf_remove_free_page() we will defer that call to the end of the
mini-transaction. (That call was already present.)

storage/innobase/btr/btr0btr.cc

@@ -746,6 +746,7 @@ void btr_page_free(dict_index_t* index, buf_block_t* block, mtr_t* mtr,
 					  : PAGE_HEADER + PAGE_BTR_SEG_TOP];
 	fseg_free_page(seg_header,
 		       index->table->space, block->page.id.page_no(), mtr);
+	buf_page_free(block->page.id, mtr, __FILE__, __LINE__);
 
 	/* The page was marked free in the allocation bitmap, but it
 	should remain exclusively latched until mtr_t::commit() or until it

storage/innobase/fsp/fsp0fsp.cc

@@ -2622,8 +2622,6 @@ fseg_free_page(
 
 	fseg_free_page_low(seg_inode, iblock, space, offset, mtr);
 
-	buf_page_free(page_id_t(space->id, offset), mtr, __FILE__, __LINE__);
-
 	DBUG_VOID_RETURN;
 }
 

storage/innobase/trx/trx0undo.cc

@@ -629,6 +629,7 @@ trx_undo_free_page(
 	fseg_free_page(TRX_UNDO_SEG_HDR + TRX_UNDO_FSEG_HEADER
 		       + header_block->frame,
 		       rseg->space, page_no, mtr);
+	buf_page_free(page_id_t(space, page_no), mtr, __FILE__, __LINE__);
 
 	const fil_addr_t last_addr = flst_get_last(
 		TRX_UNDO_SEG_HDR + TRX_UNDO_PAGE_LIST + header_block->frame);