MDEV-11254 cleanup: Remove buf_page_t::write_size

commit 6495806e removed all reads
of buf_page_t::write_size. Let us remove the field altogether.

storage/innobase/buf/buf0buf.cc

@@ -547,13 +547,13 @@ static bool buf_page_decrypt_after_read(buf_page_t* bpage, fil_space_t* space)
 decompress_with_slot:
 		ut_d(fil_page_type_validate(dst_frame));
 
-		bpage->write_size = fil_page_decompress(slot->crypt_buf,
-							dst_frame);
+		ulint write_size = fil_page_decompress(slot->crypt_buf,
+						       dst_frame);
 		slot->release();
 
-		ut_ad(!bpage->write_size || fil_page_type_validate(dst_frame));
+		ut_ad(!write_size || fil_page_type_validate(dst_frame));
 		ut_ad(space->n_pending_ios > 0);
-		return bpage->write_size != 0;
+		return write_size != 0;
 	}
 
 	if (space->crypt_data
@@ -1502,7 +1502,6 @@ buf_block_init(
 	block->page.io_fix = BUF_IO_NONE;
 	block->page.flush_observer = NULL;
 	block->page.real_size = 0;
-	block->page.write_size = 0;
 	block->modify_clock = 0;
 	block->page.slot = NULL;
 
@@ -5244,7 +5243,6 @@ buf_page_init_low(
 	bpage->access_time = 0;
 	bpage->newest_modification = 0;
 	bpage->oldest_modification = 0;
-	bpage->write_size = 0;
 	bpage->real_size = 0;
 	bpage->slot = NULL;
 

storage/innobase/include/buf0buf.h

 /*****************************************************************************
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2013, 2020 MariaDB Corporation.
+Copyright (c) 2013, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -1508,11 +1508,6 @@ class buf_page_t {
 					zip.data == NULL means an active
 					buf_pool->watch */
 
-	ulint           write_size;	/* Write size is set when this
-					page is first time written and then
-					if written again we check is TRIM
-					operation needed. */
-
 	ulint           real_size;	/*!< Real size of the page
 					Normal pages == UNIV_PAGE_SIZE
 					page compressed pages, payload