MDEV-20094 InnoDB blob allocation allocates extra extents

- InnoDB reserves the free extents unnecessarily during blob
page allocation even though btr_page_alloc() can handle
reserving the extent when the existing ran out of pages to be used.

mysql-test/suite/innodb/r/check_ibd_filesize,32k.rdiff

---- mysql-test/suite/innodb/r/check_ibd_filesize.result	2022-08-16 17:28:06.462350465 +0530
-+++ mysql-test/suite/innodb/r/check_ibd_filesize.reject	2022-08-16 17:29:25.129637040 +0530
 @@ -3,18 +3,12 @@
  # SPACE IN 5.7 THAN IN 5.6
  #
@@ -14,7 +12,7 @@
 -# bytes: 65536
 +# bytes: 131072
  INSERT INTO t1 SELECT seq,REPEAT('a',30000) FROM seq_1_to_20;
--# bytes: 4194304
+-# bytes: 2097152
 -DROP TABLE t1;
 -CREATE TABLE t1 (a INT PRIMARY KEY, b BLOB)
 -ENGINE=InnoDB ROW_FORMAT=COMPRESSED KEY_BLOCK_SIZE=1;

mysql-test/suite/innodb/r/check_ibd_filesize,4k.rdiff

---- mysql-test/suite/innodb/r/check_ibd_filesize.result	2022-08-16 17:28:06.462350465 +0530
-+++ mysql-test/suite/innodb/r/check_ibd_filesize.reject	2022-08-16 17:31:39.288769153 +0530
 @@ -3,18 +3,18 @@
  # SPACE IN 5.7 THAN IN 5.6
  #
@@ -13,7 +11,7 @@
 -# bytes: 65536
 +# bytes: 16384
  INSERT INTO t1 SELECT seq,REPEAT('a',30000) FROM seq_1_to_20;
- # bytes: 4194304
+ # bytes: 2097152
  DROP TABLE t1;
  CREATE TABLE t1 (a INT PRIMARY KEY, b BLOB)
  ENGINE=InnoDB ROW_FORMAT=COMPRESSED KEY_BLOCK_SIZE=1;

mysql-test/suite/innodb/r/check_ibd_filesize,64k.rdiff

---- mysql-test/suite/innodb/r/check_ibd_filesize.result	2022-08-16 17:28:06.462350465 +0530
-+++ mysql-test/suite/innodb/r/check_ibd_filesize.reject	2022-08-16 17:30:28.957174270 +0530
 @@ -3,18 +3,12 @@
  # SPACE IN 5.7 THAN IN 5.6
  #
@@ -14,7 +12,7 @@
 -# bytes: 65536
 +# bytes: 262144
  INSERT INTO t1 SELECT seq,REPEAT('a',30000) FROM seq_1_to_20;
--# bytes: 4194304
+-# bytes: 2097152
 -DROP TABLE t1;
 -CREATE TABLE t1 (a INT PRIMARY KEY, b BLOB)
 -ENGINE=InnoDB ROW_FORMAT=COMPRESSED KEY_BLOCK_SIZE=1;

mysql-test/suite/innodb/r/check_ibd_filesize,8k.rdiff

---- mysql-test/suite/innodb/r/check_ibd_filesize.result	2022-08-16 17:28:06.462350465 +0530
-+++ mysql-test/suite/innodb/r/check_ibd_filesize.reject	2022-08-16 17:31:03.516962339 +0530
 @@ -3,18 +3,18 @@
  # SPACE IN 5.7 THAN IN 5.6
  #
@@ -13,7 +11,7 @@
 -# bytes: 65536
 +# bytes: 32768
  INSERT INTO t1 SELECT seq,REPEAT('a',30000) FROM seq_1_to_20;
- # bytes: 4194304
+ # bytes: 2097152
  DROP TABLE t1;
  CREATE TABLE t1 (a INT PRIMARY KEY, b BLOB)
  ENGINE=InnoDB ROW_FORMAT=COMPRESSED KEY_BLOCK_SIZE=1;

mysql-test/suite/innodb/r/check_ibd_filesize.result

@@ -10,7 +10,7 @@ DROP TABLE t1;
 CREATE TABLE t1 (a INT PRIMARY KEY, b BLOB) ENGINE=InnoDB;
 # bytes: 65536
 INSERT INTO t1 SELECT seq,REPEAT('a',30000) FROM seq_1_to_20;
-# bytes: 4194304
+# bytes: 2097152
 DROP TABLE t1;
 CREATE TABLE t1 (a INT PRIMARY KEY, b BLOB)
 ENGINE=InnoDB ROW_FORMAT=COMPRESSED KEY_BLOCK_SIZE=1;

storage/innobase/btr/btr0cur.cc

@@ -7684,7 +7684,6 @@ btr_store_big_rec_extern_fields(
 			buf_block_t*	block;
 			page_t*		page;
 			const ulint	commit_freq = 4;
-			ulint		r_extents;
 
 			ut_ad(page_align(field_ref) == page_align(rec));
 
@@ -7723,21 +7722,18 @@ btr_store_big_rec_extern_fields(
 				alloc_mtr = &mtr;
 			}
 
-			if (!fsp_reserve_free_extents(&r_extents,
-						      index->table->space, 1,
-						      FSP_BLOB, alloc_mtr,
-						      1)) {
+			block = btr_page_alloc(index, hint_page_no, FSP_NO_DIR,
+					       0, alloc_mtr, &mtr);
 
-				alloc_mtr->commit();
+			if (!block) {
 				error = DB_OUT_OF_FILE_SPACE;
+				alloc_mtr->commit();
+				if (op == BTR_STORE_INSERT_BULK) {
+					mtr.commit();
+				}
 				goto func_exit;
 			}
 
-			block = btr_page_alloc(index, hint_page_no, FSP_NO_DIR,
-					       0, alloc_mtr, &mtr);
-
-			index->table->space->release_free_extents(r_extents);
-
 			if (UNIV_UNLIKELY(op == BTR_STORE_INSERT_BULK)) {
 				mtr_bulk.commit();
 			}