MDEV-12253 post-push fix: buf_read_page_low() can return DB_ERROR

The function buf_read_page_low() invokes fil_io(), which can return DB_ERROR when the requested page is out of bounds (such as when restoring a buffer pool dump). The callers should be handling that.

Author: dr-m

storage/innobase/buf/buf0rea.cc

@@ -368,6 +368,7 @@ buf_read_ahead_random(
 switch (err) {
 case DB_SUCCESS:
 case DB_TABLESPACE_TRUNCATED:
+case DB_ERROR:
 break;
 case DB_TABLESPACE_DELETED:
 ib::info() << "Random readahead trying to"
@@ -470,6 +471,7 @@ buf_read_page_background(
 switch (err) {
 case DB_SUCCESS:
 case DB_TABLESPACE_TRUNCATED:
+case DB_ERROR:
 break;
 case DB_TABLESPACE_DELETED:
 ib::info() << "trying to read page " << page_id
@@ -750,6 +752,7 @@ buf_read_ahead_linear(
 switch (err) {
 case DB_SUCCESS:
 case DB_TABLESPACE_TRUNCATED:
+case DB_ERROR:
 break;
 case DB_TABLESPACE_DELETED:
 ib::info() << "linear readahead trying to"
@@ -848,6 +851,7 @@ buf_read_ibuf_merge_pages(
 switch(err) {
 case DB_SUCCESS:
 case DB_TABLESPACE_TRUNCATED:
+case DB_ERROR:
 break;
 case DB_TABLESPACE_DELETED:
 goto tablespace_deleted;