Merge lp:~akopytov/percona-server/bug1162085-5.1 into lp:percona-server/5.1

[Alexey Kopytov]

    Bug #1162085: Percona server 5.5.30-rel30.1.465 reproducable hang

    The fix for bug #1070856 that the underlying binlog cache file is always
    larger then the offset passed to truncate_cached_file(). Which is not
    always the case, because a part of the data which has already been
    written may be in the IO_CACHE buffer, but not yet on disk.

    What happened in the test case was that the server wrote ~48K data into
    the binlog cache with 32K written to disk and the remaining part
    residing in the IO_CACHE buffer. On the ROLLBACK TO statement the server
    called truncate_cached_file() with the 48K offset, in which case
    my_chsize() actually increased the underlying file by appending 16K worth
    of zero bytes. When the remaining 16K bytes were eventually flushed to
    disk on COMMIT, my_b_flush_io_cache() appended them again to the file,
    resulting in the 64K total file size. This in turn led to
    MYSQL_BIN_LOG::write_cache() hanging when reading bogus zero bytes due
    to nonsensical zero offsets in the binlog cache.

    Fixed truncate_cached_file() to only call my_chsize() when the
    underlying cache file is larger than the passed offset.

http://jenkins.percona.com/view/PS%205.1/job/percona-server-5.1-param/530/

[Laurynas Biveinis (laurynas-biveinis)]

review: Approve

=== added file 'Percona-Server/mysql-test/suite/binlog/r/percona_bug1162085.result'
--- Percona-Server/mysql-test/suite/binlog/r/percona_bug1162085.result	1970-01-01 00:00:00 +0000
+++ Percona-Server/mysql-test/suite/binlog/r/percona_bug1162085.result	2013-04-01 14:18:23 +0000
@@ -0,0 +1,6 @@
+CREATE TABLE t1 (data LONGBLOB) ENGINE=InnoDB;
+START TRANSACTION;
+SAVEPOINT savepoint_1;
+ROLLBACK TO SAVEPOINT_1;
+COMMIT;
+DROP TABLE t1;
 
=== added file 'Percona-Server/mysql-test/suite/binlog/t/percona_bug1162085.test'
--- Percona-Server/mysql-test/suite/binlog/t/percona_bug1162085.test	1970-01-01 00:00:00 +0000
+++ Percona-Server/mysql-test/suite/binlog/t/percona_bug1162085.test	2013-04-01 14:18:23 +0000
@@ -0,0 +1,30 @@
+########################################################################
+# Bug #1162085: Percona server 5.5.30-rel30.1.465 reproducable hang
+########################################################################
+
+-- source include/have_log_bin.inc
+-- source include/have_innodb.inc
+
+CREATE TABLE t1 (data LONGBLOB) ENGINE=InnoDB;
+
+START TRANSACTION;
+
+--disable_query_log
+let $i=1024;
+while($i)
+{
+	# Don't use REPEAT() here so we generate long enough writes to the
+	# binlog cache in both stmt and row-based mode
+
+	INSERT INTO t1 (data) VALUES ('XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX');
+	dec $i;
+}
+--enable_query_log
+
+SAVEPOINT savepoint_1;
+
+ROLLBACK TO SAVEPOINT_1;
+
+COMMIT;
+
+DROP TABLE t1;
 
=== modified file 'Percona-Server/mysys/mf_cache.c'
--- Percona-Server/mysys/mf_cache.c	2012-10-25 17:55:07 +0000
+++ Percona-Server/mysys/mf_cache.c	2013-04-01 14:18:23 +0000
@@ -121,15 +121,17 @@
 }
 
 /*
-  Truncate the cached file to a given offset. The cache must be reinitialized
-  with reinit_io_cache() after this call.
+  Truncate the cached file to a given offset, if the current size is greater
+  than the offset. The cache must be reinitialized with reinit_io_cache() after
+  this call.
 */
 
 my_bool truncate_cached_file(IO_CACHE *cache, my_off_t pos)
 {
   DBUG_ENTER("truncate_cached_file");
 
-  if (my_b_inited(cache) && cache->file > -1)
+  if (my_b_inited(cache) && cache->file > -1 &&
+      my_seek(cache->file, 0L, MY_SEEK_END, MYF(MY_WME + MY_FAE)) > pos)
   {
     if (my_chsize(cache->file, pos, 0, MYF(MY_WME)))
       DBUG_RETURN(TRUE);