ocfs2: disable BUG assertions in reading blocks

According to some high-load testing, these two BUG assertions were
encountered, this led system panic.  Actually, there were some
discussions about removing these two BUG() assertions, it would not
bring any side effect.

Then, I did the the following changes,

1) use the existing macro CATCH_BH_JBD_RACES to wrap BUG() in the
   ocfs2_read_blocks_sync function like before.

2) disable the macro CATCH_BH_JBD_RACES in Makefile by default.

Link: http://lkml.kernel.org/r/1466574294-26863-1-git-send-email-ghe@suse.com
Signed-off-by: Gang He <ghe@suse.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <joseph.qi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/Makefile

@@ -1,7 +1,5 @@
 ccflags-y := -Ifs/ocfs2
 
-ccflags-y += -DCATCH_BH_JBD_RACES
-
 obj-$(CONFIG_OCFS2_FS) += 	\
 	ocfs2.o			\
 	ocfs2_stackglue.o

fs/ocfs2/buffer_head_io.c

@@ -139,11 +139,16 @@ int ocfs2_read_blocks_sync(struct ocfs2_super *osb, u64 block,
 
 		lock_buffer(bh);
 		if (buffer_jbd(bh)) {
+#ifdef CATCH_BH_JBD_RACES
 			mlog(ML_ERROR,
 			     "block %llu had the JBD bit set "
 			     "while I was in lock_buffer!",
 			     (unsigned long long)bh->b_blocknr);
 			BUG();
+#else
+			unlock_buffer(bh);
+			continue;
+#endif
 		}
 
 		clear_buffer_uptodate(bh);