From: Dan Duval <dan.duval@oracle.com>
Date: Wed, 8 Jun 2016 20:55:48 +0000 (-0400)
Subject: fix kABI breakage from "blk-mq: fix race between timeout and freeing request"
X-Git-Tag: v4.1.12-92~110^2
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=d17e724b395f17024e16740406b59fef23a718c5;p=users%2Fjedix%2Flinux-maple.git

fix kABI breakage from "blk-mq: fix race between timeout and freeing request"

Orabug: 23521058

Commit 21d62f6 ("blk-mq: fix race between timeout and freeing request")
added the element "orig_rq" to struct blk_flush_queue.  This broke kABI.

The existing blk_flush_queue structure has "holes" (padding) of 4 bytes
plus 29 bits.  This is not enough space to contain orig_rq, which is 8
bytes long.

Currently, this data structure is only used by the block-device code.
It is unlikely that a third-party module (e.g., a device driver) would
use struct blk_flush_queue, and even if one did, it would most likely
be via a pointer.

This commit moves orig_rq to the end of the structure, so that the offsets
of the existing elements remain the same as before.  It also wraps orig_rq
in "#ifndef __GENKSYMS__" to hide it from the kABI checker.

Signed-off-by: Dan Duval <dan.duval@oracle.com>
---

diff --git a/block/blk.h b/block/blk.h
index e01b5ee80fe7..412dfd780426 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -27,8 +27,10 @@ struct blk_flush_queue {
 	 * flush_rq shares tag with this rq, both can't be active
 	 * at the same time
 	 */
-	struct request		*orig_rq;
 	spinlock_t		mq_flush_lock;
+#ifndef __GENKSYMS__
+	struct request		*orig_rq;
+#endif
 };
 
 extern struct kmem_cache *blk_requestq_cachep;