X-Git-Url: https://git.camperquake.de/gitweb.cgi?a=blobdiff_plain;f=include%2Flinux%2Fblkdev_compat.h;fp=include%2Flinux%2Fblkdev_compat.h;h=3bf1f4574036eb699f5e0ca09f4ac71be47014d9;hb=3517f0b7e928e1a8e7634828fb92d194ea35004d;hp=d2e80ec88f6123283255ba4f0c80a561474386b7;hpb=1073d746d6421eb5faf8a3cf8534d82a2beb0512;p=zfs.git

diff --git a/include/linux/blkdev_compat.h b/include/linux/blkdev_compat.h
index d2e80ec..3bf1f45 100644
--- a/include/linux/blkdev_compat.h
+++ b/include/linux/blkdev_compat.h
@@ -172,6 +172,17 @@ __blk_rq_bytes(struct request *req)
 #define blk_fs_request(rq)	((rq)->cmd_type == REQ_TYPE_FS)
 #endif
 
+/*
+ * 2.6.27 API change,
+ * The blk_queue_stackable() queue flag was added in 2.6.27 to handle dm
+ * stacking drivers.  Prior to this request stacking drivers were detected
+ * by checking (q->request_fn == NULL), for earlier kernels we revert to
+ * this legacy behavior.
+ */
+#ifndef blk_queue_stackable
+#define blk_queue_stackable(q)	((q)->request_fn == NULL)
+#endif
+
 #ifndef HAVE_GET_DISK_RO
 static inline int
 get_disk_ro(struct gendisk *disk)