Linux 3.14 compat: rq_for_each_segment in dmu_req_copy

rq_for_each_segment changed from taking bio_vec * to taking bio_vec.
We provide rq_for_each_segment4 which takes both.

Signed-off-by: Chunwei Chen <[email protected]>
Signed-off-by: Richard Yao <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Issue #2124

3 files changed, 56 insertions, 8 deletions

diff --git a/config/kernel-rq-for-each_segment.m4 b/config/kernel-rq-for-each_segment.m4
index 449168d08..84ce7d1ec 100644
--- a/config/kernel-rq-for-each_segment.m4
+++ b/config/kernel-rq-for-each_segment.m4
@@ -1,10 +1,13 @@
 dnl #
 dnl # 2.6.x API change
 dnl #
+dnl # 3.14 API change
+dnl #
 AC_DEFUN([ZFS_AC_KERNEL_RQ_FOR_EACH_SEGMENT], [
-	AC_MSG_CHECKING([whether rq_for_each_segment() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
 	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
+
+	AC_MSG_CHECKING([whether rq_for_each_segment() wants bio_vec *])
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
@@ -16,8 +19,29 @@ AC_DEFUN([ZFS_AC_KERNEL_RQ_FOR_EACH_SEGMENT], [
 		AC_MSG_RESULT(yes)
 		AC_DEFINE(HAVE_RQ_FOR_EACH_SEGMENT, 1,
 		          [rq_for_each_segment() is available])
+		AC_DEFINE(HAVE_RQ_FOR_EACH_SEGMENT_BVP, 1,
+		          [rq_for_each_segment() wants bio_vec *])
+	],[
+		AC_MSG_RESULT(no)
+	])
+
+	AC_MSG_CHECKING([whether rq_for_each_segment() wants bio_vec])
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/blkdev.h>
+	],[
+		struct bio_vec bv;
+		struct req_iterator iter;
+		struct request *req = NULL;
+		rq_for_each_segment(bv, req, iter) { }
+	],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_RQ_FOR_EACH_SEGMENT, 1,
+		          [rq_for_each_segment() is available])
+		AC_DEFINE(HAVE_RQ_FOR_EACH_SEGMENT_BV, 1,
+		          [rq_for_each_segment() wants bio_vec])
 	],[
 		AC_MSG_RESULT(no)
 	])
+
 	EXTRA_KCFLAGS="$tmp_flags"
 ])
diff --git a/include/linux/blkdev_compat.h b/include/linux/blkdev_compat.h
index be22ae700..8566033fc 100644
--- a/include/linux/blkdev_compat.h
+++ b/include/linux/blkdev_compat.h
@@ -284,8 +284,32 @@ struct req_iterator {
 #define	rq_for_each_segment(bvl, _rq, _iter)                    \
 	__rq_for_each_bio(_iter.bio, _rq)                       \
 		bio_for_each_segment(bvl, _iter.bio, _iter.i)
+
+#define	HAVE_RQ_FOR_EACH_SEGMENT_BVP 1
 #endif /* HAVE_RQ_FOR_EACH_SEGMENT */
 
+/*
+ * 3.14 API change
+ * rq_for_each_segment changed from taking bio_vec * to taking bio_vec.
+ * We provide rq_for_each_segment4 which takes both.
+ * You should not modify the fields in @bv and @bvp.
+ *
+ * Note: the if-else is just to inject the assignment before the loop body.
+ */
+#ifdef HAVE_RQ_FOR_EACH_SEGMENT_BVP
+#define	rq_for_each_segment4(bv, bvp, rq, iter)	\
+	rq_for_each_segment(bvp, rq, iter)	\
+		if ((bv = *bvp), 0)		\
+			;			\
+		else
+#else
+#define	rq_for_each_segment4(bv, bvp, rq, iter)	\
+	rq_for_each_segment(bv, rq, iter)	\
+		if ((bvp = &bv), 0)		\
+			;			\
+		else
+#endif
+
 #ifdef HAVE_BIO_BVEC_ITER
 #define	BIO_BI_SECTOR(bio)	(bio)->bi_iter.bi_sector
 #define	BIO_BI_SIZE(bio)	(bio)->bi_iter.bi_size
diff --git a/module/zfs/dmu.c b/module/zfs/dmu.c
index 5d9337f65..edad9b496 100644
--- a/module/zfs/dmu.c
+++ b/module/zfs/dmu.c
@@ -1011,13 +1011,13 @@ xuio_stat_wbuf_nocopy()
 static int
 dmu_req_copy(void *arg_buf, int size, struct request *req, size_t req_offset)
 {
-	struct bio_vec *bv;
+	struct bio_vec bv, *bvp;
 	struct req_iterator iter;
 	char *bv_buf;
 	int tocpy, bv_len, bv_offset;
 	int offset = 0;
 
-	rq_for_each_segment(bv, req, iter) {
+	rq_for_each_segment4(bv, bvp, req, iter) {
 		/*
 		 * Fully consumed the passed arg_buf. We use goto here because
 		 * rq_for_each_segment is a double loop
@@ -1027,19 +1027,19 @@ dmu_req_copy(void *arg_buf, int size, struct request *req, size_t req_offset)
 			goto out;
 
 		/* Skip already copied bv */
-		if (req_offset >=  bv->bv_len) {
-			req_offset -= bv->bv_len;
+		if (req_offset >=  bv.bv_len) {
+			req_offset -= bv.bv_len;
 			continue;
 		}
 
-		bv_len = bv->bv_len - req_offset;
-		bv_offset = bv->bv_offset + req_offset;
+		bv_len = bv.bv_len - req_offset;
+		bv_offset = bv.bv_offset + req_offset;
 		req_offset = 0;
 
 		tocpy = MIN(bv_len, size - offset);
 		ASSERT3S(tocpy, >=, 0);
 
-		bv_buf = page_address(bv->bv_page) + bv_offset;
+		bv_buf = page_address(bv.bv_page) + bv_offset;
 		ASSERT3P(bv_buf, !=, NULL);
 
 		if (rq_data_dir(req) == WRITE)