block: Convert bio_for_each_segment() to bvec_iter

More prep work for immutable biovecs - with immutable bvecs drivers
won't be able to use the biovec directly, they'll need to use helpers
that take into account bio->bi_iter.bi_bvec_done.

This updates callers for the new usage without changing the
implementation yet.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "Ed L. Cashin" <ecashin@coraid.com>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Lars Ellenberg <drbd-dev@lists.linbit.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Paul Clements <Paul.Clements@steeleye.com>
Cc: Jim Paris <jim@jtan.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Yehuda Sadeh <yehuda@inktank.com>
Cc: Sage Weil <sage@inktank.com>
Cc: Alex Elder <elder@inktank.com>
Cc: ceph-devel@vger.kernel.org
Cc: Joshua Morris <josh.h.morris@us.ibm.com>
Cc: Philip Kelleher <pjk1939@linux.vnet.ibm.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Neil Brown <neilb@suse.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux390@de.ibm.com
Cc: Nagalakshmi Nandigama <Nagalakshmi.Nandigama@lsi.com>
Cc: Sreekanth Reddy <Sreekanth.Reddy@lsi.com>
Cc: support@lsi.com
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Guo Chao <yan@linux.vnet.ibm.com>
Cc: Asai Thambi S P <asamymuthupa@micron.com>
Cc: Selvan Mani <smani@micron.com>
Cc: Sam Bradshaw <sbradshaw@micron.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Quoc-Son Anh <quoc-sonx.anh@intel.com>
Cc: Sebastian Ott <sebott@linux.vnet.ibm.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Jan Kara <jack@suse.cz>
Cc: linux-m68k@lists.linux-m68k.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: drbd-user@lists.linbit.com
Cc: nbd-general@lists.sourceforge.net
Cc: cbe-oss-dev@lists.ozlabs.org
Cc: xen-devel@lists.xensource.com
Cc: virtualization@lists.linux-foundation.org
Cc: linux-raid@vger.kernel.org
Cc: linux-s390@vger.kernel.org
Cc: DL-MPTFusionLinux@lsi.com
Cc: linux-scsi@vger.kernel.org
Cc: devel@driverdev.osuosl.org
Cc: linux-fsdevel@vger.kernel.org
Cc: cluster-devel@redhat.com
Cc: linux-mm@kvack.org
Acked-by: Geoff Levand <geoff@infradead.org>
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index a8f4fe2..20e8ab3 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -1109,23 +1109,23 @@
  */
 static void zero_bio_chain(struct bio *chain, int start_ofs)
 {
-	struct bio_vec *bv;
+	struct bio_vec bv;
+	struct bvec_iter iter;
 	unsigned long flags;
 	void *buf;
-	int i;
 	int pos = 0;
 
 	while (chain) {
-		bio_for_each_segment(bv, chain, i) {
-			if (pos + bv->bv_len > start_ofs) {
+		bio_for_each_segment(bv, chain, iter) {
+			if (pos + bv.bv_len > start_ofs) {
 				int remainder = max(start_ofs - pos, 0);
-				buf = bvec_kmap_irq(bv, &flags);
+				buf = bvec_kmap_irq(&bv, &flags);
 				memset(buf + remainder, 0,
-				       bv->bv_len - remainder);
-				flush_dcache_page(bv->bv_page);
+				       bv.bv_len - remainder);
+				flush_dcache_page(bv.bv_page);
 				bvec_kunmap_irq(buf, &flags);
 			}
-			pos += bv->bv_len;
+			pos += bv.bv_len;
 		}
 
 		chain = chain->bi_next;
@@ -1173,11 +1173,11 @@
 					unsigned int len,
 					gfp_t gfpmask)
 {
-	struct bio_vec *bv;
+	struct bio_vec bv;
+	struct bvec_iter iter;
+	struct bvec_iter end_iter;
 	unsigned int resid;
-	unsigned short idx;
 	unsigned int voff;
-	unsigned short end_idx;
 	unsigned short vcnt;
 	struct bio *bio;
 
@@ -1196,22 +1196,22 @@
 	/* Find first affected segment... */
 
 	resid = offset;
-	bio_for_each_segment(bv, bio_src, idx) {
-		if (resid < bv->bv_len)
+	bio_for_each_segment(bv, bio_src, iter) {
+		if (resid < bv.bv_len)
 			break;
-		resid -= bv->bv_len;
+		resid -= bv.bv_len;
 	}
 	voff = resid;
 
 	/* ...and the last affected segment */
 
 	resid += len;
-	__bio_for_each_segment(bv, bio_src, end_idx, idx) {
-		if (resid <= bv->bv_len)
+	__bio_for_each_segment(bv, bio_src, end_iter, iter) {
+		if (resid <= bv.bv_len)
 			break;
-		resid -= bv->bv_len;
+		resid -= bv.bv_len;
 	}
-	vcnt = end_idx - idx + 1;
+	vcnt = end_iter.bi_idx = iter.bi_idx + 1;
 
 	/* Build the clone */
 
@@ -1229,7 +1229,7 @@
 	 * Copy over our part of the bio_vec, then update the first
 	 * and last (or only) entries.
 	 */
-	memcpy(&bio->bi_io_vec[0], &bio_src->bi_io_vec[idx],
+	memcpy(&bio->bi_io_vec[0], &bio_src->bi_io_vec[iter.bi_idx],
 			vcnt * sizeof (struct bio_vec));
 	bio->bi_io_vec[0].bv_offset += voff;
 	if (vcnt > 1) {