block: Convert some code to bio_for_each_segment_all()

More prep work for immutable bvecs:

A few places in the code were either open coding or using the wrong
version - fix.

After we introduce the bvec iter, it'll no longer be possible to modify
the biovec through bio_for_each_segment_all() - it doesn't increment a
pointer to the current bvec, you pass in a struct bio_vec (not a
pointer) which is updated with what the current biovec would be (taking
into account bi_bvec_done and bi_size).

So because of that it's more worthwhile to be consistent about
bio_for_each_segment()/bio_for_each_segment_all() usage.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
CC: Jens Axboe <axboe@kernel.dk>
CC: NeilBrown <neilb@suse.de>
CC: Alasdair Kergon <agk@redhat.com>
CC: dm-devel@redhat.com
CC: Alexander Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/bio.c b/fs/bio.c
index 618f904..fe3aee90 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1548,11 +1548,11 @@
  */
 void bio_set_pages_dirty(struct bio *bio)
 {
-	struct bio_vec *bvec = bio->bi_io_vec;
+	struct bio_vec *bvec;
 	int i;
 
-	for (i = 0; i < bio->bi_vcnt; i++) {
-		struct page *page = bvec[i].bv_page;
+	bio_for_each_segment_all(bvec, bio, i) {
+		struct page *page = bvec->bv_page;
 
 		if (page && !PageCompound(page))
 			set_page_dirty_lock(page);
@@ -1561,11 +1561,11 @@
 
 static void bio_release_pages(struct bio *bio)
 {
-	struct bio_vec *bvec = bio->bi_io_vec;
+	struct bio_vec *bvec;
 	int i;
 
-	for (i = 0; i < bio->bi_vcnt; i++) {
-		struct page *page = bvec[i].bv_page;
+	bio_for_each_segment_all(bvec, bio, i) {
+		struct page *page = bvec->bv_page;
 
 		if (page)
 			put_page(page);
@@ -1614,16 +1614,16 @@
 
 void bio_check_pages_dirty(struct bio *bio)
 {
-	struct bio_vec *bvec = bio->bi_io_vec;
+	struct bio_vec *bvec;
 	int nr_clean_pages = 0;
 	int i;
 
-	for (i = 0; i < bio->bi_vcnt; i++) {
-		struct page *page = bvec[i].bv_page;
+	bio_for_each_segment_all(bvec, bio, i) {
+		struct page *page = bvec->bv_page;
 
 		if (PageDirty(page) || PageCompound(page)) {
 			page_cache_release(page);
-			bvec[i].bv_page = NULL;
+			bvec->bv_page = NULL;
 		} else {
 			nr_clean_pages++;
 		}