[PATCH 24/31] block: convert to advancing variants of iov_iter_get_pages{,_alloc}()

[Al Viro <viro@xxxxxxxxxxxxxxxxxx>]

... doing revert if we end up not using some pages

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
 block/bio.c     | 15 ++++++---------
 block/blk-map.c |  7 ++++---
 2 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 51c99f2c5c90..01ab683e67be 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1190,7 +1190,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 	BUILD_BUG_ON(PAGE_PTRS_PER_BVEC < 2);
 	pages += entries_left * (PAGE_PTRS_PER_BVEC - 1);
 
-	size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
+	size = iov_iter_get_pages2(iter, pages, LONG_MAX, nr_pages, &offset);
 	if (unlikely(size <= 0))
 		return size ? size : -EFAULT;
 
@@ -1205,6 +1205,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 		} else {
 			if (WARN_ON_ONCE(bio_full(bio, len))) {
 				bio_put_pages(pages + i, left, offset);
+				iov_iter_revert(iter, left);
 				return -EINVAL;
 			}
 			__bio_add_page(bio, page, len, offset);
@@ -1212,7 +1213,6 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 		offset = 0;
 	}
 
-	iov_iter_advance(iter, size);
 	return 0;
 }
 
@@ -1227,7 +1227,6 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter)
 	ssize_t size, left;
 	unsigned len, i;
 	size_t offset;
-	int ret = 0;
 
 	if (WARN_ON_ONCE(!max_append_sectors))
 		return 0;
@@ -1240,7 +1239,7 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter)
 	BUILD_BUG_ON(PAGE_PTRS_PER_BVEC < 2);
 	pages += entries_left * (PAGE_PTRS_PER_BVEC - 1);
 
-	size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
+	size = iov_iter_get_pages2(iter, pages, LONG_MAX, nr_pages, &offset);
 	if (unlikely(size <= 0))
 		return size ? size : -EFAULT;
 
@@ -1252,16 +1251,14 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter)
 		if (bio_add_hw_page(q, bio, page, len, offset,
 				max_append_sectors, &same_page) != len) {
 			bio_put_pages(pages + i, left, offset);
-			ret = -EINVAL;
-			break;
+			iov_iter_revert(iter, left);
+			return -EINVAL;
 		}
 		if (same_page)
 			put_page(page);
 		offset = 0;
 	}
-
-	iov_iter_advance(iter, size - left);
-	return ret;
+	return 0;
 }
 
 /**
diff --git a/block/blk-map.c b/block/blk-map.c
index df8b066cd548..7196a6b64c80 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -254,7 +254,7 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
 		size_t offs, added = 0;
 		int npages;
 
-		bytes = iov_iter_get_pages_alloc(iter, &pages, LONG_MAX, &offs);
+		bytes = iov_iter_get_pages_alloc2(iter, &pages, LONG_MAX, &offs);
 		if (unlikely(bytes <= 0)) {
 			ret = bytes ? bytes : -EFAULT;
 			goto out_unmap;
@@ -284,7 +284,6 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
 				bytes -= n;
 				offs = 0;
 			}
-			iov_iter_advance(iter, added);
 		}
 		/*
 		 * release the pages we didn't map into the bio, if any
@@ -293,8 +292,10 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
 			put_page(pages[j++]);
 		kvfree(pages);
 		/* couldn't stuff something into bio? */
-		if (bytes)
+		if (bytes) {
+			iov_iter_revert(iter, bytes);
 			break;
+		}
 	}
 
 	ret = blk_rq_append_bio(rq, bio);
-- 
2.30.2