block: convert to advancing variants of iov_iter_get_pages{,_alloc}()

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

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/block/bio.c b/block/bio.c
index d6eb90d..3d3a267 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -1200,7 +1200,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
        struct page **pages = (struct page **)bv;
        ssize_t size, left;
        unsigned len, i = 0;
-       size_t offset;
+       size_t offset, trim;
        int ret = 0;
 
        /*
@@ -1218,16 +1218,19 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
         * result to ensure the bio's total size is correct. The remainder of
         * the iov data will be picked up in the next bio iteration.
         */
-       size = iov_iter_get_pages(iter, pages, UINT_MAX - bio->bi_iter.bi_size,
+       size = iov_iter_get_pages2(iter, pages, UINT_MAX - bio->bi_iter.bi_size,
                                  nr_pages, &offset);
-       if (size > 0) {
-               nr_pages = DIV_ROUND_UP(offset + size, PAGE_SIZE);
-               size = ALIGN_DOWN(size, bdev_logical_block_size(bio->bi_bdev));
-       } else
-               nr_pages = 0;
-
-       if (unlikely(size <= 0)) {
-               ret = size ? size : -EFAULT;
+       if (unlikely(size <= 0))
+               return size ? size : -EFAULT;
+
+       nr_pages = DIV_ROUND_UP(offset + size, PAGE_SIZE);
+
+       trim = size & (bdev_logical_block_size(bio->bi_bdev) - 1);
+       iov_iter_revert(iter, trim);
+
+       size -= trim;
+       if (unlikely(!size)) {
+               ret = -EFAULT;
                goto out;
        }
 
@@ -1246,7 +1249,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
                offset = 0;
        }
 
-       iov_iter_advance(iter, size - left);
+       iov_iter_revert(iter, left);
 out:
        while (i < nr_pages)
                put_page(pages[i++]);

diff --git a/block/blk-map.c b/block/blk-map.c
index df8b066..7196a6b 100644 (file)
--- 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);