block: rewrite and split __bio_copy_iov()

Rewrite __bio_copy_iov using the copy_page_{from,to}_iter helpers, and
split it into two simpler functions.

This commit should contain only literal replacements, without
functional changes.

Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dongsu Park <dongsu.park@profitbricks.com>
[hch: removed the __bio_copy_iov wrapper]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 56 insertions, 34 deletions

diff --git a/block/bio.c b/block/bio.c
index 0723d4ce8589..f66a4eae16ee 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1036,43 +1036,66 @@ static struct bio_map_data *bio_alloc_map_data(unsigned int iov_count,
                        sizeof(struct iovec) * iov_count, gfp_mask);
 }
 
-static int __bio_copy_iov(struct bio *bio, const struct iov_iter *iter,
-                          int to_user, int from_user)
+/**
+ * bio_copy_from_iter - copy all pages from iov_iter to bio
+ * @bio: The &struct bio which describes the I/O as destination
+ * @iter: iov_iter as source
+ *
+ * Copy all pages from iov_iter to bio.
+ * Returns 0 on success, or error on failure.
+ */
+static int bio_copy_from_iter(struct bio *bio, struct iov_iter iter)
 {
-        int ret = 0, i;
+        int i;
         struct bio_vec *bvec;
-        struct iov_iter iov_iter = *iter;
 
         bio_for_each_segment_all(bvec, bio, i) {
-                char *bv_addr = page_address(bvec->bv_page);
-                unsigned int bv_len = bvec->bv_len;
-
-                while (bv_len && iov_iter.count) {
-                        struct iovec iov = iov_iter_iovec(&iov_iter);
-                        unsigned int bytes = min_t(unsigned int, bv_len,
-                                                   iov.iov_len);
-
-                        if (!ret) {
-                                if (to_user)
-                                        ret = copy_to_user(iov.iov_base,
-                                                           bv_addr, bytes);
-
-                                if (from_user)
-                                        ret = copy_from_user(bv_addr,
-                                                             iov.iov_base,
-                                                             bytes);
-
-                                if (ret)
-                                        ret = -EFAULT;
-                        }
+                ssize_t ret;
 
-                        bv_len -= bytes;
-                        bv_addr += bytes;
-                        iov_iter_advance(&iov_iter, bytes);
-                }
+                ret = copy_page_from_iter(bvec->bv_page,
+                                          bvec->bv_offset,
+                                          bvec->bv_len,
+                                          &iter);
+
+                if (!iov_iter_count(&iter))
+                        break;
+
+                if (ret < bvec->bv_len)
+                        return -EFAULT;
         }
 
-        return ret;
+        return 0;
+}
+
+/**
+ * bio_copy_to_iter - copy all pages from bio to iov_iter
+ * @bio: The &struct bio which describes the I/O as source
+ * @iter: iov_iter as destination
+ *
+ * Copy all pages from bio to iov_iter.
+ * Returns 0 on success, or error on failure.
+ */
+static int bio_copy_to_iter(struct bio *bio, struct iov_iter iter)
+{
+        int i;
+        struct bio_vec *bvec;
+
+        bio_for_each_segment_all(bvec, bio, i) {
+                ssize_t ret;
+
+                ret = copy_page_to_iter(bvec->bv_page,
+                                        bvec->bv_offset,
+                                        bvec->bv_len,
+                                        &iter);
+
+                if (!iov_iter_count(&iter))
+                        break;
+
+                if (ret < bvec->bv_len)
+                        return -EFAULT;
+        }
+
+        return 0;
 }
 
 static void bio_free_pages(struct bio *bio)
@@ -1101,9 +1124,8 @@ int bio_uncopy_user(struct bio *bio)
                  * if we're in a workqueue, the request is orphaned, so
                  * don't copy into a random user address space, just free.
                  */
-                if (current->mm)
-                        ret = __bio_copy_iov(bio, &bmd->iter,
-                                             bio_data_dir(bio) == READ, 0);
+                if (current->mm && bio_data_dir(bio) == READ)
+                        ret = bio_copy_to_iter(bio, bmd->iter);
                 if (bmd->is_our_pages)
                         bio_free_pages(bio);
         }
@@ -1228,7 +1250,7 @@ struct bio *bio_copy_user_iov(struct request_queue *q,
          */
         if (((iter->type & WRITE) && (!map_data || !map_data->null_mapped)) ||
             (map_data && map_data->from_user)) {
-                ret = __bio_copy_iov(bio, iter, 0, 1);
+                ret = bio_copy_from_iter(bio, *iter);
                 if (ret)
                         goto cleanup;
         }