diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 92346a403a89c056c7d207d0ddfd186ab7348ce3..a0d3016f6c2639cbd4722501b65df16265b110d4 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8619,7 +8619,7 @@ static ssize_t check_direct_IO(struct btrfs_root *root, struct kiocb *iocb,
 		goto out;
 
 	/* If this is a write we don't need to check anymore */
-	if (iov_iter_rw(iter) == WRITE)
+	if (iov_iter_rw(iter) != READ || !iter_is_iovec(iter))
 		return 0;
 	/*
 	 * Check to make sure we don't have duplicate iov_base's in this
diff --git a/fs/splice.c b/fs/splice.c
index aa38901a4f101a963861e8cc0e211918ffa9c5bc..153d4f3bd441febd7004b1862cd218afc0ee6252 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -315,15 +315,9 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 		*ppos = kiocb.ki_pos;
 		file_accessed(in);
 	} else if (ret < 0) {
-		if (WARN_ON(to.idx != idx || to.iov_offset)) {
-			/*
-			 * a bogus ->read_iter() has copied something and still
-			 * returned an error instead of a short read.
-			 */
-			to.idx = idx;
-			to.iov_offset = 0;
-			iov_iter_advance(&to, 0); /* to free what was emitted */
-		}
+		to.idx = idx;
+		to.iov_offset = 0;
+		iov_iter_advance(&to, 0); /* to free what was emitted */
 		/*
 		 * callers of ->splice_read() expect -EAGAIN on
 		 * "can't put anything in there", rather than -EFAULT.
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 62511687385cd972b239e4d22c2924cb94b70b2f..2bc58b3fd37d27b1e6f0c11704a1cd7ae9710b18 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -319,7 +319,7 @@ xfs_file_dio_aio_read(
 	data = *to;
 	ret = __blockdev_direct_IO(iocb, inode, target->bt_bdev, &data,
 			xfs_get_blocks_direct, NULL, NULL, 0);
-	if (ret > 0) {
+	if (ret >= 0) {
 		iocb->ki_pos += ret;
 		iov_iter_advance(to, ret);
 	}
diff --git a/include/linux/uio.h b/include/linux/uio.h
index a00d525bbffa2a677113cc68d3107bbc6c836714..6e22b544d03913746e3190c21b9a1094f6e9f28a 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -109,12 +109,12 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages);
 
 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags);
 
-static inline size_t iov_iter_count(struct iov_iter *i)
+static inline size_t iov_iter_count(const struct iov_iter *i)
 {
 	return i->count;
 }
 
-static inline bool iter_is_iovec(struct iov_iter *i)
+static inline bool iter_is_iovec(const struct iov_iter *i)
 {
 	return !(i->type & (ITER_BVEC | ITER_KVEC | ITER_PIPE));
 }
diff --git a/mm/filemap.c b/mm/filemap.c
index 2f7b7783bd6b207da7c39778a43654f76f6d93b8..849f459ad0780e27bc256ff13fd52fa8c9007661 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1941,7 +1941,7 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 		file_accessed(file);
 
 		retval = mapping->a_ops->direct_IO(iocb, &data);
-		if (retval > 0) {
+		if (retval >= 0) {
 			iocb->ki_pos += retval;
 			iov_iter_advance(iter, retval);
 		}