struct file *file = iocb->ki_filp;
        struct inode *inode = file->f_mapping->host;
        struct ccc_object *obj = cl_inode2ccc(inode);
-       long count = iov_length(iter->iov, iter->nr_segs);
+       long count = iov_iter_count(iter);
        long tot_bytes = 0, result = 0;
        struct ll_inode_info *lli = ll_i2info(inode);
        unsigned long seg = 0;
 
         * we need to flush the dirty pages again to make absolutely sure
         * that any outstanding dirty pages are on disk.
         */
-       count = iov_length(iter->iov, iter->nr_segs);
+       count = iov_iter_count(iter);
        if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
                     &BTRFS_I(inode)->runtime_flags))
                filemap_fdatawrite_range(inode->i_mapping, offset, count);
 
        struct file *file = iocb->ki_filp;
        struct address_space *mapping = file->f_mapping;
        struct inode *inode = mapping->host;
+       size_t count = iov_iter_count(iter);
        ssize_t ret;
 
        ret = blockdev_direct_IO(rw, iocb, inode, iter->iov, offset,
                                 iter->nr_segs, ext2_get_block);
        if (ret < 0 && (rw & WRITE))
-               ext2_write_failed(mapping, offset +
-                                 iov_length(iter->iov, iter->nr_segs));
+               ext2_write_failed(mapping, offset + count);
        return ret;
 }
 
 
        handle_t *handle;
        ssize_t ret;
        int orphan = 0;
-       size_t count = iov_length(iter->iov, iter->nr_segs);
+       size_t count = iov_iter_count(iter);
        int retries = 0;
 
        trace_ext3_direct_IO_enter(inode, offset, count, rw);
 
        handle_t *handle;
        ssize_t ret;
        int orphan = 0;
-       size_t count = iov_length(iter->iov, iter->nr_segs);
+       size_t count = iov_iter_count(iter);
        int retries = 0;
 
        if (rw == WRITE) {
 
        struct file *file = iocb->ki_filp;
        struct inode *inode = file->f_mapping->host;
        ssize_t ret;
-       size_t count = iov_length(iter->iov, iter->nr_segs);
+       size_t count = iov_iter_count(iter);
        int overwrite = 0;
        get_block_t *get_block_func = NULL;
        int dio_flags = 0;
 {
        struct file *file = iocb->ki_filp;
        struct inode *inode = file->f_mapping->host;
+       size_t count = iov_iter_count(iter);
        ssize_t ret;
 
        /*
        if (ext4_has_inline_data(inode))
                return 0;
 
-       trace_ext4_direct_IO_enter(inode, offset, iov_length(iter->iov, iter->nr_segs), rw);
+       trace_ext4_direct_IO_enter(inode, offset, count, rw);
        if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
                ret = ext4_ext_direct_IO(rw, iocb, iter, offset);
        else
                ret = ext4_ind_direct_IO(rw, iocb, iter, offset);
-       trace_ext4_direct_IO_exit(inode, offset,
-                               iov_length(iter->iov, iter->nr_segs), rw, ret);
+       trace_ext4_direct_IO_exit(inode, offset, count, rw, ret);
        return ret;
 }
 
 
        struct file *file = iocb->ki_filp;
        struct address_space *mapping = file->f_mapping;
        struct inode *inode = mapping->host;
+       size_t count = iov_iter_count(iter);
        ssize_t ret;
 
        if (rw == WRITE) {
                 *
                 * Return 0, and fallback to normal buffered write.
                 */
-               loff_t size = offset + iov_length(iter->iov, iter->nr_segs);
+               loff_t size = offset + count;
                if (MSDOS_I(inode)->mmu_private < size)
                        return 0;
        }
        ret = blockdev_direct_IO(rw, iocb, inode, iter->iov, offset,
                                 iter->nr_segs, fat_get_block);
        if (ret < 0 && (rw & WRITE))
-               fat_write_failed(mapping, offset +
-                                iov_length(iter->iov, iter->nr_segs));
+               fat_write_failed(mapping, offset + count);
 
        return ret;
 }
 
        loff_t pos = 0;
        struct inode *inode;
        loff_t i_size;
-       size_t count = iov_length(iter->iov, iter->nr_segs);
+       size_t count = iov_iter_count(iter);
        struct fuse_io_priv *io;
 
        pos = offset;
 
         */
        if (mapping->nrpages) {
                loff_t lstart = offset & (PAGE_CACHE_SIZE - 1);
-               loff_t len = iov_length(iter->iov, iter->nr_segs);
+               loff_t len = iov_iter_count(iter);
                loff_t end = PAGE_ALIGN(offset + len) - 1;
 
                rv = 0;
 
        struct file *file = iocb->ki_filp;
        struct address_space *mapping = file->f_mapping;
        struct inode *inode = file_inode(file)->i_mapping->host;
+       size_t count = iov_iter_count(iter);
        ssize_t ret;
 
        ret = blockdev_direct_IO(rw, iocb, inode, iter->iov, offset,
         */
        if (unlikely((rw & WRITE) && ret < 0)) {
                loff_t isize = i_size_read(inode);
-               loff_t end = offset + iov_length(iter->iov, iter->nr_segs);
+               loff_t end = offset + count;
 
                if (end > isize)
                        hfs_write_failed(mapping, end);
 
        struct file *file = iocb->ki_filp;
        struct address_space *mapping = file->f_mapping;
        struct inode *inode = file_inode(file)->i_mapping->host;
+       size_t count = iov_iter_count(iter);
        ssize_t ret;
 
        ret = blockdev_direct_IO(rw, iocb, inode, iter->iov, offset, iter->nr_segs,
         */
        if (unlikely((rw & WRITE) && ret < 0)) {
                loff_t isize = i_size_read(inode);
-               loff_t end = offset + iov_length(iter->iov, iter->nr_segs);
+               loff_t end = offset + count;
 
                if (end > isize)
                        hfsplus_write_failed(mapping, end);
 
        struct file *file = iocb->ki_filp;
        struct address_space *mapping = file->f_mapping;
        struct inode *inode = file->f_mapping->host;
+       size_t count = iov_iter_count(iter);
        ssize_t ret;
 
        ret = blockdev_direct_IO(rw, iocb, inode, iter->iov, offset,
         */
        if (unlikely((rw & WRITE) && ret < 0)) {
                loff_t isize = i_size_read(inode);
-               loff_t end = offset + iov_length(iter->iov, iter->nr_segs);
+               loff_t end = offset + count;
 
                if (end > isize)
                        jfs_write_failed(mapping, end);
 
        struct nfs_direct_req *dreq;
        struct nfs_lock_context *l_ctx;
        ssize_t result = -EINVAL;
-       size_t count;
-
-       count = iov_length(iter->iov, iter->nr_segs);
+       size_t count = iov_iter_count(iter);
        nfs_add_stats(mapping->host, NFSIOS_DIRECTREADBYTES, count);
 
        dfprintk(FILE, "NFS: direct read(%pD2, %zd@%Ld)\n",
        get_dreq(dreq);
        atomic_inc(&inode->i_dio_count);
 
-       NFS_I(dreq->inode)->write_io += iov_length(iter->iov, iter->nr_segs);
+       NFS_I(dreq->inode)->write_io += iov_iter_count(iter);
        for (seg = 0; seg < iter->nr_segs; seg++) {
                const struct iovec *vec = &iter->iov[seg];
                result = nfs_direct_write_schedule_segment(&desc, vec, pos, uio);
        struct nfs_direct_req *dreq;
        struct nfs_lock_context *l_ctx;
        loff_t end;
-       size_t count;
-
-       count = iov_length(iter->iov, iter->nr_segs);
+       size_t count = iov_iter_count(iter);
        end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
 
        nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
 
        struct file *file = iocb->ki_filp;
        struct address_space *mapping = file->f_mapping;
        struct inode *inode = file->f_mapping->host;
+       size_t count = iov_iter_count(iter);
        ssize_t size;
 
        if (rw == WRITE)
         */
        if (unlikely((rw & WRITE) && size < 0)) {
                loff_t isize = i_size_read(inode);
-               loff_t end = offset + iov_length(iter->iov, iter->nr_segs);
+               loff_t end = offset + count;
 
                if (end > isize)
                        nilfs_write_failed(mapping, end);
 
 {
        struct file *file = iocb->ki_filp;
        struct inode *inode = file->f_mapping->host;
+       size_t count = iov_iter_count(iter);
        ssize_t ret;
 
        ret = blockdev_direct_IO(rw, iocb, inode, iter->iov, offset,
         */
        if (unlikely((rw & WRITE) && ret < 0)) {
                loff_t isize = i_size_read(inode);
-               loff_t end = offset + iov_length(iter->iov, iter->nr_segs);
+               loff_t end = offset + count;
 
                if ((end > isize) && inode_newsize_ok(inode, isize) == 0) {
                        truncate_setsize(inode, isize);
 
        struct file *file = iocb->ki_filp;
        struct address_space *mapping = file->f_mapping;
        struct inode *inode = mapping->host;
+       size_t count = iov_iter_count(iter);
        ssize_t ret;
 
        ret = blockdev_direct_IO(rw, iocb, inode, iter->iov, offset, iter->nr_segs,
                                  udf_get_block);
        if (unlikely(ret < 0 && (rw & WRITE)))
-               udf_write_failed(mapping, offset + iov_length(iter->iov, iter->nr_segs));
+               udf_write_failed(mapping, offset + count);
        return ret;
 }
 
 
        ssize_t                 ret;
 
        if (rw & WRITE) {
-               size_t size = iov_length(iter->iov, iter->nr_segs);
+               size_t size = iov_iter_count(iter);
 
                /*
                 * We cannot preallocate a size update transaction here as we
 
                        goto out; /* skip atime */
                size = i_size_read(inode);
                retval = filemap_write_and_wait_range(mapping, pos,
-                                       pos + iov_length(iov, nr_segs) - 1);
+                                       pos + count - 1);
                if (!retval)
                        retval = mapping->a_ops->direct_IO(READ, iocb, &i, pos);