Re: [PATCH 13/16] io_uring: add support for pre-mapped user IO buffers

On 1/9/19 5:16 AM, Christoph Hellwig wrote:

quoted

+static int io_setup_rw(int rw, struct io_kiocb *kiocb,
+		       const struct io_uring_iocb *iocb, struct iovec **iovec,
+		       struct iov_iter *iter, bool kaddr)
 {
 	void __user *buf = (void __user *)(uintptr_t)iocb->addr;
 	size_t ret;
 
-	ret = import_single_range(rw, buf, iocb->len, *iovec, iter);
+	if (!kaddr) {
+		ret = import_single_range(rw, buf, iocb->len, *iovec, iter);
+	} else {
+		struct io_ring_ctx *ctx = kiocb->ki_ctx;
+		struct io_mapped_ubuf *imu;
+		size_t len = iocb->len;
+		size_t offset;
+		int index;
+
+		/* __io_submit_one() already validated the index */
+		index = array_index_nospec(kiocb->ki_index,
+						ctx->max_reqs);
+		imu = &ctx->user_bufs[index];
+		if ((unsigned long) iocb->addr < imu->ubuf ||
+		    (unsigned long) iocb->addr + len > imu->ubuf + imu->len) {
+			ret = -EFAULT;
+			goto err;
+		}
+
+		/*
+		 * May not be a start of buffer, set size appropriately
+		 * and advance us to the beginning.
+		 */
+		offset = (unsigned long) iocb->addr - imu->ubuf;
+		iov_iter_bvec(iter, rw, imu->bvec, imu->nr_bvecs,
+				offset + len);
+		if (offset)
+			iov_iter_advance(iter, offset);
+		ret = 0;
+

Please split this code in a separate helper.

Done

quoted

 	if (unlikely(!file->f_op->read_iter))
 		goto out_fput;
 
-	ret = io_setup_rw(READ, iocb, &iovec, &iter);
+	ret = io_setup_rw(READ, kiocb, iocb, &iovec, &iter, kaddr);

And I'd personally just call that helper here based on the opcode and
avoid magic bool arguments.

Then we can also fold the switch cases, cleans it up.

quoted

+		down_write(&current->mm->mmap_sem);
+		pret = get_user_pages(ubuf, nr_pages, 1, pages, NULL);
+		up_write(&current->mm->mmap_sem);

This needs to be get_user_pages_longterm.

Done

quoted

+	 * We don't use the iovecs without fixed buffers being asked for.
+	 * Error out if they don't match.
+	 */
+	if (!(p->flags & IORING_SETUP_FIXEDBUFS) && iovecs)
+		return -EINVAL;

I don't think we need the IORING_SETUP_FIXEDBUFS flag at all, as a
non-zero iovecs pointer is enough of an indication.

Good point, no point in that redundancy. Fixed.

-- 
Jens Axboe