On Mon, Mar 27, 2023 at 11:04 AM Jens Axboe <axboe@xxxxxxxxx> wrote:
>
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -748,10 +748,21 @@ static ssize_t do_loop_readv_writev(struct file *filp, struct iov_iter *iter,
> if (flags & ~RWF_HIPRI)
> return -EOPNOTSUPP;
>
> + if (WARN_ON_ONCE(iter->iter_type != ITER_IOVEC &&
> + iter->iter_type != ITER_UBUF))
> + return -EINVAL;
Hmm. I think it might actually be nicer for the "iter_is_ubuf(iter)"
case to be outside the loop entirely, and be done before this
WARN_ON_ONCE().
If it's a single ITER_UBUF, that code really shouldn't loop at all -
it's literally just the old case of "call ->read/write with a single
buffer".
So i think I'd prefer this patch to be something along the lines of
this instead:
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -748,6 +748,19 @@ static ssize_t do_loop_readv_writev(struct file
*filp, struct iov_iter *iter,
if (flags & ~RWF_HIPRI)
return -EOPNOTSUPP;
+ /* Single user buffer? */
+ if (iter_is_ubuf(iter)) {
+ void __user *addr = iter->ubuf + iter->iov_offset;
+ size_t len = iov_iter_count(iter);
+
+ if (type == READ)
+ return filp->f_op->read(filp, addr, len, ppos);
+ return filp->f_op->write(filp, addr, len, ppos);
+ }
+
+ if (WARN_ON_ONCE(!iter_is_iovec(iter)))
+ return -EINVAL;
+
while (iov_iter_count(iter)) {
struct iovec iovec = iov_iter_iovec(iter);
ssize_t nr;
which keeps the existing iovec loop, and just adds that "is it a
simple buffer" case at the top (and the WARN_ON_ONCE() for any other
iter type).
Hmm?
Linus
