2022-10-28 02:57:55

by Al Viro

Subject: [PATCH v2 10/12] [xen] fix "direction" argument of iov_iter_kvec()

Signed-off-by: Al Viro <[email protected]>
---
drivers/xen/pvcalls-back.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
index d6f945fd4147..21b9c850a382 100644
--- a/drivers/xen/pvcalls-back.c
+++ b/drivers/xen/pvcalls-back.c
@@ -129,13 +129,13 @@ static bool pvcalls_conn_back_read(void *opaque)
if (masked_prod < masked_cons) {
vec[0].iov_base = data->in + masked_prod;
vec[0].iov_len = wanted;
- iov_iter_kvec(&msg.msg_iter, WRITE, vec, 1, wanted);
+ iov_iter_kvec(&msg.msg_iter, READ, vec, 1, wanted);
} else {
vec[0].iov_base = data->in + masked_prod;
vec[0].iov_len = array_size - masked_prod;
vec[1].iov_base = data->in;
vec[1].iov_len = wanted - vec[0].iov_len;
- iov_iter_kvec(&msg.msg_iter, WRITE, vec, 2, wanted);
+ iov_iter_kvec(&msg.msg_iter, READ, vec, 2, wanted);
}

atomic_set(&map->read, 0);
@@ -188,13 +188,13 @@ static bool pvcalls_conn_back_write(struct sock_mapping *map)
if (pvcalls_mask(prod, array_size) > pvcalls_mask(cons, array_size)) {
vec[0].iov_base = data->out + pvcalls_mask(cons, array_size);
vec[0].iov_len = size;
- iov_iter_kvec(&msg.msg_iter, READ, vec, 1, size);
+ iov_iter_kvec(&msg.msg_iter, WRITE, vec, 1, size);
} else {
vec[0].iov_base = data->out + pvcalls_mask(cons, array_size);
vec[0].iov_len = array_size - pvcalls_mask(cons, array_size);
vec[1].iov_base = data->out;
vec[1].iov_len = size - vec[0].iov_len;
- iov_iter_kvec(&msg.msg_iter, READ, vec, 2, size);
+ iov_iter_kvec(&msg.msg_iter, WRITE, vec, 2, size);
}

atomic_set(&map->write, 0);
--
2.30.2

2022-10-28 13:31:04

by John Stoffel

Subject: Re: [PATCH v2 10/12] [xen] fix "direction" argument of iov_iter_kvec()

On Fri, Oct 28, 2022 at 03:33:50AM +0100, Al Viro wrote:
> Signed-off-by: Al Viro <[email protected]>
> ---
> drivers/xen/pvcalls-back.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
> index d6f945fd4147..21b9c850a382 100644
> --- a/drivers/xen/pvcalls-back.c
> +++ b/drivers/xen/pvcalls-back.c
> @@ -129,13 +129,13 @@ static bool pvcalls_conn_back_read(void *opaque)
> if (masked_prod < masked_cons) {
> vec[0].iov_base = data->in + masked_prod;
> vec[0].iov_len = wanted;
> - iov_iter_kvec(&msg.msg_iter, WRITE, vec, 1, wanted);
> + iov_iter_kvec(&msg.msg_iter, READ, vec, 1, wanted);


Wouldn't it make more sense to use READER and WRITER here, since the
current READ/WRITE are 100% non-obvious? This is probably a bigger
change, but this just looks wrong and will be so easy for people to
screw up again and again down the line.


> } else {
> vec[0].iov_base = data->in + masked_prod;
> vec[0].iov_len = array_size - masked_prod;
> vec[1].iov_base = data->in;
> vec[1].iov_len = wanted - vec[0].iov_len;
> - iov_iter_kvec(&msg.msg_iter, WRITE, vec, 2, wanted);
> + iov_iter_kvec(&msg.msg_iter, READ, vec, 2, wanted);
> }
>
> atomic_set(&map->read, 0);
> @@ -188,13 +188,13 @@ static bool pvcalls_conn_back_write(struct sock_mapping *map)
> if (pvcalls_mask(prod, array_size) > pvcalls_mask(cons, array_size)) {
> vec[0].iov_base = data->out + pvcalls_mask(cons, array_size);
> vec[0].iov_len = size;
> - iov_iter_kvec(&msg.msg_iter, READ, vec, 1, size);
> + iov_iter_kvec(&msg.msg_iter, WRITE, vec, 1, size);
> } else {
> vec[0].iov_base = data->out + pvcalls_mask(cons, array_size);
> vec[0].iov_len = array_size - pvcalls_mask(cons, array_size);
> vec[1].iov_base = data->out;
> vec[1].iov_len = size - vec[0].iov_len;
> - iov_iter_kvec(&msg.msg_iter, READ, vec, 2, size);
> + iov_iter_kvec(&msg.msg_iter, WRITE, vec, 2, size);
> }
>
> atomic_set(&map->write, 0);
> --
> 2.30.2
>

--

2022-10-28 13:50:38

by John Stoffel

Subject: Re: [PATCH v2 10/12] [xen] fix "direction" argument of iov_iter_kvec()

On Fri, Oct 28, 2022 at 08:48:22AM -0400, John Stoffel wrote:
> On Fri, Oct 28, 2022 at 03:33:50AM +0100, Al Viro wrote:
> > Signed-off-by: Al Viro <[email protected]>
> > ---
> > drivers/xen/pvcalls-back.c | 8 ++++----
> > 1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
> > index d6f945fd4147..21b9c850a382 100644
> > --- a/drivers/xen/pvcalls-back.c
> > +++ b/drivers/xen/pvcalls-back.c
> > @@ -129,13 +129,13 @@ static bool pvcalls_conn_back_read(void *opaque)
> > if (masked_prod < masked_cons) {
> > vec[0].iov_base = data->in + masked_prod;
> > vec[0].iov_len = wanted;
> > - iov_iter_kvec(&msg.msg_iter, WRITE, vec, 1, wanted);
> > + iov_iter_kvec(&msg.msg_iter, READ, vec, 1, wanted);
>
>
> Wouldn't it make more sense to use READER and WRITER here, since the
> current READ/WRITE are 100% non-obvious? This is probably a bigger
> change, but this just looks wrong and will be so easy for people to
> screw up again and again down the line.

And if I had only made it down to patch 12, I would have seen that you
fixed this. Sorry for the noise!