Jason Wang
2019-Dec-18 05:53 UTC
[PATCH 1/1] drivers/vhost : Removes unnecessary 'else' in vhost_copy_from_user
On 2019/12/13 ??5:15, Leonardo Bras wrote:> There is no need for this else statement, given that if block will return. > This change is not supposed to change the output binary. > > It reduces identation level on most lines in this function, and also > fixes an split string on vq_err(). > > Signed-off-by: Leonardo Bras <leonardo at linux.ibm.com> > --- > drivers/vhost/vhost.c | 50 +++++++++++++++++++++---------------------- > 1 file changed, 24 insertions(+), 26 deletions(-) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index f44340b41494..b23d1b74c32f 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -824,34 +824,32 @@ static int vhost_copy_from_user(struct vhost_virtqueue *vq, void *to, > > if (!vq->iotlb) > return __copy_from_user(to, from, size); > - else { > - /* This function should be called after iotlb > - * prefetch, which means we're sure that vq > - * could be access through iotlb. So -EAGAIN should > - * not happen in this case. > - */ > - void __user *uaddr = vhost_vq_meta_fetch(vq, > - (u64)(uintptr_t)from, size, > - VHOST_ADDR_DESC); > - struct iov_iter f; > > - if (uaddr) > - return __copy_from_user(to, uaddr, size); > + /* This function should be called after iotlb > + * prefetch, which means we're sure that vq > + * could be access through iotlb. So -EAGAIN should > + * not happen in this case. > + */ > + void __user *uaddr = vhost_vq_meta_fetch(vq, > + (u64)(uintptr_t)from, size, > + VHOST_ADDR_DESC); > + struct iov_iter f;I think this will lead at least warnings from compiler. Generally, I would not bother to make changes like this especially consider it will bring troubles when trying to backporting fixes to downstream in the future. There're some more interesting things: e.g current metadata IOTLB performance is bad for dynamic mapping since it will be reset each time a new updating is coming. We can optimize this by only reset the metadata IOTLB when the updating is for metdata. Want to try this? Thanks> > - ret = translate_desc(vq, (u64)(uintptr_t)from, size, vq->iotlb_iov, > - ARRAY_SIZE(vq->iotlb_iov), > - VHOST_ACCESS_RO); > - if (ret < 0) { > - vq_err(vq, "IOTLB translation failure: uaddr " > - "%p size 0x%llx\n", from, > - (unsigned long long) size); > - goto out; > - } > - iov_iter_init(&f, READ, vq->iotlb_iov, ret, size); > - ret = copy_from_iter(to, size, &f); > - if (ret == size) > - ret = 0; > - } > + if (uaddr) > + return __copy_from_user(to, uaddr, size); > + > + ret = translate_desc(vq, (u64)(uintptr_t)from, size, vq->iotlb_iov, > + ARRAY_SIZE(vq->iotlb_iov), > + VHOST_ACCESS_RO); > + if (ret < 0) { > + vq_err(vq, "IOTLB translation failure: uaddr %p size 0x%llx\n", > + from, (unsigned long long)size); > + goto out; > + } > + iov_iter_init(&f, READ, vq->iotlb_iov, ret, size); > + ret = copy_from_iter(to, size, &f); > + if (ret == size) > + ret = 0; > > out: > return ret;