Re: [PATCH v2 1/2] iova: Remove some magazine pointer NULL checks

Ethan Zhao
2022-09-06T09:29:19Z

John,

在 2022/9/5 17:11, John Garry 写道:
> Since commit 32e92d9f6f87 ("iommu/iova: Separate out rcache init") it
> has not been possible to have NULL CPU rcache "loaded" or "prev" magazine
> pointers. As such, the checks in iova_magazine_full(),
> iova_magazine_empty(), and iova_magazine_free_pfns() may be dropped.
>
> Signed-off-by: John Garry <john.garry@huawei.com>
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> ---
> drivers/iommu/iova.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index 47d1983dfa2a..580fdf669922 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -661,9 +661,6 @@ iova_magazine_free_pfns(struct iova_magazine *mag, struct iova_domain *iovad)
> unsigned long flags;
> int i;
>
> - if (!mag)
> - return;
> -

iommu_probe_device
ops->probe_finalize(dev);
intel_iommu_probe_finalize
iommu_setup_dma_ops
iommu_dma_init_domain(domain, dma_base, dma_limit, dev)
iova_domain_init_rcaches
{
...
cpu_rcache->loaded = iova_magazine_alloc(GFP_KERNEL);
cpu_rcache->prev = iova_magazine_alloc(GFP_KERNEL);
if (!cpu_rcache->loaded || !cpu_rcache->prev) {
ret = -ENOMEM;
goto out_err;

Do you mean iova_magazine_alloc() is impossible to fail ?

Thanks,

Ethan

> spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
>
> for (i = 0 ; i < mag->size; ++i) {
> @@ -683,12 +680,12 @@ iova_magazine_free_pfns(struct iova_magazine *mag, struct iova_domain *iovad)
>
> static bool iova_magazine_full(struct iova_magazine *mag)
> {
> - return (mag && mag->size == IOVA_MAG_SIZE);
> + return mag->size == IOVA_MAG_SIZE;
> }
>
> static bool iova_magazine_empty(struct iova_magazine *mag)
> {
> - return (!mag || mag->size == 0);
> + return mag->size == 0;
> }
>
> static unsigned long iova_magazine_pop(struct iova_magazine *mag,

--
"firm, enduring, strong, and long-lived"