On 3/15/23 12:31, Kirill A. Shutemov wrote:
> MAX_ORDER is not inclusive: the maximum allocation order buddy allocator
> can deliver is MAX_ORDER-1.
>
> Fix MAX_ORDER usage in __iommu_dma_alloc_pages().
>
> Also use GENMASK() instead of hard to read "(2U << order) - 1" magic.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Robin Murphy <robin.murphy@xxxxxxx>
> Cc: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> ---
> drivers/iommu/dma-iommu.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 99b2646cb5c7..ac996fd6bd9c 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -736,7 +736,7 @@ static struct page **__iommu_dma_alloc_pages(struct device *dev,
> struct page **pages;
> unsigned int i = 0, nid = dev_to_node(dev);
>
> - order_mask &= (2U << MAX_ORDER) - 1;
> + order_mask &= GENMASK(MAX_ORDER - 1, 0);
> if (!order_mask)
> return NULL;
>
> @@ -756,7 +756,7 @@ static struct page **__iommu_dma_alloc_pages(struct device *dev,
> * than a necessity, hence using __GFP_NORETRY until
> * falling back to minimum-order allocations.
> */
> - for (order_mask &= (2U << __fls(count)) - 1;
> + for (order_mask &= GENMASK(__fls(count), 0);
> order_mask; order_mask &= ~order_size) {
> unsigned int order = __fls(order_mask);
> gfp_t alloc_flags = gfp;
