2018-12-24 13:24:25

by Souptick Joarder

Subject: [PATCH v5 6/9] iommu/dma-iommu.c: Convert to use vm_insert_range

Convert to use vm_insert_range() to map range of kernel
memory to user vma.

Signed-off-by: Souptick Joarder <[email protected]>
Reviewed-by: Matthew Wilcox <[email protected]>
---
drivers/iommu/dma-iommu.c | 13 +++----------
1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index d1b0475..de7ffd8 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -622,17 +622,10 @@ struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,

int iommu_dma_mmap(struct page **pages, size_t size, struct vm_area_struct *vma)
{
- unsigned long uaddr = vma->vm_start;
- unsigned int i, count = PAGE_ALIGN(size) >> PAGE_SHIFT;
- int ret = -ENXIO;
+ unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;

- for (i = vma->vm_pgoff; i < count && uaddr < vma->vm_end; i++) {
- ret = vm_insert_page(vma, uaddr, pages[i]);
- if (ret)
- break;
- uaddr += PAGE_SIZE;
- }
- return ret;
+ return vm_insert_range(vma, vma->vm_start, pages + vma->vm_pgoff,
+ count - vma->vm_pgoff);
}

static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys,
--
1.9.1

2018-12-24 14:32:27

by Russell King (Oracle)

Subject: Re: [PATCH v5 6/9] iommu/dma-iommu.c: Convert to use vm_insert_range

On Mon, Dec 24, 2018 at 06:55:31PM +0530, Souptick Joarder wrote:
> Convert to use vm_insert_range() to map range of kernel
> memory to user vma.
>
> Signed-off-by: Souptick Joarder <[email protected]>
> Reviewed-by: Matthew Wilcox <[email protected]>
> ---
> drivers/iommu/dma-iommu.c | 13 +++----------
> 1 file changed, 3 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index d1b0475..de7ffd8 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -622,17 +622,10 @@ struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,
>
> int iommu_dma_mmap(struct page **pages, size_t size, struct vm_area_struct *vma)
> {
> - unsigned long uaddr = vma->vm_start;
> - unsigned int i, count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> - int ret = -ENXIO;
> + unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
>
> - for (i = vma->vm_pgoff; i < count && uaddr < vma->vm_end; i++) {
> - ret = vm_insert_page(vma, uaddr, pages[i]);
> - if (ret)
> - break;
> - uaddr += PAGE_SIZE;
> - }
> - return ret;
> + return vm_insert_range(vma, vma->vm_start, pages + vma->vm_pgoff,
> + count - vma->vm_pgoff);

This introduces a new bug.

I'm not going to continue to point out in minute detail the mistakes
you are introducing, as I don't think that is helping you to learn.

Look at this closely, and see whether you can spot the mistake.
Specifically, compare the boundary conditions for the final page
that is to be inserted and the value returned by the original version
and by your version for different scenarios.

--
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