Re: [Intel-gfx] [PATCH] drm/i915/userptr: restore probe_range behaviour

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 24/10/2022 18:21, Matthew Auld wrote:
> The conversion looks harmless, however the addr value is updated inside
> the loop with the previous vm_end, which then incorrectly leads to
> for_each_vma_range() iterating over stuff outside the range we care
> about. Fix this by storing the end value separately.
> 
> Testcase: igt@gem_userptr_blits@probe
> Fixes: f683b9d61319 ("i915: use the VMA iterator")
> Reported-by: kernel test robot <oliver.sang@intel.com>
> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
> Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Yu Zhao <yuzhao@google.com>
> ---
>   drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> index b7e24476a0fd..dadb3e3fa9c8 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> @@ -427,9 +427,10 @@ probe_range(struct mm_struct *mm, unsigned long addr, unsigned long len)
>   {
>   	VMA_ITERATOR(vmi, mm, addr);
>   	struct vm_area_struct *vma;
> +	unsigned long end = addr + len;
>   
>   	mmap_read_lock(mm);
> -	for_each_vma_range(vmi, vma, addr + len) {
> +	for_each_vma_range(vmi, vma, end) {
>   		/* Check for holes, note that we also update the addr below */
>   		if (vma->vm_start > addr)
>   			break;

I am unsure of the for_each_vma_range() behaviour regarding holes. If it 
just skips overs them and continues to next VMA in the range then patch 
looks good to me. Could someone confirm?

Regards,

Tvrtko