Re: [PATCH 16/18] drm/i915: make i915_gem_mmap_ioctl wait for mmap_sem killable

[Vlastimil Babka]

On 02/29/2016 02:26 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> i915_gem_mmap_ioctl relies on mmap_sem for write. If the waiting
> task gets killed by the oom killer it would block oom_reaper from
> asynchronous address space reclaim and reduce the chances of timely OOM
> resolving. Wait for the lock in the killable mode and return with EINTR
> if the task got killed while waiting.
>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> Cc: David Airlie <airlied@xxxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

> ---
>   drivers/gpu/drm/i915/i915_gem.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index f68f34606f2f..a50136cbd332 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1754,7 +1754,10 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
>   		struct mm_struct *mm = current->mm;
>   		struct vm_area_struct *vma;
>
> -		down_write(&mm->mmap_sem);
> +		if (down_write_killable(&mm->mmap_sem)) {
> +			drm_gem_object_unreference_unlocked(obj);
> +			return -EINTR;
> +		}
>   		vma = find_vma(mm, addr);
>   		if (vma)
>   			vma->vm_page_prot =