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SubjectRe: [Intel-gfx] [PATCH] Revert "drm/i915/userptr: Acquire the page lock around set_page_dirty()"
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On 12/09/2019 13:56, Chris Wilson wrote:
> The userptr put_pages can be called from inside try_to_unmap, and so
> enters with the page lock held on one of the object's backing pages. We
> cannot take the page lock ourselves for fear of recursion.
>
> Reported-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
> Reported-by: Martin Wilck <Martin.Wilck@suse.com>
> Reported-by: Leo Kraav <leho@kraav.com>
> Fixes: aa56a292ce62 ("drm/i915/userptr: Acquire the page lock around set_page_dirty()")
> References: https://bugzilla.kernel.org/show_bug.cgi?id=203317
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: stable@vger.kernel.org
> ---
> drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 10 +---------
> 1 file changed, 1 insertion(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> index 74da35611d7c..11b231c187c5 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> @@ -672,15 +672,7 @@ i915_gem_userptr_put_pages(struct drm_i915_gem_object *obj,
>
> for_each_sgt_page(page, sgt_iter, pages) {
> if (obj->mm.dirty)
> - /*
> - * As this may not be anonymous memory (e.g. shmem)
> - * but exist on a real mapping, we have to lock
> - * the page in order to dirty it -- holding
> - * the page reference is not sufficient to
> - * prevent the inode from being truncated.
> - * Play safe and take the lock.
> - */
> - set_page_dirty_lock(page);
> + set_page_dirty(page);
>
> mark_page_accessed(page);
> put_page(page);
>

Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko

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