On 17/03/16 09:37, Chris Wilson wrote:
Although the long term future of get_user_pages_locked() itself is
doubtful, the kernel currently recommends:

/* get_user_pages should be phased out in favor of
  * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
  * should use get_user_pages because it cannot pass
  * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
  */

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
  drivers/gpu/drm/i915/i915_gem_userptr.c | 14 ++++++++------
  1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c 
b/drivers/gpu/drm/i915/i915_gem_userptr.c
index 54088a4d6498..fa7d8a8b66ef 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -500,20 +500,22 @@ __i915_gem_userptr_get_pages_worker(struct work_struct 
*_work)
                pvec = drm_malloc_ab(npages, sizeof(struct page *));
        if (pvec != NULL) {
                struct mm_struct *mm = obj->userptr.mm->mm;
+               int locked = 1;

                down_read(&mm->mmap_sem);
                while (pinned < npages) {
-                       ret = get_user_pages(work->task, mm,
-                                            obj->userptr.ptr + pinned * 
PAGE_SIZE,
-                                            npages - pinned,
-                                            !obj->userptr.read_only, 0,
-                                            pvec + pinned, NULL);
+                       ret = get_user_pages_locked(work->task, mm,
+                                                   obj->userptr.ptr + pinned * 
PAGE_SIZE,
+                                                   npages - pinned,
+                                                   !obj->userptr.read_only, 0,
+                                                   pvec + pinned, &locked);
                        if (ret < 0)
                                break;

                        pinned += ret;
                }
-               up_read(&mm->mmap_sem);
+               if (locked)
+                       up_read(&mm->mmap_sem);
        }

        mutex_lock(&dev->struct_mutex);


Reviewed-by: Tvrtko Ursulin <tvrtko.ursu...@intel.com>

Is it just cleanup or actually improves some real (as in hit by someone) scenario?

Regards,

Tvrtko
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