Enable gup to retry and fault the pages outside of the mmap_sem lock in
our worker. As we are inside our worker, outside of any critical path,
we can allow the mmap_sem lock to be dropped in order to service a page
fault; this in turn allows the mm to populate the page using a slow
fault handler.
Testcase: igt/gem_userptr/userfault
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
index dd104b0e2071..54ebc7ab71bc 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
@@ -459,26 +459,31 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
if (pvec != NULL) {
struct mm_struct *mm = obj->userptr.mm->mm;
unsigned int flags = 0;
+ int locked = 0;
if (!i915_gem_object_is_readonly(obj))
flags |= FOLL_WRITE;
ret = -EFAULT;
if (mmget_not_zero(mm)) {
- down_read(&mm->mmap_sem);
while (pinned < npages) {
+ if (!locked) {
+ down_read(&mm->mmap_sem);
+ locked = 1;
+ }
ret = get_user_pages_remote
(work->task, mm,
obj->userptr.ptr + pinned * PAGE_SIZE,
npages - pinned,
flags,
- pvec + pinned, NULL, NULL);
+ pvec + pinned, NULL, &locked);
if (ret < 0)
break;
pinned += ret;
}
- up_read(&mm->mmap_sem);
+ if (locked)
+ up_read(&mm->mmap_sem);
mmput(mm);
}
}
--
2.24.0
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