[RFC PATCH 155/162] drm/i915: Use a ww transaction in the fault handler

[Matthew Auld]

From: Thomas Hellström <thomas.hellst...@intel.com>

Prefer a ww transaction rather than a single object lock to
enable sleeping lock eviction if reached by the fault
handler.

Signed-off-by: Thomas Hellström <thomas.hellst...@intel.com>
Cc: Matthew Auld <matthew.a...@intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_mman.c | 45 +++++++++++++-----------
 1 file changed, 24 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c 
b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index 33ccd4d665d4..a9526cc309d3 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -238,6 +238,7 @@ static vm_fault_t vm_fault_cpu(struct vm_fault *vmf)
        struct vm_area_struct *area = vmf->vma;
        struct i915_mmap_offset *mmo = area->vm_private_data;
        struct drm_i915_gem_object *obj = mmo->obj;
+       struct i915_gem_ww_ctx ww;
        resource_size_t iomap;
        int err;
 
@@ -246,33 +247,35 @@ static vm_fault_t vm_fault_cpu(struct vm_fault *vmf)
                     area->vm_flags & VM_WRITE))
                return VM_FAULT_SIGBUS;
 
-       if (i915_gem_object_lock_interruptible(obj, NULL))
-               return VM_FAULT_NOPAGE;
+       for_i915_gem_ww(&ww, err, true) {
+               err = i915_gem_object_lock(obj, &ww);
+               if (err)
+                       continue;
 
-       err = i915_gem_object_pin_pages(obj);
-       if (err)
-               goto out;
+               err = i915_gem_object_pin_pages(obj);
+               if (err)
+                       continue;
 
-       iomap = -1;
-       if (!i915_gem_object_has_struct_page(obj)) {
-               iomap = obj->mm.region->iomap.base;
-               iomap -= obj->mm.region->region.start;
-       }
+               iomap = -1;
+               if (!i915_gem_object_has_struct_page(obj)) {
+                       iomap = obj->mm.region->iomap.base;
+                       iomap -= obj->mm.region->region.start;
+               }
 
-       /* PTEs are revoked in obj->ops->put_pages() */
-       err = remap_io_sg(area,
-                         area->vm_start, area->vm_end - area->vm_start,
-                         obj->mm.pages->sgl, iomap);
+               /* PTEs are revoked in obj->ops->put_pages() */
+               err = remap_io_sg(area,
+                                 area->vm_start, area->vm_end - area->vm_start,
+                                 obj->mm.pages->sgl, iomap);
 
-       if (area->vm_flags & VM_WRITE) {
-               GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
-               obj->mm.dirty = true;
-       }
+               if (area->vm_flags & VM_WRITE) {
+                       GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
+                       obj->mm.dirty = true;
+               }
 
-       i915_gem_object_unpin_pages(obj);
+               i915_gem_object_unpin_pages(obj);
+               /* Implicit unlock */
+       }
 
-out:
-       i915_gem_object_unlock(obj);
        return i915_error_to_vmf_fault(err);
 }
 
-- 
2.26.2

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