Re: [PATCH 1/1] drm/i915:Do not use kfree() to free kmem_cache_alloc() return value

From: kbuild test robot
Date: Wed Apr 04 2018 - 09:03:40 EST


Hi Xidong,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on drm-intel/for-linux-next]
[also build test WARNING on v4.16 next-20180403]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url: https://github.com/0day-ci/linux/commits/Xidong-Wang/drm-i915-Do-not-use-kfree-to-free-kmem_cache_alloc-return-value/20180404-193341
base: git://anongit.freedesktop.org/drm-intel for-linux-next
config: i386-randconfig-a1-201813 (attached as .config)
compiler: gcc-4.9 (Debian 4.9.4-2) 4.9.4
reproduce:
# save the attached .config to linux build tree
make ARCH=i386

All warnings (new ones prefixed by >>):

drivers/gpu//drm/i915/i915_gem_execbuffer.c: In function 'eb_lookup_vmas':
>> drivers/gpu//drm/i915/i915_gem_execbuffer.c:731:20: warning: passing argument 1 of 'kmem_cache_free' from incompatible pointer type
kmem_cache_free(lut);
^
In file included from include/linux/reservation.h:44:0,
from drivers/gpu//drm/i915/i915_gem_execbuffer.c:30:
include/linux/slab.h:356:6: note: expected 'struct kmem_cache *' but argument is of type 'struct i915_lut_handle *'
void kmem_cache_free(struct kmem_cache *, void *);
^
drivers/gpu//drm/i915/i915_gem_execbuffer.c:731:4: error: too few arguments to function 'kmem_cache_free'
kmem_cache_free(lut);
^
In file included from include/linux/reservation.h:44:0,
from drivers/gpu//drm/i915/i915_gem_execbuffer.c:30:
include/linux/slab.h:356:6: note: declared here
void kmem_cache_free(struct kmem_cache *, void *);
^

vim +/kmem_cache_free +731 drivers/gpu//drm/i915/i915_gem_execbuffer.c

685
686 static int eb_lookup_vmas(struct i915_execbuffer *eb)
687 {
688 struct radix_tree_root *handles_vma = &eb->ctx->handles_vma;
689 struct drm_i915_gem_object *obj;
690 unsigned int i;
691 int err;
692
693 if (unlikely(i915_gem_context_is_closed(eb->ctx)))
694 return -ENOENT;
695
696 if (unlikely(i915_gem_context_is_banned(eb->ctx)))
697 return -EIO;
698
699 INIT_LIST_HEAD(&eb->relocs);
700 INIT_LIST_HEAD(&eb->unbound);
701
702 for (i = 0; i < eb->buffer_count; i++) {
703 u32 handle = eb->exec[i].handle;
704 struct i915_lut_handle *lut;
705 struct i915_vma *vma;
706
707 vma = radix_tree_lookup(handles_vma, handle);
708 if (likely(vma))
709 goto add_vma;
710
711 obj = i915_gem_object_lookup(eb->file, handle);
712 if (unlikely(!obj)) {
713 err = -ENOENT;
714 goto err_vma;
715 }
716
717 vma = i915_vma_instance(obj, eb->vm, NULL);
718 if (unlikely(IS_ERR(vma))) {
719 err = PTR_ERR(vma);
720 goto err_obj;
721 }
722
723 lut = kmem_cache_alloc(eb->i915->luts, GFP_KERNEL);
724 if (unlikely(!lut)) {
725 err = -ENOMEM;
726 goto err_obj;
727 }
728
729 err = radix_tree_insert(handles_vma, handle, vma);
730 if (unlikely(err)) {
> 731 kmem_cache_free(lut);
732 goto err_obj;
733 }
734
735 /* transfer ref to ctx */
736 vma->open_count++;
737 list_add(&lut->obj_link, &obj->lut_list);
738 list_add(&lut->ctx_link, &eb->ctx->handles_list);
739 lut->ctx = eb->ctx;
740 lut->handle = handle;
741
742 add_vma:
743 err = eb_add_vma(eb, i, vma);
744 if (unlikely(err))
745 goto err_vma;
746
747 GEM_BUG_ON(vma != eb->vma[i]);
748 GEM_BUG_ON(vma->exec_flags != &eb->flags[i]);
749 }
750
751 /* take note of the batch buffer before we might reorder the lists */
752 i = eb_batch_index(eb);
753 eb->batch = eb->vma[i];
754 GEM_BUG_ON(eb->batch->exec_flags != &eb->flags[i]);
755
756 /*
757 * SNA is doing fancy tricks with compressing batch buffers, which leads
758 * to negative relocation deltas. Usually that works out ok since the
759 * relocate address is still positive, except when the batch is placed
760 * very low in the GTT. Ensure this doesn't happen.
761 *
762 * Note that actual hangs have only been observed on gen7, but for
763 * paranoia do it everywhere.
764 */
765 if (!(eb->flags[i] & EXEC_OBJECT_PINNED))
766 eb->flags[i] |= __EXEC_OBJECT_NEEDS_BIAS;
767 if (eb->reloc_cache.has_fence)
768 eb->flags[i] |= EXEC_OBJECT_NEEDS_FENCE;
769
770 eb->args->flags |= __EXEC_VALIDATED;
771 return eb_reserve(eb);
772
773 err_obj:
774 i915_gem_object_put(obj);
775 err_vma:
776 eb->vma[i] = NULL;
777 return err;
778 }
779

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