On Wed, Jun 26, 2024 at 05:36:43PM +0200, Nirmoy Das wrote:
> Hi Rodrigo,
>
> On 6/26/2024 5:24 PM, Rodrigo Vivi wrote:
>
> On Wed, Jun 26, 2024 at 04:33:18PM +0200, Nirmoy Das wrote:
>
> >We report object allocation failures to userspace with ENOMEM
> >so add __GFP_NOWARN to remove superfluous oom warnings.
>
> >Closes: [1]https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/4936
> >Cc: Andi Shyti [2]<andi.shyti at linux.intel.com>
> >Signed-off-by: Nirmoy Das [3]<nirmoy.das at intel.com>
> >---
> > drivers/gpu/drm/i915/i915_scatterlist.c | 8 ++++----
> > 1 file changed, 4 insertions(+), 4 deletions(-)
>
> >diff --git a/drivers/gpu/drm/i915/i915_scatterlist.c b/drivers/gpu/drm/i915/i915_scatterlist.c
> >index e93d2538f298..4d830740946d 100644
> >--- a/drivers/gpu/drm/i915/i915_scatterlist.c
> >+++ b/drivers/gpu/drm/i915/i915_scatterlist.c
> >@@ -90,7 +90,7 @@ struct i915_refct_sgt *i915_rsgt_from_mm_node(const struct drm_mm_node *node,
> >
> > GEM_BUG_ON(!max_segment);
> >
> >- rsgt = kmalloc(sizeof(*rsgt), GFP_KERNEL);
> >+ rsgt = kmalloc(sizeof(*rsgt), GFP_KERNEL | __GFP_NOWARN);
> > if (!rsgt)
> > return ERR_PTR(-ENOMEM);
>
> is it really safe?
> I don't believe we can guarantee a good fallback plan here if allocation fails.
> __i915_refct_sgt_init
> might end up in a null dereference, no?!
>
> Kernel is now returning ENOMEM and also throwing a oom warning stack.
> With __GFP_NOWARN
>
> the oom warning stack won't be there in the dmesg but userspace will still
> get ENOMEM as expected.
doh! I had missunderstand the flag. Thanks for the confirmation.
Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
BTW, what email clients are you using recently?
it is hard to parse your responses lately. Please check if it is really
sending/replying as text-only mode.
>
> Let me know if got your question correctly.
>
> Regards,
>
> Nirmoy
>
>
>
> >
> >@@ -104,7 +104,7 @@ struct i915_refct_sgt *i915_rsgt_from_mm_node(const struct drm_mm_node *node,
> > }
> >
> > if (sg_alloc_table(st, DIV_ROUND_UP_ULL(node->size, segment_pages),
> >- GFP_KERNEL)) {
> >+ GFP_KERNEL | __GFP_NOWARN)) {
> > i915_refct_sgt_put(rsgt);
> > return ERR_PTR(-ENOMEM);
> > }
> >@@ -178,7 +178,7 @@ struct i915_refct_sgt *i915_rsgt_from_buddy_resource(struct ttm_resource *res,
> > GEM_BUG_ON(list_empty(blocks));
> > GEM_BUG_ON(!max_segment);
> >
> >- rsgt = kmalloc(sizeof(*rsgt), GFP_KERNEL);
> >+ rsgt = kmalloc(sizeof(*rsgt), GFP_KERNEL | __GFP_NOWARN);
> > if (!rsgt)
> > return ERR_PTR(-ENOMEM);
> >
> >@@ -190,7 +190,7 @@ struct i915_refct_sgt *i915_rsgt_from_buddy_resource(struct ttm_resource *res,
> > return ERR_PTR(-E2BIG);
> > }
> >
> >- if (sg_alloc_table(st, PFN_UP(res->size), GFP_KERNEL)) {
> >+ if (sg_alloc_table(st, PFN_UP(res->size), GFP_KERNEL | __GFP_NOWARN)) {
> > i915_refct_sgt_put(rsgt);
> > return ERR_PTR(-ENOMEM);
> > }
> >--
> >2.42.0
>
> References
>
> Visible links
> 1. https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/4936
> 2. mailto:andi.shyti at linux.intel.com
> 3. mailto:nirmoy.das at intel.com