Messages in this thread | | | Date | Wed, 13 Mar 2024 12:43:52 +0000 | Subject | Re: [PATCH] direct-dma: WARN_ON_ONCE when the page is not addressable by device's coherent_dma_mask | From | Robin Murphy <> |
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On 2024-03-13 12:19 pm, John Hsu wrote: > From: JohnHsu <john.hsu@mediatek.com> > > The dma_direct_alloc() may return null in some cases. For example, the > allocated page is not addressable for the device's coherent_dma_mask, > and the allocated page will be assigned to null. > > This patch can WARN_ON_ONCE() when the returned page is null in > dma_direct_alloc. It helps the developers position the root cause of > allocation failure rapidly.
No. Failure to allocate a buffer can happen for any number of reasons, it is not specific to dma-direct, and in some cases it is even expected, hence why DMA_ATTR_NO_WARN exists. And either way it's still not a condition worthy of panicking when panic_on_warn is in use.
Sure, this may well be a handy development hack for debugging a particular driver which isn't handling failure correctly, but it is not suitable for mainline.
Thanks, Robin.
> Signed-off-by: JohnHsu <john.hsu@mediatek.com> > --- > kernel/dma/direct.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > index 9596ae1aa0da..a73b8ad1ef9e 100644 > --- a/kernel/dma/direct.c > +++ b/kernel/dma/direct.c > @@ -156,6 +156,8 @@ static struct page *__dma_direct_alloc_pages(struct device *dev, size_t size, > } > } > > + WARN_ON_ONCE(!page); > + > return page; > } >
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