linux-kernel - [PATCH] direct-dma: WARN_ON_ONCE when the page is not addressable by device's coherent_dma

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Date: Wed, 13 Mar 2024 20:19:30 +0800
From: John Hsu <john.hsu@...iatek.com>
To: Christoph Hellwig <hch@....de>, Marek Szyprowski
	<m.szyprowski@...sung.com>, Robin Murphy <robin.murphy@....com>, "Matthias
 Brugger" <matthias.bgg@...il.com>, AngeloGioacchino Del Regno
	<angelogioacchino.delregno@...labora.com>
CC: <surenb@...gle.com>, John Hsu <john.hsu@...iatek.com>, Chinwen Chang
	<chinwen.change@...iatek.com>, Casper Li <casper.li@...iatek.com>, "Kuan-Ying
 Lee" <Kuan-Ying.Lee@...iatek.com>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-mediatek@...ts.infradead.org>
Subject: [PATCH] direct-dma: WARN_ON_ONCE when the page is not addressable by device's coherent_dma_mask

From: JohnHsu <john.hsu@...iatek.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.

Signed-off-by: JohnHsu <john.hsu@...iatek.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;
 }
 
-- 
2.18.0