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From: Halil Pasic <pasic@linux.ibm.com>
To: Christoph Hellwig <hch@lst.de>,
	Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: linux-s390@vger.kernel.org, Janosch Frank <frankja@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	Peter Oberparleiter <oberpar@linux.ibm.com>,
	linux-kernel@vger.kernel.org, Halil Pasic <pasic@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	iommu@lists.linux-foundation.org
Subject: [RFC PATCH 3/3] dma-mapping: warn on harmful GFP_* flags
Date: Mon, 23 Sep 2019 14:34:18 +0200
Message-ID: <20190923123418.22695-4-pasic@linux.ibm.com> (raw)
In-Reply-To: <20190923123418.22695-1-pasic@linux.ibm.com>

The commit message of commit 57bf5a8963f8 ("dma-mapping: clear harmful
GFP_* flags in common code") says that probably warn when we encounter
harmful GFP_* flags which we clean -- because the client code is best
case silly if not buggy. I concur with that.

Let's warn once when we encounter silly GFP_* flags. The guys caring
about the respective client code will hopefully fix these soon.

Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
---

I'm not too happy with my warning message. Suggestions welcome!
---
 include/linux/dma-mapping.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 5024bc863fa7..299f36ac8668 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -823,6 +823,9 @@ extern gfp_t dma_override_gfp_flags(struct device *dev, gfp_t flags);
 static inline gfp_t dma_override_gfp_flags(struct device *dev, gfp_t flags)
 {
 	/* let the implementation decide on the zone to allocate from: */
+	dev_WARN_ONCE(dev,
+		      flags & (__GFP_DMA32 | __GFP_DMA | __GFP_HIGHMEM),
+		      "fixme: don't dma_alloc with any of: __GFP_DMA32, __GFP_DMA, __GFP_HIGHMEM\n");
 	return flags & ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM);
 }
 #endif
-- 
2.17.1

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      parent reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-23 12:34 [RFC PATCH 0/3] fix dma_mask for CCW devices Halil Pasic
2019-09-23 12:34 ` [RFC PATCH 1/3] dma-mapping: make overriding GFP_* flags arch customizable Halil Pasic
2019-09-23 15:21   ` Christoph Hellwig
2019-09-26 12:37     ` Halil Pasic
2019-09-26 13:04       ` Robin Murphy
2019-09-27  0:33         ` Halil Pasic
2019-09-27 21:21           ` Christoph Hellwig
2019-09-23 12:34 ` [RFC PATCH 2/3] s390/virtio: fix virtio-ccw DMA without PV Halil Pasic
2019-09-23 12:34 ` Halil Pasic [this message]

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