Re: [PATCH 15/15] dma-mapping: bypass indirect calls for dma-direct

Thierry Reding
2018-12-20T16:44:25Z

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On Fri, Dec 07, 2018 at 11:07:20AM -0800, Christoph Hellwig wrote:
[...]
> diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
> index 0b18cfbdde95..fc84c81029d9 100644
> --- a/kernel/dma/mapping.c
> +++ b/kernel/dma/mapping.c
[...]
> @@ -397,9 +404,9 @@ int dma_supported(struct device *dev, u64 mask)
> {
> const struct dma_map_ops *ops = get_dma_ops(dev);
>
> - if (!ops)
> - return 0;
> - if (!ops->dma_supported)
> + if (dma_is_direct(ops))
> + return dma_direct_supported(dev, mask);
> + if (ops->dma_supported)
> return 1;
> return ops->dma_supported(dev, mask);
> }

Hi Christoph,

This hunk causes a crash on boot for me. It looks like a ! got lost in
the rework here. The following patch fixes the crash for me and restores
the logic of the op->dma_supported check.

Feel free to squash this patch into the above if you prefer that.

Thierry

--- >8 ---
From c502b29ab01fa857e81c78cd574d4d22d7d20e09 Mon Sep 17 00:00:00 2001
From: Thierry Reding <treding@nvidia.com>
Date: Thu, 20 Dec 2018 17:35:47 +0100
Subject: [PATCH] dma-mapping: Fix inverted logic in dma_supported()

The cleanup in commit 356da6d0cde3 ("dma-mapping: bypass indirect calls
for dma-direct") accidentally inverted the logic in the check for the
presence of a ->dma_supported() callback. Switch this back to the way it
was to prevent a crash on boot.

Fixes: 356da6d0cde3 ("dma-mapping: bypass indirect calls for dma-direct")
Signed-off-by: Thierry Reding <treding@nvidia.com>
---
kernel/dma/mapping.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index fc84c81029d9..d7c34d2d1ba5 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -406,7 +406,7 @@ int dma_supported(struct device *dev, u64 mask)

if (dma_is_direct(ops))
return dma_direct_supported(dev, mask);
- if (ops->dma_supported)
+ if (!ops->dma_supported)
return 1;
return ops->dma_supported(dev, mask);
}
--
2.19.1

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