[PATCH,resend] Fix strange panic message selection logic when swiotlb fills up

[PATCH,resend] Fix strange panic message selection logic when swiotlb fills up

[Casey Dahlin]

swiotlb_full in lib/swiotlb.c throws one of two panic messages based on whether
the direction of transfer is from the device or to the device. The logic around
this is somewhat weird in the case of bidirectional transfers. It appears to
want to throw both in succession, but since its a panic only the first makes it.

This patch adds a third, separate error for DMA_BIDIRECTIONAL to make things a
bit clearer.

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>

---
 lib/swiotlb.c |   15 +++++++++------
 1 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index bffe6d7..35e01b3 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -625,12 +625,15 @@ swiotlb_full(struct device *dev, size_t size, int dir, int do_panic)
 	printk(KERN_ERR "DMA: Out of SW-IOMMU space for %zu bytes at "
 	       "device %s\n", size, dev ? dev_name(dev) : "?");
 
-	if (size > io_tlb_overflow && do_panic) {
-		if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)
-			panic("DMA: Memory would be corrupted\n");
-		if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
-			panic("DMA: Random memory would be DMAed\n");
-	}
+	if (size <= io_tlb_overflow || !do_panic)
+		return;
+
+	if (dir == DMA_BIDIRECTIONAL)
+		panic("DMA: Random memory could be corrupted or DMAed\n");
+	if (dir == DMA_FROM_DEVICE)
+		panic("DMA: Memory would be corrupted\n");
+	if (dir == DMA_TO_DEVICE)
+		panic("DMA: Random memory would be DMAed\n");
 }
 
 /*

Re: [PATCH,resend] Fix strange panic message selection logic when swiotlb fills up

[Andrew Morton]

On Thu, 20 Aug 2009 15:52:28 -0400
Casey Dahlin <cdahlin@redhat.com> wrote:

> swiotlb_full in lib/swiotlb.c throws one of two panic messages based on whether
> the direction of transfer is from the device or to the device. The logic around
> this is somewhat weird in the case of bidirectional transfers. It appears to
> want to throw both in succession, but since its a panic only the first makes it.
> 
> This patch adds a third, separate error for DMA_BIDIRECTIONAL to make things a
> bit clearer.
> 
> Signed-off-by: Casey Dahlin <cdahlin@redhat.com>
> 
> ---
>  lib/swiotlb.c |   15 +++++++++------
>  1 files changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> index bffe6d7..35e01b3 100644
> --- a/lib/swiotlb.c
> +++ b/lib/swiotlb.c
> @@ -625,12 +625,15 @@ swiotlb_full(struct device *dev, size_t size, int dir, int do_panic)
>  	printk(KERN_ERR "DMA: Out of SW-IOMMU space for %zu bytes at "
>  	       "device %s\n", size, dev ? dev_name(dev) : "?");
>  
> -	if (size > io_tlb_overflow && do_panic) {
> -		if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)
> -			panic("DMA: Memory would be corrupted\n");
> -		if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
> -			panic("DMA: Random memory would be DMAed\n");
> -	}
> +	if (size <= io_tlb_overflow || !do_panic)
> +		return;
> +
> +	if (dir == DMA_BIDIRECTIONAL)
> +		panic("DMA: Random memory could be corrupted or DMAed\n");
> +	if (dir == DMA_FROM_DEVICE)
> +		panic("DMA: Memory would be corrupted\n");
> +	if (dir == DMA_TO_DEVICE)
> +		panic("DMA: Random memory would be DMAed\n");
>  }
>  

Seems sane to me.

While we're there, how about we make the final message less ambiguous? 

--- a/lib/swiotlb.c~lib-swiotlbc-fix-strange-panic-message-selection-logic-when-swiotlb-fills-up-fix
+++ a/lib/swiotlb.c
@@ -633,7 +633,7 @@ swiotlb_full(struct device *dev, size_t 
 	if (dir == DMA_FROM_DEVICE)
 		panic("DMA: Memory would be corrupted\n");
 	if (dir == DMA_TO_DEVICE)
-		panic("DMA: Random memory would be DMAed\n");
+		panic("DMA: Random memory would be DMAed from\n");
 }
 
 /*
_