[PATCH V2] dma-mapping: Set dma_mem pointer as NULL after it's freed

[PATCH V2] dma-mapping: Set dma_mem pointer as NULL after it's freed

[joakim.zhang]

From: Joakim Zhang <joakim.zhang@cixtech.com>

Reproduced with below sequence:
dma_declare_coherent_memory()->dma_release_coherent_memory()
->dma_declare_coherent_memory()->"return -EBUSY" error

It will return -EBUSY from the dma_assign_coherent_memory()
in dma_declare_coherent_memory(), the reason is that dev->dma_mem
pointer has not been set to NULL after it's freed.

Fixes: cf65a0f6f6ff ("dma-mapping: move all DMA mapping code to kernel/dma")
Signed-off-by: Joakim Zhang <joakim.zhang@cixtech.com>
---
ChangeLogs:
V1->V2:
	* remove _dma_release_coherent_memory() from
	rmem_dma_device_release()
	* update commit message
---
 kernel/dma/coherent.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/coherent.c b/kernel/dma/coherent.c
index c21abc77c53e..ff5683a57f77 100644
--- a/kernel/dma/coherent.c
+++ b/kernel/dma/coherent.c
@@ -132,8 +132,10 @@ int dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr,
 
 void dma_release_coherent_memory(struct device *dev)
 {
-	if (dev)
+	if (dev) {
 		_dma_release_coherent_memory(dev->dma_mem);
+		dev->dma_mem = NULL;
+	}
 }
 
 static void *__dma_alloc_from_coherent(struct device *dev,
-- 
2.25.1

Re: [PATCH V2] dma-mapping: Set dma_mem pointer as NULL after it's freed

[Christoph Hellwig]

I've applied this after fixing the whitespace errors.

But we really need to get remoteporc off messing with the reserved
regions itself and retire this API entirely.

RE: [PATCH V2] dma-mapping: Set dma_mem pointer as NULL after it's freed

[Joakim Zhang]

Hi Christoph Hellwig,

> -----Original Message-----
> From: Christoph Hellwig <hch@lst.de>
> Sent: Friday, December 15, 2023 7:32 PM
> To: Joakim Zhang <joakim.zhang@cixtech.com>
> Cc: hch@lst.de; m.szyprowski@samsung.com; robin.murphy@arm.com;
> iommu@lists.linux.dev; linux-kernel@vger.kernel.org; cix-kernel-upstream
> <cix-kernel-upstream@cixtech.com>
> Subject: Re: [PATCH V2] dma-mapping: Set dma_mem pointer as NULL after
> it's freed
> 
> I've applied this after fixing the whitespace errors.
> 
> But we really need to get remoteporc off messing with the reserved regions
> itself and retire this API entirely.

Indeed, I met this issue when debugging remoteproc, this API maybe useful since some system would not support device tree, but still want to reserve memory in the driver.