Re: [PATCH] iommu: Properly pass gfp_t in _iommu_map() to avoid atomic sleeping

Re: [PATCH] iommu: Properly pass gfp_t in _iommu_map() to avoid atomic sleeping

[Yong Wu]

On Mon, 2021-02-01 at 17:06 -0800, Douglas Anderson wrote:
> Sleeping while atomic = bad.  Let's fix an obvious typo to try to avoid it.
> 
> The warning that was seen (on a downstream kernel with the problematic
> patch backported):
> 
>  BUG: sleeping function called from invalid context at mm/page_alloc.c:4726
>  in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 9, name: ksoftirqd/0
>  CPU: 0 PID: 9 Comm: ksoftirqd/0 Not tainted 5.4.93-12508-gc10c93e28e39 #1
>  Call trace:
>   dump_backtrace+0x0/0x154
>   show_stack+0x20/0x2c
>   dump_stack+0xa0/0xfc
>   ___might_sleep+0x11c/0x12c
>   __might_sleep+0x50/0x84
>   __alloc_pages_nodemask+0xf8/0x2bc
>   __arm_lpae_alloc_pages+0x48/0x1b4
>   __arm_lpae_map+0x124/0x274
>   __arm_lpae_map+0x1cc/0x274
>   arm_lpae_map+0x140/0x170
>   arm_smmu_map+0x78/0xbc
>   __iommu_map+0xd4/0x210
>   _iommu_map+0x4c/0x84
>   iommu_map_atomic+0x44/0x58
>   __iommu_dma_map+0x8c/0xc4
>   iommu_dma_map_page+0xac/0xf0
> 
> Fixes: d8c1df02ac7f ("iommu: Move iotlb_sync_map out from __iommu_map")
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

oh. This is my fault. Thanks for the fix.

Reviewed-by: Yong Wu <yong.wu@mediatek.com>

> ---
> I haven't done any serious testing on this.  I saw a report of the
> warning and the fix seemed obvious so I'm shooting it out.
> 
>  drivers/iommu/iommu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 3d099a31ddca..2b06b01850d5 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2441,7 +2441,7 @@ static int _iommu_map(struct iommu_domain *domain, unsigned long iova,
>  	const struct iommu_ops *ops = domain->ops;
>  	int ret;
>  
> -	ret = __iommu_map(domain, iova, paddr, size, prot, GFP_KERNEL);
> +	ret = __iommu_map(domain, iova, paddr, size, prot, gfp);
>  	if (ret == 0 && ops->iotlb_sync_map)
>  		ops->iotlb_sync_map(domain, iova, size);
>  

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