Re: [PATCH net-next v7 2/2] page_pool: Track DMA-mapped pages and unmap them when destroying the pool

[Alexander Lobakin <aleksander.lobakin@intel.com>]

From: Alexander Lobakin <aleksander.lobakin@intel.com>
Date: Fri, 4 Apr 2025 17:55:43 +0200

> From: Toke Høiland-Jørgensen <toke@redhat.com>
> Date: Fri, 04 Apr 2025 12:18:36 +0200
> 
>> When enabling DMA mapping in page_pool, pages are kept DMA mapped until
>> they are released from the pool, to avoid the overhead of re-mapping the
>> pages every time they are used. This causes resource leaks and/or
>> crashes when there are pages still outstanding while the device is torn
>> down, because page_pool will attempt an unmap through a non-existent DMA
>> device on the subsequent page return.
> 
> [...]
> 
>> -#define PP_MAGIC_MASK ~0x3UL
>> +#define PP_MAGIC_MASK ~(PP_DMA_INDEX_MASK | 0x3UL)
>>  
>>  /**
>>   * struct page_pool_params - page pool parameters
>> @@ -173,10 +212,10 @@ struct page_pool {
>>  	int cpuid;
>>  	u32 pages_state_hold_cnt;
>>  
>> -	bool has_init_callback:1;	/* slow::init_callback is set */
>> +	bool dma_sync;			/* Perform DMA sync for device */
> 
> Yunsheng said this change to a full bool is redundant in the v6 thread
> ¯\_(ツ)_/¯


Under v5, sorree >_<

> I hope you've read it.
> 
>>  	bool dma_map:1;			/* Perform DMA mapping */
>> -	bool dma_sync:1;		/* Perform DMA sync for device */
>>  	bool dma_sync_for_cpu:1;	/* Perform DMA sync for cpu */
>> +	bool has_init_callback:1;	/* slow::init_callback is set */
>>  #ifdef CONFIG_PAGE_POOL_STATS
>>  	bool system:1;			/* This is a global percpu pool */
>>  #endif

Thanks,
Olek