On Fri, 30 Jun 2023 17:34:02 +0200 Alexander Lobakin wrote:

quoted

I am not a fan of having the page pool force the syncing either. Last
I knew I thought the PP_FLAG_DMA_SYNC_DEV was meant to be set by the  

Please follow the logics of the patch.

1. The driver sets DMA_SYNC_DEV.
2. PP tries to shortcut and replaces it with MAYBE_SYNC.
3. If dma_need_sync() returns true for some page, it gets replaced back
   to DMA_SYNC_DEV, no further dma_need_sync() calls for that pool.

OR

1. The driver doesn't set DMA_SYNC_DEV.
2. PP doesn't turn on MAYBE_SYNC.
3. No dma_need_sync() tests.

Where does PP force syncs for drivers which don't need them?

I think both Alex and I got confused about what's going on here.

Could you reshuffle the code somehow to make it more obvious?
Rename the flag, perhaps put it in a different field than 
the driver-set PP flags?