Re: [Intel-gfx] [PATCH 3/6] drm/i915: use vmap in shmem_pin_map

[Christoph Hellwig]

On Tue, Sep 22, 2020 at 09:23:59AM +0100, Tvrtko Ursulin wrote:
> If I understood this sub-thread correctly, iterating and freeing the pages 
> via the vmapped ptes, so no need for a
> shmem_read_mapping_page_gfp loop in shmem_unpin_map looks plausible to me.
>
> I did not get the reference to kernel/dma/remap.c though,

What I mean is the code in dma_common_find_pages, which returns the
page array for freeing.

>
> and also not sure 
> how to do the error unwind path in shmem_pin_map at which point the 
> allocated vm area hasn't been fully populated yet. Hand-roll the loop 
> walking vm area struct in there?

Yes.  What I originally did (re-created as I didn't save it) would be
something like this:

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