Messages in this thread |  | | Subject | Re: [Intel-gfx] [PATCH 3/6] drm/i915: use vmap in shmem_pin_map | From | Tvrtko Ursulin <> | Date | Tue, 22 Sep 2020 09:23:59 +0100 |
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On 22/09/2020 07:22, Christoph Hellwig wrote: > On Mon, Sep 21, 2020 at 08:11:57PM +0100, Matthew Wilcox wrote: >> This is awkward. I'd like it if we had a vfree() variant which called >> put_page() instead of __free_pages(). I'd like it even more if we >> used release_pages() instead of our own loop that called put_page(). > > Note that we don't need a new vfree variant, we can do this manually if > we want, take a look at kernel/dma/remap.c. But I thought this code > intentionally doesn't want to do that to avoid locking in the memory > for the pages array. Maybe the i915 maintainers can clarify.
+ Chris & Matt who were involved with this part of i915.
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, 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?
Regards,
Tvrtko
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