Re: [PATCH v2 1/4] usb: usbfs: Enforce page requirements for mmap

[Christoph Hellwig]

On Mon, May 15, 2023 at 09:09:55PM +0800, Ruihan Li wrote:
> To address these issues, this patch introduces hcd_alloc_coherent_pages,
> which addresses the above two problems. Specifically,
> hcd_alloc_coherent_pages uses gen_pool_dma_alloc_align instead of
> gen_pool_dma_alloc to ensure that the memory is page-aligned. To replace
> kmalloc, hcd_alloc_coherent_pages directly allocates pages by calling
> __get_free_pages.

This looks reasonable in that it fixes the bug.  But I really don't
like how it makes the mess of USB allocation APIs even messier :P

Not really your faul, but someone really needs to look into the usb
memory allocators and DMA mapping, which is tied to that and just as
bad.