Re: [RFC PATCH] usb: host: xhci: allow __GFP_FS in dma allocation

Oliver Neukum
2019-05-23T12:45:11Z

On So, 2019-05-19 at 22:56 -0700, Christoph Hellwig wrote:
> Folks, you can't just pass arbitary GFP_ flags to dma allocation
> routines, beause very often they are not just wrappers around
> the page allocator.
>
> So no, you can't just fine grained control the flags, but the
> existing code is just as buggy.
>
> Please switch to use memalloc_noio_save() instead.

Thinking about this again, we have a problem. We introduced
memalloc_noio_save() in 3.10 . Hence the code should have been
correct in v4.14. Which means that either
6518202970c1 "(mm/cma: remove unsupported gfp_mask
parameter from cma_alloc()"
is buggy, or the original issue with a delay of 2 seconds
still exist.

Do we need to do something?

Regards
Oliver