Re: [PATCH 3/6] block, fs: assert that key paths use iovecs, and nothing else

John Hubbard
2022-02-27T22:28:02Z

On 2/27/22 14:15, Al Viro wrote:
> On Sun, Feb 27, 2022 at 01:34:31AM -0800, jhubbard.send.patches@gmail.com wrote:
>> From: John Hubbard <jhubbard@nvidia.com>
>>
>> Upcoming changes to Direct IO will change it from acquiring pages via
>> get_user_pages_fast(), to calling pin_user_pages_fast() instead.
>>
>> Place a few assertions at key points, that the pages are IOVEC (user
>> pages), to enforce the assumptions that there are no kernel or pipe or
>> other odd variations being passed.
>
> Umm... And what should happen when O_DIRECT file gets passed to splice()?

Hi Al,

First of all, full disclosure: I still haven't worked through how
splice() handles pages in all cases. I was hoping to defer it, by
limiting this series to not *all* of the original callers of
iov_iter_get_pages*().

This series leaves the splice() code pointing to iov_iter_get_pages(),
but maybe that's not possible after all.

Any advice or ideas about how to solve the O_DIRECT-to-splice() is very
welcome.

thanks,
--
John Hubbard
NVIDIA