On 4/19/23 21:15, Jens Axboe wrote:
On 4/19/23 12:24?PM, Jason Gunthorpe wrote:
On Wed, Apr 19, 2023 at 07:23:00PM +0100, Matthew Wilcox wrote:
On Wed, Apr 19, 2023 at 07:18:26PM +0100, Lorenzo Stoakes wrote:
So even if I did the FOLL_ALLOW_BROKEN_FILE_MAPPING patch series first, I
would still need to come along and delete a bunch of your code
afterwards. And unfortunately Pavel's recent change which insists on not
having different vm_file's across VMAs for the buffer would have to be
reverted so I expect it might not be entirely without discussion.
I don't even understand why Pavel wanted to make this change. The
commit log really doesn't say.
commit edd478269640
Author: Pavel Begunkov <asml.silence@xxxxxxxxx>
Date: Wed Feb 22 14:36:48 2023 +0000
io_uring/rsrc: disallow multi-source reg buffers
If two or more mappings go back to back to each other they can be passed
into io_uring to be registered as a single registered buffer. That would
even work if mappings came from different sources, e.g. it's possible to
mix in this way anon pages and pages from shmem or hugetlb. That is not
a problem but it'd rather be less prone if we forbid such mixing.
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
It even says "That is not a problem"! So why was this patch merged
if it's not fixing a problem?
It's now standing in the way of an actual cleanup. So why don't we
revert it? There must be more to it than this ...
https://lore.kernel.org/all/61ded378-51a8-1dcb-b631-fda1903248a9@xxxxxxxxx/
Let's just kill that patch that, I can add a revert for 6.4. I had
forgotten about that patch and guess I didn't realize that most of the
issue do in fact just stem from that.
Well, we're now trading uapi sanity for cleanups, I don't know
what I should take out of it.
--
Pavel Begunkov
