On 4/19/23 2:15 PM, 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. https://git.kernel.dk/cgit/linux-block/commit/?h=for-6.4/io_uring&id=fbd3aaf37886d3645b1bd6920f6298f5884049f8 -- Jens Axboe
