From: Pavel Begunkov <asml.silence@gmail.com>
To: Jason Gunthorpe <jgg@nvidia.com>, Lorenzo Stoakes <lstoakes@gmail.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Matthew Wilcox <willy@infradead.org>,
David Hildenbrand <david@redhat.com>,
Jens Axboe <axboe@kernel.dk>,
io-uring@vger.kernel.org
Subject: Re: [PATCH 5/7] io_uring: rsrc: use FOLL_SAME_FILE on pin_user_pages()
Date: Tue, 18 Apr 2023 17:35:48 +0100 [thread overview]
Message-ID: <16b33cfe-acb2-760e-7e87-8a837f84fc66@gmail.com> (raw)
In-Reply-To: <c19b3651-624b-f60e-3e63-fe9fadc6981f@gmail.com>
On 4/18/23 17:25, Pavel Begunkov wrote:
> On 4/17/23 13:56, Jason Gunthorpe wrote:
>> On Sat, Apr 15, 2023 at 12:27:45AM +0100, Lorenzo Stoakes wrote:
>>> Commit edd478269640 ("io_uring/rsrc: disallow multi-source reg buffers")
>>> prevents io_pin_pages() from pinning pages spanning multiple VMAs with
>>> permitted characteristics (anon/huge), requiring that all VMAs share the
>>> same vm_file.
>>
>> That commmit doesn't really explain why io_uring is doing such a weird
>> thing.
>>
>> What exactly is the problem with mixing struct pages from different
>> files and why of all the GUP users does only io_uring need to care
>> about this?
>
> Simply because it doesn't seem sane to mix and register buffers of
> different "nature" as one. It's not a huge deal for currently allowed
> types, e.g. mixing normal and huge anon pages, but it's rather a matter
> of time before it gets extended, and then I'll certainly become a
> problem. We've been asked just recently to allow registering bufs
> provided mapped by some specific driver, or there might be DMA mapped
> memory in the future.
>
> Rejecting based on vmas might be too conservative, I agree and am all
> for if someone can help to make it right.
For some reason I thought it was rejecting if involves more than
one different vma. ->vm_file checks still sound fair to me, but in
any case, open to changing it.
--
Pavel Begunkov
next prev parent reply other threads:[~2023-04-18 16:36 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-14 23:25 [PATCH 0/7] remove the vmas parameter from GUP APIs Lorenzo Stoakes
2023-04-14 23:27 ` [PATCH 1/7] mm/gup: remove unused vmas parameter from get_user_pages() Lorenzo Stoakes
2023-04-15 5:27 ` Greg Kroah-Hartman
2023-04-17 13:01 ` Jason Gunthorpe
2023-04-14 23:27 ` [PATCH 2/7] mm/gup: remove unused vmas parameter from pin_user_pages_remote() Lorenzo Stoakes
2023-04-17 13:02 ` Jason Gunthorpe
2023-04-14 23:27 ` [PATCH 3/7] mm/gup: remove vmas parameter from get_user_pages_remote() Lorenzo Stoakes
2023-04-15 0:25 ` Tetsuo Handa
2023-04-15 8:11 ` Lorenzo Stoakes
2023-04-17 13:09 ` Jason Gunthorpe
2023-04-17 13:13 ` Lorenzo Stoakes
2023-04-17 13:16 ` Jason Gunthorpe
2023-04-17 13:23 ` Lorenzo Stoakes
2023-04-17 15:07 ` Eric W. Biederman
2023-04-17 15:14 ` Lorenzo Stoakes
2023-04-14 23:27 ` [PATCH 4/7] mm/gup: introduce the FOLL_SAME_FILE GUP flag Lorenzo Stoakes
2023-04-17 13:14 ` Jason Gunthorpe
2023-04-17 13:25 ` Lorenzo Stoakes
2023-04-17 13:27 ` Jason Gunthorpe
2023-04-14 23:27 ` [PATCH 5/7] io_uring: rsrc: use FOLL_SAME_FILE on pin_user_pages() Lorenzo Stoakes
2023-04-17 12:56 ` Jason Gunthorpe
2023-04-17 13:19 ` Lorenzo Stoakes
2023-04-17 13:26 ` Jason Gunthorpe
2023-04-17 14:00 ` Lorenzo Stoakes
2023-04-17 14:15 ` Jason Gunthorpe
2023-04-17 15:20 ` Lorenzo Stoakes
2023-04-17 19:00 ` Lorenzo Stoakes
2023-04-17 19:24 ` Jason Gunthorpe
2023-04-17 19:45 ` Lorenzo Stoakes
2023-04-18 16:25 ` Pavel Begunkov
2023-04-18 16:35 ` Pavel Begunkov [this message]
2023-04-18 16:36 ` Jason Gunthorpe
2023-04-18 17:25 ` Pavel Begunkov
2023-04-18 18:19 ` Jason Gunthorpe
2023-04-14 23:27 ` [PATCH 6/7] mm/gup: remove vmas parameter from pin_user_pages() Lorenzo Stoakes
2023-04-14 23:27 ` [PATCH 7/7] mm/gup: remove vmas array from internal GUP functions Lorenzo Stoakes
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=16b33cfe-acb2-760e-7e87-8a837f84fc66@gmail.com \
--to=asml.silence@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=axboe@kernel.dk \
--cc=david@redhat.com \
--cc=io-uring@vger.kernel.org \
--cc=jgg@nvidia.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lstoakes@gmail.com \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).