From: David Hildenbrand <david@redhat.com>
To: Lorenzo Stoakes <lstoakes@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH v3 4/7] mm/gup: introduce the FOLL_SAME_FILE GUP flag
Date: Mon, 17 Apr 2023 13:13:58 +0200 [thread overview]
Message-ID: <e4087551-c5d3-e82d-3c4e-dcfa476a971e@redhat.com> (raw)
In-Reply-To: <2feedd2bad6fd1ec4bc4639f9d9012c5ae2faf1f.1681558407.git.lstoakes@gmail.com>
On 15.04.23 14:09, Lorenzo Stoakes wrote:
> This flag causes GUP to assert that all VMAs within the input range possess
> the same vma->vm_file. If not, the operation fails.
>
> This is part of a patch series which eliminates the vmas parameter from the
> GUP API, implementing the one remaining assertion within the entire kernel
> that requires access to the VMAs associated with a GUP range.
>
> Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
[...]
> ---
> &start, &nr_pages, i,
> @@ -1595,7 +1603,7 @@ long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start,
> * We want to report -EINVAL instead of -EFAULT for any permission
> * problems or incompatible mappings.
> */
> - if (check_vma_flags(vma, gup_flags))
> + if (check_vma_flags(vma, vma->vm_file, gup_flags))
> return -EINVAL;
FOLL_SAME_FILE is never set here, just pass NULL instead of vma->vm_file.
As we're not allowing to drop the mmap lock, why can't io_uring simply
go over all VMAs once, after pinning succeeded, and make sure that the
files match (or even before pinning)?
In most cases, we're dealing with a single VMA only, it's not like the
common case is that io_uring pins accross 100s of VMAs.
So I really wonder if the GUP complexity is justified by something.
(removing the VMAs is certainly a welcome surprise -- as it doesn't make
any sense when used with FOLL_UNLOCKABLE).
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2023-04-17 11:14 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-15 12:09 [PATCH v3 0/7] remove the vmas parameter from GUP APIs Lorenzo Stoakes
2023-04-15 12:09 ` [PATCH v3 1/7] mm/gup: remove unused vmas parameter from get_user_pages() Lorenzo Stoakes
2023-04-17 10:55 ` David Hildenbrand
2023-04-15 12:09 ` [PATCH v3 2/7] mm/gup: remove unused vmas parameter from pin_user_pages_remote() Lorenzo Stoakes
2023-04-17 10:55 ` David Hildenbrand
2023-04-15 12:09 ` [PATCH v3 3/7] mm/gup: remove vmas parameter from get_user_pages_remote() Lorenzo Stoakes
2023-04-17 10:52 ` Catalin Marinas
2023-04-17 11:01 ` David Hildenbrand
2023-04-15 12:09 ` [PATCH v3 4/7] mm/gup: introduce the FOLL_SAME_FILE GUP flag Lorenzo Stoakes
2023-04-17 11:13 ` David Hildenbrand [this message]
2023-04-17 11:27 ` Lorenzo Stoakes
2023-04-15 12:09 ` [PATCH v3 5/7] io_uring: rsrc: use FOLL_SAME_FILE on pin_user_pages() Lorenzo Stoakes
2023-04-15 12:09 ` [PATCH v3 6/7] mm/gup: remove vmas parameter from pin_user_pages() Lorenzo Stoakes
2023-04-17 11:14 ` David Hildenbrand
2023-04-17 11:59 ` Dennis Dalessandro
2023-04-15 12:09 ` [PATCH v3 7/7] mm/gup: remove vmas array from internal GUP functions Lorenzo Stoakes
2023-04-17 11:15 ` David Hildenbrand
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