From: Tomasz Figa <tfiga@chromium.org>
To: David Hildenbrand <david@redhat.com>,
Hans Verkuil <hverkuil@xs4all.nl>,
Marek Szyprowski <m.szyprowski@samsung.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
linux-arm-kernel@lists.infradead.org,
linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org,
linux-media@vger.kernel.org, linux-kselftest@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Jason Gunthorpe <jgg@ziepe.ca>,
John Hubbard <jhubbard@nvidia.com>, Peter Xu <peterx@redhat.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Hugh Dickins <hughd@google.com>, Nadav Amit <namit@vmware.com>,
Vlastimil Babka <vbabka@suse.cz>,
Matthew Wilcox <willy@infradead.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Muchun Song <songmuchun@bytedance.com>,
Lucas Stach <l.stach@pengutronix.de>,
David Airlie <airlied@gmail.com>,
Oded Gabbay <ogabbay@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Mauro Carvalho Chehab <mchehab@kernel.org>
Subject: Re: [PATCH RFC 16/19] mm/frame-vector: remove FOLL_FORCE usage
Date: Tue, 8 Nov 2022 13:45:57 +0900 [thread overview]
Message-ID: <CAAFQd5C3Ba1WhjYJF_7tW06mgvzoz9KTakNo+Tz8h_f6dGKzHQ@mail.gmail.com> (raw)
In-Reply-To: <20221107161740.144456-17-david@redhat.com>
Hi David,
On Tue, Nov 8, 2022 at 1:19 AM David Hildenbrand <david@redhat.com> wrote:
>
> FOLL_FORCE is really only for debugger access. According to commit
> 707947247e95 ("media: videobuf2-vmalloc: get_userptr: buffers are always
> writable"), the pinned pages are always writable.
Actually that patch is only a workaround to temporarily disable
support for read-only pages as they seemed to suffer from some
corruption issues in the retrieved user pages. We expect to support
read-only pages as hardware input after. That said, FOLL_FORCE doesn't
sound like the right thing even in that case, but I don't know the
background behind it being added here in the first place. +Hans
Verkuil +Marek Szyprowski do you happen to remember anything about it?
Best regards,
Tomasz
>
> FOLL_FORCE in this case seems to be a legacy leftover. Let's just remove
> it.
>
> Cc: Tomasz Figa <tfiga@chromium.org>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> drivers/media/common/videobuf2/frame_vector.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/media/common/videobuf2/frame_vector.c b/drivers/media/common/videobuf2/frame_vector.c
> index 542dde9d2609..062e98148c53 100644
> --- a/drivers/media/common/videobuf2/frame_vector.c
> +++ b/drivers/media/common/videobuf2/frame_vector.c
> @@ -50,7 +50,7 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
> start = untagged_addr(start);
>
> ret = pin_user_pages_fast(start, nr_frames,
> - FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM,
> + FOLL_WRITE | FOLL_LONGTERM,
> (struct page **)(vec->ptrs));
> if (ret > 0) {
> vec->got_ref = true;
> --
> 2.38.1
>
next prev parent reply other threads:[~2022-11-08 4:46 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-07 16:17 [PATCH RFC 00/19] mm/gup: remove FOLL_FORCE usage from drivers (reliable R/O long-term pinning) David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 01/19] selftests/vm: anon_cow: prepare for non-anonymous COW tests David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 02/19] selftests/vm: cow: basic COW tests for non-anonymous pages David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 03/19] selftests/vm: cow: R/O long-term pinning reliability tests for non-anon pages David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 04/19] mm: add early FAULT_FLAG_UNSHARE consistency checks David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 05/19] mm: add early FAULT_FLAG_WRITE " David Hildenbrand
2022-11-07 19:03 ` Nadav Amit
2022-11-07 19:27 ` David Hildenbrand
2022-11-07 19:50 ` Nadav Amit
2022-11-07 16:17 ` [PATCH RFC 06/19] mm: rework handling in do_wp_page() based on private vs. shared mappings David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 07/19] mm: don't call vm_ops->huge_fault() in wp_huge_pmd()/wp_huge_pud() for private mappings David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 08/19] mm: extend FAULT_FLAG_UNSHARE support to anything in a COW mapping David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 09/19] mm/gup: reliable R/O long-term pinning in COW mappings David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 10/19] RDMA/umem: remove FOLL_FORCE usage David Hildenbrand
2022-11-14 8:30 ` Leon Romanovsky
2022-11-07 16:17 ` [PATCH RFC 11/19] RDMA/usnic: " David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 12/19] RDMA/siw: " David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 13/19] media: videobuf-dma-sg: " David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 14/19] drm/etnaviv: " David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 15/19] media: pci/ivtv: " David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 16/19] mm/frame-vector: " David Hildenbrand
2022-11-08 4:45 ` Tomasz Figa [this message]
2022-11-08 9:40 ` David Hildenbrand
2022-11-22 12:25 ` Hans Verkuil
2022-11-22 12:38 ` David Hildenbrand
2022-11-22 14:07 ` Hans Verkuil
2022-11-22 15:03 ` David Hildenbrand
2022-11-22 17:33 ` Linus Torvalds
2022-11-07 16:17 ` [PATCH RFC 17/19] drm/exynos: " David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 18/19] RDMA/hw/qib/qib_user_pages: " David Hildenbrand
2022-11-07 16:17 ` [PATCH RFC 19/19] habanalabs: " David Hildenbrand
2022-11-07 21:25 ` Oded Gabbay
2022-11-07 17:27 ` [PATCH RFC 00/19] mm/gup: remove FOLL_FORCE usage from drivers (reliable R/O long-term pinning) Linus Torvalds
2022-11-08 9:29 ` David Hildenbrand
2022-11-14 6:03 ` Christoph Hellwig
2022-11-14 8:07 ` David Hildenbrand
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