From: Jan Kara <jack@suse.cz>
To: John Hubbard <jhubbard@nvidia.com>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Alex Williamson" <alex.williamson@redhat.com>,
"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
"Björn Töpel" <bjorn.topel@intel.com>,
"Christoph Hellwig" <hch@infradead.org>,
"Dan Williams" <dan.j.williams@intel.com>,
"Daniel Vetter" <daniel@ffwll.ch>,
"Dave Chinner" <david@fromorbit.com>,
"David Airlie" <airlied@linux.ie>,
"David S . Miller" <davem@davemloft.net>,
"Ira Weiny" <ira.weiny@intel.com>, "Jan Kara" <jack@suse.cz>,
"Jason Gunthorpe" <jgg@ziepe.ca>, "Jens Axboe" <axboe@kernel.dk>,
"Jonathan Corbet" <corbet@lwn.net>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Magnus Karlsson" <magnus.karlsson@intel.com>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Michal Hocko" <mhocko@suse.com>,
"Mike Kravetz" <mike.kravetz@oracle.com>,
"Paul Mackerras" <paulus@samba.org>,
"Shuah Khan" <shuah@kernel.org>,
"Vlastimil Babka" <vbabka@suse.cz>,
bpf@vger.kernel.org, dri-devel@lists.freedesktop.org,
kvm@vger.kernel.org, linux-block@vger.kernel.org,
linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org,
linux-rdma@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
netdev@vger.kernel.org, linux-mm@kvack.org,
LKML <linux-kernel@vger.kernel.org>,
"Christoph Hellwig" <hch@lst.de>,
"Leon Romanovsky" <leonro@mellanox.com>
Subject: Re: [PATCH v8 08/26] mm/gup: allow FOLL_FORCE for get_user_pages_fast()
Date: Tue, 10 Dec 2019 11:28:18 +0100 [thread overview]
Message-ID: <20191210102818.GF1551@quack2.suse.cz> (raw)
In-Reply-To: <20191209225344.99740-9-jhubbard@nvidia.com>
On Mon 09-12-19 14:53:26, John Hubbard wrote:
> Commit 817be129e6f2 ("mm: validate get_user_pages_fast flags") allowed
> only FOLL_WRITE and FOLL_LONGTERM to be passed to get_user_pages_fast().
> This, combined with the fact that get_user_pages_fast() falls back to
> "slow gup", which *does* accept FOLL_FORCE, leads to an odd situation:
> if you need FOLL_FORCE, you cannot call get_user_pages_fast().
>
> There does not appear to be any reason for filtering out FOLL_FORCE.
> There is nothing in the _fast() implementation that requires that we
> avoid writing to the pages. So it appears to have been an oversight.
>
> Fix by allowing FOLL_FORCE to be set for get_user_pages_fast().
>
> Fixes: 817be129e6f2 ("mm: validate get_user_pages_fast flags")
> Cc: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Looks good to me. You can add:
Reviewed-by: Jan Kara <jack@suse.cz>
Honza
> ---
> mm/gup.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index c0c56888e7cc..958ab0757389 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2414,7 +2414,8 @@ int get_user_pages_fast(unsigned long start, int nr_pages,
> unsigned long addr, len, end;
> int nr = 0, ret = 0;
>
> - if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM)))
> + if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
> + FOLL_FORCE)))
> return -EINVAL;
>
> start = untagged_addr(start) & PAGE_MASK;
> --
> 2.24.0
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2019-12-10 10:28 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-09 22:53 [PATCH v8 00/26] mm/gup: track dma-pinned pages: FOLL_PIN John Hubbard
2019-12-09 22:53 ` [PATCH v8 01/26] mm/gup: factor out duplicate code from four routines John Hubbard
2019-12-09 22:53 ` [PATCH v8 02/26] mm/gup: move try_get_compound_head() to top, fix minor issues John Hubbard
2019-12-09 22:53 ` [PATCH v8 03/26] mm: Cleanup __put_devmap_managed_page() vs ->page_free() John Hubbard
2019-12-09 22:53 ` [PATCH v8 04/26] mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages John Hubbard
2019-12-09 22:53 ` [PATCH v8 05/26] goldish_pipe: rename local pin_user_pages() routine John Hubbard
2019-12-09 22:53 ` [PATCH v8 06/26] mm: fix get_user_pages_remote()'s handling of FOLL_LONGTERM John Hubbard
2019-12-09 22:53 ` [PATCH v8 07/26] vfio: fix FOLL_LONGTERM use, simplify get_user_pages_remote() call John Hubbard
2019-12-09 22:53 ` [PATCH v8 08/26] mm/gup: allow FOLL_FORCE for get_user_pages_fast() John Hubbard
2019-12-10 10:28 ` Jan Kara [this message]
2019-12-09 22:53 ` [PATCH v8 09/26] IB/umem: use get_user_pages_fast() to pin DMA pages John Hubbard
2019-12-09 22:53 ` [PATCH v8 10/26] mm/gup: introduce pin_user_pages*() and FOLL_PIN John Hubbard
2019-12-09 22:53 ` [PATCH v8 11/26] goldish_pipe: convert to pin_user_pages() and put_user_page() John Hubbard
2019-12-09 22:53 ` [PATCH v8 12/26] IB/{core,hw,umem}: set FOLL_PIN via pin_user_pages*(), fix up ODP John Hubbard
2019-12-09 22:53 ` [PATCH v8 13/26] mm/process_vm_access: set FOLL_PIN via pin_user_pages_remote() John Hubbard
2019-12-09 22:53 ` [PATCH v8 14/26] drm/via: set FOLL_PIN via pin_user_pages_fast() John Hubbard
2019-12-09 22:53 ` [PATCH v8 15/26] fs/io_uring: set FOLL_PIN via pin_user_pages() John Hubbard
2019-12-09 22:53 ` [PATCH v8 16/26] net/xdp: " John Hubbard
2019-12-09 22:53 ` [PATCH v8 17/26] media/v4l2-core: set pages dirty upon releasing DMA buffers John Hubbard
2019-12-10 0:56 ` Andrew Morton
2019-12-10 5:48 ` John Hubbard
2019-12-10 10:17 ` Jan Kara
2019-12-09 22:53 ` [PATCH v8 18/26] media/v4l2-core: pin_user_pages (FOLL_PIN) and put_user_page() conversion John Hubbard
2019-12-09 22:53 ` [PATCH v8 19/26] vfio, mm: " John Hubbard
2019-12-09 22:53 ` [PATCH v8 20/26] powerpc: book3s64: convert to pin_user_pages() and put_user_page() John Hubbard
2019-12-09 23:46 ` John Hubbard
2019-12-10 5:53 ` John Hubbard
2019-12-11 0:49 ` Andrew Morton
2019-12-09 22:53 ` [PATCH v8 21/26] mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding "1" John Hubbard
2019-12-09 22:53 ` [PATCH v8 22/26] mm, tree-wide: rename put_user_page*() to unpin_user_page*() John Hubbard
2019-12-09 22:53 ` [PATCH v8 23/26] mm/gup: pass flags arg to __gup_device_* functions John Hubbard
2019-12-10 12:49 ` Jan Kara
2019-12-11 0:27 ` John Hubbard
2019-12-09 22:53 ` [PATCH v8 24/26] mm/gup: track FOLL_PIN pages John Hubbard
2019-12-10 13:39 ` Jan Kara
2019-12-11 0:27 ` John Hubbard
2019-12-09 22:53 ` [PATCH v8 25/26] mm/gup_benchmark: support pin_user_pages() and related calls John Hubbard
2019-12-09 22:53 ` [PATCH v8 26/26] selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage John Hubbard
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