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Tue, 07 Jan 2020 14:46:00 -0800 From: John Hubbard To: Andrew Morton Subject: [PATCH v12 08/22] mm/gup: allow FOLL_FORCE for get_user_pages_fast() Date: Tue, 7 Jan 2020 14:45:44 -0800 Message-ID: <20200107224558.2362728-9-jhubbard@nvidia.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200107224558.2362728-1-jhubbard@nvidia.com> References: <20200107224558.2362728-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public Content-Transfer-Encoding: quoted-printable Content-Type: text/plain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1578437148; bh=TKqZFchMOwUlq4p7fLQxPoHAtQiavcs6JsnhT764GJ8=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Transfer-Encoding:Content-Type; b=mG+9fbuPmRlJzn1vkUiL8z+GBw7cTMpiOq//DKxiIsJyjBuW9nskzY9Db1uGxi6bP 3ZIAqNsLjmLRXPSbZYVOBFeMoUwUnDTSa2wxsZxFLuqr5GC9/g9zXt/3Cl7pp+uB71 +IADVEr0VJBH1KiohQW5IgXZN2GTRvi5Xhu9ckuMd8e+2RukQAYcLu5Bad1ZsQoRx5 Z3jS4qtWjHSMNbGSC8r3PEh6d5BoRfQGRPbEhr7FdaPV1nqridJwm1WzOvlvps8ckB t1Bggqn6B8DKgBmn4XZpBuPSSSwSbgVZdTWliRoZQ/RSe00MsS0frDzgg6WKn0Gpod Ob3FCZwyu+hXw== X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michal Hocko , Jan Kara , kvm@vger.kernel.org, linux-doc@vger.kernel.org, David Airlie , Dave Chinner , dri-devel@lists.freedesktop.org, LKML , linux-mm@kvack.org, Paul Mackerras , linux-kselftest@vger.kernel.org, Ira Weiny , Christoph Hellwig , Jonathan Corbet , linux-rdma@vger.kernel.org, Christoph Hellwig , Jason Gunthorpe , Vlastimil Babka , =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= , linux-media@vger.kernel.org, Shuah Khan , John Hubbard , linux-block@vger.kernel.org, Leon Romanovsky , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , Al Viro , "Kirill A . Shutemov" , Dan Williams , Mauro Carvalho Chehab , Magnus Karlsson , Jens Axboe , netdev@vger.kernel.org, Alex Williamson , Daniel Vetter , linux-fsdevel@vger.kernel.org, bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, "David S . Miller" , Mike Kravetz Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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 Reviewed-by: Leon Romanovsky Reviewed-by: Jan Kara Signed-off-by: John Hubbard --- mm/gup.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/gup.c b/mm/gup.c index b61bd5c469ae..a594bc708367 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2411,7 +2411,8 @@ int get_user_pages_fast(unsigned long start, int nr_p= ages, unsigned long addr, len, end; int nr =3D 0, ret =3D 0; =20 - if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM))) + if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | + FOLL_FORCE))) return -EINVAL; =20 start =3D untagged_addr(start) & PAGE_MASK; --=20 2.24.1