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[73.69.118.222]) by smtp.gmail.com with ESMTPSA id z20sm11934536qkz.37.2021.01.18.20.39.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Jan 2021 20:39:34 -0800 (PST) From: Pavel Tatashin To: pasha.tatashin@soleen.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, vbabka@suse.cz, mhocko@suse.com, david@redhat.com, osalvador@suse.de, dan.j.williams@intel.com, sashal@kernel.org, tyhicks@linux.microsoft.com, iamjoonsoo.kim@lge.com, mike.kravetz@oracle.com, rostedt@goodmis.org, mingo@redhat.com, jgg@ziepe.ca, peterz@infradead.org, mgorman@suse.de, willy@infradead.org, rientjes@google.com, jhubbard@nvidia.com, linux-doc@vger.kernel.org, ira.weiny@intel.com, linux-kselftest@vger.kernel.org Subject: [PATCH v5 08/14] mm/gup: do not allow zero page for pinned pages Date: Mon, 18 Jan 2021 23:39:14 -0500 Message-Id: <20210119043920.155044-9-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210119043920.155044-1-pasha.tatashin@soleen.com> References: <20210119043920.155044-1-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Zero page should not be used for long term pinned pages. Once pages are pinned their physical addresses cannot changed until they are unpinne= d. Guarantee to always return real pages when they are pinned by adding FOLL_WRITE. Signed-off-by: Pavel Tatashin --- mm/gup.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/mm/gup.c b/mm/gup.c index 857b273e32ac..9a817652f501 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1668,8 +1668,16 @@ static long __gup_longterm_locked(struct mm_struct= *mm, unsigned long flags =3D 0; long rc; =20 - if (gup_flags & FOLL_LONGTERM) + if (gup_flags & FOLL_LONGTERM) { + /* + * We are long term pinning pages and their PA's should not + * change until unpinned. Without FOLL_WRITE we might get zero + * page which we do not want. Force creating normal + * pages by adding FOLL_WRITE. + */ + gup_flags |=3D FOLL_WRITE; flags =3D memalloc_pin_save(); + } =20 rc =3D __get_user_pages_locked(mm, start, nr_pages, pages, vmas, NULL, gup_flags); --=20 2.25.1