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Shutemov" , Michal Hocko , Mike Kravetz , Shuah Khan , Vlastimil Babka , Matthew Wilcox , , , , , , LKML , John Hubbard , "Kirill A . Shutemov" Subject: [PATCH v4 06/12] mm/gup: require FOLL_GET for get_user_pages_fast() Date: Tue, 4 Feb 2020 15:41:11 -0800 Message-ID: <20200204234117.2974687-7-jhubbard@nvidia.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200204234117.2974687-1-jhubbard@nvidia.com> References: <20200204234117.2974687-1-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=1580859624; bh=zdKJN+80LnhrM42H0YcEzysuucpfBmwOwmXaeST0eWY=; 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=Hb/gerXT22GLw8iVFdPyAv3XiaXjEYBvlRWtPvGdEtt2raRBr3YXTXHDZWDLJKqvr QQhv24bxvrZjAzedXXOmacEKcn2KHtiQXq/gabkWLEeq1wNRDWtMOqXDZIetzCJ6dr jRYALutzOa79coLTnY9tbgzoQNtppuhKtLsvVRZraWmQf9yl7VlH3J3pmNUO3sspTL oB8sCEG8Y2KUZ1VDXEuoAbOyyAfSu7xlQ+QmIKzlWQRHAtxFL9Ti9c5EUqjkEdSyJ9 qsusZbaG5CbklkB1oj3dzPnZOR1IOlT8gy343wZQGLPSHzXcDr/SAdX71eGx+9JyIZ NtX2KhzHU1kjw== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Internal to mm/gup.c, require that get_user_pages_fast() and __get_user_pages_fast() identify themselves, by setting FOLL_GET. This is required in order to be able to make decisions based on "FOLL_PIN, or FOLL_GET, or both or neither are set", in upcoming patches. Acked-by: Kirill A. Shutemov Reviewed-by: Jan Kara Signed-off-by: John Hubbard --- mm/gup.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index e5f75e886663..c8affbea2019 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2390,6 +2390,14 @@ int __get_user_pages_fast(unsigned long start, int n= r_pages, int write, unsigned long len, end; unsigned long flags; int nr =3D 0; + /* + * Internally (within mm/gup.c), gup fast variants must set FOLL_GET, + * because gup fast is always a "pin with a +1 page refcount" request. + */ + unsigned int gup_flags =3D FOLL_GET; + + if (write) + gup_flags |=3D FOLL_WRITE; =20 start =3D untagged_addr(start) & PAGE_MASK; len =3D (unsigned long) nr_pages << PAGE_SHIFT; @@ -2415,7 +2423,7 @@ int __get_user_pages_fast(unsigned long start, int nr= _pages, int write, if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) && gup_fast_permitted(start, end)) { local_irq_save(flags); - gup_pgd_range(start, end, write ? FOLL_WRITE : 0, pages, &nr); + gup_pgd_range(start, end, gup_flags, pages, &nr); local_irq_restore(flags); } =20 @@ -2454,7 +2462,7 @@ static int internal_get_user_pages_fast(unsigned long= start, int nr_pages, int nr =3D 0, ret =3D 0; =20 if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | - FOLL_FORCE | FOLL_PIN))) + FOLL_FORCE | FOLL_PIN | FOLL_GET))) return -EINVAL; =20 start =3D untagged_addr(start) & PAGE_MASK; @@ -2521,6 +2529,13 @@ int get_user_pages_fast(unsigned long start, int nr_= pages, if (WARN_ON_ONCE(gup_flags & FOLL_PIN)) return -EINVAL; =20 + /* + * The caller may or may not have explicitly set FOLL_GET; either way is + * OK. However, internally (within mm/gup.c), gup fast variants must set + * FOLL_GET, because gup fast is always a "pin with a +1 page refcount" + * request. + */ + gup_flags |=3D FOLL_GET; return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages); } EXPORT_SYMBOL_GPL(get_user_pages_fast); --=20 2.25.0