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Tue, 20 Apr 2021 13:28:03 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EA5B34C044; Tue, 20 Apr 2021 13:27:58 +0000 (GMT) Received: from linux.ibm.com (unknown [9.145.82.136]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Tue, 20 Apr 2021 13:27:58 +0000 (GMT) Date: Tue, 20 Apr 2021 16:27:56 +0300 From: Mike Rapoport To: David Hildenbrand Cc: Mike Rapoport , Andrew Morton , Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , Elena Reshetova , "H. Peter Anvin" , Ingo Molnar , James Bottomley , "Kirill A. Shutemov" , Matthew Wilcox , Matthew Garrett , Mark Rutland , Michal Hocko , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , "Rafael J. Wysocki" , Rick Edgecombe , Roman Gushchin , Shakeel Butt , Shuah Khan , Thomas Gleixner , Tycho Andersen , Will Deacon , Yury Norov , linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org, x86@kernel.org Subject: Re: [PATCH v2 1/2] secretmem/gup: don't check if page is secretmem without reference Message-ID: References: <20210420131611.8259-1-rppt@kernel.org> <20210420131611.8259-2-rppt@kernel.org> <95b7fa81-f72e-c63f-0456-4c25dee8a5eb@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <95b7fa81-f72e-c63f-0456-4c25dee8a5eb@redhat.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: umV0ysjUL103wxbfICo-4xhYTSyDzIUb X-Proofpoint-ORIG-GUID: dTV5P955knNPQLGIoMCHqafXwNzdKxMI X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.761 definitions=2021-04-20_06:2021-04-20, 2021-04-20 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 phishscore=0 impostorscore=0 priorityscore=1501 lowpriorityscore=0 spamscore=0 mlxscore=0 mlxlogscore=682 bulkscore=0 suspectscore=0 adultscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104200098 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210420_062849_083552_5084CD08 X-CRM114-Status: GOOD ( 30.62 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Apr 20, 2021 at 03:19:56PM +0200, David Hildenbrand wrote: > On 20.04.21 15:16, Mike Rapoport wrote: > > From: Mike Rapoport > > > > The check in gup_pte_range() whether a page belongs to a secretmem mapping > > is performed before grabbing the page reference. > > > > To avoid potential race move the check after try_grab_compound_head(). > > > > Signed-off-by: Mike Rapoport > > --- > > mm/gup.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/mm/gup.c b/mm/gup.c > > index c3a17b189064..4b58c016e949 100644 > > --- a/mm/gup.c > > +++ b/mm/gup.c > > @@ -2080,13 +2080,13 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, > > VM_BUG_ON(!pfn_valid(pte_pfn(pte))); > > page = pte_page(pte); > > - if (page_is_secretmem(page)) > > - goto pte_unmap; > > - > > head = try_grab_compound_head(page, 1, flags); > > if (!head) > > goto pte_unmap; > > + if (page_is_secretmem(page)) > > + goto pte_unmap; > > + > > Looking at the hunk below, I wonder if you're missing a put_compound_head(). Hmm, yes. > (also, I'd do if unlikely(page_is_secretmem()) but that's a different > discussion) I don't mind, actually. I don't think there would be massive secretmem usage soon. > > if (unlikely(pte_val(pte) != pte_val(*ptep))) { > > put_compound_head(head, 1, flags); > > goto pte_unmap; > > > > > -- > Thanks, > > David / dhildenb > -- Sincerely yours, Mike. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel