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[193.116.93.94]) by smtp.gmail.com with ESMTPSA id p63sm611660pfb.70.2019.06.06.20.58.06 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Thu, 06 Jun 2019 20:58:08 -0700 (PDT) From: Nicholas Piggin To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH 2/2] powerpc/64s: __find_linux_pte synchronization vs pmdp_invalidate Date: Fri, 7 Jun 2019 13:56:36 +1000 Message-Id: <20190607035636.5446-2-npiggin@gmail.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190607035636.5446-1-npiggin@gmail.com> References: <20190607035636.5446-1-npiggin@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: "Aneesh Kumar K . V" , Nicholas Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" The change to pmdp_invalidate to mark the pmd with _PAGE_INVALID broke the synchronisation against lock free lookups, __find_linux_pte's pmd_none check no longer returns true for such cases. Fix this by adding a check for this condition as well. Fixes: da7ad366b497 ("powerpc/mm/book3s: Update pmd_present to look at _PAGE_PRESENT bit") Cc: Christophe Leroy Suggested-by: Aneesh Kumar K.V Signed-off-by: Nicholas Piggin --- arch/powerpc/mm/pgtable.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c index db4a6253df92..533fc6fa6726 100644 --- a/arch/powerpc/mm/pgtable.c +++ b/arch/powerpc/mm/pgtable.c @@ -372,13 +372,25 @@ pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea, pdshift = PMD_SHIFT; pmdp = pmd_offset(&pud, ea); pmd = READ_ONCE(*pmdp); + /* - * A hugepage collapse is captured by pmd_none, because - * it mark the pmd none and do a hpte invalidate. + * A hugepage collapse is captured by this condition, see + * pmdp_collapse_flush. */ if (pmd_none(pmd)) return NULL; +#ifdef CONFIG_PPC_BOOK3S_64 + /* + * A hugepage split is captured by this condition, see + * pmdp_invalidate. + * + * Huge page modification can be caught here too. + */ + if (pmd_is_serializing(pmd)) + return NULL; +#endif + if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) { if (is_thp) *is_thp = true; -- 2.20.1