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Wed, 06 Mar 2024 05:42:18 -0500 X-MC-Unique: w92BStQdNuqU_EljwB5_jw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6AC0E800267; Wed, 6 Mar 2024 10:42:17 +0000 (UTC) Received: from x1n.redhat.com (unknown [10.72.116.8]) by smtp.corp.redhat.com (Postfix) with ESMTP id A7360111E3F3; Wed, 6 Mar 2024 10:42:11 +0000 (UTC) From: peterx@redhat.com To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH RFC 03/13] mm/gup: Check p4d presence before going on Date: Wed, 6 Mar 2024 18:41:37 +0800 Message-ID: <20240306104147.193052-4-peterx@redhat.com> In-Reply-To: <20240306104147.193052-1-peterx@redhat.com> References: <20240306104147.193052-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.3 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: linux-arm-kernel@lists.infradead.org, x86@kernel.org, Muchun Song , peterx@redhat.com, Matthew Wilcox , Jason Gunthorpe , sparclinux@vger.kernel.org, Andrew Morton , linuxppc-dev@lists.ozlabs.org, Mike Rapoport Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Peter Xu Currently there should have no p4d swap entries so it may not matter much, however this may help us to rule out swap entries in pXd_huge() API, which will include p4d_huge(). The p4d_present() checks make it 100% clear that we won't rely on p4d_huge() for swap entries. Signed-off-by: Peter Xu --- mm/gup.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 69a777f4fc5c..f87a7d90f2ae 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -776,7 +776,7 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma, p4dp = p4d_offset(pgdp, address); p4d = READ_ONCE(*p4dp); - if (p4d_none(p4d)) + if (p4d_none(p4d) || !p4d_present(p4d)) return no_page_table(vma, flags); BUILD_BUG_ON(p4d_huge(p4d)); if (unlikely(p4d_bad(p4d))) @@ -3069,7 +3069,7 @@ static int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, unsigned lo p4d_t p4d = READ_ONCE(*p4dp); next = p4d_addr_end(addr, end); - if (p4d_none(p4d)) + if (p4d_none(p4d) || !p4d_present(p4d)) return 0; BUILD_BUG_ON(p4d_huge(p4d)); if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) { -- 2.44.0