From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 619B0C41535 for ; Tue, 19 Dec 2023 08:04:07 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=dWpnqajn; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=dWpnqajn; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4SvTjf0MV0z3vwQ for ; Tue, 19 Dec 2023 19:04:06 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=dWpnqajn; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=dWpnqajn; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=redhat.com (client-ip=170.10.129.124; helo=us-smtp-delivery-124.mimecast.com; envelope-from=peterx@redhat.com; receiver=lists.ozlabs.org) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 lists.ozlabs.org (Postfix) with ESMTPS id 4SvTZR3g4tz3cZ5 for ; Tue, 19 Dec 2023 18:57:51 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1702972669; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=7UtlH+qJqHqzo7Y62yc3egVvRJlUYI/8xtDdmttQSUc=; b=dWpnqajnIS6t0poXHub88EEkAVFLtvNfDcZYmNwfq0K9ycxtYfrLE83crz01BlaHJyERD9 8sEyLnTm+7wPv+mfNzYcfdAr/FJorCk1gU7lE2wH0r6n242Jwk4IUA46mn3I4A3bAi0u+3 a00fMFt3IuYrpdQC8reNUl1OS9UOafI= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1702972669; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=7UtlH+qJqHqzo7Y62yc3egVvRJlUYI/8xtDdmttQSUc=; b=dWpnqajnIS6t0poXHub88EEkAVFLtvNfDcZYmNwfq0K9ycxtYfrLE83crz01BlaHJyERD9 8sEyLnTm+7wPv+mfNzYcfdAr/FJorCk1gU7lE2wH0r6n242Jwk4IUA46mn3I4A3bAi0u+3 a00fMFt3IuYrpdQC8reNUl1OS9UOafI= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-197-HHPXr_gTMGKJxc1F8Y3Vvw-1; Tue, 19 Dec 2023 02:57:42 -0500 X-MC-Unique: HHPXr_gTMGKJxc1F8Y3Vvw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (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 13EAF1C0513F; Tue, 19 Dec 2023 07:57:41 +0000 (UTC) Received: from x1n.redhat.com (unknown [10.72.116.117]) by smtp.corp.redhat.com (Postfix) with ESMTP id D699F2026D66; Tue, 19 Dec 2023 07:57:28 +0000 (UTC) From: peterx@redhat.com To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 09/13] mm/gup: Cache *pudp in follow_pud_mask() Date: Tue, 19 Dec 2023 15:55:34 +0800 Message-ID: <20231219075538.414708-10-peterx@redhat.com> In-Reply-To: <20231219075538.414708-1-peterx@redhat.com> References: <20231219075538.414708-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.4 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: James Houghton , David Hildenbrand , Yang Shi , peterx@redhat.com, Andrew Jones , Matthew Wilcox , linux-riscv@lists.infradead.org, Andrea Arcangeli , Christoph Hellwig , "Aneesh Kumar K . V" , Vlastimil Babka , Jason Gunthorpe , Axel Rasmussen , Rik van Riel , John Hubbard , "Kirill A . Shutemov" , linux-arm-kernel@lists.infradead.org, Lorenzo Stoakes , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Mike Rapoport , Mike Kravetz Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Peter Xu Introduce "pud_t pud" in the function, so the code won't dereference *pudp multiple time. Not only because that looks less straightforward, but also because if the dereference really happened, it's not clear whether there can be race to see different *pudp values if it's being modified at the same time. Signed-off-by: Peter Xu --- mm/gup.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 6c0d82fa8cc7..97e87b7a15c3 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -753,26 +753,27 @@ static struct page *follow_pud_mask(struct vm_area_struct *vma, unsigned int flags, struct follow_page_context *ctx) { - pud_t *pud; + pud_t *pudp, pud; spinlock_t *ptl; struct page *page; struct mm_struct *mm = vma->vm_mm; - pud = pud_offset(p4dp, address); - if (pud_none(*pud)) + pudp = pud_offset(p4dp, address); + pud = *pudp; + if (pud_none(pud)) return no_page_table(vma, flags, address); - if (pud_devmap(*pud)) { - ptl = pud_lock(mm, pud); - page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap); + if (pud_devmap(pud)) { + ptl = pud_lock(mm, pudp); + page = follow_devmap_pud(vma, address, pudp, flags, &ctx->pgmap); spin_unlock(ptl); if (page) return page; return no_page_table(vma, flags, address); } - if (unlikely(pud_bad(*pud))) + if (unlikely(pud_bad(pud))) return no_page_table(vma, flags, address); - return follow_pmd_mask(vma, address, pud, flags, ctx); + return follow_pmd_mask(vma, address, pudp, flags, ctx); } static struct page *follow_p4d_mask(struct vm_area_struct *vma, -- 2.41.0