From patchwork Tue Dec 19 07:55:34 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Xu X-Patchwork-Id: 13497974 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 DA2B6C46CA2 for ; Tue, 19 Dec 2023 07:57:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=rUEJVz8fL/+JtAOkxuzmsa9GEm/Az5tjRIm3Vf7VwEQ=; b=EWUT66nxaW42OX FE5k19G2yqs7CuYhhG9mX7yWdQR9rgbQyDN0UK1XG4G4GCPem12JhJoq+Q5pJDgyg0xlnnESSR20i SX0DHgcgKk5/3hSi0QkKm/LJF9u90f0yGtt2+aJfka+rDPJbnuP6SZRC/qymTkqWjfQmp/7OcZNzK 0Z93Yd7RzB4u318Qj/psakxswduVsy/yPGWHiKLzPN9BW0a5Whs/lEj3g6kKFCqMbV7nxiBIoyhTJ upyFP+T2ZtQ90T2faONN0jQuxktwSvQr8njDEoFXvbR4FVHp9ZqVm5U3QgLryAqn/2p4mk/eDO3kG HipRnV4C41hq3MfJpC6g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1rFUzC-00DC9A-1n; Tue, 19 Dec 2023 07:57:54 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1rFUz8-00DC4m-0t for linux-riscv@lists.infradead.org; Tue, 19 Dec 2023 07:57:52 +0000 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 Cc: Matthew Wilcox , Christophe Leroy , Lorenzo Stoakes , David Hildenbrand , Vlastimil Babka , Mike Kravetz , Mike Rapoport , Christoph Hellwig , John Hubbard , Andrew Jones , linux-arm-kernel@lists.infradead.org, Michael Ellerman , "Kirill A . Shutemov" , linuxppc-dev@lists.ozlabs.org, Rik van Riel , linux-riscv@lists.infradead.org, Yang Shi , James Houghton , "Aneesh Kumar K . V" , Andrew Morton , Jason Gunthorpe , Andrea Arcangeli , peterx@redhat.com, Axel Rasmussen 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 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.4 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231218_235750_390721_4C3ADC07 X-CRM114-Status: GOOD ( 12.95 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org 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 Acked-by: James Houghton --- 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,