From patchwork Fri Dec 20 15:38:26 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Steven Price X-Patchwork-Id: 11305799 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2A786109A for ; Fri, 20 Dec 2019 15:38:38 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F1B9421655 for ; Fri, 20 Dec 2019 15:38:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F1B9421655 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 359828E019F; Fri, 20 Dec 2019 10:38:37 -0500 (EST) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 309D58E019D; Fri, 20 Dec 2019 10:38:37 -0500 (EST) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 220058E019F; Fri, 20 Dec 2019 10:38:37 -0500 (EST) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0019.hostedemail.com [216.40.44.19]) by kanga.kvack.org (Postfix) with ESMTP id 0C3FA8E019D for ; Fri, 20 Dec 2019 10:38:37 -0500 (EST) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id 7FE2A181AEF09 for ; Fri, 20 Dec 2019 15:38:36 +0000 (UTC) X-FDA: 76285927032.09.hand22_2dfac9ad68404 X-Spam-Summary: 2,0,0,44e445f0f3dbac83,d41d8cd98f00b204,steven.price@arm.com,:jglisse@redhat.com:akpm@linux-foundation.org:linux-kernel@vger.kernel.org::steven.price@arm.com:thomas_os@shipmail.org,RULES_HIT:41:69:152:355:379:541:800:960:973:988:989:1260:1261:1277:1311:1313:1314:1345:1437:1515:1516:1518:1534:1542:1593:1594:1711:1730:1747:1777:1792:1981:2194:2199:2393:2559:2562:2730:3138:3139:3140:3141:3142:3354:3865:3866:3867:3868:3870:3871:3872:4250:4321:4605:5007:6117:6119:6261:7875:7903:8634:8660:9036:9592:10004:10400:11026:11232:11658:11914:12114:12297:12517:12519:12555:12895:12986:13148:13161:13229:13230:13894:14093:14097:14181:14394:14659:14721:21080:21450:21451:21627:21990:30012:30034:30054:30070,0,RBL:217.140.110.172:@arm.com:.lbl8.mailshell.net-62.2.0.100 64.100.201.201,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:36,LUA_SUMMARY:none X-HE-Tag: hand22_2dfac9ad68404 X-Filterd-Recvd-Size: 3504 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf11.hostedemail.com (Postfix) with ESMTP for ; Fri, 20 Dec 2019 15:38:35 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E063D30E; Fri, 20 Dec 2019 07:38:34 -0800 (PST) Received: from e112269-lin.cambridge.arm.com (e112269-lin.cambridge.arm.com [10.1.194.52]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 069513F6CF; Fri, 20 Dec 2019 07:38:33 -0800 (PST) From: Steven Price To: =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Steven Price , =?utf-8?q?Thomas_Hellstr=C3=B6m?= Subject: [PATCH] mm/hmm: Cleanup hmm_vma_walk_pud()/walk_pud_range() Date: Fri, 20 Dec 2019 15:38:26 +0000 Message-Id: <20191220153826.24229-1-steven.price@arm.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: There are a number of minor misuses of the page table APIs in hmm_vma_walk_pud(): If the pud_trans_huge_lock() hasn't been obtained it might be because the PUD is unstable, so we should retry. If it has been obtained then there's no need for a READ_ONCE, and the PUD cannot be pud_none() or !pud_present() so these paths are dead code. Finally in walk_pud_range(), after a call to split_huge_pud() the code should check pud_trans_unstable() rather than pud_none() to decide whether the PUD should be retried. Suggested-by: Thomas Hellström (VMware) Signed-off-by: Steven Price Reviewed-by: Thomas Hellstrom --- This is based on top of my "Generic page walk and ptdump" series and fixes some pre-existing bugs spotted by Thomas. mm/hmm.c | 16 +++++----------- mm/pagewalk.c | 2 +- 2 files changed, 6 insertions(+), 12 deletions(-) diff --git a/mm/hmm.c b/mm/hmm.c index a71295e99968..d4aae4dcc6e8 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -480,28 +480,22 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end, int ret = 0; spinlock_t *ptl = pud_trans_huge_lock(pudp, walk->vma); - if (!ptl) + if (!ptl) { + if (pud_trans_unstable(pudp)) + walk->action = ACTION_AGAIN; return 0; + } /* Normally we don't want to split the huge page */ walk->action = ACTION_CONTINUE; - pud = READ_ONCE(*pudp); - if (pud_none(pud)) { - ret = hmm_vma_walk_hole(start, end, -1, walk); - goto out_unlock; - } + pud = *pudp; if (pud_huge(pud) && pud_devmap(pud)) { unsigned long i, npages, pfn; uint64_t *pfns, cpu_flags; bool fault, write_fault; - if (!pud_present(pud)) { - ret = hmm_vma_walk_hole(start, end, -1, walk); - goto out_unlock; - } - i = (addr - range->start) >> PAGE_SHIFT; npages = (end - addr) >> PAGE_SHIFT; pfns = &range->pfns[i]; diff --git a/mm/pagewalk.c b/mm/pagewalk.c index 5895ce4f1a85..4598f545b869 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -154,7 +154,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, if (walk->vma) split_huge_pud(walk->vma, pud, addr); - if (pud_none(*pud)) + if (pud_trans_unstable(pud)) goto again; err = walk_pmd_range(pud, addr, next, walk);