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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55803C3F2D3 for ; Fri, 28 Feb 2020 22:34:51 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 230A124650 for ; Fri, 28 Feb 2020 22:34:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 230A124650 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B62B06B0005; Fri, 28 Feb 2020 17:34:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id AEC896B0006; Fri, 28 Feb 2020 17:34:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9DB416B0007; Fri, 28 Feb 2020 17:34:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 81AB46B0005 for ; Fri, 28 Feb 2020 17:34:50 -0500 (EST) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 438DE180257C0 for ; Fri, 28 Feb 2020 22:34:50 +0000 (UTC) X-FDA: 76540991940.02.party41_2a2824e5ab346 X-HE-Tag: party41_2a2824e5ab346 X-Filterd-Recvd-Size: 6032 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by imf06.hostedemail.com (Postfix) with ESMTP for ; Fri, 28 Feb 2020 22:34:49 +0000 (UTC) X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Feb 2020 14:34:48 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,497,1574150400"; d="scan'208";a="257263297" Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by orsmga002.jf.intel.com with ESMTP; 28 Feb 2020 14:34:47 -0800 Date: Fri, 28 Feb 2020 14:34:47 -0800 From: Ira Weiny To: Pingfan Liu Cc: linux-mm@kvack.org, Andrew Morton , Mike Rapoport , Dan Williams , Matthew Wilcox , John Hubbard , "Aneesh Kumar K.V" , Keith Busch , Christoph Hellwig , Shuah Khan , linux-kernel@vger.kernel.org Subject: Re: [PATCHv5 2/3] mm/gup: fix omission of check on FOLL_LONGTERM in gup fast path Message-ID: <20200228223446.GA4658@iweiny-DESK2.sc.intel.com> References: <1582889550-9101-1-git-send-email-kernelfans@gmail.com> <1582889550-9101-3-git-send-email-kernelfans@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1582889550-9101-3-git-send-email-kernelfans@gmail.com> User-Agent: Mutt/1.11.1 (2018-12-01) 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: On Fri, Feb 28, 2020 at 07:32:29PM +0800, Pingfan Liu wrote: > FOLL_LONGTERM suggests a pin which is going to be given to hardware and > can't move. It would truncate CMA permanently and should be excluded. I don't understand what is 'truncated' here? I generally agree with Jason that this is going to be confusing to the user. Ira > > FOLL_LONGTERM has already been checked in the slow path, but not checked in > the fast path, which means a possible leak of CMA page to longterm pinned > requirement through this crack. > > Place a check in try_get_compound_head() in the fast path. > > Some note about the check: > Huge page's subpages have the same migrate type due to either > allocation from a free_list[] or alloc_contig_range() with param > MIGRATE_MOVABLE. So it is enough to check on a single subpage > by is_migrate_cma_page(subpage) > > Signed-off-by: Pingfan Liu > Cc: Ira Weiny > Cc: Andrew Morton > Cc: Mike Rapoport > Cc: Dan Williams > Cc: Matthew Wilcox > Cc: John Hubbard > Cc: "Aneesh Kumar K.V" > Cc: Keith Busch > Cc: Christoph Hellwig > Cc: Shuah Khan > To: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > --- > mm/gup.c | 26 +++++++++++++++++++------- > 1 file changed, 19 insertions(+), 7 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index cd8075e..f0d6804 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -33,9 +33,21 @@ struct follow_page_context { > * Return the compound head page with ref appropriately incremented, > * or NULL if that failed. > */ > -static inline struct page *try_get_compound_head(struct page *page, int refs) > +static inline struct page *try_get_compound_head(struct page *page, int refs, > + unsigned int flags) > { > - struct page *head = compound_head(page); > + struct page *head; > + > + /* > + * Huge page's subpages have the same migrate type due to either > + * allocation from a free_list[] or alloc_contig_range() with param > + * MIGRATE_MOVABLE. So it is enough to check on a single subpage. > + */ > + if (unlikely(flags & FOLL_LONGTERM) && > + is_migrate_cma_page(page)) > + return NULL; > + > + head = compound_head(page); > > if (WARN_ON_ONCE(page_ref_count(head) < 0)) > return NULL; > @@ -1908,7 +1920,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, > VM_BUG_ON(!pfn_valid(pte_pfn(pte))); > page = pte_page(pte); > > - head = try_get_compound_head(page, 1); > + head = try_get_compound_head(page, 1, flags); > if (!head) > goto pte_unmap; > > @@ -2083,7 +2095,7 @@ static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr, > page = head + ((addr & (sz-1)) >> PAGE_SHIFT); > refs = record_subpages(page, addr, end, pages + *nr); > > - head = try_get_compound_head(head, refs); > + head = try_get_compound_head(head, refs, flags); > if (!head) > return 0; > > @@ -2142,7 +2154,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, > page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); > refs = record_subpages(page, addr, end, pages + *nr); > > - head = try_get_compound_head(pmd_page(orig), refs); > + head = try_get_compound_head(pmd_page(orig), refs, flags); > if (!head) > return 0; > > @@ -2174,7 +2186,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, > page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); > refs = record_subpages(page, addr, end, pages + *nr); > > - head = try_get_compound_head(pud_page(orig), refs); > + head = try_get_compound_head(pud_page(orig), refs, flags); > if (!head) > return 0; > > @@ -2203,7 +2215,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, > page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); > refs = record_subpages(page, addr, end, pages + *nr); > > - head = try_get_compound_head(pgd_page(orig), refs); > + head = try_get_compound_head(pgd_page(orig), refs, flags); > if (!head) > return 0; > > -- > 2.7.5 > >