From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:38130 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726764AbgB2Kvc (ORCPT ); Sat, 29 Feb 2020 05:51:32 -0500 Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 01TAnLs3009853 for ; Sat, 29 Feb 2020 05:51:31 -0500 Received: from e06smtp01.uk.ibm.com (e06smtp01.uk.ibm.com [195.75.94.97]) by mx0a-001b2d01.pphosted.com with ESMTP id 2yfmwt9sms-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Sat, 29 Feb 2020 05:51:31 -0500 Received: from localhost by e06smtp01.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sat, 29 Feb 2020 10:51:28 -0000 Date: Sat, 29 Feb 2020 11:51:19 +0100 From: Claudio Imbrenda Subject: Re: [RFC v1 1/2] mm/gup: fixup for 9947ea2c1e608e32 "mm/gup: track FOLL_PIN pages" In-Reply-To: References: <20200228154322.329228-1-imbrenda@linux.ibm.com> <20200228154322.329228-3-imbrenda@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-Id: <20200229115119.3562c73e@p-imbrenda> Sender: linux-s390-owner@vger.kernel.org List-ID: To: John Hubbard Cc: linux-next@vger.kernel.org, akpm@linux-foundation.org, borntraeger@de.ibm.com, david@redhat.com, aarcange@redhat.com, linux-mm@kvack.org, frankja@linux.ibm.com, sfr@canb.auug.org.au, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Jan Kara , "Kirill A. Shutemov" On Fri, 28 Feb 2020 15:08:35 -0800 John Hubbard wrote: > On 2/28/20 7:43 AM, Claudio Imbrenda wrote: > > In case pin fails, we need to unpin, a simple put_page will not be > > enough > > > > Signed-off-by: Claudio Imbrenda > > --- > > mm/gup.c | 5 ++++- > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > diff --git a/mm/gup.c b/mm/gup.c > > index f589299b0d4a..0b9a806898f3 100644 > > --- a/mm/gup.c > > +++ b/mm/gup.c > > @@ -2134,7 +2134,10 @@ static int gup_pte_range(pmd_t pmd, unsigned > > long addr, unsigned long end, goto pte_unmap; > > > > if (unlikely(pte_val(pte) != pte_val(*ptep))) { > > - put_page(head); > > + if (flags & FOLL_GET) > > + put_page(head); > > + else if (flags & FOLL_PIN) > > + unpin_user_page(head); > > Hi Claudio, > > Instead, I think that should actually be: > > put_compound_head(page, 1, flags); that makes sense, yes :) I'll fix it in the next iteration > > which does a bit more (bug checks and /proc/vmstat instrumentation) > than your diff, but has the same basic idea: call the right "put" > function. > > ...oh, actually, I see you have the commit hash in the subject line. > Instead, it should be in the commit description. Let's maybe change > the subject line to approx: > > mm/gup: Fix a missing put_compound_head() call in gup_pte_range() > > And the write up...how about something like this, if you like it: > > > try_grab_compound_head() must be undone via put_compound_head(), not > put_page(). This was missed in the original implementation of the > gup/dma tracking patch, so fix it now. > > Fixes: 0ea2781c3de4 ("mm/gup: track FOLL_PIN pages") > > > > (Aside: I'm using the linux-next commit hash. How does one get the > correct hash before it goes to mainline? I guess maintainer scripts > fix all those up?) my idea was that my patch should be used as fix-up, so the actual content of the commit message is not relevant > It's also good to Cc some reviewers in case I'm overlooking > something, so I'm adding Jan and Kirill. > > thanks,