From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=4Ufl=ZR=kvack.org=owner-linux-mm@kernel.org>
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=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,
	MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT
	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 5179EC432C0
	for <linux-mm@archiver.kernel.org>; Mon, 25 Nov 2019 23:10:51 +0000 (UTC)
Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17])
	by mail.kernel.org (Postfix) with ESMTP id 098502075C
	for <linux-mm@archiver.kernel.org>; Mon, 25 Nov 2019 23:10:51 +0000 (UTC)
Authentication-Results: mail.kernel.org;
	dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="AUXeRtgX"
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 098502075C
Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com
Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org
Received: by kanga.kvack.org (Postfix)
	id 40D576B028C; Mon, 25 Nov 2019 18:10:47 -0500 (EST)
Received: by kanga.kvack.org (Postfix, from userid 40)
	id 3C4FF6B028E; Mon, 25 Nov 2019 18:10:47 -0500 (EST)
X-Delivered-To: int-list-linux-mm@kvack.org
Received: by kanga.kvack.org (Postfix, from userid 63042)
	id 175BA6B028D; Mon, 25 Nov 2019 18:10:47 -0500 (EST)
X-Delivered-To: linux-mm@kvack.org
Received: from forelay.hostedemail.com (smtprelay0173.hostedemail.com [216.40.44.173])
	by kanga.kvack.org (Postfix) with ESMTP id C1FBF6B028E
	for <linux-mm@kvack.org>; Mon, 25 Nov 2019 18:10:46 -0500 (EST)
Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251])
	by forelay02.hostedemail.com (Postfix) with SMTP id 7460137E7
	for <linux-mm@kvack.org>; Mon, 25 Nov 2019 23:10:46 +0000 (UTC)
X-FDA: 76196346492.04.burn20_40e35588fda08
X-HE-Tag: burn20_40e35588fda08
X-Filterd-Recvd-Size: 9349
Received: from hqemgate15.nvidia.com (hqemgate15.nvidia.com [216.228.121.64])
	by imf19.hostedemail.com (Postfix) with ESMTP
	for <linux-mm@kvack.org>; Mon, 25 Nov 2019 23:10:45 +0000 (UTC)
Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate15.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA)
	id <B5ddc5f6b0000>; Mon, 25 Nov 2019 15:10:35 -0800
Received: from hqmail.nvidia.com ([172.20.161.6])
  by hqpgpgate101.nvidia.com (PGP Universal service);
  Mon, 25 Nov 2019 15:10:41 -0800
X-PGP-Universal: processed;
	by hqpgpgate101.nvidia.com on Mon, 25 Nov 2019 15:10:41 -0800
Received: from HQMAIL109.nvidia.com (172.20.187.15) by HQMAIL101.nvidia.com
 (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Mon, 25 Nov
 2019 23:10:41 +0000
Received: from HQMAIL111.nvidia.com (172.20.187.18) by HQMAIL109.nvidia.com
 (172.20.187.15) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Mon, 25 Nov
 2019 23:10:40 +0000
Received: from rnnvemgw01.nvidia.com (10.128.109.123) by HQMAIL111.nvidia.com
 (172.20.187.18) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend
 Transport; Mon, 25 Nov 2019 23:10:39 +0000
Received: from blueforge.nvidia.com (Not Verified[10.110.48.28]) by rnnvemgw01.nvidia.com with Trustwave SEG (v7,5,8,10121)
	id <B5ddc5f6e0000>; Mon, 25 Nov 2019 15:10:39 -0800
From: John Hubbard <jhubbard@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>
CC: Al Viro <viro@zeniv.linux.org.uk>, Alex Williamson
	<alex.williamson@redhat.com>, Benjamin Herrenschmidt
	<benh@kernel.crashing.org>, =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?=
	<bjorn.topel@intel.com>, Christoph Hellwig <hch@infradead.org>, Dan Williams
	<dan.j.williams@intel.com>, Daniel Vetter <daniel@ffwll.ch>, Dave Chinner
	<david@fromorbit.com>, David Airlie <airlied@linux.ie>, "David S . Miller"
	<davem@davemloft.net>, Ira Weiny <ira.weiny@intel.com>, Jan Kara
	<jack@suse.cz>, Jason Gunthorpe <jgg@ziepe.ca>, Jens Axboe <axboe@kernel.dk>,
	Jonathan Corbet <corbet@lwn.net>, =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?=
	<jglisse@redhat.com>, Magnus Karlsson <magnus.karlsson@intel.com>, "Mauro
 Carvalho Chehab" <mchehab@kernel.org>, Michael Ellerman <mpe@ellerman.id.au>,
	Michal Hocko <mhocko@suse.com>, Mike Kravetz <mike.kravetz@oracle.com>, "Paul
 Mackerras" <paulus@samba.org>, Shuah Khan <shuah@kernel.org>, Vlastimil Babka
	<vbabka@suse.cz>, <bpf@vger.kernel.org>, <dri-devel@lists.freedesktop.org>,
	<kvm@vger.kernel.org>, <linux-block@vger.kernel.org>,
	<linux-doc@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>,
	<linux-kselftest@vger.kernel.org>, <linux-media@vger.kernel.org>,
	<linux-rdma@vger.kernel.org>, <linuxppc-dev@lists.ozlabs.org>,
	<netdev@vger.kernel.org>, <linux-mm@kvack.org>, LKML
	<linux-kernel@vger.kernel.org>, John Hubbard <jhubbard@nvidia.com>,
	"Christoph Hellwig" <hch@lst.de>, "Aneesh Kumar K . V"
	<aneesh.kumar@linux.ibm.com>
Subject: [PATCH v2 01/19] mm/gup: factor out duplicate code from four routines
Date: Mon, 25 Nov 2019 15:10:17 -0800
Message-ID: <20191125231035.1539120-2-jhubbard@nvidia.com>
X-Mailer: git-send-email 2.24.0
In-Reply-To: <20191125231035.1539120-1-jhubbard@nvidia.com>
References: <20191125231035.1539120-1-jhubbard@nvidia.com>
MIME-Version: 1.0
X-NVConfidentiality: public
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1;
	t=1574723435; bh=NjEUDVUY50BsRhke7z2S9TxhDwSe8KFPL35zO7aJjtI=;
	h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer:
	 In-Reply-To:References:MIME-Version:X-NVConfidentiality:
	 Content-Type:Content-Transfer-Encoding;
	b=AUXeRtgX8uwRAN8QQIpBLTFu2Igu3gY6iu0Hlx88BQB7lRXY/SqqRQ8j4e9qcHuvu
	 8ud0fzDtYb7HpYVsQbFF0DMrLY/yh/0ABPdjgosaeLXJYJI+NUQLwFuoaQkhFI3jCZ
	 zbwXJWVN3RZSk/oRUDlsXyigEypZrXCI6Ws6sq4dbhRPfHTPbc1ZHXql8om55mOQof
	 4d8V5UMpqSpP0YKSoV8UYFeDMTXGzt6Iy386zmq6Ii56RT3IOxIe4jWPtu6JQrfCXL
	 7raAc1f0Nwt3ij+KHnYiU86hF9jF05mgsLywy0Mgbyn+olUBs5eef+xe6U2jH+724x
	 drRVMfvI1tV6w==
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: <linux-mm.kvack.org>

There are four locations in gup.c that have a fair amount of code
duplication. This means that changing one requires making the same
changes in four places, not to mention reading the same code four
times, and wondering if there are subtle differences.

Factor out the common code into static functions, thus reducing the
overall line count and the code's complexity.

Also, take the opportunity to slightly improve the efficiency of the
error cases, by doing a mass subtraction of the refcount, surrounded
by get_page()/put_page().

Also, further simplify (slightly), by waiting until the the successful
end of each routine, to increment *nr.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: J=C3=A9r=C3=B4me Glisse <jglisse@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 mm/gup.c | 91 ++++++++++++++++++++++----------------------------------
 1 file changed, 36 insertions(+), 55 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 7646bf993b25..f764432914c4 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1978,6 +1978,25 @@ static int __gup_device_huge_pud(pud_t pud, pud_t *p=
udp, unsigned long addr,
 }
 #endif
=20
+static int record_subpages(struct page *page, unsigned long addr,
+			   unsigned long end, struct page **pages)
+{
+	int nr;
+
+	for (nr =3D 0; addr !=3D end; addr +=3D PAGE_SIZE)
+		pages[nr++] =3D page++;
+
+	return nr;
+}
+
+static void put_compound_head(struct page *page, int refs)
+{
+	/* Do a get_page() first, in case refs =3D=3D page->_refcount */
+	get_page(page);
+	page_ref_sub(page, refs);
+	put_page(page);
+}
+
 #ifdef CONFIG_ARCH_HAS_HUGEPD
 static unsigned long hugepte_addr_end(unsigned long addr, unsigned long en=
d,
 				      unsigned long sz)
@@ -2007,32 +2026,20 @@ static int gup_hugepte(pte_t *ptep, unsigned long s=
z, unsigned long addr,
 	/* hugepages are never "special" */
 	VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
=20
-	refs =3D 0;
 	head =3D pte_page(pte);
-
 	page =3D head + ((addr & (sz-1)) >> PAGE_SHIFT);
-	do {
-		VM_BUG_ON(compound_head(page) !=3D head);
-		pages[*nr] =3D page;
-		(*nr)++;
-		page++;
-		refs++;
-	} while (addr +=3D PAGE_SIZE, addr !=3D end);
+	refs =3D record_subpages(page, addr, end, pages + *nr);
=20
 	head =3D try_get_compound_head(head, refs);
-	if (!head) {
-		*nr -=3D refs;
+	if (!head)
 		return 0;
-	}
=20
 	if (unlikely(pte_val(pte) !=3D pte_val(*ptep))) {
-		/* Could be optimized better */
-		*nr -=3D refs;
-		while (refs--)
-			put_page(head);
+		put_compound_head(head, refs);
 		return 0;
 	}
=20
+	*nr +=3D refs;
 	SetPageReferenced(head);
 	return 1;
 }
@@ -2079,28 +2086,19 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, un=
signed long addr,
 		return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr);
 	}
=20
-	refs =3D 0;
 	page =3D pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
-	do {
-		pages[*nr] =3D page;
-		(*nr)++;
-		page++;
-		refs++;
-	} while (addr +=3D PAGE_SIZE, addr !=3D end);
+	refs =3D record_subpages(page, addr, end, pages + *nr);
=20
 	head =3D try_get_compound_head(pmd_page(orig), refs);
-	if (!head) {
-		*nr -=3D refs;
+	if (!head)
 		return 0;
-	}
=20
 	if (unlikely(pmd_val(orig) !=3D pmd_val(*pmdp))) {
-		*nr -=3D refs;
-		while (refs--)
-			put_page(head);
+		put_compound_head(head, refs);
 		return 0;
 	}
=20
+	*nr +=3D refs;
 	SetPageReferenced(head);
 	return 1;
 }
@@ -2120,28 +2118,19 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, un=
signed long addr,
 		return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr);
 	}
=20
-	refs =3D 0;
 	page =3D pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
-	do {
-		pages[*nr] =3D page;
-		(*nr)++;
-		page++;
-		refs++;
-	} while (addr +=3D PAGE_SIZE, addr !=3D end);
+	refs =3D record_subpages(page, addr, end, pages + *nr);
=20
 	head =3D try_get_compound_head(pud_page(orig), refs);
-	if (!head) {
-		*nr -=3D refs;
+	if (!head)
 		return 0;
-	}
=20
 	if (unlikely(pud_val(orig) !=3D pud_val(*pudp))) {
-		*nr -=3D refs;
-		while (refs--)
-			put_page(head);
+		put_compound_head(head, refs);
 		return 0;
 	}
=20
+	*nr +=3D refs;
 	SetPageReferenced(head);
 	return 1;
 }
@@ -2157,28 +2146,20 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, un=
signed long addr,
 		return 0;
=20
 	BUILD_BUG_ON(pgd_devmap(orig));
-	refs =3D 0;
+
 	page =3D pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
-	do {
-		pages[*nr] =3D page;
-		(*nr)++;
-		page++;
-		refs++;
-	} while (addr +=3D PAGE_SIZE, addr !=3D end);
+	refs =3D record_subpages(page, addr, end, pages + *nr);
=20
 	head =3D try_get_compound_head(pgd_page(orig), refs);
-	if (!head) {
-		*nr -=3D refs;
+	if (!head)
 		return 0;
-	}
=20
 	if (unlikely(pgd_val(orig) !=3D pgd_val(*pgdp))) {
-		*nr -=3D refs;
-		while (refs--)
-			put_page(head);
+		put_compound_head(head, refs);
 		return 0;
 	}
=20
+	*nr +=3D refs;
 	SetPageReferenced(head);
 	return 1;
 }
--=20
2.24.0