From patchwork Thu Apr 5 21:03:50 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 10325463 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 7AC3D6032A for ; Thu, 5 Apr 2018 21:04:06 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 6988029287 for ; Thu, 5 Apr 2018 21:04:06 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5CDC9293C3; Thu, 5 Apr 2018 21:04:06 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E577129287 for ; Thu, 5 Apr 2018 21:04:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751558AbeDEVD4 (ORCPT ); Thu, 5 Apr 2018 17:03:56 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:41556 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751470AbeDEVDx (ORCPT ); Thu, 5 Apr 2018 17:03:53 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6B5084068024; Thu, 5 Apr 2018 21:03:52 +0000 (UTC) Received: from redhat.com (ovpn-122-62.rdu2.redhat.com [10.10.122.62]) by smtp.corp.redhat.com (Postfix) with SMTP id 1E4E9AB58A; Thu, 5 Apr 2018 21:03:51 +0000 (UTC) Date: Fri, 6 Apr 2018 00:03:50 +0300 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: "Kirill A . Shutemov" , Andrew Morton , Huang Ying , Jonathan Corbet , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Thorsten Leemhuis , Ralf Baechle , James Hogan , Martin Schwidefsky , Heiko Carstens , Yoshinori Sato , Rich Felker , "David S. Miller" , linux-mips@linux-mips.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 3/3] mm/gup: document return value Message-ID: <1522962072-182137-6-git-send-email-mst@redhat.com> References: <1522962072-182137-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1522962072-182137-1-git-send-email-mst@redhat.com> X-Mutt-Fcc: =sent X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Thu, 05 Apr 2018 21:03:52 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Thu, 05 Apr 2018 21:03:52 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'mst@redhat.com' RCPT:'' Sender: linux-sh-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP __get_user_pages_fast handles errors differently from get_user_pages_fast: the former always returns the number of pages pinned, the later might return a negative error code. Signed-off-by: Michael S. Tsirkin --- arch/mips/mm/gup.c | 2 ++ arch/s390/mm/gup.c | 2 ++ arch/sh/mm/gup.c | 2 ++ arch/sparc/mm/gup.c | 4 ++++ mm/gup.c | 4 +++- mm/util.c | 6 ++++-- 6 files changed, 17 insertions(+), 3 deletions(-) diff --git a/arch/mips/mm/gup.c b/arch/mips/mm/gup.c index 1e4658e..5a4875ca 100644 --- a/arch/mips/mm/gup.c +++ b/arch/mips/mm/gup.c @@ -178,6 +178,8 @@ static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, /* * Like get_user_pages_fast() except its IRQ-safe in that it won't fall * back to the regular GUP. + * Note a difference with get_user_pages_fast: this always returns the + * number of pages pinned, 0 if no pages were pinned. */ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c index 05c8abd..2809d11 100644 --- a/arch/s390/mm/gup.c +++ b/arch/s390/mm/gup.c @@ -220,6 +220,8 @@ static inline int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, /* * Like get_user_pages_fast() except its IRQ-safe in that it won't fall * back to the regular GUP. + * Note a difference with get_user_pages_fast: this always returns the + * number of pages pinned, 0 if no pages were pinned. */ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) diff --git a/arch/sh/mm/gup.c b/arch/sh/mm/gup.c index 8045b5b..56c86ca 100644 --- a/arch/sh/mm/gup.c +++ b/arch/sh/mm/gup.c @@ -160,6 +160,8 @@ static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, /* * Like get_user_pages_fast() except its IRQ-safe in that it won't fall * back to the regular GUP. + * Note a difference with get_user_pages_fast: this always returns the + * number of pages pinned, 0 if no pages were pinned. */ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) diff --git a/arch/sparc/mm/gup.c b/arch/sparc/mm/gup.c index 5335ba3..ca3eb69 100644 --- a/arch/sparc/mm/gup.c +++ b/arch/sparc/mm/gup.c @@ -192,6 +192,10 @@ static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, return 1; } +/* + * Note a difference with get_user_pages_fast: this always returns the + * number of pages pinned, 0 if no pages were pinned. + */ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) { diff --git a/mm/gup.c b/mm/gup.c index 8f3a064..5cb5bb1 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1740,7 +1740,9 @@ bool gup_fast_permitted(unsigned long start, int nr_pages, int write) /* * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to - * the regular GUP. It will only return non-negative values. + * the regular GUP. + * Note a difference with get_user_pages_fast: this always returns the + * number of pages pinned, 0 if no pages were pinned. */ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) diff --git a/mm/util.c b/mm/util.c index c125050..db2f005 100644 --- a/mm/util.c +++ b/mm/util.c @@ -297,8 +297,10 @@ void arch_pick_mmap_layout(struct mm_struct *mm) /* * Like get_user_pages_fast() except its IRQ-safe in that it won't fall * back to the regular GUP. - * If the architecture not support this function, simply return with no - * page pinned + * Note a difference with get_user_pages_fast: this always returns the + * number of pages pinned, 0 if no pages were pinned. + * If the architecture does not support this function, simply return with no + * pages pinned. */ int __weak __get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages)