From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: [patch 005/131] mm/gup: introduce pin_user_pages_fast_only() Date: Wed, 03 Jun 2020 15:56:34 -0700 Message-ID: <20200603225634.7zNxWRQ9k%akpm@linux-foundation.org> References: <20200603155549.e041363450869eaae4c7f05b@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:37806 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725863AbgFCW4f (ORCPT ); Wed, 3 Jun 2020 18:56:35 -0400 In-Reply-To: <20200603155549.e041363450869eaae4c7f05b@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: airlied@linux.ie, akpm@linux-foundation.org, chris@chris-wilson.co.uk, daniel@ffwll.ch, jani.nikula@linux.intel.com, jhubbard@nvidia.com, joonas.lahtinen@linux.intel.com, jrdr.linux@gmail.com, linux-mm@kvack.org, matthew.auld@intel.com, mm-commits@vger.kernel.org, rodrigo.vivi@intel.com, torvalds@linux-foundation.org, tvrtko.ursulin@intel.com, willy@infradead.org From: John Hubbard Subject: mm/gup: introduce pin_user_pages_fast_only() This is the FOLL_PIN equivalent of __get_user_pages_fast(), except with a more descriptive name, and gup_flags instead of a boolean "write" in the argument list. Link: http://lkml.kernel.org/r/20200519002124.2025955-4-jhubbard@nvidia.com Signed-off-by: John Hubbard Reviewed-by: Chris Wilson Cc: Daniel Vetter Cc: David Airlie Cc: Jani Nikula Cc: "Joonas Lahtinen" Cc: Matthew Auld Cc: Matthew Wilcox Cc: Rodrigo Vivi Cc: Souptick Joarder Cc: Tvrtko Ursulin Signed-off-by: Andrew Morton --- include/linux/mm.h | 2 ++ mm/gup.c | 36 ++++++++++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+) --- a/include/linux/mm.h~mm-gup-introduce-pin_user_pages_fast_only +++ a/include/linux/mm.h @@ -1827,6 +1827,8 @@ extern int mprotect_fixup(struct vm_area */ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages); +int pin_user_pages_fast_only(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages); /* * per-process(per-mm_struct) statistics. */ --- a/mm/gup.c~mm-gup-introduce-pin_user_pages_fast_only +++ a/mm/gup.c @@ -2913,6 +2913,42 @@ int pin_user_pages_fast(unsigned long st } EXPORT_SYMBOL_GPL(pin_user_pages_fast); +/* + * This is the FOLL_PIN equivalent of __get_user_pages_fast(). Behavior is the + * same, except that this one sets FOLL_PIN instead of FOLL_GET. + * + * The API rules are the same, too: no negative values may be returned. + */ +int pin_user_pages_fast_only(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages) +{ + int nr_pinned; + + /* + * FOLL_GET and FOLL_PIN are mutually exclusive. Note that the API + * rules require returning 0, rather than -errno: + */ + if (WARN_ON_ONCE(gup_flags & FOLL_GET)) + return 0; + /* + * FOLL_FAST_ONLY is required in order to match the API description of + * this routine: no fall back to regular ("slow") GUP. + */ + gup_flags |= (FOLL_PIN | FOLL_FAST_ONLY); + nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags, + pages); + /* + * This routine is not allowed to return negative values. However, + * internal_get_user_pages_fast() *can* return -errno. Therefore, + * correct for that here: + */ + if (nr_pinned < 0) + nr_pinned = 0; + + return nr_pinned; +} +EXPORT_SYMBOL_GPL(pin_user_pages_fast_only); + /** * pin_user_pages_remote() - pin pages of a remote process (task != current) * _