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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 77995C433EF for ; Tue, 1 Feb 2022 20:58:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231172AbiBAU6a (ORCPT ); Tue, 1 Feb 2022 15:58:30 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:59360 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242667AbiBAU60 (ORCPT ); Tue, 1 Feb 2022 15:58:26 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id BFC9C6176B for ; Tue, 1 Feb 2022 20:58:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D01C3C340EB; Tue, 1 Feb 2022 20:58:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1643749105; bh=uySinXV1IVIh+JM81IdO1rcp+QoS/7A0vzCC4Lz+FXw=; h=Date:To:From:Subject:From; b=VOrvN6nQI0oy57WzGwshQkwFnD+O/pMzzciiIogvKNsihRLW5/GSYXrLMKWyqG016 EWuBzdMYOBhKoJNRARHGi9eDRDp+5qQfkvW/3OMBRxbKrTtQGY+BwctK6vzfvJM1aW 3tlSiB3FRFeNlArOjrc6k0p+ZAhCq23PSPBffLVc= Received: by hp1 (sSMTP sendmail emulation); Tue, 01 Feb 2022 12:58:23 -0800 Date: Tue, 01 Feb 2022 12:58:23 -0800 To: mm-commits@vger.kernel.org, peterx@redhat.com, kirill.shutemov@linux.intel.com, jgg@ziepe.ca, jgg@nvidia.com, jack@suse.cz, david@redhat.com, alex.williamson@redhat.com, aarcange@redhat.com, jhubbard@nvidia.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-gup-remove-get_user_pages_locked.patch added to -mm tree Message-Id: <20220201205823.D01C3C340EB@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm/gup: remove get_user_pages_locked() has been added to the -mm tree. Its filename is mm-gup-remove-get_user_pages_locked.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-gup-remove-get_user_pages_locked.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-gup-remove-get_user_pages_locked.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: John Hubbard Subject: mm/gup: remove get_user_pages_locked() There is only one caller of get_user_pages_locked(). The purpose of get_user_pages_locked() is to allow for unlocking the mmap_lock when reading a page from the disk during a page fault (hidden behind VM_FAULT_RETRY). The idea is to reduce contention on the heavily-used mmap_lock. (Thanks to Jan Kara for clearly pointing that out, and in fact I've used some of his wording here.) However, it is unlikely for lookup_node() to take a page fault. With that in mind, change over to calling get_user_pages_fast(). This simplifies the code, runs a little faster in the expected case, and allows removing get_user_pages_locked() entirely. Link: https://lkml.kernel.org/r/20220201101108.306062-5-jhubbard@nvidia.com Signed-off-by: John Hubbard Suggested-by: Jason Gunthorpe Cc: Jan Kara Cc: Alex Williamson Cc: Andrea Arcangeli Cc: David Hildenbrand Cc: Jason Gunthorpe Cc: Kirill A. Shutemov Cc: Peter Xu Signed-off-by: Andrew Morton --- include/linux/mm.h | 2 - mm/gup.c | 59 ------------------------------------------- mm/mempolicy.c | 21 ++++++--------- 3 files changed, 9 insertions(+), 73 deletions(-) --- a/include/linux/mm.h~mm-gup-remove-get_user_pages_locked +++ a/include/linux/mm.h @@ -1916,8 +1916,6 @@ long get_user_pages(unsigned long start, long pin_user_pages(unsigned long start, unsigned long nr_pages, unsigned int gup_flags, struct page **pages, struct vm_area_struct **vmas); -long get_user_pages_locked(unsigned long start, unsigned long nr_pages, - unsigned int gup_flags, struct page **pages, int *locked); long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, struct page **pages, unsigned int gup_flags); long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages, --- a/mm/gup.c~mm-gup-remove-get_user_pages_locked +++ a/mm/gup.c @@ -2119,65 +2119,6 @@ long get_user_pages(unsigned long start, } EXPORT_SYMBOL(get_user_pages); -/** - * get_user_pages_locked() - variant of get_user_pages() - * - * @start: starting user address - * @nr_pages: number of pages from start to pin - * @gup_flags: flags modifying lookup behaviour - * @pages: array that receives pointers to the pages pinned. - * Should be at least nr_pages long. Or NULL, if caller - * only intends to ensure the pages are faulted in. - * @locked: pointer to lock flag indicating whether lock is held and - * subsequently whether VM_FAULT_RETRY functionality can be - * utilised. Lock must initially be held. - * - * It is suitable to replace the form: - * - * mmap_read_lock(mm); - * do_something() - * get_user_pages(mm, ..., pages, NULL); - * mmap_read_unlock(mm); - * - * to: - * - * int locked = 1; - * mmap_read_lock(mm); - * do_something() - * get_user_pages_locked(mm, ..., pages, &locked); - * if (locked) - * mmap_read_unlock(mm); - * - * We can leverage the VM_FAULT_RETRY functionality in the page fault - * paths better by using either get_user_pages_locked() or - * get_user_pages_unlocked(). - * - */ -long get_user_pages_locked(unsigned long start, unsigned long nr_pages, - unsigned int gup_flags, struct page **pages, - int *locked) -{ - /* - * FIXME: Current FOLL_LONGTERM behavior is incompatible with - * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on - * vmas. As there are no users of this flag in this call we simply - * disallow this option for now. - */ - if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM)) - return -EINVAL; - /* - * FOLL_PIN must only be set internally by the pin_user_pages*() APIs, - * never directly by the caller, so enforce that: - */ - if (WARN_ON_ONCE(gup_flags & FOLL_PIN)) - return -EINVAL; - - return __get_user_pages_locked(current->mm, start, nr_pages, - pages, NULL, locked, - gup_flags | FOLL_TOUCH); -} -EXPORT_SYMBOL(get_user_pages_locked); - /* * get_user_pages_unlocked() is suitable to replace the form: * --- a/mm/mempolicy.c~mm-gup-remove-get_user_pages_locked +++ a/mm/mempolicy.c @@ -907,17 +907,14 @@ static void get_policy_nodemask(struct m static int lookup_node(struct mm_struct *mm, unsigned long addr) { struct page *p = NULL; - int err; + int ret; - int locked = 1; - err = get_user_pages_locked(addr & PAGE_MASK, 1, 0, &p, &locked); - if (err > 0) { - err = page_to_nid(p); + ret = get_user_pages_fast(addr & PAGE_MASK, 1, 0, &p); + if (ret > 0) { + ret = page_to_nid(p); put_page(p); } - if (locked) - mmap_read_unlock(mm); - return err; + return ret; } /* Retrieve NUMA policy */ @@ -968,14 +965,14 @@ static long do_get_mempolicy(int *policy if (flags & MPOL_F_NODE) { if (flags & MPOL_F_ADDR) { /* - * Take a refcount on the mpol, lookup_node() - * will drop the mmap_lock, so after calling - * lookup_node() only "pol" remains valid, "vma" - * is stale. + * Take a refcount on the mpol, because we are about to + * drop the mmap_lock, after which only "pol" remains + * valid, "vma" is stale. */ pol_refcount = pol; vma = NULL; mpol_get(pol); + mmap_read_unlock(mm); err = lookup_node(mm, addr); if (err < 0) goto out; _ Patches currently in -mm which might be from jhubbard@nvidia.com are mm-gup-clean-up-follow_pfn_pte-slightly.patch mm-gup-remove-unused-pin_user_pages_locked.patch mm-gup-remove-get_user_pages_locked.patch