From patchwork Wed Mar 3 17:52:35 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Brian Geffon X-Patchwork-Id: 12113989 Return-Path: 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=-11.6 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_INVALID,DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 64793C433DB for ; Wed, 3 Mar 2021 17:53:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D514B64EE8 for ; Wed, 3 Mar 2021 17:53:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D514B64EE8 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 43AC48D018E; Wed, 3 Mar 2021 12:53:07 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 411F38D0157; Wed, 3 Mar 2021 12:53:07 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2D9EE8D018E; Wed, 3 Mar 2021 12:53:07 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0158.hostedemail.com [216.40.44.158]) by kanga.kvack.org (Postfix) with ESMTP id 11D2E8D0157 for ; Wed, 3 Mar 2021 12:53:07 -0500 (EST) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id C7AFA9418 for ; Wed, 3 Mar 2021 17:53:06 +0000 (UTC) X-FDA: 77879309172.08.0DB61F2 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) by imf18.hostedemail.com (Postfix) with ESMTP id 83BF920053E9 for ; Wed, 3 Mar 2021 17:53:02 +0000 (UTC) Received: by mail-yb1-f202.google.com with SMTP id l10so27883050ybt.6 for ; Wed, 03 Mar 2021 09:53:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:message-id:mime-version:subject:from:to:cc; bh=eQ1N4syBqhEslbSb0mdNs2OlZNLITnu4bJ8FJAo60h4=; b=OLQjJT0J9gD2SzMgodm1GHn6v88aUuM7RgUuzmOJG3tKUlRF4p/HNeovouVQxPrtDQ W3cfRVvYPVJf0PUgUTTg9KacNDQGjtV0t41hSbwQbAvjBMnZuTFT0x9eS3UEQXMttKn5 ltADl2+jM89/kQclQtWNkvS4ijrLyucXx0nZ0G4250rFdxWhgpLFaNyjqkIjosUfi07f sxRA7jMw0Py89UrFDAZ05uf6A7fvoblcOv74/leSiKt2Rn7WthMRqXMWZxSbJNoxNPsb Yyw+KEashPMBUEdqc6pmvhLyZ6GOk4foNIMP/6DrXY9D1XhFPoR0Yi1Y+cwIFFGlZmbv 8CCw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:message-id:mime-version:subject:from :to:cc; bh=eQ1N4syBqhEslbSb0mdNs2OlZNLITnu4bJ8FJAo60h4=; b=hBVYa4CiBKa4UqXzZF3V5yerK+pjRcQ6kYq582zcIjShYlfppd5ImPCxcK2jnskvAm zKXLscOE8+UjKm2N6awtvWTxu6AAGj3Y7vJUq3pwYW03rDOQm0Vhg+cMAHRT7B1rf8GT ZKrTU6NS85GvsyCTBX4ns1Sqv+L2ajdKmiUXYT/fG18zpmaj21SJOuliilIhFFhGGdUt qJgMUsmADM8WI4ZunoR8Lt4FQS13+fUDuINTFyXtfwHyi+DdRAndw2/e0f1W5J2B9mf5 r+ApjwJLw3t1LzL2OokoEqlOqMTr/5WtMaLtI7i/gzRA6vb3h7pCMQ1lYiGWlV+A8K26 BlFg== X-Gm-Message-State: AOAM531WQITJD26pEtty2wyOi9YxZz95OM9Tt3/LNw7m9Zfx/Gl+XhTt 7PGY48iDG2NDq7WdpVuWUxHCO2jVdkSE X-Google-Smtp-Source: ABdhPJwnyqDHV+MfT760BeCIxgKo4yidtHHzI6Ce9X1wfCm1ty1jRfE6ZB+qqj7wRE676p0RC6J7UICzudl5 X-Received: from bg.sfo.corp.google.com ([2620:15c:8:10:60ab:b78:20ae:fc05]) (user=bgeffon job=sendgmr) by 2002:a25:e795:: with SMTP id e143mr523308ybh.509.1614793981739; Wed, 03 Mar 2021 09:53:01 -0800 (PST) Date: Wed, 3 Mar 2021 09:52:35 -0800 Message-Id: <20210303175235.3308220-1-bgeffon@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.31.0.rc0.254.gbdcc3b1a9d-goog Subject: [PATCH] mm: Allow shmem mappings with MREMAP_DONTUNMAP From: Brian Geffon To: Andrew Morton Cc: Axel Rasmussen , Lokesh Gidra , Mike Rapoport , Peter Xu , Hugh Dickins , "Michael S . Tsirkin" , Brian Geffon , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andy Lutomirski , Vlastimil Babka , Andrea Arcangeli , Sonny Rao , Minchan Kim , "Kirill A . Shutemov" X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 83BF920053E9 X-Stat-Signature: 9p1rrffxd168kqrsp9cbtae93bhapfkc Received-SPF: none (flex--bgeffon.bounces.google.com>: No applicable sender policy available) receiver=imf18; identity=mailfrom; envelope-from="<3_cw_YAcKCJ49ECDDMLEMMEJC.AMKJGLSV-KKIT8AI.MPE@flex--bgeffon.bounces.google.com>"; helo=mail-yb1-f202.google.com; client-ip=209.85.219.202 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614793982-644073 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: Currently MREMAP_DONTUNMAP only accepts private anonymous mappings. This change will widen the support to include shmem mappings. The primary use case is to support MREMAP_DONTUNMAP on mappings which may have been created from a memfd. Lokesh Gidra who works on the Android JVM, provided an explanation of how such a feature will improve Android JVM garbage collection: "Android is developing a new garbage collector (GC), based on userfaultfd. The garbage collector will use userfaultfd (uffd) on the java heap during compaction. On accessing any uncompacted page, the application threads will find it missing, at which point the thread will create the compacted page and then use UFFDIO_COPY ioctl to get it mapped and then resume execution. Before starting this compaction, in a stop-the-world pause the heap will be mremap(MREMAP_DONTUNMAP) so that the java heap is ready to receive UFFD_EVENT_PAGEFAULT events after resuming execution. To speedup mremap operations, pagetable movement was optimized by moving PUD entries instead of PTE entries [1]. It was necessary as mremap of even modest sized memory ranges also took several milliseconds, and stopping the application for that long isn't acceptable in response-time sensitive cases. With UFFDIO_CONTINUE feature [2], it will be even more efficient to implement this GC, particularly the 'non-moveable' portions of the heap. It will also help in reducing the need to copy (UFFDIO_COPY) the pages. However, for this to work, the java heap has to be on a 'shared' vma. Currently MREMAP_DONTUNMAP only supports private anonymous mappings, this patch will enable using UFFDIO_CONTINUE for the new userfaultfd-based heap compaction." [1] https://lore.kernel.org/linux-mm/20201215030730.NC3CU98e4%25akpm@linux-foundation.org/ [2] https://lore.kernel.org/linux-mm/20210302000133.272579-1-axelrasmussen@google.com/ Signed-off-by: Brian Geffon Tested-by: Lokesh Gidra Signed-off-by: Linus Torvalds --- mm/mremap.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/mm/mremap.c b/mm/mremap.c index ec8f840399ed..6934d199da54 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -653,8 +653,7 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr, return ERR_PTR(-EINVAL); } - if (flags & MREMAP_DONTUNMAP && (!vma_is_anonymous(vma) || - vma->vm_flags & VM_SHARED)) + if (flags & MREMAP_DONTUNMAP && !(vma_is_anonymous(vma) || vma_is_shmem(vma))) return ERR_PTR(-EINVAL); if (is_vm_hugetlb_page(vma))