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 X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, URIBL_BLOCKED,USER_AGENT_MUTT 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 851DDC4321D for ; Thu, 16 Aug 2018 02:47:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 43A6121477 for ; Thu, 16 Aug 2018 02:47:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Ku9QaMy9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 43A6121477 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387854AbeHPFmO (ORCPT ); Thu, 16 Aug 2018 01:42:14 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:58306 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731184AbeHPFmO (ORCPT ); Thu, 16 Aug 2018 01:42:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=faxjcFdpEC766ltR91iVAfQ1HE+MjueEHAx3zpkEd7Q=; b=Ku9QaMy9FLJ5qGCaxVnhHOQDM A9o5Nzy1xlHFtCjhZK9aieqAWJAB3wJGFaWvyOTxNeEdOeZPnWcfgr7KrvznfzCyW5ztZd/pUaXGg up+0N21FJpWnUyD7dBQYQ/RYcfg9LwU59aBVWsVXCagaElpoN3cC9WDUKkalUeCZCmGYYS1xvFCUa 1KITCFOEj2BFgUPhmGux5VmnCoPTbIXTUeUZl37CdSPJmE6xZCG1d0yi53f38Hmh1wxSBlzH6D0BO m4G+VT1UYr5+J3XQbtKinIG9Er7FI4OONkAk/wX01LzzZ/KaITlPdITNIs101bLO+S1dY503pr7NW EeGRRJ0zQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1fq8JI-0006wT-OO; Thu, 16 Aug 2018 02:46:52 +0000 Date: Wed, 15 Aug 2018 19:46:52 -0700 From: Matthew Wilcox To: Yang Shi Cc: mhocko@kernel.org, ldufour@linux.vnet.ibm.com, kirill@shutemov.name, vbabka@suse.cz, akpm@linux-foundation.org, peterz@infradead.org, mingo@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC v8 PATCH 3/5] mm: mmap: zap pages with read mmap_sem in munmap Message-ID: <20180816024652.GA11808@bombadil.infradead.org> References: <1534358990-85530-1-git-send-email-yang.shi@linux.alibaba.com> <1534358990-85530-4-git-send-email-yang.shi@linux.alibaba.com> <20180815191606.GA4201@bombadil.infradead.org> <20180815210946.GA28919@bombadil.infradead.org> <78e658dd-bdb0-09ca-9af5-b523c7ff529f@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <78e658dd-bdb0-09ca-9af5-b523c7ff529f@linux.alibaba.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 15, 2018 at 02:54:13PM -0700, Yang Shi wrote: > > > On 8/15/18 2:09 PM, Matthew Wilcox wrote: > > On Wed, Aug 15, 2018 at 12:16:06PM -0700, Matthew Wilcox wrote: > > > (not even compiled, and I can see a good opportunity for combining the > > > VM_LOCKED loop with the has_uprobes loop) > > I was rushing to get that sent earlier. Here it is tidied up to > > actually compile. > > Thanks for the example. Yes, I believe the code still can be compacted to > save some lines. However, the cover letter and the commit log of this patch > has elaborated the discussion in the earlier reviews about why we do it in > this way. You mean the other callers which need to hold mmap_sem write-locked for longer? I hadn't really considered those; how about this? mmap.c | 47 +++++++++++++++++++++++++++++------------------ 1 file changed, 29 insertions(+), 18 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index de699523c0b7..06dc31d1da8c 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2798,11 +2798,11 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma, * work. This now handles partial unmappings. * Jeremy Fitzhardinge */ -int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, - struct list_head *uf) +static int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len, + struct list_head *uf, bool downgrade) { unsigned long end; - struct vm_area_struct *vma, *prev, *last; + struct vm_area_struct *vma, *prev, *last, *tmp; if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start) return -EINVAL; @@ -2816,7 +2816,7 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, if (!vma) return 0; prev = vma->vm_prev; - /* we have start < vma->vm_end */ + /* we have start < vma->vm_end */ /* if it doesn't overlap, we have nothing.. */ end = start + len; @@ -2873,18 +2873,22 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, /* * unlock any mlock()ed ranges before detaching vmas + * and check to see if there's any reason we might have to hold + * the mmap_sem write-locked while unmapping regions. */ - if (mm->locked_vm) { - struct vm_area_struct *tmp = vma; - while (tmp && tmp->vm_start < end) { - if (tmp->vm_flags & VM_LOCKED) { - mm->locked_vm -= vma_pages(tmp); - munlock_vma_pages_all(tmp); - } - tmp = tmp->vm_next; + for (tmp = vma; tmp && tmp->vm_start < end; tmp = tmp->vm_next) { + if (tmp->vm_flags & VM_LOCKED) { + mm->locked_vm -= vma_pages(tmp); + munlock_vma_pages_all(tmp); } + if (tmp->vm_file && + has_uprobes(tmp, tmp->vm_start, tmp->vm_end)) + downgrade = false; } + if (downgrade) + downgrade_write(&mm->mmap_sem); + /* * Remove the vma's, and unmap the actual pages */ @@ -2896,7 +2900,13 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, /* Fix up all other VM information */ remove_vma_list(mm, vma); - return 0; + return downgrade ? 1 : 0; +} + +int do_unmap(struct mm_struct *mm, unsigned long start, size_t len, + struct list_head *uf) +{ + return __do_munmap(mm, start, len, uf, false); } int vm_munmap(unsigned long start, size_t len) @@ -2905,11 +2915,12 @@ int vm_munmap(unsigned long start, size_t len) struct mm_struct *mm = current->mm; LIST_HEAD(uf); - if (down_write_killable(&mm->mmap_sem)) - return -EINTR; - - ret = do_munmap(mm, start, len, &uf); - up_write(&mm->mmap_sem); + down_write(&mm->mmap_sem); + ret = __do_munmap(mm, start, len, &uf, true); + if (ret == 1) + up_read(&mm->mmap_sem); + else + up_write(&mm->mmap_sem); userfaultfd_unmap_complete(mm, &uf); return ret; }