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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 0ED89C3F2C6 for ; Sat, 7 Mar 2020 23:47:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DACFA2075A for ; Sat, 7 Mar 2020 23:47:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583624867; bh=sO2549TXeIeA/LiuWHdqg4t8QGOOV438IVO1eJHrkPU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=T+F1HzC63DfXPJqN5vmbjXftlLaF9UsWvWdPxYT/gMrLcI+XCyuuJVmeOGwLNdmFl hd1VRHbOSLzCPk1eE0oQBmZW5iuXyo/Q3CT5yDf0wxwmSLyIJIGU7FwlZHM+MC8q5E oWUR4QYbX5i+zN8LUc2LtYOGu7cTz54MLFDyzymw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726300AbgCGXrq (ORCPT ); Sat, 7 Mar 2020 18:47:46 -0500 Received: from mail.kernel.org ([198.145.29.99]:43408 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726109AbgCGXrq (ORCPT ); Sat, 7 Mar 2020 18:47:46 -0500 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 15B582070A; Sat, 7 Mar 2020 23:47:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583624865; bh=sO2549TXeIeA/LiuWHdqg4t8QGOOV438IVO1eJHrkPU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=retgJCHFk2bDFrUXZSlHH4zCjGooNSMmNg1dTKxvBs96tHWW3KF/zkp2bwFn5mIca 8nqLP7nJFnULtVzV9JqCSH1p4kOIwZDSnaxEUPYFlHhlwNLZqwiIZlivrUVKyb6iVs G65ErDyoEdgzPQnwTjpN41sZ2GJddNk9wQ331gJs= Date: Sat, 7 Mar 2020 15:47:44 -0800 From: Andrew Morton To: Jaewon Kim Cc: walken@google.com, bp@suse.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, jaewon31.kim@gmail.com Subject: Re: [PATCH] mm: mmap: show vm_unmapped_area error log Message-Id: <20200307154744.acd523831b45efa8d0fc1dfa@linux-foundation.org> In-Reply-To: <5E61EAB6.5080609@samsung.com> References: <20200304030206.1706-1-jaewon31.kim@samsung.com> <5E605749.9050509@samsung.com> <20200305202443.8de3598558336b1d75afbba7@linux-foundation.org> <5E61EAB6.5080609@samsung.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 6 Mar 2020 15:16:22 +0900 Jaewon Kim wrote: > > Even on 64 bit kernel, the mmap failure can happen for a 32 bit task. > Virtual memory space shortage of a task on mmap is reported to userspace > as -ENOMEM. It can be confused as physical memory shortage of overall > system. > > The vm_unmapped_area can be called to by some drivers or other kernel > core system like filesystem. It can be hard to know which code layer > returns the -ENOMEM. > > Print error log of vm_unmapped_area with rate limited. Without rate > limited, soft lockup ocurrs on infinite mmap sytem call. > > i.e.) > <4>[ 68.556470] [2: mmap_infinite:12363] mmap: vm_unmapped_area err:-12 total_vm:0xf4c08 flags:0x1 len:0x100000 low:0x8000 high:0xf4583000 mask:0x0 offset:0x0 > > ... > > --- a/include/linux/mm.h > +++ b/include/linux/mm.h This patch was messed up by your email client (tabs expanded to spaces). > @@ -27,6 +27,7 @@ > #include > #include > #include > +#include > > struct mempolicy; > struct anon_vma; > @@ -2379,10 +2380,20 @@ extern unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info); > static inline unsigned long > vm_unmapped_area(struct vm_unmapped_area_info *info) > { > + unsigned long addr; > + > if (info->flags & VM_UNMAPPED_AREA_TOPDOWN) > - return unmapped_area_topdown(info); > + addr = unmapped_area_topdown(info); > else > - return unmapped_area(info); > + addr = unmapped_area(info); > + > + if (IS_ERR_VALUE(addr)) { > + pr_warn_ratelimited("%s err:%ld total_vm:0x%lx flags:0x%lx len:0x%lx low:0x%lx high:0x%lx mask:0x%lx offset:0x%lx\n", > + __func__, addr, current->mm->total_vm, info->flags, > + info->length, info->low_limit, info->high_limit, > + info->align_mask, info->align_offset); > + } > + return addr; > } pr_warn_ratelimited() contains static state. Using it in an inlined function means that each callsite gets its own copy of that state, so we're ratelimiting the vm_unmapped_area() output on a per-callsite basis, not on a kernelwide basis. Maybe that's what we want, maybe it's not. But I think vm_unmapped_area() has become too large to be inlined anyway, so I suggest making it a regular out-of-line function in mmap.c. I don't believe that function needs to be exported to modules.