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=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 116DFC433ED for ; Tue, 11 May 2021 07:09:19 +0000 (UTC) Received: from kanga.kvack.org (unknown [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9A5116187E for ; Tue, 11 May 2021 07:09:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9A5116187E 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 5A1716B006E; Tue, 11 May 2021 03:09:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5784B6B0071; Tue, 11 May 2021 03:09:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 41A3C6B0072; Tue, 11 May 2021 03:09:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0122.hostedemail.com [216.40.44.122]) by kanga.kvack.org (Postfix) with ESMTP id 278D86B006E for ; Tue, 11 May 2021 03:09:10 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id D77256D7F for ; Tue, 11 May 2021 07:09:09 +0000 (UTC) X-FDA: 78128073618.26.C724114 Received: from mail-pj1-f47.google.com (mail-pj1-f47.google.com [209.85.216.47]) by imf17.hostedemail.com (Postfix) with ESMTP id 5A38E4080F47 for ; Tue, 11 May 2021 07:09:04 +0000 (UTC) Received: by mail-pj1-f47.google.com with SMTP id gc22-20020a17090b3116b02901558435aec1so819835pjb.4 for ; Tue, 11 May 2021 00:09:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=3+IQnDGiGzfsA3AGqRi0KPWLiqj3hTQA1bwpyeFQR/k=; b=q57sD6p4GNZJbAu0n7qDkkopCSXtMKbL5tU0UVYhcU9U+QsrdRyltbLVCscEqqduMs KBGqn3l9NYQK772kjwJLmc2wIkANlLPXYcQKS7yLJ5lDpJdQeVBgvcn6MwOOA2Laptl+ G3LyZJRrFi8v84ltLC3uTWfNVmOKXxqq9hF9YsjK8ZYHWVM3LOWUZO3CC53dRzTGumOF 5EA3P0pXsQLfDkMaY0K+a8BZIFXZ1OQlYyZi3X0gcjh7GS2jFOBe6v9ZbQInFJIuW6XN 9yKaY9NSsVIcCTMHWOB0SIZC3uDdO2EQF+/UKMfEgHd4A1L8vBd+hyndf3g4j98Y/+Do iJlw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=3+IQnDGiGzfsA3AGqRi0KPWLiqj3hTQA1bwpyeFQR/k=; b=WGNWz1mAb/2P6q6E02O9T07q+3SLhKc+oFLEUYs3WduxW1UKGJEaQmMcQ6doyPO01E rG5s+71chkhjR/td0oCjMQHxxhCe6iLPEtJFBkVdG6Qfzs17j41oztcg/Z/x3gepTaGi D78Vccm+en3uxiyNDa0o+UmrLK72JpkG3O16WzYDLJzCIzq9IQVCaD2XysNQtKVBCiNs kkS6hoGMgGEzyA0p3TprojwYJYGrXjDKvPnM+wlwq6DSILpnG/0keCK0PcFkcbYA03mZ TTadumZJ2B8JHhJZ94Ew6PoSjaOj5udhVR9ywd67Qk2yK0rCgb84/GVMTybeULbS4UKj 6rvA== X-Gm-Message-State: AOAM531mTDzYval3UiXpdCQyLHtf3d4Tag0Aq6WvtUerJWDA9CFiPPIx en/oy++WeQc6Go+FfL3ayRzD9Sg5v76WJt855Z3Prw== X-Google-Smtp-Source: ABdhPJwSNVT6H6zpwhz466Gw56oRHLWnvPP3hTVy3Hi13Mpsw5kK+kcWiyr/BwgQvh0sIrXjp15uOW9ka9Q+7tNd3Xs= X-Received: by 2002:a17:902:7c85:b029:ed:893d:ec7c with SMTP id y5-20020a1709027c85b02900ed893dec7cmr27819732pll.82.1620716948255; Tue, 11 May 2021 00:09:08 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Mina Almasry Date: Tue, 11 May 2021 00:08:56 -0700 Message-ID: Subject: Re: resv_huge_page underflow with userfaultfd test To: Axel Rasmussen Cc: Mike Kravetz , Linux-MM , Andrea Arcangeli , Peter Xu Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=google.com header.s=20161025 header.b=q57sD6p4; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf17.hostedemail.com: domain of almasrymina@google.com designates 209.85.216.47 as permitted sender) smtp.mailfrom=almasrymina@google.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 5A38E4080F47 X-Stat-Signature: m9bqkrru5u9ft1snu1i7gr386ofm8w4t Received-SPF: none (google.com>: No applicable sender policy available) receiver=imf17; identity=mailfrom; envelope-from=""; helo=mail-pj1-f47.google.com; client-ip=209.85.216.47 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620716944-391598 X-Bogosity: Ham, tests=bogofilter, spamicity=0.098412, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, May 10, 2021 at 11:46 PM Axel Rasmussen wrote: > > Thanks for the investigation, Mike! > > Mina, since hugetlb_mcopy_atomic_pte is specific to userfaultfd, I'm > happy to take a deeper look at it this week as well. > > For context, we have seen the WARN_ON Mina described trigger in > production before, but were never able to reproduce it. The > userfaultfd self test turns out to reproduce it reliably, so the > thinking up to this point was that it just happened to reproduce some > non-userfaultfd-specific issue. But from Mike's description, it seems > this bug is very specific to userfaultfd after all. :) > That's fine, I'll take an initial look at least. If I end up being roped into userfaultfd stuff way over my head I'll solicit your help or punt it over to you.Thanks!