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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8FDAC04A94 for ; Thu, 10 Aug 2023 22:16:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 188D46B0072; Thu, 10 Aug 2023 18:16:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 13A176B0074; Thu, 10 Aug 2023 18:16:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 029956B0078; Thu, 10 Aug 2023 18:16:50 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id E9DAD6B0072 for ; Thu, 10 Aug 2023 18:16:50 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id BC3771A035B for ; Thu, 10 Aug 2023 22:16:50 +0000 (UTC) X-FDA: 81109605780.02.F730006 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf20.hostedemail.com (Postfix) with ESMTP id 631311C0014 for ; Thu, 10 Aug 2023 22:16:48 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b="Wu9JD/vL"; dmarc=none; spf=none (imf20.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1691705808; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=kZPovxlvK/roVyxwyrIHXjZdgR6OfruTG8lx5laTMjE=; b=wyoiU23z9n2qLiMa8e0+vlcGkR+7PjLHMqDYvB9s1N5TnI+xNHrvsSVltMcRa3BIJ1fQMC 5xahkGk0mKWEP1OixPjIxnTTSS+lSIYYDGgNq5OLm61VNGQkcNy4FaTSR4qIyq3w/EXgez p3rFaS4LfkZFfayjO280GP63G82TqoU= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b="Wu9JD/vL"; dmarc=none; spf=none (imf20.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1691705808; a=rsa-sha256; cv=none; b=uPoKJt+DfKDKMHoqdWvqVmlFvdfziob8YSqqYHgIZlqbh+rDARk/LVfdcGaFnbrp+AVljq DdscFx31fK7bPrGt3qLveXM1dnH98omhcAG9rkT+rP8Y7e7nG9fQlwCvVKgM4EAKo4YIOx /lilAzOEhl5ZKqUuPnr0d/2FC6utaZU= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=kZPovxlvK/roVyxwyrIHXjZdgR6OfruTG8lx5laTMjE=; b=Wu9JD/vLovqSrk7O9Ir9t5qFsz B7QVo0bG4GprbraPb6elzFPJ3NE/0hGrj9rgwFwVX0NDoTwdn5+NFUTNBSqdhXrTeSAegMaRIfYS3 sBlOmjAdS7vP+kUu7bSDI8NMwxfhWi0JJ6PeN1v0CCn1P9iRRp1bNjkboCR6gCltj0pWY2RPXoqir tzEbcfCPZm/LCQ50fGWMeFvYFV7mNpl1EQZOQC1XHuGqWbUk4gkZ7IYoX3rgb94KtusmIUVxgv1kp 30OyN/78yXUBl3imywAb+maKp42gUxHzQxhb0MVHJ0rrbZWzqjQOSRMDTeHddGq8L6aUWWwHyjyhy RMI8I8aQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qUDwr-00F0qE-VO; Thu, 10 Aug 2023 22:16:06 +0000 Date: Thu, 10 Aug 2023 23:16:05 +0100 From: Matthew Wilcox To: Suren Baghdasaryan Cc: David Hildenbrand , akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, michel@lespinasse.org, liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz, minchan@google.com, dave@stgolabs.net, punit.agrawal@bytedance.com, lstoakes@gmail.com, hdanton@sina.com, apopple@nvidia.com, peterx@redhat.com, ying.huang@intel.com, yuzhao@google.com, dhowells@redhat.com, hughd@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, pasha.tatashin@soleen.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v7 0/6] Per-VMA lock support for swap and userfaults Message-ID: References: <20230630211957.1341547-1-surenb@google.com> <0ab6524a-6917-efe2-de69-f07fb5cdd9d2@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Stat-Signature: q7famdbxthgq7sa1ednba73jgwfrg1xi X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 631311C0014 X-HE-Tag: 1691705808-531923 X-HE-Meta: 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 ff6KFASt 9we/7NB9EoUfEQXAuhvLWbmq84+eebDt1LUXKcNwKXHo5oMPi0TzG+NJIfFsNrh9tHJUwk8VnBct7ZHarfQS4SwpP4FZsJaitlJnxc6yTydW2E6cZVaz+xO5gSFa2lqT7EYvG6B1O07OcYng= 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: On Thu, Aug 10, 2023 at 06:24:15AM +0000, Suren Baghdasaryan wrote: > Ok, I think I found the issue. wp_page_shared() -> > fault_dirty_shared_page() can drop mmap_lock (see the comment saying > "Drop the mmap_lock before waiting on IO, if we can...", therefore we > have to ensure we are not doing this under per-VMA lock. ... or we could change maybe_unlock_mmap_for_io() the same way that we changed folio_lock_or_retry(): +++ b/mm/internal.h @@ -706,7 +706,7 @@ static inline struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf, if (fault_flag_allow_retry_first(flags) && !(flags & FAULT_FLAG_RETRY_NOWAIT)) { fpin = get_file(vmf->vma->vm_file); - mmap_read_unlock(vmf->vma->vm_mm); + release_fault_lock(vmf); } return fpin; } What do you think? > I think what happens is that this path is racing with another page > fault which took mmap_lock for read. fault_dirty_shared_page() > releases this lock which was taken by another page faulting thread and > that thread generates an assertion when it finds out the lock it just > took got released from under it. I'm confused that our debugging didn't catch this earlier. lockdep should always catch this.