From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 569A12EEE91; Sat, 29 Aug 2026 01:38:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787967484; cv=none; b=dA9t29ldOTZdrDRJfheGvJ7qR0wyHKdE38xt0GCja4tur9toXgeA5twUhDWWzcAtcHeLPrCuj1VXETllJlCdwU0f7hK6LBvgSvqyjnXCjSVouR4x7OzYsGZnBnWuMGk7EUvTGg6K297ORH4pro+VhBPuJQ1xRQ+Y7xtcxfLTkGo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787967484; c=relaxed/simple; bh=sA9f04kJnVsxUeKi3yRTD+8qO8r+eN7yclYtlHVkVIM=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=I0TmVH+XnXZI81Gw1KSNzg2jPFrNr/gj5x5bx0/c+nL/pc3HUew9QP7t4maQ8xdt/yTSi6uHpdVg/YYCHVjJ8jPVrxScQCAtFyW1I5FhNBiQ94ZuARLM/buIMkXvCrrene8KHs94SQMeREOGlwmZ1P9e5A6zl/iBi1WRoJO1hqc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=1ooxQzN1; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="1ooxQzN1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3A55E1F000E9; Sat, 29 Aug 2026 01:38:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1787967482; bh=EJ9sY7xCOOkZU7fkNPcRup0wxQveVJYgj0rNuabJsg8=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=1ooxQzN1/Iis7wo4qiD0UQM20Iq0wgdIB/2Da6G96vQezHcr2GL1PY8otynXf4F/m Zoyo5eezro3XDif4O45Ll5elF47hRGsxQTfydbJr6YHQenjtHLrTy/RFznmw/1il2u jrr67O1j2x2g829K+t8kiKwhd/QkYrxyzlzEmTIs= Date: Fri, 28 Aug 2026 18:38:01 -0700 From: Andrew Morton To: James Houghton Cc: Lance Yang , David Hildenbrand , Lorenzo Stoakes , Zi Yan , Baolin Wang , liam@infradead.org, Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Usama Arif , Yang Shi , zokeefe@google.com, hughd@google.com, Kiryl Shutsemau , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] mm/khugepaged: Don't install PMDs in uffd-minor-registered VMAs Message-Id: <20260828183801.04fd2d2a6af837cb45b60e0f@linux-foundation.org> In-Reply-To: References: <20260828222640.1638457-1-jthoughton@google.com> <20260828173302.29778f1bf802a1db932778ad@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Fri, 28 Aug 2026 18:18:11 -0700 James Houghton wrote: > On Fri, Aug 28, 2026 at 6:09 PM James Houghton wrote: > > > > On Fri, Aug 28, 2026 at 5:33 PM Andrew Morton wrote: > > > Wondering what Lance tested. Was he able to reproduce the bug? > > > > I assume he just re-ran my repro, but yeah I'm not sure, heh. Lance, > > what did you test? > > Ah, just to be clear, I linked a repro on v1. Here[1] is that repro. > Sorry, slipped my mind to also include it in the notes for this v2. > > [1] https://gist.github.com/48ca/d399bf534158e80241fb4937ef1ff664 Cool thanks, I'll slap this into the changelog. # ./a.out TAP version 13 1..1 madvise(MADV_COLLAPSE) succeeded ioctl(UFFDIO_CONTINUE) failed: File exists (errno=17) not ok 1 - memfd userfaultfd MINOR continue test We do have a ton of uffd selftesting code in there. Adding this case to uffd-unit-tests.c would presumably be pretty simple. We don't really have a policy on adding a test-case after fixing something - it's common practice but why? We already fixed it!