From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 9F72A358D3D; Tue, 14 Apr 2026 10:02:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776160923; cv=none; b=cmmKUbFYAp7qbd211iS7RFFq8SrWLJBwJlEcfIK0n39squmf3TBoOz+VncE3bxgELyC3HVpUwJf9+Yw6mOwveVmKIe4P1ROXg3/Of6HVm3abbHZf4aG2OEjOJLuqsHbfAMI3bdbeKcq+IIsOihWPRyufba9kGqJZuy5A35xGayM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776160923; c=relaxed/simple; bh=hEMZcMIZS6WzhX6ssC5Ou6uax693W51NviYWtwo2rRA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=u61aRHblzF4EwnuZ0rk3g83GkiLsbrB2qCRnTWeXw7/XTV6LScrz2mpQbI+xdmW1wH1jr4UY48c97rDf36sRCl3kZhjGWoCKSmpEJLRA9RCE7nLKnTlWVj2ZxaFdZ8kl+Q0RtM3cem9KlDlyt95S+RUy09ax+9X0MBKyQrHI8r8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cTkwm5Ak; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cTkwm5Ak" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B43BC19425; Tue, 14 Apr 2026 10:01:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776160923; bh=hEMZcMIZS6WzhX6ssC5Ou6uax693W51NviYWtwo2rRA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=cTkwm5AkJiR1Kcxa/iRawXT6asz/JNVsLox7hbLmD9WpHY7NrEJd0Np2KuvxhcZDz sMaAP+k4X0urnbfFoLZQpcaU4aNgNC0XwfdcCQD+ESiBBIxU+ZvoszTRtcjUI65D8S yrFLpaZnwOKgbWmUofGYDgDBEW2J63ChT28SH9ICE6sUVeQgJ/y3qlXLYHwUIYsiAQ E7TWJseSLHDOHWVwq7qHeySCAlKpIVrSmgG4vBwSHFoD8R6Q67XHPHvoUmZVbL7UCb +kcIQBbMgItyBP0yzr0beiuX9rKIeGi7QmP4ON+0eabVuxDAiL0MuLwp5JsV/gvthf nGppsJGfgIE0w== Message-ID: Date: Tue, 14 Apr 2026 12:01:56 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/2] selftests/mm: verify droppable mappings cannot be locked To: anthony.yznaga@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: akpm@linux-foundation.org, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, jannh@google.com, pfalcato@suse.de, Jason@zx2c4.com, shuah@kernel.org References: <20260409234915.11723-1-anthony.yznaga@oracle.com> <20260409234915.11723-3-anthony.yznaga@oracle.com> <7a318c3c-7ccb-4f95-a416-19d09f42c97f@kernel.org> <38fd3d86-f080-4b3a-a931-8ddae1a420ae@oracle.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 4/13/26 23:54, anthony.yznaga@oracle.com wrote: > > On 4/13/26 12:46 PM, David Hildenbrand (Arm) wrote: >>> It's correct though mlock2 would also work since it's been in glibc for >>> several years now. I just matched the existing tests. mlock2_ is a >>> simple wrapper around syscall in tools/testing/selftests/mm/mlock2.h, >>> and it was introduced when the mlock2 syscall was introduced. A trailing >>> rather than a preceding underscore is...unfortunate. >> Interesting ... and confusing :) >> >>> >>> The intent was to skip the tests if compiled with headers where >>> MAP_DROPPABLE isn't defined rather than force the value and get EINVAL >>> because the kernel doesn't know about it. This way EINVAL can be flagged >>> as a test failure and not skipped since it would likely indicate a test >>> or kernel bug. >> Note that the kernel headers you are compiling against don't imply >> anything about the kernel that is actually running! So the argument >> regarding EINVAL doesn't really hold. > > Yes, I see that now. > > >> >> But note that we, in general, try to compile against the in-tree headers. >> >> See >> >> commit 75d60eb30daafb966db0e45f38e4cdeb5e5ed79c >> Author: Lorenzo Stoakes >> Date:   Mon Oct 28 14:13:30 2024 +0000 >> >>      tools: testing: update tools UAPI header for mman-common.h >> >>      Import the new MADV_GUARD_INSTALL/REMOVE madvise flags. >> >> And looking into it, I already see MAP_DROPPABLE there as well, so is >> any special handling here even needed? >> > I'd say no special handling is needed. Right, so the #ifdef is not required at all. > If this test is compiled on with > a kernel that has MAP_DROPPABLE but run on an older kernel without > MAP_DROPPABLE, should it fail? Or should it interpret the EINVAL as a > sufficient reason to assume MAP_DROPPABLE is not supported and to skip > the result? My current thinking is it should fail because the EINVAL > could have another cause. Ah, you want to sense for MAP_DROPPABLE support in older kernels. I guess treating -EINVAL as "not supported on old kernel" is good enough. Looking at tools/testing/selftests/mm/droppable.c, we seem to not perform any such checks ... unfortunately. -- Cheers, David