From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx107.postini.com [74.125.245.107]) by kanga.kvack.org (Postfix) with SMTP id 7F4156B0132 for ; Mon, 11 Jun 2012 10:28:15 -0400 (EDT) MIME-Version: 1.0 Message-ID: Date: Mon, 11 Jun 2012 07:27:56 -0700 (PDT) From: Dan Magenheimer Subject: RE: [PATCH v3 04/10] mm: frontswap: split out __frontswap_unuse_pages References: <1339325468-30614-1-git-send-email-levinsasha928@gmail.com> <1339325468-30614-5-git-send-email-levinsasha928@gmail.com> <4FD5856C.5060708@kernel.org> <1339410650.4999.38.camel@lappy> In-Reply-To: <1339410650.4999.38.camel@lappy> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Sasha Levin , Minchan Kim Cc: Konrad Wilk , linux-mm@kvack.org, linux-kernel@vger.kernel.org > From: Sasha Levin [mailto:levinsasha928@gmail.com] > Subject: Re: [PATCH v3 04/10] mm: frontswap: split out __frontswap_unuse_= pages >=20 > > > +=09assert_spin_locked(&swap_lock); > > > > Normally, we should use this assertion when we can't find swap_lock is = hold or not easily > > by complicated call depth or unexpected use-case like general function. > > But I expect this function's caller is very limited, not complicated. > > Just comment write down isn't enough? >=20 > Is there a reason not to do it though? Debugging a case where this > function is called without a swaplock and causes corruption won't be > easy. I'm not sure of the correct kernel style but I like the fact that assert_spin_locked both documents the lock requirement and tests it at runtime. I don't know the correct kernel syntax but is it possible to make this code be functional when the kernel "debug" option is on, but a no-op when "debug" is disabled? IMHO, that would be the ideal solution. =20 > > > +=09for (type =3D swap_list.head; type >=3D 0; type =3D si->next) { > > > +=09=09si =3D swap_info[type]; > > > +=09=09si_frontswap_pages =3D atomic_read(&si->frontswap_pages); > > > +=09=09if (total_pages_to_unuse < si_frontswap_pages) { > > > +=09=09=09pages =3D pages_to_unuse =3D total_pages_to_unuse; > > > +=09=09} else { > > > +=09=09=09pages =3D si_frontswap_pages; > > > +=09=09=09pages_to_unuse =3D 0; /* unuse all */ > > > +=09=09} > > > +=09=09/* ensure there is enough RAM to fetch pages from frontswap */ > > > +=09=09if (security_vm_enough_memory_mm(current->mm, pages)) { > > > +=09=09=09ret =3D -ENOMEM; > > > > > > Nipick: > > I am not sure detailed error returning would be good. > > Caller doesn't matter it now but it can consider it in future. > > Hmm, >=20 > Is there a reason to avoid returning a meaningful error when it's pretty > easy? I'm certainly not an expert on kernel style (as this whole series of patches demonstrates :-) but I think setting a meaningful error code is useful documentation and plans for future users that might use the error code. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org