From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx101.postini.com [74.125.245.101]) by kanga.kvack.org (Postfix) with SMTP id 6DC2B6B0134 for ; Mon, 11 Jun 2012 10:31:30 -0400 (EDT) Received: by wibhn14 with SMTP id hn14so3521833wib.2 for ; Mon, 11 Jun 2012 07:31:28 -0700 (PDT) MIME-Version: 1.0 Reply-To: konrad@darnok.org In-Reply-To: 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> Date: Mon, 11 Jun 2012 10:31:28 -0400 Message-ID: Subject: Re: [PATCH v3 04/10] mm: frontswap: split out __frontswap_unuse_pages From: Konrad Rzeszutek Wilk Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Dan Magenheimer Cc: Sasha Levin , Minchan Kim , Konrad Wilk , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Mon, Jun 11, 2012 at 10:27 AM, Dan Magenheimer wrote: >> From: Sasha Levin [mailto:levinsasha928@gmail.com] >> Subject: Re: [PATCH v3 04/10] mm: frontswap: split out __frontswap_unuse= _pages >> >> > > + assert_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? >> >> 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. The kernel style is to do " 3) Separate your changes. Separate _logical changes_ into a single patch file. " So it is fine, but it should be in its own patch. > > 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. > >> > > + for (type =3D swap_list.head; type >=3D 0; type =3D si->next) { >> > > + =A0 =A0 =A0 =A0 si =3D swap_info[type]; >> > > + =A0 =A0 =A0 =A0 si_frontswap_pages =3D atomic_read(&si->frontswap_= pages); >> > > + =A0 =A0 =A0 =A0 if (total_pages_to_unuse < si_frontswap_pages) { >> > > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 pages =3D pages_to_unuse =3D total= _pages_to_unuse; >> > > + =A0 =A0 =A0 =A0 } else { >> > > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 pages =3D si_frontswap_pages; >> > > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 pages_to_unuse =3D 0; /* unuse all= */ >> > > + =A0 =A0 =A0 =A0 } >> > > + =A0 =A0 =A0 =A0 /* ensure there is enough RAM to fetch pages from = frontswap */ >> > > + =A0 =A0 =A0 =A0 if (security_vm_enough_memory_mm(current->mm, page= s)) { >> > > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ret =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, >> >> 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. Aye. -- 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