Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755210Ab2FKObb (ORCPT ); Mon, 11 Jun 2012 10:31:31 -0400 Received: from mail-wg0-f44.google.com ([74.125.82.44]:50214 "EHLO mail-wg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754006Ab2FKOb3 convert rfc822-to-8bit (ORCPT ); Mon, 11 Jun 2012 10:31:29 -0400 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 X-Google-Sender-Auth: _xtnjzs0DYufReIVHA8fcI28cng Message-ID: Subject: Re: [PATCH v3 04/10] mm: frontswap: split out __frontswap_unuse_pages From: Konrad Rzeszutek Wilk To: Dan Magenheimer Cc: Sasha Levin , Minchan Kim , Konrad Wilk , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2647 Lines: 66 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 = swap_list.head; type >= 0; type = si->next) { >> > > + ? ? ? ? si = swap_info[type]; >> > > + ? ? ? ? si_frontswap_pages = atomic_read(&si->frontswap_pages); >> > > + ? ? ? ? if (total_pages_to_unuse < si_frontswap_pages) { >> > > + ? ? ? ? ? ? ? ? pages = pages_to_unuse = total_pages_to_unuse; >> > > + ? ? ? ? } else { >> > > + ? ? ? ? ? ? ? ? pages = si_frontswap_pages; >> > > + ? ? ? ? ? ? ? ? pages_to_unuse = 0; /* unuse all */ >> > > + ? ? ? ? } >> > > + ? ? ? ? /* ensure there is enough RAM to fetch pages from frontswap */ >> > > + ? ? ? ? if (security_vm_enough_memory_mm(current->mm, pages)) { >> > > + ? ? ? ? ? ? ? ? ret = -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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/