From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f51.google.com (mail-pa0-f51.google.com [209.85.220.51]) by kanga.kvack.org (Postfix) with ESMTP id 1FDE06B0005 for ; Wed, 24 Feb 2016 20:07:32 -0500 (EST) Received: by mail-pa0-f51.google.com with SMTP id yy13so22108875pab.3 for ; Wed, 24 Feb 2016 17:07:32 -0800 (PST) Received: from mail-pf0-x234.google.com (mail-pf0-x234.google.com. [2607:f8b0:400e:c00::234]) by mx.google.com with ESMTPS id lf12si8411683pab.207.2016.02.24.17.07.31 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Feb 2016 17:07:31 -0800 (PST) Received: by mail-pf0-x234.google.com with SMTP id e127so22638955pfe.3 for ; Wed, 24 Feb 2016 17:07:31 -0800 (PST) Message-ID: <1456362446.22049.20.camel@gmail.com> Subject: Re: [PATCH] mm, memory hotplug: print more failure information for online_pages From: Chen Yucong Date: Thu, 25 Feb 2016 09:07:26 +0800 In-Reply-To: References: <1456300925-20415-1-git-send-email-slaoub@gmail.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: akpm@linux-foundation.org, vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Wed, 2016-02-24 at 13:33 -0800, David Rientjes wrote: > On Wed, 24 Feb 2016, Chen Yucong wrote: > > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > > index c832ef3..e4b6dec3 100644 > > --- a/mm/memory_hotplug.c > > +++ b/mm/memory_hotplug.c > > @@ -1059,10 +1059,9 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ > > > > ret = memory_notify(MEM_GOING_ONLINE, &arg); > > ret = notifier_to_errno(ret); > > - if (ret) { > > - memory_notify(MEM_CANCEL_ONLINE, &arg); > > - return ret; > > - } > > + if (ret) > > + goto failed_addition; > > + > > /* > > * If this zone is not populated, then it is not in zonelist. > > * This means the page allocator ignores this zone. > > @@ -1080,12 +1079,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ > > if (need_zonelists_rebuild) > > zone_pcp_reset(zone); > > mutex_unlock(&zonelists_mutex); > > - printk(KERN_DEBUG "online_pages [mem %#010llx-%#010llx] failed\n", > > - (unsigned long long) pfn << PAGE_SHIFT, > > - (((unsigned long long) pfn + nr_pages) > > - << PAGE_SHIFT) - 1); > > - memory_notify(MEM_CANCEL_ONLINE, &arg); > > - return ret; > > + goto failed_addition; > > } > > > > zone->present_pages += onlined_pages; > > @@ -1118,6 +1112,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ > > if (onlined_pages) > > memory_notify(MEM_ONLINE, &arg); > > return 0; > > + > > +failed_addition: > > + pr_info("online_pages [mem %#010llx-%#010llx] failed\n", > > + (unsigned long long) pfn << PAGE_SHIFT, > > + (((unsigned long long) pfn + nr_pages) << PAGE_SHIFT) - 1); > > + memory_notify(MEM_CANCEL_ONLINE, &arg); > > + return ret; > > } > > #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */ > > > > Please explain how the conversion from KERN_DEBUG to KERN_INFO level is > better? Like __offline_pages(), printk() in online_pages() is used for reporting an failed addition rather than debug information. Another reason is that pr_debug() is not an exact equivalent of printk(KERN_DEBUG ...) /* If you are writing a driver, please use dev_dbg instead */ #if defined(CONFIG_DYNAMIC_DEBUG) /* dynamic_pr_debug() uses pr_fmt() internally so we don't need it here */ #define pr_debug(fmt, ...) \ dynamic_pr_debug(fmt, ##__VA_ARGS__) #elif defined(DEBUG) #define pr_debug(fmt, ...) \ printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) #else #define pr_debug(fmt, ...) \ no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) #endif > If the onlining returns an error value, which it will, why do we need to > leave an artifact behind in the kernel log that it failed? In __offline_pages(), we can find the following snippet: ... ret = memory_notify(MEM_GOING_OFFLINE, &arg); ret = notifier_to_errno(ret); if (ret) goto failed_removal; ... offlined_pages = check_pages_isolated(start_pfn, end_pfn); if (offlined_pages < 0) { ret = -EBUSY; goto failed_removal; } ... failed_removal: printk(KERN_INFO "memory offlining [mem %#010llx-%#010llx] ... Similarly, there's no single cause for failed online_pages operation. So if memory_notify(MEM_GOING_ONLINE, &arg) returns an error value, the result of online_pages is also ""online_pages [mem %#010llx-% #010llx] failed\n". thx! cyc -- 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