Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751936Ab3HTIOc (ORCPT ); Tue, 20 Aug 2013 04:14:32 -0400 Received: from mail-pa0-f45.google.com ([209.85.220.45]:52721 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751238Ab3HTIO3 (ORCPT ); Tue, 20 Aug 2013 04:14:29 -0400 Message-ID: <52132523.6040702@gmail.com> Date: Tue, 20 Aug 2013 16:13:23 +0800 From: Chen Gang F T User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: Chen Gang CC: Cyrill Gorcunov , Mel Gorman , kosaki.motohiro@jp.fujitsu.com, riel@redhat.com, hughd@google.com, xemul@parallels.com, rientjes@google.com, Wanpeng Li , Andrew Morton , linux-mm@kvack.org, "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 0/3] mm: mempolicy: the failure processing about mpol_to_str() References: <5212E8DF.5020209@asianux.com> <20130820053036.GB18673@moon> <52130194.4030903@asianux.com> <20130820064730.GD18673@moon> <52131F48.1030002@asianux.com> <52132011.60501@asianux.com> <52132432.3050308@asianux.com> In-Reply-To: <52132432.3050308@asianux.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5414 Lines: 155 On 08/20/2013 04:09 PM, Chen Gang wrote: > On 08/20/2013 03:51 PM, Chen Gang wrote: >> On 08/20/2013 03:48 PM, Chen Gang wrote: >>> On 08/20/2013 02:47 PM, Cyrill Gorcunov wrote: >>>> On Tue, Aug 20, 2013 at 01:41:40PM +0800, Chen Gang wrote: >>>>> >>>>>> sure you'll have to change shmem_show_mpol statement to return int code. >>>>>> Won't this be more short and convenient? >>>>>> >>>>>> >>>>> >>>>> Hmm... if return -ENOSPC, in common processing, it still need continue >>>>> (but need let outside know about the string truncation). >>>>> >>>>> So I still suggest to give more check for it. >>>> >>>> I still don't like adding additional code like >>>> >>>> + ret = mpol_to_str(buffer, sizeof(buffer), mpol); >>>> + if (ret < 0) >>>> + switch (ret) { >>>> + case -ENOSPC: >>>> + printk(KERN_WARNING >>>> + "in %s: string is truncated in mpol_to_str().\n", >>>> + __func__); >> >> Oh, that need 'break' in my original patch. :-) >> >>>> + default: >>>> + printk(KERN_ERR >>>> + "in %s: call mpol_to_str() fail, errcode: %d. buffer: %p, size: %zu, pol: %p\n", >>>> + __func__, ret, buffer, sizeof(buffer), mpol); >>>> + return; >>>> + } >>>> >>>> this code is pretty neat for debugging purpose I think but in most case (if >>>> only I've not missed something obvious) it simply won't be the case. >>>> >>> >>> For mpol_to_str(), it is for printing string, I suggest to fill buffer >>> as full as possible like another printing string functions, -ENOSPC is >>> not critical error, callers may can bear it, and still want to continue. >>> >>> For 2 callers, I still suggest to process '-ENOSPC' and continue, it is >>> really not a critical error, they can continue. >>> >>> For the 'default' error processing: >>> >>> I still suggest to 'printk' in shmem_show_mpol(), because when failure occurs, it has no return value to mark the failure to upper caller. >>> Hmm... but for show_numa_map(), may remove the 'printk', only return the error code is OK. :-) >>> >>> >>> Thanks. >>> > > Oh, for '-ENOSPC', it means critical error, it is my fault. > > So, for simplify thinking and implementation, use your patch below is OK > to me (but I suggest to print error information in the none return value > function). > > :-) > >>>> Won't somthing like below do the same but with smaller code change? >>>> Note I've not even compiled it but it shows the idea. >>>> --- >>>> fs/proc/task_mmu.c | 4 +++- >>>> mm/shmem.c | 17 +++++++++-------- >>>> 2 files changed, 12 insertions(+), 9 deletions(-) >>>> >>>> Index: linux-2.6.git/fs/proc/task_mmu.c >>>> =================================================================== >>>> --- linux-2.6.git.orig/fs/proc/task_mmu.c >>>> +++ linux-2.6.git/fs/proc/task_mmu.c >>>> @@ -1402,8 +1402,10 @@ static int show_numa_map(struct seq_file >>>> walk.mm = mm; >>>> >>>> pol = get_vma_policy(task, vma, vma->vm_start); >>>> - mpol_to_str(buffer, sizeof(buffer), pol); >>>> + n = mpol_to_str(buffer, sizeof(buffer), pol); >>>> mpol_cond_put(pol); >>>> + if (n < 0) >>>> + return n; >>>> >>>> seq_printf(m, "%08lx %s", vma->vm_start, buffer); >>>> >>>> Index: linux-2.6.git/mm/shmem.c >>>> =================================================================== >>>> --- linux-2.6.git.orig/mm/shmem.c >>>> +++ linux-2.6.git/mm/shmem.c >>>> @@ -883,16 +883,20 @@ redirty: >>>> >>>> #ifdef CONFIG_NUMA >>>> #ifdef CONFIG_TMPFS >>>> -static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol) >>>> +static int shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol) >>>> { >>>> char buffer[64]; >>>> + int ret; >>>> >>>> if (!mpol || mpol->mode == MPOL_DEFAULT) >>>> - return; /* show nothing */ >>>> + return 0; /* show nothing */ >>>> >>>> - mpol_to_str(buffer, sizeof(buffer), mpol); >>>> + ret = mpol_to_str(buffer, sizeof(buffer), mpol); >>>> + if (ret < 0) >>>> + return ret; >>>> >>>> seq_printf(seq, ",mpol=%s", buffer); >>>> + return 0; >>>> } >>>> >>>> static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo) >>>> @@ -951,9 +955,7 @@ static struct page *shmem_alloc_page(gfp >>>> } >>>> #else /* !CONFIG_NUMA */ >>>> #ifdef CONFIG_TMPFS >>>> -static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol) >>>> -{ >>>> -} >>>> +static inline int shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol) { return 0; } >>>> #endif /* CONFIG_TMPFS */ >>>> >>>> static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp, >>>> @@ -2577,8 +2579,7 @@ static int shmem_show_options(struct seq >>>> if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID)) >>>> seq_printf(seq, ",gid=%u", >>>> from_kgid_munged(&init_user_ns, sbinfo->gid)); >>>> - shmem_show_mpol(seq, sbinfo->mpol); >>>> - return 0; >>>> + return shmem_show_mpol(seq, sbinfo->mpol); >>>> } >>>> #endif /* CONFIG_TMPFS */ >>>> >>>> >>>> Oh, you have done, sorry. >>> >>> >> >> > > -- Chen Gang -- 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/