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.
>
>> 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 */
>>
>>
>>
>
>
--
Chen Gang
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