Re: [PATCH v2] fs/proc/page: Refactoring to reduce code duplication.

[Liu Ye <liuyerd@163.com>]

在 2025/3/17 18:24, David Hildenbrand 写道:
> On 17.03.25 11:07, Liu Ye wrote:
>> From: Liu Ye <liuye@kylinos.cn>
>>
>> The function kpageflags_read and kpagecgroup_read is quite similar
>> to kpagecount_read. Consider refactoring common code into a helper
>> function to reduce code duplication.
>>
>> Signed-off-by: Liu Ye <liuye@kylinos.cn>
>>
>> ---
>> V2 : Use an enumeration to indicate the operation to be performed
>> to avoid passing functions.
>> ---
>> ---
>>   fs/proc/page.c | 166 +++++++++++++++++--------------------------------
>>   1 file changed, 58 insertions(+), 108 deletions(-)
>>
>> diff --git a/fs/proc/page.c b/fs/proc/page.c
>> index a55f5acefa97..66f454330a87 100644
>> --- a/fs/proc/page.c
>> +++ b/fs/proc/page.c
>> @@ -22,6 +22,14 @@
>>   #define KPMMASK (KPMSIZE - 1)
>>   #define KPMBITS (KPMSIZE * BITS_PER_BYTE)
>>   +enum kpage_operation {
>> +    KPAGE_FLAGS,
>> +    KPAGE_COUNT,
>> +#ifdef CONFIG_MEMCG
>> +    KPAGE_CGROUP,
>> +#endif
>> +};
>> +
>>   static inline unsigned long get_max_dump_pfn(void)
>>   {
>>   #ifdef CONFIG_SPARSEMEM
>> @@ -37,19 +45,17 @@ static inline unsigned long get_max_dump_pfn(void)
>>   #endif
>>   }
>>   -/* /proc/kpagecount - an array exposing page mapcounts
>> - *
>> - * Each entry is a u64 representing the corresponding
>> - * physical page mapcount.
>> - */
>> -static ssize_t kpagecount_read(struct file *file, char __user *buf,
>> -                 size_t count, loff_t *ppos)
>> +static ssize_t kpage_read(struct file *file, char __user *buf,
>> +        size_t count, loff_t *ppos,
>> +        enum kpage_operation op)
>>   {
>>       const unsigned long max_dump_pfn = get_max_dump_pfn();
>>       u64 __user *out = (u64 __user *)buf;
>> +    struct page *ppage;
>>       unsigned long src = *ppos;
>>       unsigned long pfn;
>>       ssize_t ret = 0;
>> +    u64 info;
>>         pfn = src / KPMSIZE;
>>       if (src & KPMMASK || count & KPMMASK)
>> @@ -59,19 +65,29 @@ static ssize_t kpagecount_read(struct file *file, char __user *buf,
>>       count = min_t(unsigned long, count, (max_dump_pfn * KPMSIZE) - src);
>>         while (count > 0) {
>> -        struct page *page;
>> -        u64 mapcount = 0;
>> -
>> -        /*
>> -         * TODO: ZONE_DEVICE support requires to identify
>> -         * memmaps that were actually initialized.
>> -         */
>> -        page = pfn_to_online_page(pfn);
>> -        if (page)
>> -            mapcount = folio_precise_page_mapcount(page_folio(page),
>> -                                   page);
>> -
>> -        if (put_user(mapcount, out)) {
>> +        ppage = pfn_to_online_page(pfn);
>> +
>> +        if (ppage) {
>> +            switch (op) {
>> +            case KPAGE_FLAGS:
>> +                info = stable_page_flags(ppage);
>> +                break;
>> +            case KPAGE_COUNT:
>> +                info = folio_precise_page_mapcount(page_folio(ppage), ppage);
>> +                break;
>> +#ifdef CONFIG_MEMCG
>> +            case KPAGE_CGROUP:
>> +                info = page_cgroup_ino(ppage);
>> +                break;
>> +#endif
>
> In general, LGTM.
>
> I do wonder if we should just get rid of the two "#ifdef CONFIG_MEMCG" by adding
> a stub for page_cgroup_ino().
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 57664e2a8fb7b..24248f4dcc971 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1788,6 +1788,11 @@ static inline void count_objcg_events(struct obj_cgroup *objcg,
>  {
>  }
>  
> +static inline ino_t page_cgroup_ino(struct page *page)
> +{
> +       return 0;
> +}
> +
>  #endif /* CONFIG_MEMCG */
>  
>  #if defined(CONFIG_MEMCG) && defined(CONFIG_ZSWAP)
>
>
Agreed. I’ll add a stub for page_cgroup_ino() and remove the #ifdef CONFIG_MEMCG.

like this.

diff --git a/fs/proc/page.c b/fs/proc/page.c
index 66f454330a87..cbadbf9568a1 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -25,9 +25,7 @@
 enum kpage_operation {
        KPAGE_FLAGS,
        KPAGE_COUNT,
-#ifdef CONFIG_MEMCG
        KPAGE_CGROUP,
-#endif
 };
 
 static inline unsigned long get_max_dump_pfn(void)
@@ -75,11 +73,9 @@ static ssize_t kpage_read(struct file *file, char __user *buf,
                        case KPAGE_COUNT:
                                info = folio_precise_page_mapcount(page_folio(ppage), ppage);
                                break;
-#ifdef CONFIG_MEMCG
                        case KPAGE_CGROUP:
                                info = page_cgroup_ino(ppage);
                                break;
-#endif
                        default:
                                info = 0;
                                break;
@@ -262,7 +258,6 @@ static const struct proc_ops kpageflags_proc_ops = {
 };
 
 #ifdef CONFIG_MEMCG
-
 static ssize_t kpagecgroup_read(struct file *file, char __user *buf,
                size_t count, loff_t *ppos)
 {
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 6e74b8254d9b..e806e2ebf5b8 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1794,6 +1794,10 @@ static inline void count_objcg_events(struct obj_cgroup *objcg,
 {
 }
 
+static inline ino_t page_cgroup_ino(struct page *page)
+{
+       return 0;
+}
 #endif /* CONFIG_MEMCG */
 
 #if defined(CONFIG_MEMCG) && defined(CONFIG_ZSWAP)