Re: [PATCH v4] fs/proc/page: Refactoring to reduce code duplication.

[Liu Ye <liuyerd@163.com>]

Friendly ping.

在 2025/3/18 14:32, Liu Ye 写道:
> 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>
>
> ---
> V4 : Update code remake patch.
> V3 : Add a stub for page_cgroup_ino and remove the #ifdef CONFIG_MEMCG.
> V2 : Use an enumeration to indicate the operation to be performed
> to avoid passing functions.
> ---
> ---
>  fs/proc/page.c             | 161 +++++++++++++------------------------
>  include/linux/memcontrol.h |   4 +
>  2 files changed, 58 insertions(+), 107 deletions(-)
>
> diff --git a/fs/proc/page.c b/fs/proc/page.c
> index 23fc771100ae..999af26c7298 100644
> --- a/fs/proc/page.c
> +++ b/fs/proc/page.c
> @@ -22,6 +22,12 @@
>  #define KPMMASK (KPMSIZE - 1)
>  #define KPMBITS (KPMSIZE * BITS_PER_BYTE)
>  
> +enum kpage_operation {
> +	KPAGE_FLAGS,
> +	KPAGE_COUNT,
> +	KPAGE_CGROUP,
> +};
> +
>  static inline unsigned long get_max_dump_pfn(void)
>  {
>  #ifdef CONFIG_SPARSEMEM
> @@ -37,19 +43,17 @@ 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 *page;
>  	unsigned long src = *ppos;
>  	unsigned long pfn;
>  	ssize_t ret = 0;
> +	u64 info;
>  
>  	pfn = src / KPMSIZE;
>  	if (src & KPMMASK || count & KPMMASK)
> @@ -59,24 +63,34 @@ 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) {
> -			struct folio *folio = page_folio(page);
>  
> -			if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT))
> -				mapcount = folio_precise_page_mapcount(folio, page);
> -			else
> -				mapcount = folio_average_page_mapcount(folio);
> -		}
> -
> -		if (put_user(mapcount, out)) {
> +		if (page) {
> +			switch (op) {
> +			case KPAGE_FLAGS:
> +				info = stable_page_flags(page);
> +				break;
> +			case KPAGE_COUNT:
> +				if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT))
> +					info = folio_precise_page_mapcount(page_folio(page), page);
> +				else
> +					info = folio_average_page_mapcount(page_folio(page));
> +				break;
> +			case KPAGE_CGROUP:
> +				info = page_cgroup_ino(page);
> +				break;
> +			default:
> +				info = 0;
> +				break;
> +			}
> +		} else
> +			info = 0;
> +
> +		if (put_user(info, out)) {
>  			ret = -EFAULT;
>  			break;
>  		}
> @@ -94,17 +108,23 @@ static ssize_t kpagecount_read(struct file *file, char __user *buf,
>  	return ret;
>  }
>  
> +/* /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)
> +{
> +	return kpage_read(file, buf, count, ppos, KPAGE_COUNT);
> +}
> +
>  static const struct proc_ops kpagecount_proc_ops = {
>  	.proc_flags	= PROC_ENTRY_PERMANENT,
>  	.proc_lseek	= mem_lseek,
>  	.proc_read	= kpagecount_read,
>  };
>  
> -/* /proc/kpageflags - an array exposing page flags
> - *
> - * Each entry is a u64 representing the corresponding
> - * physical page flags.
> - */
>  
>  static inline u64 kpf_copy_bit(u64 kflags, int ubit, int kbit)
>  {
> @@ -225,47 +245,17 @@ u64 stable_page_flags(const struct page *page)
>  #endif
>  
>  	return u;
> -};
> +}
>  
> +/* /proc/kpageflags - an array exposing page flags
> + *
> + * Each entry is a u64 representing the corresponding
> + * physical page flags.
> + */
>  static ssize_t kpageflags_read(struct file *file, char __user *buf,
> -			     size_t count, loff_t *ppos)
> +		size_t count, loff_t *ppos)
>  {
> -	const unsigned long max_dump_pfn = get_max_dump_pfn();
> -	u64 __user *out = (u64 __user *)buf;
> -	unsigned long src = *ppos;
> -	unsigned long pfn;
> -	ssize_t ret = 0;
> -
> -	pfn = src / KPMSIZE;
> -	if (src & KPMMASK || count & KPMMASK)
> -		return -EINVAL;
> -	if (src >= max_dump_pfn * KPMSIZE)
> -		return 0;
> -	count = min_t(unsigned long, count, (max_dump_pfn * KPMSIZE) - src);
> -
> -	while (count > 0) {
> -		/*
> -		 * TODO: ZONE_DEVICE support requires to identify
> -		 * memmaps that were actually initialized.
> -		 */
> -		struct page *page = pfn_to_online_page(pfn);
> -
> -		if (put_user(stable_page_flags(page), out)) {
> -			ret = -EFAULT;
> -			break;
> -		}
> -
> -		pfn++;
> -		out++;
> -		count -= KPMSIZE;
> -
> -		cond_resched();
> -	}
> -
> -	*ppos += (char __user *)out - buf;
> -	if (!ret)
> -		ret = (char __user *)out - buf;
> -	return ret;
> +	return kpage_read(file, buf, count, ppos, KPAGE_FLAGS);
>  }
>  
>  static const struct proc_ops kpageflags_proc_ops = {
> @@ -276,53 +266,10 @@ 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)
> +		size_t count, loff_t *ppos)
>  {
> -	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 ino;
> -
> -	pfn = src / KPMSIZE;
> -	if (src & KPMMASK || count & KPMMASK)
> -		return -EINVAL;
> -	if (src >= max_dump_pfn * KPMSIZE)
> -		return 0;
> -	count = min_t(unsigned long, count, (max_dump_pfn * KPMSIZE) - src);
> -
> -	while (count > 0) {
> -		/*
> -		 * TODO: ZONE_DEVICE support requires to identify
> -		 * memmaps that were actually initialized.
> -		 */
> -		ppage = pfn_to_online_page(pfn);
> -
> -		if (ppage)
> -			ino = page_cgroup_ino(ppage);
> -		else
> -			ino = 0;
> -
> -		if (put_user(ino, out)) {
> -			ret = -EFAULT;
> -			break;
> -		}
> -
> -		pfn++;
> -		out++;
> -		count -= KPMSIZE;
> -
> -		cond_resched();
> -	}
> -
> -	*ppos += (char __user *)out - buf;
> -	if (!ret)
> -		ret = (char __user *)out - buf;
> -	return ret;
> +	return kpage_read(file, buf, count, ppos, KPAGE_CGROUP);
>  }
> -
>  static const struct proc_ops kpagecgroup_proc_ops = {
>  	.proc_flags	= PROC_ENTRY_PERMANENT,
>  	.proc_lseek	= mem_lseek,
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 53364526d877..5264d148bdd9 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1793,6 +1793,10 @@ 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)