On 8/18/22 04:24, Kassey Li wrote:
> It is too slow to dump all the pages, in some usage we just want dump
> a given start pfn, for example: CMA range or a single page.
>
> To speed up and save time, this change allows specify start pfn
> by add llseek for page_onwer.
>
> Suggested-by: Vlastimil Babka <vbabka@xxxxxxx>
> Signed-off-by: Kassey Li <quic_yingangl@xxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> Documentation/mm/page_owner.rst | 5 +++++
> mm/page_owner.c | 24 +++++++++++++++++++++---
> 2 files changed, 26 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/mm/page_owner.rst b/Documentation/mm/page_owner.rst
> index f5c954afe97c..f18fd8907049 100644
> --- a/Documentation/mm/page_owner.rst
> +++ b/Documentation/mm/page_owner.rst
> @@ -94,6 +94,11 @@ Usage
> Page allocated via order XXX, ...
> PFN XXX ...
> // Detailed stack
> + By default, it will do full pfn dump, to start with a given pfn,
> + page_owner supports fseek.
> +
> + FILE *fp = fopen("/sys/kernel/debug/page_owner", "r");
> + fseek(fp, pfn_start, SEEK_SET);
>
> The ``page_owner_sort`` tool ignores ``PFN`` rows, puts the remaining rows
> in buf, uses regexp to extract the page order value, counts the times
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index e4c6f3f1695b..25720d81bc26 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -497,8 +497,10 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
> return -EINVAL;
>
> page = NULL;
> - pfn = min_low_pfn + *ppos;
> -
> + if (*ppos == 0)
> + pfn = min_low_pfn;
> + else
> + pfn = *ppos;
> /* Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area */
> while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0)
> pfn++;
> @@ -561,7 +563,7 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
> continue;
>
> /* Record the next PFN to read in the file offset */
> - *ppos = (pfn - min_low_pfn) + 1;
> + *ppos = pfn + 1;
>
> return print_page_owner(buf, count, pfn, page,
> page_owner, handle);
> @@ -570,6 +572,21 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
> return 0;
> }
>
> +static loff_t lseek_page_owner(struct file *file, loff_t offset, int orig)
> +{
> + switch (orig) {
> + case SEEK_SET:
> + file->f_pos = offset;
> + break;
> + case SEEK_CUR:
> + file->f_pos += offset;
> + break;
> + default:
> + return -EINVAL;
> + }
> + return file->f_pos;
> +}
> +
> static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
> {
> unsigned long pfn = zone->zone_start_pfn;
> @@ -660,6 +677,7 @@ static void init_early_allocated_pages(void)
>
> static const struct file_operations proc_page_owner_operations = {
> .read = read_page_owner,
> + .llseek = lseek_page_owner,
> };
>
> static int __init pageowner_init(void)
