On 8/8/22 09:36, Kassey Li wrote:
> There is usage to dump a given cma region page_owner
> instead of all page's.
>
> This change allows to specify a ppos as start_pfn
> by fseek.
>
> Any invalid ppos will be skipped, so it did not
> broken the origin dump feature.
>
> Suggested-by: Vlastimil Babka (SUSE) <vbabka@xxxxxxxxxx>
Thanks, but please change it to Vlastimil Babka <vbabka@xxxxxxx>
It was some mistake between me and thunderbird that it was sent from @k.o.
> Signed-off-by: Kassey Li <quic_yingangl@xxxxxxxxxxx>
> ---
> mm/page_owner.c | 20 ++++++++++++++++++--
> 1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index e4c6f3f1695b..231b1877af99 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -497,8 +497,8 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
> return -EINVAL;
>
> page = NULL;
> - pfn = min_low_pfn + *ppos;
>
> + pfn = *ppos;
Maybe we could still optimize the typical case a bit such that when it's 0,
we skip to min_low_pfn immediately.
> /* 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 +561,7 @@ 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 +570,21 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
> return 0;
> }
>
> +static loff_t llseek_page_owner(struct file *file, loff_t offset, int whence)
> +{
> + loff_t retval = 0;
> + switch (whence) {
> + case SEEK_CUR:
It's not correct for SEEK_CUR to behave like this, no?
Can we perhaps reuse the existing mem_lseek() ?
Also we should update Documentation/mm/page_owner.rst to document the lseek
support and that it works with a pfn.
Thanks!
> + case SEEK_SET:
> + file->f_pos = offset;
> + break;
> + default:
> + retval = -ENXIO;
> + }
> +
> + return retval;
> +}
> +
> static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
> {
> unsigned long pfn = zone->zone_start_pfn;
> @@ -660,6 +675,7 @@ static void init_early_allocated_pages(void)
>
> static const struct file_operations proc_page_owner_operations = {
> .read = read_page_owner,
> + .llseek = llseek_page_owner,
> };
>
> static int __init pageowner_init(void)
