Hi,
On Thu, Feb 02, 2023 at 04:29:12PM +0500, Muhammad Usama Anjum wrote:
> This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear
> the info about page table entries. The following operations are supported
> in this ioctl:
> - Get the information if the pages have been written-to (PAGE_IS_WRITTEN),
> file mapped (PAGE_IS_FILE), present (PAGE_IS_PRESENT) or swapped
> (PAGE_IS_SWAPPED).
> - Write-protect the pages (PAGEMAP_WP_ENGAGE) to start finding which
> pages have been written-to.
> - Find pages which have been written-to and write protect the pages
> (atomic PAGE_IS_WRITTEN + PAGEMAP_WP_ENGAGE)
>
> +/*
> + * struct pagemap_scan_arg - Pagemap ioctl argument
> + * @start: Starting address of the region
> + * @len: Length of the region (All the pages in this length are included)
> + * @vec: Address of page_region struct array for output
> + * @vec_len: Length of the page_region struct array
> + * @max_pages: Optional max return pages
> + * @flags: Flags for the IOCTL
> + * @required_mask: Required mask - All of these bits have to be set in the PTE
> + * @anyof_mask: Any mask - Any of these bits are set in the PTE
> + * @excluded_mask: Exclude mask - None of these bits are set in the PTE
> + * @return_mask: Bits that are to be reported in page_region
> + */
> +struct pagemap_scan_arg {
> + __u64 start;
> + __u64 len;
> + __u64 vec;
> + __u64 vec_len;
> + __u32 max_pages;
> + __u32 flags;
> + __u64 required_mask;
> + __u64 anyof_mask;
> + __u64 excluded_mask;
> + __u64 return_mask;
> +};
After Nadav's comment I've realized I missed the API part :)
A few quick notes for now:
* The arg struct is fixed, so it would be impossible to extend the API
later. Following the clone3() example, I'd add 'size' field to the
pagemam_scan_arg so that it would be possible to add new fields afterwards.
* Please make flags __u64, just in case
* Put size and flags at the beginning of the struct, e.g.
strucr pagemap_scan_arg {
size_t size;
__u64 flags;
/* all the rest */
};
> +
> +/* Special flags */
> +#define PAGEMAP_WP_ENGAGE (1 << 0)
> +
> #endif /* _UAPI_LINUX_FS_H */
> --
> 2.30.2
>
--
Sincerely yours,
Mike.
