Re: [PATCH v3 0/4] Implement IOCTL to get and clear soft dirty PTE

[Muhammad Usama Anjum]

On 10/18/22 3:48 PM, Greg KH wrote:
> On Tue, Oct 18, 2022 at 03:36:24PM +0500, Muhammad Usama Anjum wrote:
> > /**
> >   * struct pagemap_sd_args - Soft-dirty IOCTL argument
> >   * @start:		Starting address
> >   * @len:		Length of the region
> >   * @vec:		Output page_region struct array
> >   * @vec_len:		Length of the page_region struct array
> >   * @max_out_page:	Optional max output pages (It must be less than vec_len if
> > specified)
> >   * @flags:		Special flags for the IOCTL
> >   * @rmask:		Special flags for the IOCTL
> >   * @amask:		Special flags for the IOCTL
> >   * @emask:		Special flags for the IOCTL
>
> What do you mean exactly by "special flags"?
Sorry typo in the comments above. Optional flag can be specified in the 
flag. At the moment, there is only one flag(PAGEMAP_NO_REUSED_REGIONS).

/**
 * struct pagemap_sd_args - Soft-dirty IOCTL argument
 * @start:		Starting address
 * @len:		Length of the region
 * @vec:		Output page_region struct array
 * @vec_len:		Length of the page_region struct array
 * @max_out_page:	Optional max output pages (It must be less than 
vec_len if specified)
 * @flags:		Special flags for the IOCTL
 * @rmask:		Required mask - All of these bits have to be set
 * @amask:		Any mask - Any of these bits are set
 * @emask:		Exclude mask - None of these bits are set
 * @rmask:		Bits that have to be reported to the user in page_region
 */
struct pagemap_scan_args {
	__u64 __user start;
	__u64 len;
	__u64 __user vec;
	__u64 vec_len;
	__u32 max_out_page;
	__u32 flags;
	__u32 rmask;
	__u32 amask;
	__u32 emask;
	__u32 rmask;
};

> >   * @__reserved:		Reserved member to preserve data alignment. Must be 0.
> >   */
> > struct pagemap_sd_args {
> > 	__u64 __user start;
> > 	__u64 len;
> > 	__u64 __user vec; // page_region
>
> __user is a marking for a pointer, not a u64, right?  Now the fact that
> you treat it like a pointer later in the kernel is different, but that
> shouldn't be on the uapi header file.  You can put it in the kerneldoc,
> which you did not do.
I'll update.

> thanks,
>
> greg k-h