Re: [PATCH 6/9] PM / Hibernate: split snapshot_read_next

[Rafael J. Wysocki]

On Wednesday, June 02, 2010, Jiri Slaby wrote:
> When writing the snapshot, do the initialization and header write in
> a separate function. This makes the code more readable and lowers
> complexity of snapshot_read_next.

This one looks good, but it seems to depend on [3/9] and [4/9].  Does it?

> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxx>
> ---
>  kernel/power/power.h    |    2 +
>  kernel/power/snapshot.c |   65 ++++++++++++++++++++++++++++++----------------
>  kernel/power/swap.c     |   14 +++-------
>  3 files changed, 48 insertions(+), 33 deletions(-)
> 
> diff --git a/kernel/power/power.h b/kernel/power/power.h
> index 812b66c..ff3f63f 100644
> --- a/kernel/power/power.h
> +++ b/kernel/power/power.h
> @@ -171,6 +171,8 @@ struct hibernate_io_ops {
>  
>  extern unsigned int snapshot_additional_pages(struct zone *zone);
>  extern unsigned long snapshot_get_image_size(void);
> +extern int snapshot_write_init(struct hibernate_io_handle *io_handle,
> +		struct snapshot_handle *handle);
>  extern int snapshot_read_next(struct snapshot_handle *handle);
>  extern int snapshot_write_next(struct snapshot_handle *handle);
>  extern void snapshot_write_finalize(struct snapshot_handle *handle);
> diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
> index 25ce010..4600d15 100644
> --- a/kernel/power/snapshot.c
> +++ b/kernel/power/snapshot.c
> @@ -1598,10 +1598,46 @@ pack_pfns(unsigned long *buf, struct memory_bitmap *bm)
>  }
>  
>  /**
> + *	snapshot_write_init - initialization before writing the snapshot to
> + *	a backing storage
> + *
> + *	This function *must* be called before snapshot_read_next to initialize
> + *	@handle and write a header.
> + *
> + *	@io_handle: handle used when writing the initial info onto storage
> + *	@handle: snapshot handle to init
> + */
> +int snapshot_write_init(struct hibernate_io_handle *io_handle,
> +		struct snapshot_handle *handle)
> +{
> +	int ret;
> +
> +	/* This makes the buffer be freed by swsusp_free() */
> +	buffer = get_image_page(GFP_ATOMIC, PG_ANY);
> +	if (!buffer)
> +		return -ENOMEM;
> +	init_header(buffer);
> +	ret = hib_buffer_init_write(io_handle);
> +	if (ret)
> +		return ret;
> +	ret = hib_buffer_write(io_handle, buffer, sizeof(struct swsusp_info));
> +	if (ret)
> +		goto finish;
> +	hib_buffer_finish_write(io_handle);
> +	memory_bm_position_reset(&orig_bm);
> +	memory_bm_position_reset(&copy_bm);
> +	handle->buffer = buffer;
> +	return 0;
> +finish:
> +	hib_buffer_finish_write(io_handle);
> +	return ret;
> +}
> +
> +/**
>   *	snapshot_read_next - used for reading the system memory snapshot.
>   *
> - *	On the first call to it @handle should point to a zeroed
> - *	snapshot_handle structure.  The structure gets updated and a pointer
> + *	Before calling this function, snapshot_write_init has to be called with
> + *	handle passed as @handle here. The structure gets updated and a pointer
>   *	to it should be passed to this function every next time.
>   *
>   *	On success the function returns a positive number.  Then, the caller
> @@ -1613,31 +1649,12 @@ pack_pfns(unsigned long *buf, struct memory_bitmap *bm)
>   *	structure pointed to by @handle is not updated and should not be used
>   *	any more.
>   */
> -
>  int snapshot_read_next(struct snapshot_handle *handle)
>  {
> -	if (handle->cur > nr_meta_pages + nr_copy_pages)
> -		return 0;
> -
> -	if (!buffer) {
> -		/* This makes the buffer be freed by swsusp_free() */
> -		buffer = get_image_page(GFP_ATOMIC, PG_ANY);
> -		if (!buffer)
> -			return -ENOMEM;
> -	}
> -	if (!handle->cur) {
> -		int error;
> -
> -		error = init_header((struct swsusp_info *)buffer);
> -		if (error)
> -			return error;
> -		handle->buffer = buffer;
> -		memory_bm_position_reset(&orig_bm);
> -		memory_bm_position_reset(&copy_bm);
> -	} else if (handle->cur <= nr_meta_pages) {
> +	if (handle->cur < nr_meta_pages) {
>  		memset(buffer, 0, PAGE_SIZE);
>  		pack_pfns(buffer, &orig_bm);
> -	} else {
> +	} else if (handle->cur < nr_meta_pages + nr_copy_pages) {
>  		struct page *page;
>  
>  		page = pfn_to_page(memory_bm_next_pfn(&copy_bm));
> @@ -1655,6 +1672,8 @@ int snapshot_read_next(struct snapshot_handle *handle)
>  		} else {
>  			handle->buffer = page_address(page);
>  		}
> +	} else {
> +		return 0;
>  	}
>  	handle->cur++;
>  	return PAGE_SIZE;
> diff --git a/kernel/power/swap.c b/kernel/power/swap.c
> index f09494e..9b319f1 100644
> --- a/kernel/power/swap.c
> +++ b/kernel/power/swap.c
> @@ -448,7 +448,6 @@ int swsusp_write(unsigned int flags)
>  {
>  	struct hibernate_io_handle *io_handle;
>  	struct snapshot_handle snapshot;
> -	struct swsusp_info *header;
>  	unsigned long pages;
>  	int error;
>  
> @@ -464,17 +463,12 @@ int swsusp_write(unsigned int flags)
>  		goto out_finish;
>  	}
>  	memset(&snapshot, 0, sizeof(struct snapshot_handle));
> -	error = snapshot_read_next(&snapshot);
> -	if (error < PAGE_SIZE) {
> -		if (error >= 0)
> -			error = -EFAULT;
> -
> +	error = snapshot_write_init(io_handle, &snapshot);
> +	if (error) {
> +		printk(KERN_ERR "PM: Cannot init writer\n");
>  		goto out_finish;
>  	}
> -	header = (struct swsusp_info *)data_of(snapshot);
> -	error = hibernate_io_ops->write_page(io_handle, header, NULL);
> -	if (!error)
> -		error = save_image(io_handle, &snapshot, pages - 1);
> +	error = save_image(io_handle, &snapshot, pages - 1);
>  out_finish:
>  	error = hibernate_io_ops->writer_finish(io_handle, flags, error);
>  	return error;
> 

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