Date:	Thu, 24 Jun 2010 17:20:52 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	pavel@....cz, linux-pm@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, jirislaby@...il.com
Subject: Re: [PATCH 1/9] PM / Hibernate: swap, switch to hibernate_io_handle

On Wednesday, June 02, 2010, Jiri Slaby wrote:
> Hi,

Hi,

> I addressed the comments I got on the previous RFC.

Well, some of them. :-)

> I left the handles in place, the functions in hibernate_io_ops now works on
> them. Further I got rid of the memory barriers and minimized global variables
> as much as possible. Comments welcome.

One general comment first.  Can we just simply assume that the kernel won't
do _any_ transformations of image data in the case when s2disk is used?

I think that's going to simplify things quite a bit.

> --
> 
> Some code, which will be moved out of swap.c, will know nothing about
> swap. There will be also other than swap writers later, so that it
> won't make sense at all.
> 
> So introduce a new structure called hibernate_io_handle which
> currently contains only a pointer to private data, but is independent
> on I/O reader/writer actually used. Private data are swap_map_handle
> for now.
> 
> This structure is allocated in _start and freed in _finish. This will
> correspond to the later introduction of hibernate_io_ops where users
> will do handle=start->repeat{read/write(handle)}->finish(handle).
> I.e. they will operate on handle instead of global variables.

OK

This one looks good.

> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> Cc: "Rafael J. Wysocki" <rjw@...k.pl>
> ---
>  kernel/power/power.h |   24 ++++++++++
>  kernel/power/swap.c  |  114 +++++++++++++++++++++++++++++++------------------
>  2 files changed, 96 insertions(+), 42 deletions(-)
> 
> diff --git a/kernel/power/power.h b/kernel/power/power.h
> index 006270f..7427d54 100644
> --- a/kernel/power/power.h
> +++ b/kernel/power/power.h
> @@ -1,3 +1,4 @@
> +#include <linux/slab.h> /* kzalloc */
>  #include <linux/suspend.h>
>  #include <linux/suspend_ioctls.h>
>  #include <linux/utsname.h>
> @@ -115,6 +116,29 @@ struct snapshot_handle {
>   */
>  #define data_of(handle)	((handle).buffer)
>  
> +/**
> + * struct hibernate_io_handle - handle for image I/O processing
> + *
> + * @priv: private data for each processor (swap_map_handle etc.)
> + */
> +struct hibernate_io_handle {
> +	void *priv;
> +};
> +
> +/**
> + * hib_io_handle_alloc - allocate io handle with priv_size for private data
> + *
> + * @priv_size: the sie to allocate behind hibernate_io_handle for private use
> + */
> +static inline struct hibernate_io_handle *hib_io_handle_alloc(size_t priv_size)
> +{
> +	struct hibernate_io_handle *ret;
> +	ret = kzalloc(sizeof(*ret) + priv_size, GFP_KERNEL);
> +	if (ret)
> +		ret->priv = ret + 1;
> +	return ret;
> +}
> +
>  extern unsigned int snapshot_additional_pages(struct zone *zone);
>  extern unsigned long snapshot_get_image_size(void);
>  extern int snapshot_read_next(struct snapshot_handle *handle);
> diff --git a/kernel/power/swap.c b/kernel/power/swap.c
> index b0bb217..7096d20 100644
> --- a/kernel/power/swap.c
> +++ b/kernel/power/swap.c
> @@ -268,8 +268,10 @@ static void release_swap_writer(struct swap_map_handle *handle)
>  	handle->cur = NULL;
>  }
>  
> -static int get_swap_writer(struct swap_map_handle *handle)
> +static struct hibernate_io_handle *get_swap_writer(void)
>  {
> +	struct hibernate_io_handle *io_handle;
> +	struct swap_map_handle *handle;
>  	int ret;
>  
>  	ret = swsusp_swap_check();
> @@ -277,12 +279,18 @@ static int get_swap_writer(struct swap_map_handle *handle)
>  		if (ret != -ENOSPC)
>  			printk(KERN_ERR "PM: Cannot find swap device, try "
>  					"swapon -a.\n");
> -		return ret;
> +		return ERR_PTR(ret);
>  	}
> +	io_handle = hib_io_handle_alloc(sizeof(*handle));
> +	if (!io_handle) {
> +		ret = -ENOMEM;
> +		goto err_close;
> +	}
> +	handle = io_handle->priv;
>  	handle->cur = (struct swap_map_page *)get_zeroed_page(GFP_KERNEL);
>  	if (!handle->cur) {
>  		ret = -ENOMEM;
> -		goto err_close;
> +		goto err_free;
>  	}
>  	handle->cur_swap = alloc_swapdev_block(root_swap);
>  	if (!handle->cur_swap) {
> @@ -291,17 +299,20 @@ static int get_swap_writer(struct swap_map_handle *handle)
>  	}
>  	handle->k = 0;
>  	handle->first_sector = handle->cur_swap;
> -	return 0;
> +	return io_handle;
>  err_rel:
>  	release_swap_writer(handle);
>  err_close:
>  	swsusp_close(FMODE_WRITE);
> -	return ret;
> +err_free:
> +	kfree(io_handle);
> +	return ERR_PTR(ret);
>  }
>  
> -static int swap_write_page(struct swap_map_handle *handle, void *buf,
> -				struct bio **bio_chain)
> +static int swap_write_page(struct hibernate_io_handle *io_handle, void *buf,
> +		struct bio **bio_chain)
>  {
> +	struct swap_map_handle *handle = io_handle->priv;
>  	int error = 0;
>  	sector_t offset;
>  
> @@ -339,9 +350,11 @@ static int flush_swap_writer(struct swap_map_handle *handle)
>  		return -EINVAL;
>  }
>  
> -static int swap_writer_finish(struct swap_map_handle *handle,
> +static int swap_writer_finish(struct hibernate_io_handle *io_handle,
>  		unsigned int flags, int error)
>  {
> +	struct swap_map_handle *handle = io_handle->priv;
> +
>  	if (!error) {
>  		flush_swap_writer(handle);
>  		printk(KERN_INFO "PM: S");
> @@ -352,6 +365,7 @@ static int swap_writer_finish(struct swap_map_handle *handle,
>  	if (error)
>  		free_all_swap_pages(root_swap);
>  	release_swap_writer(handle);
> +	kfree(io_handle);
>  	swsusp_close(FMODE_WRITE);
>  
>  	return error;
> @@ -361,8 +375,8 @@ static int swap_writer_finish(struct swap_map_handle *handle,
>   *	save_image - save the suspend image data
>   */
>  
> -static int save_image(struct swap_map_handle *handle,
> -                      struct snapshot_handle *snapshot,
> +static int save_image(struct hibernate_io_handle *io_handle,
> +		      struct snapshot_handle *snapshot,
>                        unsigned int nr_to_write)
>  {
>  	unsigned int m;
> @@ -385,7 +399,7 @@ static int save_image(struct swap_map_handle *handle,
>  		ret = snapshot_read_next(snapshot);
>  		if (ret <= 0)
>  			break;
> -		ret = swap_write_page(handle, data_of(*snapshot), &bio);
> +		ret = swap_write_page(io_handle, data_of(*snapshot), &bio);
>  		if (ret)
>  			break;
>  		if (!(nr_pages % m))
> @@ -431,17 +445,17 @@ static int enough_swap(unsigned int nr_pages)
>  
>  int swsusp_write(unsigned int flags)
>  {
> -	struct swap_map_handle handle;
> +	struct hibernate_io_handle *io_handle;
>  	struct snapshot_handle snapshot;
>  	struct swsusp_info *header;
>  	unsigned long pages;
>  	int error;
>  
>  	pages = snapshot_get_image_size();
> -	error = get_swap_writer(&handle);
> -	if (error) {
> +	io_handle = get_swap_writer();
> +	if (IS_ERR(io_handle)) {
>  		printk(KERN_ERR "PM: Cannot get swap writer\n");
> -		return error;
> +		return PTR_ERR(io_handle);
>  	}
>  	if (!enough_swap(pages)) {
>  		printk(KERN_ERR "PM: Not enough free swap\n");
> @@ -457,11 +471,11 @@ int swsusp_write(unsigned int flags)
>  		goto out_finish;
>  	}
>  	header = (struct swsusp_info *)data_of(snapshot);
> -	error = swap_write_page(&handle, header, NULL);
> +	error = swap_write_page(io_handle, header, NULL);
>  	if (!error)
> -		error = save_image(&handle, &snapshot, pages - 1);
> +		error = save_image(io_handle, &snapshot, pages - 1);
>  out_finish:
> -	error = swap_writer_finish(&handle, flags, error);
> +	error = swap_writer_finish(io_handle, flags, error);
>  	return error;
>  }
>  
> @@ -477,32 +491,43 @@ static void release_swap_reader(struct swap_map_handle *handle)
>  	handle->cur = NULL;
>  }
>  
> -static int get_swap_reader(struct swap_map_handle *handle,
> -		unsigned int *flags_p)
> +static struct hibernate_io_handle *get_swap_reader(unsigned int *flags_p)
>  {
> +	struct hibernate_io_handle *io_handle;
> +	struct swap_map_handle *handle;
>  	int error;
>  
>  	*flags_p = swsusp_header->flags;
>  
>  	if (!swsusp_header->image) /* how can this happen? */
> -		return -EINVAL;
> +		return ERR_PTR(-EINVAL);
>  
> +	io_handle = hib_io_handle_alloc(sizeof(*handle));
> +	if (!io_handle)
> +		return ERR_PTR(-ENOMEM);
> +	handle = io_handle->priv;
>  	handle->cur = (struct swap_map_page *)get_zeroed_page(__GFP_WAIT | __GFP_HIGH);
> -	if (!handle->cur)
> -		return -ENOMEM;
> +	if (!handle->cur) {
> +		error = -ENOMEM;
> +		goto err_free;
> +	}
>  
>  	error = hib_bio_read_page(swsusp_header->image, handle->cur, NULL);
> -	if (error) {
> -		release_swap_reader(handle);
> -		return error;
> -	}
> +	if (error)
> +		goto err_rel;
>  	handle->k = 0;
> -	return 0;
> +	return io_handle;
> +err_rel:
> +	release_swap_reader(handle);
> +err_free:
> +	kfree(io_handle);
> +	return ERR_PTR(error);
>  }
>  
> -static int swap_read_page(struct swap_map_handle *handle, void *buf,
> -				struct bio **bio_chain)
> +static int swap_read_page(struct hibernate_io_handle *io_handle, void *buf,
> +		struct bio **bio_chain)
>  {
> +	struct swap_map_handle *handle = io_handle->priv;
>  	sector_t offset;
>  	int error;
>  
> @@ -526,22 +551,25 @@ static int swap_read_page(struct swap_map_handle *handle, void *buf,
>  	return error;
>  }
>  
> -static int swap_reader_finish(struct swap_map_handle *handle)
> +static int swap_reader_finish(struct hibernate_io_handle *io_handle)
>  {
> +	struct swap_map_handle *handle = io_handle->priv;
> +
>  	release_swap_reader(handle);
> +	kfree(io_handle);
>  
>  	return 0;
>  }
>  
>  /**
> - *	load_image - load the image using the swap map handle
> + *	load_image - load the image
>   *	@handle and the snapshot handle @snapshot
>   *	(assume there are @nr_pages pages to load)
>   */
>  
> -static int load_image(struct swap_map_handle *handle,
> -                      struct snapshot_handle *snapshot,
> -                      unsigned int nr_to_read)
> +static int load_image(struct hibernate_io_handle *io_handle,
> +		      struct snapshot_handle *snapshot,
> +		      unsigned int nr_to_read)
>  {
>  	unsigned int m;
>  	int error = 0;
> @@ -563,7 +591,7 @@ static int load_image(struct swap_map_handle *handle,
>  		error = snapshot_write_next(snapshot);
>  		if (error <= 0)
>  			break;
> -		error = swap_read_page(handle, data_of(*snapshot), &bio);
> +		error = swap_read_page(io_handle, data_of(*snapshot), &bio);
>  		if (error)
>  			break;
>  		if (snapshot->sync_read)
> @@ -598,7 +626,7 @@ static int load_image(struct swap_map_handle *handle,
>  int swsusp_read(unsigned int *flags_p)
>  {
>  	int error;
> -	struct swap_map_handle handle;
> +	struct hibernate_io_handle *io_handle;
>  	struct snapshot_handle snapshot;
>  	struct swsusp_info *header;
>  
> @@ -607,14 +635,16 @@ int swsusp_read(unsigned int *flags_p)
>  	if (error < PAGE_SIZE)
>  		return error < 0 ? error : -EFAULT;
>  	header = (struct swsusp_info *)data_of(snapshot);
> -	error = get_swap_reader(&handle, flags_p);
> -	if (error)
> +	io_handle = get_swap_reader(flags_p);
> +	if (IS_ERR(io_handle)) {
> +		error = PTR_ERR(io_handle);
>  		goto end;
> +	}
>  	if (!error)
> -		error = swap_read_page(&handle, header, NULL);
> +		error = swap_read_page(io_handle, header, NULL);
>  	if (!error)
> -		error = load_image(&handle, &snapshot, header->pages - 1);
> -	swap_reader_finish(&handle);
> +		error = load_image(io_handle, &snapshot, header->pages - 1);
> +	swap_reader_finish(io_handle);
>  end:
>  	if (!error)
>  		pr_debug("PM: Image successfully loaded\n");
> 

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