Re: [RFC 12/15] PM / Hibernate: split snapshot_read_next

Rafael J. Wysocki
2010-03-25T22:44:39Z

On Tuesday 23 March 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.

Good idea overall, but ->

> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
> Cc: Nigel Cunningham <ncunningham@crca.org.au>
> Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
> ---
> kernel/power/power.h | 1 +
> kernel/power/snapshot.c | 63 +++++++++++++++++++++++++++++-----------------
> kernel/power/swap.c | 14 +++-------
> 3 files changed, 45 insertions(+), 33 deletions(-)
>
> diff --git a/kernel/power/power.h b/kernel/power/power.h
> index 50a888a..638a97c 100644
> --- a/kernel/power/power.h
> +++ b/kernel/power/power.h
> @@ -130,6 +130,7 @@ struct sws_module_ops {
>
> extern unsigned int snapshot_additional_pages(struct zone *zone);
> extern unsigned long snapshot_get_image_size(void);
> +extern int snapshot_write_init(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 7918351..c8864de 100644
> --- a/kernel/power/snapshot.c
> +++ b/kernel/power/snapshot.c
> @@ -1597,10 +1597,44 @@ 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.
> + *
> + * @handle: snapshot handle to init
> + */
> +int snapshot_write_init(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 = sws_rw_buffer_init(1);

-> That's hardly readable. You could define something like
HIBERNATE_WRITING and HIBERNATE_READING and pass one of them instead of the '1'.
Or something.

Likewise in a few places below.

[Or even better IMO, define hibernate_write_buffer_init() and
hibernate_read_buffer_init() etc.]

> + if (ret)
> + return ret;
> + ret = sws_rw_buffer(1, buffer, sizeof(struct swsusp_info));
> + if (ret)
> + goto finish;
> + sws_rw_buffer_finish(1);
> + memory_bm_position_reset(&orig_bm);
> + memory_bm_position_reset(&copy_bm);
> + handle->buffer = buffer;
> + return 0;
> +finish:
> + sws_rw_buffer_finish(1);
> + 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

Rafael