On Mon, Jan 07, 2013 at 02:24:38PM -0600, Seth Jennings wrote:
> swap_writepage() is currently where frontswap hooks into the swap
> write path to capture pages with the frontswap_store() function.
> However, if a frontswap backend wants to "resume" the writeback of
> a page to the swap device, it can't call swap_writepage() as
> the page will simply reenter the backend.
>
> This patch separates swap_writepage() into a top and bottom half, the
> bottom half named __swap_writepage() to allow a frontswap backend,
> like zswap, to resume writeback beyond the frontswap_store() hook and
> by notified when the writeback completes.
>
> Signed-off-by: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx>
Looks good to me except few nitpicks.
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
> ---
> include/linux/swap.h | 4 ++++
> mm/page_io.c | 22 +++++++++++++++++-----
> mm/swap_state.c | 2 +-
> 3 files changed, 22 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 8c66486..a3da829 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -321,6 +321,9 @@ static inline void mem_cgroup_uncharge_swap(swp_entry_t ent)
> /* linux/mm/page_io.c */
> extern int swap_readpage(struct page *);
> extern int swap_writepage(struct page *page, struct writeback_control *wbc);
> +extern void end_swap_bio_write(struct bio *bio, int err);
> +extern int __swap_writepage(struct page *page, struct writeback_control *wbc,
> + void (*end_write_func)(struct bio *, int));
> extern int swap_set_page_dirty(struct page *page);
> extern void end_swap_bio_read(struct bio *bio, int err);
>
> @@ -335,6 +338,7 @@ extern struct address_space swapper_space;
> extern void show_swap_cache_info(void);
> extern int add_to_swap(struct page *);
> extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);
> +extern int __add_to_swap_cache(struct page *page, swp_entry_t entry);
What's related __add_to_swap_cache with this patch?
> extern void __delete_from_swap_cache(struct page *);
> extern void delete_from_swap_cache(struct page *);
> extern void free_page_and_swap_cache(struct page *);
> diff --git a/mm/page_io.c b/mm/page_io.c
> index c535d39..806085e 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -43,7 +43,7 @@ static struct bio *get_swap_bio(gfp_t gfp_flags,
> return bio;
> }
>
> -static void end_swap_bio_write(struct bio *bio, int err)
> +void end_swap_bio_write(struct bio *bio, int err)
Why do you remove static in this patch? It's not related to the patch.
> {
> const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
> struct page *page = bio->bi_io_vec[0].bv_page;
> @@ -180,15 +180,16 @@ bad_bmap:
> goto out;
> }
>
> +int __swap_writepage(struct page *page, struct writeback_control *wbc,
> + void (*end_write_func)(struct bio *, int));
> +
> /*
> * We may have stale swap cache pages in memory: notice
> * them here and get rid of the unnecessary final write.
> */
> int swap_writepage(struct page *page, struct writeback_control *wbc)
> {
> - struct bio *bio;
> - int ret = 0, rw = WRITE;
> - struct swap_info_struct *sis = page_swap_info(page);
> + int ret = 0;
>
> if (try_to_free_swap(page)) {
> unlock_page(page);
> @@ -200,6 +201,17 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
> end_page_writeback(page);
> goto out;
> }
> + ret = __swap_writepage(page, wbc, end_swap_bio_write);
> +out:
> + return ret;
> +}
> +
> +int __swap_writepage(struct page *page, struct writeback_control *wbc,
> + void (*end_write_func)(struct bio *, int))
> +{
> + struct bio *bio;
> + int ret = 0, rw = WRITE;
> + struct swap_info_struct *sis = page_swap_info(page);
>
> if (sis->flags & SWP_FILE) {
> struct kiocb kiocb;
> @@ -227,7 +239,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
> return ret;
> }
>
> - bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
> + bio = get_swap_bio(GFP_NOIO, page, end_write_func);
> if (bio == NULL) {
> set_page_dirty(page);
> unlock_page(page);
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 0cb36fb..7eded9c 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -67,7 +67,7 @@ void show_swap_cache_info(void)
> * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
> * but sets SwapCache flag and private instead of mapping and index.
> */
> -static int __add_to_swap_cache(struct page *page, swp_entry_t entry)
> +int __add_to_swap_cache(struct page *page, swp_entry_t entry)
Ditto
> {
> int error;
>
> --
> 1.7.9.5
>
> --
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--
Kind regards,
Minchan Kim
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