Commit 2f772e6c authored by Seth Jennings's avatar Seth Jennings Committed by Linus Torvalds
Browse files

mm: break up swap_writepage() for frontswap backends 



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.

__add_to_swap_cache() is also made non-static so that the page for which
writeback is to be resumed can be added to the swap cache.

Signed-off-by: default avatarSeth Jennings <sjenning@linux.vnet.ibm.com>
Signed-off-by: default avatarBob Liu <bob.liu@oracle.com>
Acked-by: default avatarMinchan Kim <minchan@kernel.org>
Reviewed-by: default avatarDan Magenheimer <dan.magenheimer@oracle.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e8420a8e

include/linux/swap.h

+2 −0
Original line number Diff line number Diff line
@@ -330,6 +330,7 @@ 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 int __swap_writepage(struct page *page, struct writeback_control *wbc);

extern int swap_set_page_dirty(struct page *page);

extern void end_swap_bio_read(struct bio *bio, int err);
@@ -345,6 +346,7 @@ extern unsigned long total_swapcache_pages(void); 
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);

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 *);

mm/page_io.c

+11 −3
Original line number Diff line number Diff line
@@ -185,9 +185,7 @@ bad_bmap: 
 */

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);
@@ -199,6 +197,16 @@ int swap_writepage(struct page *page, struct writeback_control *wbc) 
		end_page_writeback(page);

		goto out;

	}

	ret = __swap_writepage(page, wbc);

out:

	return ret;

}



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);



	if (sis->flags & SWP_FILE) {

		struct kiocb kiocb;

mm/swap_state.c

+1 −1
Original line number Diff line number Diff line
@@ -78,7 +78,7 @@ 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)

{

	int error;

	struct address_space *address_space;

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