The patch titled
Subject: mm: break up swap_writepage() for frontswap backends
has been added to the -mm tree. Its filename is
mm-break-up-swap_writepage-for-frontswap-backends.patch
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------------------------------------------------------
From: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx>
Subject: 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: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Bob Liu <bob.liu@xxxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
Reviewed-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/swap.h | 2 ++
mm/page_io.c | 14 +++++++++++---
mm/swap_state.c | 2 +-
3 files changed, 14 insertions(+), 4 deletions(-)
diff -puN include/linux/swap.h~mm-break-up-swap_writepage-for-frontswap-backends include/linux/swap.h
--- a/include/linux/swap.h~mm-break-up-swap_writepage-for-frontswap-backends
+++ a/include/linux/swap.h
@@ -330,6 +330,7 @@ static inline void mem_cgroup_uncharge_s
/* 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_pag
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 *);
diff -puN mm/page_io.c~mm-break-up-swap_writepage-for-frontswap-backends mm/page_io.c
--- a/mm/page_io.c~mm-break-up-swap_writepage-for-frontswap-backends
+++ a/mm/page_io.c
@@ -184,9 +184,7 @@ 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);
@@ -198,6 +196,16 @@ int swap_writepage(struct page *page, st
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;
diff -puN mm/swap_state.c~mm-break-up-swap_writepage-for-frontswap-backends mm/swap_state.c
--- a/mm/swap_state.c~mm-break-up-swap_writepage-for-frontswap-backends
+++ a/mm/swap_state.c
@@ -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;
_
Patches currently in -mm which might be from sjenning@xxxxxxxxxxxxxxxxxx are
mm-break-up-swap_writepage-for-frontswap-backends.patch
mm-allow-for-outstanding-swap-writeback-accounting.patch
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