The patch titled
Subject: mm: allow for outstanding swap writeback accounting
has been added to the -mm tree. Its filename is
mm-allow-for-outstanding-swap-writeback-accounting.patch
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------------------------------------------------------
From: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx>
Subject: mm: allow for outstanding swap writeback accounting
To prevent flooding the swap device with writebacks, frontswap backends
need to count and limit the number of outstanding writebacks. The
incrementing of the counter can be done before the call to
__swap_writepage(). However, the caller must receive a notification when
the writeback completes in order to decrement the counter.
To achieve this functionality, this patch modifies __swap_writepage() to
take the bio completion callback function as an argument.
end_swap_bio_write(), the normal bio completion function, is also made
non-static so that code doing the accounting can call it after the
accounting is done.
There should be no behavioural change to existing code.
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 | 4 +++-
mm/page_io.c | 9 +++++----
2 files changed, 8 insertions(+), 5 deletions(-)
diff -puN include/linux/swap.h~mm-allow-for-outstanding-swap-writeback-accounting include/linux/swap.h
--- a/include/linux/swap.h~mm-allow-for-outstanding-swap-writeback-accounting
+++ a/include/linux/swap.h
@@ -330,7 +330,9 @@ 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 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);
diff -puN mm/page_io.c~mm-allow-for-outstanding-swap-writeback-accounting mm/page_io.c
--- a/mm/page_io.c~mm-allow-for-outstanding-swap-writeback-accounting
+++ a/mm/page_io.c
@@ -41,7 +41,7 @@ static struct bio *get_swap_bio(gfp_t gf
return bio;
}
-static void end_swap_bio_write(struct bio *bio, int err)
+void end_swap_bio_write(struct bio *bio, int err)
{
const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
struct page *page = bio->bi_io_vec[0].bv_page;
@@ -196,12 +196,13 @@ int swap_writepage(struct page *page, st
end_page_writeback(page);
goto out;
}
- ret = __swap_writepage(page, wbc);
+ ret = __swap_writepage(page, wbc, end_swap_bio_write);
out:
return ret;
}
-int __swap_writepage(struct page *page, struct writeback_control *wbc)
+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;
@@ -233,7 +234,7 @@ int __swap_writepage(struct page *page,
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);
_
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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