The patch titled
mm: reuse_swap_page replaces can_share_swap_page
has been removed from the -mm tree. Its filename was
mm-reuse_swap_page-replaces-can_share_swap_page.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: mm: reuse_swap_page replaces can_share_swap_page
From: Hugh Dickins <hugh@xxxxxxxxxxx>
A good place to free up old swap is where do_wp_page(), or do_swap_page(),
is about to redirty the page: the data on disk is then stale and won't be
read again; and if we do decide to write the page out later, using the
previous swap location makes an unnecessary disk seek very likely.
So give can_share_swap_page() the side-effect of delete_from_swap_cache()
when it safely can. And can_share_swap_page() was always a misleading
name, the more so if it has a side-effect: rename it reuse_swap_page().
Irrelevant cleanup nearby: remove swap_token_default_timeout definition
from swap.h: it's used nowhere.
Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>
Cc: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Robin Holt <holt@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/swap.h | 6 ++----
mm/memory.c | 4 ++--
mm/swapfile.c | 15 +++++++++++----
3 files changed, 15 insertions(+), 10 deletions(-)
diff -puN include/linux/swap.h~mm-reuse_swap_page-replaces-can_share_swap_page include/linux/swap.h
--- a/include/linux/swap.h~mm-reuse_swap_page-replaces-can_share_swap_page
+++ a/include/linux/swap.h
@@ -304,7 +304,7 @@ extern unsigned int count_swap_pages(int
extern sector_t map_swap_page(struct swap_info_struct *, pgoff_t);
extern sector_t swapdev_block(int, pgoff_t);
extern struct swap_info_struct *get_swap_info_struct(unsigned);
-extern int can_share_swap_page(struct page *);
+extern int reuse_swap_page(struct page *);
extern int remove_exclusive_swap_page(struct page *);
extern int remove_exclusive_swap_page_ref(struct page *);
struct backing_dev_info;
@@ -372,8 +372,6 @@ static inline struct page *lookup_swap_c
return NULL;
}
-#define can_share_swap_page(p) (page_mapcount(p) == 1)
-
static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
gfp_t gfp_mask)
{
@@ -388,7 +386,7 @@ static inline void delete_from_swap_cach
{
}
-#define swap_token_default_timeout 0
+#define reuse_swap_page(page) (page_mapcount(page) == 1)
static inline int remove_exclusive_swap_page(struct page *p)
{
diff -puN mm/memory.c~mm-reuse_swap_page-replaces-can_share_swap_page mm/memory.c
--- a/mm/memory.c~mm-reuse_swap_page-replaces-can_share_swap_page
+++ a/mm/memory.c
@@ -1861,7 +1861,7 @@ static int do_wp_page(struct mm_struct *
}
page_cache_release(old_page);
}
- reuse = can_share_swap_page(old_page);
+ reuse = reuse_swap_page(old_page);
unlock_page(old_page);
} else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
(VM_WRITE|VM_SHARED))) {
@@ -2392,7 +2392,7 @@ static int do_swap_page(struct mm_struct
inc_mm_counter(mm, anon_rss);
pte = mk_pte(page, vma->vm_page_prot);
- if (write_access && can_share_swap_page(page)) {
+ if (write_access && reuse_swap_page(page)) {
pte = maybe_mkwrite(pte_mkdirty(pte), vma);
write_access = 0;
}
diff -puN mm/swapfile.c~mm-reuse_swap_page-replaces-can_share_swap_page mm/swapfile.c
--- a/mm/swapfile.c~mm-reuse_swap_page-replaces-can_share_swap_page
+++ a/mm/swapfile.c
@@ -326,17 +326,24 @@ static inline int page_swapcount(struct
}
/*
- * We can use this swap cache entry directly
- * if there are no other references to it.
+ * We can write to an anon page without COW if there are no other references
+ * to it. And as a side-effect, free up its swap: because the old content
+ * on disk will never be read, and seeking back there to write new content
+ * later would only waste time away from clustering.
*/
-int can_share_swap_page(struct page *page)
+int reuse_swap_page(struct page *page)
{
int count;
VM_BUG_ON(!PageLocked(page));
count = page_mapcount(page);
- if (count <= 1 && PageSwapCache(page))
+ if (count <= 1 && PageSwapCache(page)) {
count += page_swapcount(page);
+ if (count == 1 && !PageWriteback(page)) {
+ delete_from_swap_cache(page);
+ SetPageDirty(page);
+ }
+ }
return count == 1;
}
_
Patches currently in -mm which might be from hugh@xxxxxxxxxxx are
origin.patch
linux-next.patch
mark-complex-bitopsh-inlines-as-__always_inline.patch
clocksource-pass-clocksource-to-read-callback.patch
clocksource-pass-clocksource-to-read-callback-sparc-cleanup.patch
bio-zero-inlined-bio_vec.patch
page_fault-retry-with-nopage_retry.patch
page_fault-retry-with-nopage_retry-fix.patch
page_fault-retry-with-nopage_retry-fix-fix.patch
mm-shmemc-fix-division-by-zero.patch
getrusage-fill-ru_maxrss-value.patch
memcg-handle-swap-caches.patch
memcg-handle-swap-caches-build-fix.patch
memcg-swap-cgroup-for-remembering-usage.patch
memcg-memswap-controller-core.patch
memcg-memswap-controller-core-make-resize-limit-hold-mutex.patch
memcg-memswap-controller-core-swapcache-fixes.patch
memcg-revert-gfp-mask-fix.patch
memcg-check-group-leader-fix.patch
memcg-memoryswap-controller-fix-limit-check.patch
memcg-swapout-refcnt-fix.patch
memcg-hierarchy-avoid-unnecessary-reclaim.patch
inactive_anon_is_low-move-to-vmscan.patch
mm-introduce-zone_reclaim-struct.patch
mm-add-zone-nr_pages-helper-function.patch
mm-make-get_scan_ratio-safe-for-memcg.patch
memcg-add-null-check-to-page_cgroup_zoneinfo.patch
memcg-add-inactive_anon_is_low.patch
memcg-add-mem_cgroup_zone_nr_pages.patch
memcg-add-zone_reclaim_stat.patch
memcg-add-zone_reclaim_stat-reclaim-stat-trivial-fixes-fix.patch
memcg-remove-mem_cgroup_cal_reclaim.patch
memcg-show-reclaim-stat.patch
memcg-rename-scan-global-lru.patch
memcg-protect-prev_priority.patch
memcg-swappiness.patch
memcg-explain-details-and-test-document.patch
memcg-fix-swap-accounting-leak-v3.patch
memcg-fix-swap-accounting-leak-doc-fix.patch
memcg-fix-shmems-swap-accounting.patch
prio_tree-debugging-patch.patch
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