The patch titled mm: reuse_swap_page replaces can_share_swap_page has been added to the -mm tree. Its filename is mm-reuse_swap_page-replaces-can_share_swap_page.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this 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 @@ -307,7 +307,7 @@ 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; @@ -375,8 +375,6 @@ 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) { @@ -391,7 +389,7 @@ 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 @@ -1832,7 +1832,7 @@ 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))) { @@ -2363,7 +2363,7 @@ 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 linux-next.patch mm-dont-mark_page_accessed-in-shmem_fault.patch mm-apply_to_range-call-pte-function-with-lazy-updates.patch mm-remove-cgroup_mm_owner_callbacks.patch mm-remove-aop_writepage_activate.patch mm-remove-gfp_highuser_pagecache.patch mm-add-setclearpageswapcache-stubs.patch mm-replace-some-bug_ons-by-vm_bug_ons.patch mm-add_active_or_unevictable-into-rmap.patch mm-make-page_lock_anon_vma-static.patch mm-further-cleanup-page_add_new_anon_rmap.patch mm-gup-persist-for-write-permission.patch mm-wp-lock-page-before-deciding-cow.patch mm-reuse_swap_page-replaces-can_share_swap_page.patch mm-try_to_free_swap-replaces-remove_exclusive_swap_page.patch mm-try_to_unuse-check-removing-right-swap.patch mm-remove-try_to_munlock-from-vmscan.patch mm-remove-gfp_mask-from-add_to_swap.patch mm-add-add_to_swap-stub.patch mm-optimize-get_scan_ratio-for-no-swap.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 prio_tree-debugging-patch.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html