The patch titled mm: try_to_free_swap replaces remove_exclusive_swap_page has been removed from the -mm tree. Its filename was mm-try_to_free_swap-replaces-remove_exclusive_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: try_to_free_swap replaces remove_exclusive_swap_page From: Hugh Dickins <hugh@xxxxxxxxxxx> remove_exclusive_swap_page(): its problem is in living up to its name. It doesn't matter if someone else has a reference to the page (raised page_count); it doesn't matter if the page is mapped into userspace (raised page_mapcount - though that hints it may be worth keeping the swap): all that matters is that there be no more references to the swap (and no writeback in progress). swapoff (try_to_unuse) has been removing pages from swapcache for years, with no concern for page count or page mapcount, and we used to have a comment in lookup_swap_cache() recognizing that: if you go for a page of swapcache, you'll get the right page, but it could have been removed from swapcache by the time you get page lock. So, give up asking for exclusivity: get rid of remove_exclusive_swap_page(), and remove_exclusive_swap_page_ref() and remove_exclusive_swap_page_count() which were spawned for the recent LRU work: replace them by the simpler try_to_free_swap() which just checks page_swapcount(). Similarly, remove the page_count limitation from free_swap_and_count(), but assume that it's worth holding on to the swap if page is mapped and swap nowhere near full. Add a vm_swap_full() test in free_swap_cache()? It would be consistent, but I think we probably have enough for now. Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx> Cc: Lee Schermerhorn <lee.schermerhorn@xxxxxx> Cc: 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 | 10 +---- mm/memory.c | 2 - mm/page_io.c | 2 - mm/swap.c | 3 - mm/swap_state.c | 8 ++-- mm/swapfile.c | 70 +++++++---------------------------------- mm/vmscan.c | 2 - 7 files changed, 22 insertions(+), 75 deletions(-) diff -puN include/linux/swap.h~mm-try_to_free_swap-replaces-remove_exclusive_swap_page include/linux/swap.h --- a/include/linux/swap.h~mm-try_to_free_swap-replaces-remove_exclusive_swap_page +++ a/include/linux/swap.h @@ -305,8 +305,7 @@ extern sector_t map_swap_page(struct swa extern sector_t swapdev_block(int, pgoff_t); extern struct swap_info_struct *get_swap_info_struct(unsigned); extern int reuse_swap_page(struct page *); -extern int remove_exclusive_swap_page(struct page *); -extern int remove_exclusive_swap_page_ref(struct page *); +extern int try_to_free_swap(struct page *); struct backing_dev_info; /* linux/mm/thrash.c */ @@ -388,12 +387,7 @@ static inline void delete_from_swap_cach #define reuse_swap_page(page) (page_mapcount(page) == 1) -static inline int remove_exclusive_swap_page(struct page *p) -{ - return 0; -} - -static inline int remove_exclusive_swap_page_ref(struct page *page) +static inline int try_to_free_swap(struct page *page) { return 0; } diff -puN mm/memory.c~mm-try_to_free_swap-replaces-remove_exclusive_swap_page mm/memory.c --- a/mm/memory.c~mm-try_to_free_swap-replaces-remove_exclusive_swap_page +++ a/mm/memory.c @@ -2403,7 +2403,7 @@ static int do_swap_page(struct mm_struct swap_free(entry); if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page)) - remove_exclusive_swap_page(page); + try_to_free_swap(page); unlock_page(page); if (write_access) { diff -puN mm/page_io.c~mm-try_to_free_swap-replaces-remove_exclusive_swap_page mm/page_io.c --- a/mm/page_io.c~mm-try_to_free_swap-replaces-remove_exclusive_swap_page +++ a/mm/page_io.c @@ -98,7 +98,7 @@ int swap_writepage(struct page *page, st struct bio *bio; int ret = 0, rw = WRITE; - if (remove_exclusive_swap_page(page)) { + if (try_to_free_swap(page)) { unlock_page(page); goto out; } diff -puN mm/swap.c~mm-try_to_free_swap-replaces-remove_exclusive_swap_page mm/swap.c --- a/mm/swap.c~mm-try_to_free_swap-replaces-remove_exclusive_swap_page +++ a/mm/swap.c @@ -454,8 +454,7 @@ void pagevec_swap_free(struct pagevec *p struct page *page = pvec->pages[i]; if (PageSwapCache(page) && trylock_page(page)) { - if (PageSwapCache(page)) - remove_exclusive_swap_page_ref(page); + try_to_free_swap(page); unlock_page(page); } } diff -puN mm/swap_state.c~mm-try_to_free_swap-replaces-remove_exclusive_swap_page mm/swap_state.c --- a/mm/swap_state.c~mm-try_to_free_swap-replaces-remove_exclusive_swap_page +++ a/mm/swap_state.c @@ -195,14 +195,14 @@ void delete_from_swap_cache(struct page * If we are the only user, then try to free up the swap cache. * * Its ok to check for PageSwapCache without the page lock - * here because we are going to recheck again inside - * exclusive_swap_page() _with_ the lock. + * here because we are going to recheck again inside + * try_to_free_swap() _with_ the lock. * - Marcelo */ static inline void free_swap_cache(struct page *page) { - if (PageSwapCache(page) && trylock_page(page)) { - remove_exclusive_swap_page(page); + if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) { + try_to_free_swap(page); unlock_page(page); } } diff -puN mm/swapfile.c~mm-try_to_free_swap-replaces-remove_exclusive_swap_page mm/swapfile.c --- a/mm/swapfile.c~mm-try_to_free_swap-replaces-remove_exclusive_swap_page +++ a/mm/swapfile.c @@ -348,68 +348,23 @@ int reuse_swap_page(struct page *page) } /* - * Work out if there are any other processes sharing this - * swap cache page. Free it if you can. Return success. + * If swap is getting full, or if there are no more mappings of this page, + * then try_to_free_swap is called to free its swap space. */ -static int remove_exclusive_swap_page_count(struct page *page, int count) +int try_to_free_swap(struct page *page) { - int retval; - struct swap_info_struct * p; - swp_entry_t entry; - VM_BUG_ON(!PageLocked(page)); if (!PageSwapCache(page)) return 0; if (PageWriteback(page)) return 0; - if (page_count(page) != count) /* us + cache + ptes */ - return 0; - - entry.val = page_private(page); - p = swap_info_get(entry); - if (!p) + if (page_swapcount(page)) return 0; - /* Is the only swap cache user the cache itself? */ - retval = 0; - if (p->swap_map[swp_offset(entry)] == 1) { - /* Recheck the page count with the swapcache lock held.. */ - spin_lock_irq(&swapper_space.tree_lock); - if ((page_count(page) == count) && !PageWriteback(page)) { - __delete_from_swap_cache(page); - SetPageDirty(page); - retval = 1; - } - spin_unlock_irq(&swapper_space.tree_lock); - } - spin_unlock(&swap_lock); - - if (retval) { - swap_free(entry); - page_cache_release(page); - } - - return retval; -} - -/* - * Most of the time the page should have two references: one for the - * process and one for the swap cache. - */ -int remove_exclusive_swap_page(struct page *page) -{ - return remove_exclusive_swap_page_count(page, 2); -} - -/* - * The pageout code holds an extra reference to the page. That raises - * the reference count to test for to 2 for a page that is only in the - * swap cache plus 1 for each process that maps the page. - */ -int remove_exclusive_swap_page_ref(struct page *page) -{ - return remove_exclusive_swap_page_count(page, 2 + page_mapcount(page)); + delete_from_swap_cache(page); + SetPageDirty(page); + return 1; } /* @@ -436,13 +391,12 @@ void free_swap_and_cache(swp_entry_t ent spin_unlock(&swap_lock); } if (page) { - int one_user; - - one_user = (page_count(page) == 2); - /* Only cache user (+us), or swap space full? Free it! */ - /* Also recheck PageSwapCache after page is locked (above) */ + /* + * Not mapped elsewhere, or swap space full? Free it! + * Also recheck PageSwapCache now page is locked (above). + */ if (PageSwapCache(page) && !PageWriteback(page) && - (one_user || vm_swap_full())) { + (!page_mapped(page) || vm_swap_full())) { delete_from_swap_cache(page); SetPageDirty(page); } diff -puN mm/vmscan.c~mm-try_to_free_swap-replaces-remove_exclusive_swap_page mm/vmscan.c --- a/mm/vmscan.c~mm-try_to_free_swap-replaces-remove_exclusive_swap_page +++ a/mm/vmscan.c @@ -759,7 +759,7 @@ cull_mlocked: activate_locked: /* Not a candidate for swapping, so reclaim swap space. */ if (PageSwapCache(page) && vm_swap_full()) - remove_exclusive_swap_page_ref(page); + try_to_free_swap(page); VM_BUG_ON(PageActive(page)); SetPageActive(page); pgactivate++; _ 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 -- 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