diff options
| -rw-r--r-- | include/linux/ksm.h | 7 | ||||
| -rw-r--r-- | mm/ksm.c | 30 | ||||
| -rw-r--r-- | mm/memory.c | 16 |
3 files changed, 49 insertions, 4 deletions
diff --git a/include/linux/ksm.h b/include/linux/ksm.h index 161e8164abcf..e48b1e453ff5 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -53,6 +53,8 @@ struct page *ksm_might_need_to_copy(struct page *page, void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc); void ksm_migrate_page(struct page *newpage, struct page *oldpage); +bool reuse_ksm_page(struct page *page, + struct vm_area_struct *vma, unsigned long address); #else /* !CONFIG_KSM */ @@ -86,6 +88,11 @@ static inline void rmap_walk_ksm(struct page *page, static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage) { } +static inline bool reuse_ksm_page(struct page *page, + struct vm_area_struct *vma, unsigned long address) +{ + return false; +} #endif /* CONFIG_MMU */ #endif /* !CONFIG_KSM */ @@ -706,8 +706,9 @@ again: * case this node is no longer referenced, and should be freed; * however, it might mean that the page is under page_ref_freeze(). * The __remove_mapping() case is easy, again the node is now stale; - * but if page is swapcache in migrate_page_move_mapping(), it might - * still be our page, in which case it's essential to keep the node. + * the same is in reuse_ksm_page() case; but if page is swapcache + * in migrate_page_move_mapping(), it might still be our page, + * in which case it's essential to keep the node. */ while (!get_page_unless_zero(page)) { /* @@ -2642,6 +2643,31 @@ again: goto again; } +bool reuse_ksm_page(struct page *page, + struct vm_area_struct *vma, + unsigned long address) +{ +#ifdef CONFIG_DEBUG_VM + if (WARN_ON(is_zero_pfn(page_to_pfn(page))) || + WARN_ON(!page_mapped(page)) || + WARN_ON(!PageLocked(page))) { + dump_page(page, "reuse_ksm_page"); + return false; + } +#endif + + if (PageSwapCache(page) || !page_stable_node(page)) + return false; + /* Prohibit parallel get_ksm_page() */ + if (!page_ref_freeze(page, 1)) + return false; + + page_move_anon_rmap(page, vma); + page->index = linear_page_index(vma, address); + page_ref_unfreeze(page, 1); + + return true; +} #ifdef CONFIG_MIGRATION void ksm_migrate_page(struct page *newpage, struct page *oldpage) { diff --git a/mm/memory.c b/mm/memory.c index eb40f32295d2..222da66f16b4 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2505,8 +2505,11 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) * Take out anonymous pages first, anonymous shared vmas are * not dirty accountable. */ - if (PageAnon(vmf->page) && !PageKsm(vmf->page)) { + if (PageAnon(vmf->page)) { int total_map_swapcount; + if (PageKsm(vmf->page) && (PageSwapCache(vmf->page) || + page_count(vmf->page) != 1)) + goto copy; if (!trylock_page(vmf->page)) { get_page(vmf->page); pte_unmap_unlock(vmf->pte, vmf->ptl); @@ -2521,6 +2524,15 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) } put_page(vmf->page); } + if (PageKsm(vmf->page)) { + bool reused = reuse_ksm_page(vmf->page, vmf->vma, + vmf->address); + unlock_page(vmf->page); + if (!reused) + goto copy; + wp_page_reuse(vmf); + return VM_FAULT_WRITE; + } if (reuse_swap_page(vmf->page, &total_map_swapcount)) { if (total_map_swapcount == 1) { /* @@ -2541,7 +2553,7 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) (VM_WRITE|VM_SHARED))) { return wp_page_shared(vmf); } - +copy: /* * Ok, we need to copy. Oh, well.. */ |