X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=mm%2Fksm.c;h=56a0da1f9979d7eaa9d85cbc0b20ef76215e4abf;hb=925cc71e512a29e2594bcc17dc58d0a0e9c4d524;hp=e8e9a2bca809d23d6ff11abf2e03ffc925ce51c5;hpb=6514d511dbe5a77b4bdc0a7e26fd679585112e1e;p=safe%2Fjmp%2Flinux-2.6 diff --git a/mm/ksm.c b/mm/ksm.c index e8e9a2b..56a0da1 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -29,11 +29,13 @@ #include #include #include +#include #include #include #include #include +#include "internal.h" /* * A few notes about the KSM scanning process, @@ -106,34 +108,46 @@ struct ksm_scan { }; /** + * struct stable_node - node of the stable rbtree + * @node: rb node of this ksm page in the stable tree + * @hlist: hlist head of rmap_items using this ksm page + * @kpfn: page frame number of this ksm page + */ +struct stable_node { + struct rb_node node; + struct hlist_head hlist; + unsigned long kpfn; +}; + +/** * struct rmap_item - reverse mapping item for virtual addresses * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list - * @filler: unused space we're making available in this patch + * @anon_vma: pointer to anon_vma for this mm,address, when in stable tree * @mm: the memory structure this rmap_item is pointing into * @address: the virtual address this rmap_item tracks (+ flags in low bits) * @oldchecksum: previous checksum of the page at that virtual address - * @node: rb_node of this rmap_item in either unstable or stable tree - * @next: next rmap_item hanging off the same node of the stable tree - * @prev: previous rmap_item hanging off the same node of the stable tree + * @node: rb node of this rmap_item in the unstable tree + * @head: pointer to stable_node heading this list in the stable tree + * @hlist: link into hlist of rmap_items hanging off that stable_node */ struct rmap_item { struct rmap_item *rmap_list; - unsigned long filler; + struct anon_vma *anon_vma; /* when stable */ struct mm_struct *mm; unsigned long address; /* + low bits used for flags below */ + unsigned int oldchecksum; /* when unstable */ union { - unsigned int oldchecksum; /* when unstable */ - struct rmap_item *next; /* when stable */ - }; - union { - struct rb_node node; /* when tree node */ - struct rmap_item *prev; /* in stable list */ + struct rb_node node; /* when node of unstable tree */ + struct { /* when listed from stable tree */ + struct stable_node *head; + struct hlist_node hlist; + }; }; }; #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ -#define NODE_FLAG 0x100 /* is a node of unstable or stable tree */ -#define STABLE_FLAG 0x200 /* is a node or list item of stable tree */ +#define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */ +#define STABLE_FLAG 0x200 /* is listed from the stable tree */ /* The stable and unstable tree heads */ static struct rb_root root_stable_tree = RB_ROOT; @@ -150,6 +164,7 @@ static struct ksm_scan ksm_scan = { }; static struct kmem_cache *rmap_item_cache; +static struct kmem_cache *stable_node_cache; static struct kmem_cache *mm_slot_cache; /* The number of nodes in the stable tree */ @@ -164,9 +179,6 @@ static unsigned long ksm_pages_unshared; /* The number of rmap_items in use: to calculate pages_volatile */ static unsigned long ksm_rmap_items; -/* Limit on the number of unswappable pages used */ -static unsigned long ksm_max_kernel_pages; - /* Number of pages ksmd should scan in one batch */ static unsigned int ksm_thread_pages_to_scan = 100; @@ -192,13 +204,19 @@ static int __init ksm_slab_init(void) if (!rmap_item_cache) goto out; + stable_node_cache = KSM_KMEM_CACHE(stable_node, 0); + if (!stable_node_cache) + goto out_free1; + mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); if (!mm_slot_cache) - goto out_free; + goto out_free2; return 0; -out_free: +out_free2: + kmem_cache_destroy(stable_node_cache); +out_free1: kmem_cache_destroy(rmap_item_cache); out: return -ENOMEM; @@ -207,6 +225,7 @@ out: static void __init ksm_slab_free(void) { kmem_cache_destroy(mm_slot_cache); + kmem_cache_destroy(stable_node_cache); kmem_cache_destroy(rmap_item_cache); mm_slot_cache = NULL; } @@ -228,6 +247,16 @@ static inline void free_rmap_item(struct rmap_item *rmap_item) kmem_cache_free(rmap_item_cache, rmap_item); } +static inline struct stable_node *alloc_stable_node(void) +{ + return kmem_cache_alloc(stable_node_cache, GFP_KERNEL); +} + +static inline void free_stable_node(struct stable_node *stable_node) +{ + kmem_cache_free(stable_node_cache, stable_node); +} + static inline struct mm_slot *alloc_mm_slot(void) { if (!mm_slot_cache) /* initialization failed */ @@ -285,6 +314,25 @@ static inline int in_stable_tree(struct rmap_item *rmap_item) return rmap_item->address & STABLE_FLAG; } +static void hold_anon_vma(struct rmap_item *rmap_item, + struct anon_vma *anon_vma) +{ + rmap_item->anon_vma = anon_vma; + atomic_inc(&anon_vma->ksm_refcount); +} + +static void drop_anon_vma(struct rmap_item *rmap_item) +{ + struct anon_vma *anon_vma = rmap_item->anon_vma; + + if (atomic_dec_and_lock(&anon_vma->ksm_refcount, &anon_vma->lock)) { + int empty = list_empty(&anon_vma->head); + spin_unlock(&anon_vma->lock); + if (empty) + anon_vma_free(anon_vma); + } +} + /* * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's * page tables after it has passed through ksm_exit() - which, if necessary, @@ -363,6 +411,12 @@ static void break_cow(struct rmap_item *rmap_item) unsigned long addr = rmap_item->address; struct vm_area_struct *vma; + /* + * It is not an accident that whenever we want to break COW + * to undo, we also need to drop a reference to the anon_vma. + */ + drop_anon_vma(rmap_item); + down_read(&mm->mmap_sem); if (ksm_test_exit(mm)) goto out; @@ -406,21 +460,77 @@ out: page = NULL; return page; } +static void remove_node_from_stable_tree(struct stable_node *stable_node) +{ + struct rmap_item *rmap_item; + struct hlist_node *hlist; + + hlist_for_each_entry(rmap_item, hlist, &stable_node->hlist, hlist) { + if (rmap_item->hlist.next) + ksm_pages_sharing--; + else + ksm_pages_shared--; + drop_anon_vma(rmap_item); + rmap_item->address &= PAGE_MASK; + cond_resched(); + } + + rb_erase(&stable_node->node, &root_stable_tree); + free_stable_node(stable_node); +} + /* - * get_ksm_page: checks if the page at the virtual address in rmap_item - * is still PageKsm, in which case we can trust the content of the page, - * and it returns the gotten page; but NULL if the page has been zapped. + * get_ksm_page: checks if the page indicated by the stable node + * is still its ksm page, despite having held no reference to it. + * In which case we can trust the content of the page, and it + * returns the gotten page; but if the page has now been zapped, + * remove the stale node from the stable tree and return NULL. + * + * You would expect the stable_node to hold a reference to the ksm page. + * But if it increments the page's count, swapping out has to wait for + * ksmd to come around again before it can free the page, which may take + * seconds or even minutes: much too unresponsive. So instead we use a + * "keyhole reference": access to the ksm page from the stable node peeps + * out through its keyhole to see if that page still holds the right key, + * pointing back to this stable node. This relies on freeing a PageAnon + * page to reset its page->mapping to NULL, and relies on no other use of + * a page to put something that might look like our key in page->mapping. + * + * include/linux/pagemap.h page_cache_get_speculative() is a good reference, + * but this is different - made simpler by ksm_thread_mutex being held, but + * interesting for assuming that no other use of the struct page could ever + * put our expected_mapping into page->mapping (or a field of the union which + * coincides with page->mapping). The RCU calls are not for KSM at all, but + * to keep the page_count protocol described with page_cache_get_speculative. + * + * Note: it is possible that get_ksm_page() will return NULL one moment, + * then page the next, if the page is in between page_freeze_refs() and + * page_unfreeze_refs(): this shouldn't be a problem anywhere, the page + * is on its way to being freed; but it is an anomaly to bear in mind. */ -static struct page *get_ksm_page(struct rmap_item *rmap_item) +static struct page *get_ksm_page(struct stable_node *stable_node) { struct page *page; - - page = get_mergeable_page(rmap_item); - if (page && !PageKsm(page)) { + void *expected_mapping; + + page = pfn_to_page(stable_node->kpfn); + expected_mapping = (void *)stable_node + + (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); + rcu_read_lock(); + if (page->mapping != expected_mapping) + goto stale; + if (!get_page_unless_zero(page)) + goto stale; + if (page->mapping != expected_mapping) { put_page(page); - page = NULL; + goto stale; } + rcu_read_unlock(); return page; +stale: + rcu_read_unlock(); + remove_node_from_stable_tree(stable_node); + return NULL; } /* @@ -429,36 +539,29 @@ static struct page *get_ksm_page(struct rmap_item *rmap_item) */ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) { - if (in_stable_tree(rmap_item)) { - struct rmap_item *next_item = rmap_item->next; - - if (rmap_item->address & NODE_FLAG) { - if (next_item) { - rb_replace_node(&rmap_item->node, - &next_item->node, - &root_stable_tree); - next_item->address |= NODE_FLAG; - ksm_pages_sharing--; - } else { - rb_erase(&rmap_item->node, &root_stable_tree); - ksm_pages_shared--; - } - } else { - struct rmap_item *prev_item = rmap_item->prev; + if (rmap_item->address & STABLE_FLAG) { + struct stable_node *stable_node; + struct page *page; - BUG_ON(prev_item->next != rmap_item); - prev_item->next = next_item; - if (next_item) { - BUG_ON(next_item->prev != rmap_item); - next_item->prev = rmap_item->prev; - } + stable_node = rmap_item->head; + page = get_ksm_page(stable_node); + if (!page) + goto out; + + lock_page(page); + hlist_del(&rmap_item->hlist); + unlock_page(page); + put_page(page); + + if (stable_node->hlist.first) ksm_pages_sharing--; - } + else + ksm_pages_shared--; - rmap_item->next = NULL; + drop_anon_vma(rmap_item); rmap_item->address &= PAGE_MASK; - } else if (rmap_item->address & NODE_FLAG) { + } else if (rmap_item->address & UNSTABLE_FLAG) { unsigned char age; /* * Usually ksmd can and must skip the rb_erase, because @@ -475,7 +578,7 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) ksm_pages_unshared--; rmap_item->address &= PAGE_MASK; } - +out: cond_resched(); /* we're called from many long loops */ } @@ -707,7 +810,7 @@ static int replace_page(struct vm_area_struct *vma, struct page *page, } get_page(kpage); - page_add_ksm_rmap(kpage); + page_add_anon_rmap(kpage, vma, addr); flush_cache_page(vma, addr, pte_pfn(*ptep)); ptep_clear_flush(vma, addr, ptep); @@ -726,8 +829,8 @@ out: * try_to_merge_one_page - take two pages and merge them into one * @vma: the vma that holds the pte pointing to page * @page: the PageAnon page that we want to replace with kpage - * @kpage: the PageKsm page (or newly allocated page which page_add_ksm_rmap - * will make PageKsm) that we want to map instead of page + * @kpage: the PageKsm page that we want to map instead of page, + * or NULL the first time when we want to use page as kpage. * * This function returns 0 if the pages were merged, -EFAULT otherwise. */ @@ -737,6 +840,9 @@ static int try_to_merge_one_page(struct vm_area_struct *vma, pte_t orig_pte = __pte(0); int err = -EFAULT; + if (page == kpage) /* ksm page forked */ + return 0; + if (!(vma->vm_flags & VM_MERGEABLE)) goto out; if (!PageAnon(page)) @@ -757,9 +863,29 @@ static int try_to_merge_one_page(struct vm_area_struct *vma, * ptes are necessarily already write-protected. But in either * case, we need to lock and check page_count is not raised. */ - if (write_protect_page(vma, page, &orig_pte) == 0 && - pages_identical(page, kpage)) - err = replace_page(vma, page, kpage, orig_pte); + if (write_protect_page(vma, page, &orig_pte) == 0) { + if (!kpage) { + /* + * While we hold page lock, upgrade page from + * PageAnon+anon_vma to PageKsm+NULL stable_node: + * stable_tree_insert() will update stable_node. + */ + set_page_stable_node(page, NULL); + mark_page_accessed(page); + err = 0; + } else if (pages_identical(page, kpage)) + err = replace_page(vma, page, kpage, orig_pte); + } + + if ((vma->vm_flags & VM_LOCKED) && kpage && !err) { + munlock_vma_page(page); + if (!PageMlocked(kpage)) { + unlock_page(page); + lock_page(kpage); + mlock_vma_page(kpage); + page = kpage; /* for final unlock */ + } + } unlock_page(page); out: @@ -787,6 +913,11 @@ static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, goto out; err = try_to_merge_one_page(vma, page, kpage); + if (err) + goto out; + + /* Must get reference to anon_vma while still holding mmap_sem */ + hold_anon_vma(rmap_item, vma->anon_vma); out: up_read(&mm->mmap_sem); return err; @@ -799,7 +930,7 @@ out: * This function returns the kpage if we successfully merged two identical * pages into one ksm page, NULL otherwise. * - * Note that this function allocates a new kernel page: if one of the pages + * Note that this function upgrades page to ksm page: if one of the pages * is already a ksm page, try_to_merge_with_ksm_page should be used. */ static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, @@ -807,38 +938,12 @@ static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, struct rmap_item *tree_rmap_item, struct page *tree_page) { - struct mm_struct *mm = rmap_item->mm; - struct vm_area_struct *vma; - struct page *kpage; - int err = -EFAULT; - - /* - * The number of nodes in the stable tree - * is the number of kernel pages that we hold. - */ - if (ksm_max_kernel_pages && - ksm_max_kernel_pages <= ksm_pages_shared) - return NULL; - - kpage = alloc_page(GFP_HIGHUSER); - if (!kpage) - return NULL; - - down_read(&mm->mmap_sem); - if (ksm_test_exit(mm)) - goto up; - vma = find_vma(mm, rmap_item->address); - if (!vma || vma->vm_start > rmap_item->address) - goto up; - - copy_user_highpage(kpage, page, rmap_item->address, vma); - err = try_to_merge_one_page(vma, page, kpage); -up: - up_read(&mm->mmap_sem); + int err; + err = try_to_merge_with_ksm_page(rmap_item, page, NULL); if (!err) { err = try_to_merge_with_ksm_page(tree_rmap_item, - tree_page, kpage); + tree_page, page); /* * If that fails, we have a ksm page with only one pte * pointing to it: so break it. @@ -846,11 +951,7 @@ up: if (err) break_cow(rmap_item); } - if (err) { - put_page(kpage); - kpage = NULL; - } - return kpage; + return err ? NULL : page; } /* @@ -859,31 +960,28 @@ up: * This function checks if there is a page inside the stable tree * with identical content to the page that we are scanning right now. * - * This function return rmap_item pointer to the identical item if found, + * This function returns the stable tree node of identical content if found, * NULL otherwise. */ -static struct rmap_item *stable_tree_search(struct page *page, - struct page **tree_pagep) +static struct page *stable_tree_search(struct page *page) { struct rb_node *node = root_stable_tree.rb_node; + struct stable_node *stable_node; + + stable_node = page_stable_node(page); + if (stable_node) { /* ksm page forked */ + get_page(page); + return page; + } while (node) { - struct rmap_item *tree_rmap_item, *next_rmap_item; struct page *tree_page; int ret; - tree_rmap_item = rb_entry(node, struct rmap_item, node); - while (tree_rmap_item) { - BUG_ON(!in_stable_tree(tree_rmap_item)); - cond_resched(); - tree_page = get_ksm_page(tree_rmap_item); - if (tree_page) - break; - next_rmap_item = tree_rmap_item->next; - remove_rmap_item_from_tree(tree_rmap_item); - tree_rmap_item = next_rmap_item; - } - if (!tree_rmap_item) + cond_resched(); + stable_node = rb_entry(node, struct stable_node, node); + tree_page = get_ksm_page(stable_node); + if (!tree_page) return NULL; ret = memcmp_pages(page, tree_page); @@ -894,10 +992,8 @@ static struct rmap_item *stable_tree_search(struct page *page, } else if (ret > 0) { put_page(tree_page); node = node->rb_right; - } else { - *tree_pagep = tree_page; - return tree_rmap_item; - } + } else + return tree_page; } return NULL; @@ -907,31 +1003,23 @@ static struct rmap_item *stable_tree_search(struct page *page, * stable_tree_insert - insert rmap_item pointing to new ksm page * into the stable tree. * - * This function returns rmap_item if success, NULL otherwise. + * This function returns the stable tree node just allocated on success, + * NULL otherwise. */ -static struct rmap_item *stable_tree_insert(struct page *kpage, - struct rmap_item *rmap_item) +static struct stable_node *stable_tree_insert(struct page *kpage) { struct rb_node **new = &root_stable_tree.rb_node; struct rb_node *parent = NULL; + struct stable_node *stable_node; while (*new) { - struct rmap_item *tree_rmap_item, *next_rmap_item; struct page *tree_page; int ret; - tree_rmap_item = rb_entry(*new, struct rmap_item, node); - while (tree_rmap_item) { - BUG_ON(!in_stable_tree(tree_rmap_item)); - cond_resched(); - tree_page = get_ksm_page(tree_rmap_item); - if (tree_page) - break; - next_rmap_item = tree_rmap_item->next; - remove_rmap_item_from_tree(tree_rmap_item); - tree_rmap_item = next_rmap_item; - } - if (!tree_rmap_item) + cond_resched(); + stable_node = rb_entry(*new, struct stable_node, node); + tree_page = get_ksm_page(stable_node); + if (!tree_page) return NULL; ret = memcmp_pages(kpage, tree_page); @@ -952,13 +1040,19 @@ static struct rmap_item *stable_tree_insert(struct page *kpage, } } - rmap_item->address |= NODE_FLAG | STABLE_FLAG; - rmap_item->next = NULL; - rb_link_node(&rmap_item->node, parent, new); - rb_insert_color(&rmap_item->node, &root_stable_tree); + stable_node = alloc_stable_node(); + if (!stable_node) + return NULL; - ksm_pages_shared++; - return rmap_item; + rb_link_node(&stable_node->node, parent, new); + rb_insert_color(&stable_node->node, &root_stable_tree); + + INIT_HLIST_HEAD(&stable_node->hlist); + + stable_node->kpfn = page_to_pfn(kpage); + set_page_stable_node(kpage, stable_node); + + return stable_node; } /* @@ -1018,7 +1112,7 @@ struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, } } - rmap_item->address |= NODE_FLAG; + rmap_item->address |= UNSTABLE_FLAG; rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); rb_link_node(&rmap_item->node, parent, new); rb_insert_color(&rmap_item->node, &root_unstable_tree); @@ -1033,18 +1127,16 @@ struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, * the same ksm page. */ static void stable_tree_append(struct rmap_item *rmap_item, - struct rmap_item *tree_rmap_item) + struct stable_node *stable_node) { - rmap_item->next = tree_rmap_item->next; - rmap_item->prev = tree_rmap_item; - - if (tree_rmap_item->next) - tree_rmap_item->next->prev = rmap_item; - - tree_rmap_item->next = rmap_item; + rmap_item->head = stable_node; rmap_item->address |= STABLE_FLAG; + hlist_add_head(&rmap_item->hlist, &stable_node->hlist); - ksm_pages_sharing++; + if (rmap_item->hlist.next) + ksm_pages_sharing++; + else + ksm_pages_shared++; } /* @@ -1060,6 +1152,7 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) { struct rmap_item *tree_rmap_item; struct page *tree_page = NULL; + struct stable_node *stable_node; struct page *kpage; unsigned int checksum; int err; @@ -1067,39 +1160,27 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) remove_rmap_item_from_tree(rmap_item); /* We first start with searching the page inside the stable tree */ - tree_rmap_item = stable_tree_search(page, &tree_page); - if (tree_rmap_item) { - kpage = tree_page; - if (page == kpage) /* forked */ - err = 0; - else - err = try_to_merge_with_ksm_page(rmap_item, - page, kpage); + kpage = stable_tree_search(page); + if (kpage) { + err = try_to_merge_with_ksm_page(rmap_item, page, kpage); if (!err) { /* * The page was successfully merged: * add its rmap_item to the stable tree. */ - stable_tree_append(rmap_item, tree_rmap_item); + lock_page(kpage); + stable_tree_append(rmap_item, page_stable_node(kpage)); + unlock_page(kpage); } put_page(kpage); return; } /* - * A ksm page might have got here by fork, but its other - * references have already been removed from the stable tree. - * Or it might be left over from a break_ksm which failed - * when the mem_cgroup had reached its limit: try again now. - */ - if (PageKsm(page)) - break_cow(rmap_item); - - /* - * In case the hash value of the page was changed from the last time we - * have calculated it, this page to be changed frequely, therefore we - * don't want to insert it to the unstable tree, and we don't want to - * waste our time to search if there is something identical to it there. + * If the hash value of the page has changed from the last time + * we calculated it, this page is changing frequently: therefore we + * don't want to insert it in the unstable tree, and we don't want + * to waste our time searching for something identical to it there. */ checksum = calc_checksum(page); if (rmap_item->oldchecksum != checksum) { @@ -1121,19 +1202,24 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) if (kpage) { remove_rmap_item_from_tree(tree_rmap_item); + lock_page(kpage); + stable_node = stable_tree_insert(kpage); + if (stable_node) { + stable_tree_append(tree_rmap_item, stable_node); + stable_tree_append(rmap_item, stable_node); + } + unlock_page(kpage); + /* * If we fail to insert the page into the stable tree, * we will have 2 virtual addresses that are pointing * to a ksm page left outside the stable tree, * in which case we need to break_cow on both. */ - if (stable_tree_insert(kpage, tree_rmap_item)) - stable_tree_append(rmap_item, tree_rmap_item); - else { + if (!stable_node) { break_cow(tree_rmap_item); break_cow(rmap_item); } - put_page(kpage); } } } @@ -1290,14 +1376,6 @@ static void ksm_do_scan(unsigned int scan_npages) return; if (!PageKsm(page) || !in_stable_tree(rmap_item)) cmp_and_merge_page(page, rmap_item); - else if (page_mapcount(page) == 1) { - /* - * Replace now-unshared ksm page by ordinary page. - */ - break_cow(rmap_item); - remove_rmap_item_from_tree(rmap_item); - rmap_item->oldchecksum = calc_checksum(page); - } put_page(page); } } @@ -1342,7 +1420,7 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start, if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | VM_PFNMAP | VM_IO | VM_DONTEXPAND | VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | - VM_MIXEDMAP | VM_SAO)) + VM_NONLINEAR | VM_MIXEDMAP | VM_SAO)) return 0; /* just ignore the advice */ if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { @@ -1440,6 +1518,249 @@ void __ksm_exit(struct mm_struct *mm) } } +struct page *ksm_does_need_to_copy(struct page *page, + struct vm_area_struct *vma, unsigned long address) +{ + struct page *new_page; + + unlock_page(page); /* any racers will COW it, not modify it */ + + new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); + if (new_page) { + copy_user_highpage(new_page, page, address, vma); + + SetPageDirty(new_page); + __SetPageUptodate(new_page); + SetPageSwapBacked(new_page); + __set_page_locked(new_page); + + if (page_evictable(new_page, vma)) + lru_cache_add_lru(new_page, LRU_ACTIVE_ANON); + else + add_page_to_unevictable_list(new_page); + } + + page_cache_release(page); + return new_page; +} + +int page_referenced_ksm(struct page *page, struct mem_cgroup *memcg, + unsigned long *vm_flags) +{ + struct stable_node *stable_node; + struct rmap_item *rmap_item; + struct hlist_node *hlist; + unsigned int mapcount = page_mapcount(page); + int referenced = 0; + int search_new_forks = 0; + + VM_BUG_ON(!PageKsm(page)); + VM_BUG_ON(!PageLocked(page)); + + stable_node = page_stable_node(page); + if (!stable_node) + return 0; +again: + hlist_for_each_entry(rmap_item, hlist, &stable_node->hlist, hlist) { + struct anon_vma *anon_vma = rmap_item->anon_vma; + struct vm_area_struct *vma; + + spin_lock(&anon_vma->lock); + list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { + if (rmap_item->address < vma->vm_start || + rmap_item->address >= vma->vm_end) + continue; + /* + * Initially we examine only the vma which covers this + * rmap_item; but later, if there is still work to do, + * we examine covering vmas in other mms: in case they + * were forked from the original since ksmd passed. + */ + if ((rmap_item->mm == vma->vm_mm) == search_new_forks) + continue; + + if (memcg && !mm_match_cgroup(vma->vm_mm, memcg)) + continue; + + referenced += page_referenced_one(page, vma, + rmap_item->address, &mapcount, vm_flags); + if (!search_new_forks || !mapcount) + break; + } + spin_unlock(&anon_vma->lock); + if (!mapcount) + goto out; + } + if (!search_new_forks++) + goto again; +out: + return referenced; +} + +int try_to_unmap_ksm(struct page *page, enum ttu_flags flags) +{ + struct stable_node *stable_node; + struct hlist_node *hlist; + struct rmap_item *rmap_item; + int ret = SWAP_AGAIN; + int search_new_forks = 0; + + VM_BUG_ON(!PageKsm(page)); + VM_BUG_ON(!PageLocked(page)); + + stable_node = page_stable_node(page); + if (!stable_node) + return SWAP_FAIL; +again: + hlist_for_each_entry(rmap_item, hlist, &stable_node->hlist, hlist) { + struct anon_vma *anon_vma = rmap_item->anon_vma; + struct vm_area_struct *vma; + + spin_lock(&anon_vma->lock); + list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { + if (rmap_item->address < vma->vm_start || + rmap_item->address >= vma->vm_end) + continue; + /* + * Initially we examine only the vma which covers this + * rmap_item; but later, if there is still work to do, + * we examine covering vmas in other mms: in case they + * were forked from the original since ksmd passed. + */ + if ((rmap_item->mm == vma->vm_mm) == search_new_forks) + continue; + + ret = try_to_unmap_one(page, vma, + rmap_item->address, flags); + if (ret != SWAP_AGAIN || !page_mapped(page)) { + spin_unlock(&anon_vma->lock); + goto out; + } + } + spin_unlock(&anon_vma->lock); + } + if (!search_new_forks++) + goto again; +out: + return ret; +} + +#ifdef CONFIG_MIGRATION +int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page *, + struct vm_area_struct *, unsigned long, void *), void *arg) +{ + struct stable_node *stable_node; + struct hlist_node *hlist; + struct rmap_item *rmap_item; + int ret = SWAP_AGAIN; + int search_new_forks = 0; + + VM_BUG_ON(!PageKsm(page)); + VM_BUG_ON(!PageLocked(page)); + + stable_node = page_stable_node(page); + if (!stable_node) + return ret; +again: + hlist_for_each_entry(rmap_item, hlist, &stable_node->hlist, hlist) { + struct anon_vma *anon_vma = rmap_item->anon_vma; + struct vm_area_struct *vma; + + spin_lock(&anon_vma->lock); + list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { + if (rmap_item->address < vma->vm_start || + rmap_item->address >= vma->vm_end) + continue; + /* + * Initially we examine only the vma which covers this + * rmap_item; but later, if there is still work to do, + * we examine covering vmas in other mms: in case they + * were forked from the original since ksmd passed. + */ + if ((rmap_item->mm == vma->vm_mm) == search_new_forks) + continue; + + ret = rmap_one(page, vma, rmap_item->address, arg); + if (ret != SWAP_AGAIN) { + spin_unlock(&anon_vma->lock); + goto out; + } + } + spin_unlock(&anon_vma->lock); + } + if (!search_new_forks++) + goto again; +out: + return ret; +} + +void ksm_migrate_page(struct page *newpage, struct page *oldpage) +{ + struct stable_node *stable_node; + + VM_BUG_ON(!PageLocked(oldpage)); + VM_BUG_ON(!PageLocked(newpage)); + VM_BUG_ON(newpage->mapping != oldpage->mapping); + + stable_node = page_stable_node(newpage); + if (stable_node) { + VM_BUG_ON(stable_node->kpfn != page_to_pfn(oldpage)); + stable_node->kpfn = page_to_pfn(newpage); + } +} +#endif /* CONFIG_MIGRATION */ + +#ifdef CONFIG_MEMORY_HOTREMOVE +static struct stable_node *ksm_check_stable_tree(unsigned long start_pfn, + unsigned long end_pfn) +{ + struct rb_node *node; + + for (node = rb_first(&root_stable_tree); node; node = rb_next(node)) { + struct stable_node *stable_node; + + stable_node = rb_entry(node, struct stable_node, node); + if (stable_node->kpfn >= start_pfn && + stable_node->kpfn < end_pfn) + return stable_node; + } + return NULL; +} + +static int ksm_memory_callback(struct notifier_block *self, + unsigned long action, void *arg) +{ + struct memory_notify *mn = arg; + struct stable_node *stable_node; + + switch (action) { + case MEM_GOING_OFFLINE: + /* + * Keep it very simple for now: just lock out ksmd and + * MADV_UNMERGEABLE while any memory is going offline. + */ + mutex_lock(&ksm_thread_mutex); + break; + + case MEM_OFFLINE: + /* + * Most of the work is done by page migration; but there might + * be a few stable_nodes left over, still pointing to struct + * pages which have been offlined: prune those from the tree. + */ + while ((stable_node = ksm_check_stable_tree(mn->start_pfn, + mn->start_pfn + mn->nr_pages)) != NULL) + remove_node_from_stable_tree(stable_node); + /* fallthrough */ + + case MEM_CANCEL_OFFLINE: + mutex_unlock(&ksm_thread_mutex); + break; + } + return NOTIFY_OK; +} +#endif /* CONFIG_MEMORY_HOTREMOVE */ + #ifdef CONFIG_SYSFS /* * This all compiles without CONFIG_SYSFS, but is a waste of space. @@ -1518,8 +1839,8 @@ static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, /* * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, - * breaking COW to free the unswappable pages_shared (but leaves - * mm_slots on the list for when ksmd may be set running again). + * breaking COW to free the pages_shared (but leaves mm_slots + * on the list for when ksmd may be set running again). */ mutex_lock(&ksm_thread_mutex); @@ -1544,29 +1865,6 @@ static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, } KSM_ATTR(run); -static ssize_t max_kernel_pages_store(struct kobject *kobj, - struct kobj_attribute *attr, - const char *buf, size_t count) -{ - int err; - unsigned long nr_pages; - - err = strict_strtoul(buf, 10, &nr_pages); - if (err) - return -EINVAL; - - ksm_max_kernel_pages = nr_pages; - - return count; -} - -static ssize_t max_kernel_pages_show(struct kobject *kobj, - struct kobj_attribute *attr, char *buf) -{ - return sprintf(buf, "%lu\n", ksm_max_kernel_pages); -} -KSM_ATTR(max_kernel_pages); - static ssize_t pages_shared_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { @@ -1616,7 +1914,6 @@ static struct attribute *ksm_attrs[] = { &sleep_millisecs_attr.attr, &pages_to_scan_attr.attr, &run_attr.attr, - &max_kernel_pages_attr.attr, &pages_shared_attr.attr, &pages_sharing_attr.attr, &pages_unshared_attr.attr, @@ -1636,8 +1933,6 @@ static int __init ksm_init(void) struct task_struct *ksm_thread; int err; - ksm_max_kernel_pages = totalram_pages / 4; - err = ksm_slab_init(); if (err) goto out; @@ -1665,6 +1960,13 @@ static int __init ksm_init(void) #endif /* CONFIG_SYSFS */ +#ifdef CONFIG_MEMORY_HOTREMOVE + /* + * Choose a high priority since the callback takes ksm_thread_mutex: + * later callbacks could only be taking locks which nest within that. + */ + hotplug_memory_notifier(ksm_memory_callback, 100); +#endif return 0; out_free2: