diff options
Diffstat (limited to 'mm/ksm.c')
| -rw-r--r-- | mm/ksm.c | 1012 |
1 files changed, 700 insertions, 312 deletions
@@ -33,11 +33,22 @@ #include <linux/mmu_notifier.h> #include <linux/swap.h> #include <linux/ksm.h> -#include <linux/hash.h> +#include <linux/hashtable.h> +#include <linux/freezer.h> +#include <linux/oom.h> +#include <linux/numa.h> #include <asm/tlbflush.h> #include "internal.h" +#ifdef CONFIG_NUMA +#define NUMA(x) (x) +#define DO_NUMA(x) do { (x); } while (0) +#else +#define NUMA(x) (0) +#define DO_NUMA(x) do { } while (0) +#endif + /* * A few notes about the KSM scanning process, * to make it easier to understand the data structures below: @@ -76,6 +87,9 @@ * take 10 attempts to find a page in the unstable tree, once it is found, * it is secured in the stable tree. (When we scan a new page, we first * compare it against the stable tree, and then against the unstable tree.) + * + * If the merge_across_nodes tunable is unset, then KSM maintains multiple + * stable trees and multiple unstable trees: one of each for each NUMA node. */ /** @@ -111,19 +125,32 @@ struct ksm_scan { /** * struct stable_node - node of the stable rbtree * @node: rb node of this ksm page in the stable tree + * @head: (overlaying parent) &migrate_nodes indicates temporarily on that list + * @list: linked into migrate_nodes, pending placement in the proper node tree * @hlist: hlist head of rmap_items using this ksm page - * @kpfn: page frame number of this ksm page + * @kpfn: page frame number of this ksm page (perhaps temporarily on wrong nid) + * @nid: NUMA node id of stable tree in which linked (may not match kpfn) */ struct stable_node { - struct rb_node node; + union { + struct rb_node node; /* when node of stable tree */ + struct { /* when listed for migration */ + struct list_head *head; + struct list_head list; + }; + }; struct hlist_head hlist; unsigned long kpfn; +#ifdef CONFIG_NUMA + int nid; +#endif }; /** * struct rmap_item - reverse mapping item for virtual addresses * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list * @anon_vma: pointer to anon_vma for this mm,address, when in stable tree + * @nid: NUMA node id of unstable tree in which linked (may not match page) * @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 @@ -133,7 +160,12 @@ struct stable_node { */ struct rmap_item { struct rmap_item *rmap_list; - struct anon_vma *anon_vma; /* when stable */ + union { + struct anon_vma *anon_vma; /* when stable */ +#ifdef CONFIG_NUMA + int nid; /* when node of unstable tree */ +#endif + }; struct mm_struct *mm; unsigned long address; /* + low bits used for flags below */ unsigned int oldchecksum; /* when unstable */ @@ -151,12 +183,16 @@ struct rmap_item { #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; -static struct rb_root root_unstable_tree = RB_ROOT; +static struct rb_root one_stable_tree[1] = { RB_ROOT }; +static struct rb_root one_unstable_tree[1] = { RB_ROOT }; +static struct rb_root *root_stable_tree = one_stable_tree; +static struct rb_root *root_unstable_tree = one_unstable_tree; + +/* Recently migrated nodes of stable tree, pending proper placement */ +static LIST_HEAD(migrate_nodes); -#define MM_SLOTS_HASH_SHIFT 10 -#define MM_SLOTS_HASH_HEADS (1 << MM_SLOTS_HASH_SHIFT) -static struct hlist_head mm_slots_hash[MM_SLOTS_HASH_HEADS]; +#define MM_SLOTS_HASH_BITS 10 +static DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); static struct mm_slot ksm_mm_head = { .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list), @@ -187,10 +223,21 @@ static unsigned int ksm_thread_pages_to_scan = 100; /* Milliseconds ksmd should sleep between batches */ static unsigned int ksm_thread_sleep_millisecs = 20; +#ifdef CONFIG_NUMA +/* Zeroed when merging across nodes is not allowed */ +static unsigned int ksm_merge_across_nodes = 1; +static int ksm_nr_node_ids = 1; +#else +#define ksm_merge_across_nodes 1U +#define ksm_nr_node_ids 1 +#endif + #define KSM_RUN_STOP 0 #define KSM_RUN_MERGE 1 #define KSM_RUN_UNMERGE 2 -static unsigned int ksm_run = KSM_RUN_STOP; +#define KSM_RUN_OFFLINE 4 +static unsigned long ksm_run = KSM_RUN_STOP; +static void wait_while_offlining(void); static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); static DEFINE_MUTEX(ksm_thread_mutex); @@ -273,45 +320,20 @@ static inline void free_mm_slot(struct mm_slot *mm_slot) static struct mm_slot *get_mm_slot(struct mm_struct *mm) { - struct mm_slot *mm_slot; - struct hlist_head *bucket; - struct hlist_node *node; + struct mm_slot *slot; + + hash_for_each_possible(mm_slots_hash, slot, link, (unsigned long)mm) + if (slot->mm == mm) + return slot; - bucket = &mm_slots_hash[hash_ptr(mm, MM_SLOTS_HASH_SHIFT)]; - hlist_for_each_entry(mm_slot, node, bucket, link) { - if (mm == mm_slot->mm) - return mm_slot; - } return NULL; } static void insert_to_mm_slots_hash(struct mm_struct *mm, struct mm_slot *mm_slot) { - struct hlist_head *bucket; - - bucket = &mm_slots_hash[hash_ptr(mm, MM_SLOTS_HASH_SHIFT)]; mm_slot->mm = mm; - hlist_add_head(&mm_slot->link, bucket); -} - -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; - get_anon_vma(anon_vma); -} - -static void ksm_drop_anon_vma(struct rmap_item *rmap_item) -{ - struct anon_vma *anon_vma = rmap_item->anon_vma; - - drop_anon_vma(anon_vma); + hash_add(mm_slots_hash, &mm_slot->link, (unsigned long)mm); } /* @@ -345,7 +367,7 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr) do { cond_resched(); - page = follow_page(vma, addr, FOLL_GET); + page = follow_page(vma, addr, FOLL_GET | FOLL_MIGRATION); if (IS_ERR_OR_NULL(page)) break; if (PageKsm(page)) @@ -386,6 +408,20 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr) return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; } +static struct vm_area_struct *find_mergeable_vma(struct mm_struct *mm, + unsigned long addr) +{ + struct vm_area_struct *vma; + if (ksm_test_exit(mm)) + return NULL; + vma = find_vma(mm, addr); + if (!vma || vma->vm_start > addr) + return NULL; + if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) + return NULL; + return vma; +} + static void break_cow(struct rmap_item *rmap_item) { struct mm_struct *mm = rmap_item->mm; @@ -396,21 +432,29 @@ static void break_cow(struct rmap_item *rmap_item) * 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. */ - ksm_drop_anon_vma(rmap_item); + put_anon_vma(rmap_item->anon_vma); down_read(&mm->mmap_sem); - if (ksm_test_exit(mm)) - goto out; - vma = find_vma(mm, addr); - if (!vma || vma->vm_start > addr) - goto out; - if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) - goto out; - break_ksm(vma, addr); -out: + vma = find_mergeable_vma(mm, addr); + if (vma) + break_ksm(vma, addr); up_read(&mm->mmap_sem); } +static struct page *page_trans_compound_anon(struct page *page) +{ + if (PageTransCompound(page)) { + struct page *head = compound_head(page); + /* + * head may actually be splitted and freed from under + * us but it's ok here. + */ + if (PageAnon(head)) + return head; + } + return NULL; +} + static struct page *get_mergeable_page(struct rmap_item *rmap_item) { struct mm_struct *mm = rmap_item->mm; @@ -419,18 +463,14 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item) struct page *page; down_read(&mm->mmap_sem); - if (ksm_test_exit(mm)) - goto out; - vma = find_vma(mm, addr); - if (!vma || vma->vm_start > addr) - goto out; - if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) + vma = find_mergeable_vma(mm, addr); + if (!vma) goto out; page = follow_page(vma, addr, FOLL_GET); if (IS_ERR_OR_NULL(page)) goto out; - if (PageAnon(page)) { + if (PageAnon(page) || page_trans_compound_anon(page)) { flush_anon_page(vma, page, addr); flush_dcache_page(page); } else { @@ -441,22 +481,36 @@ out: page = NULL; return page; } +/* + * This helper is used for getting right index into array of tree roots. + * When merge_across_nodes knob is set to 1, there are only two rb-trees for + * stable and unstable pages from all nodes with roots in index 0. Otherwise, + * every node has its own stable and unstable tree. + */ +static inline int get_kpfn_nid(unsigned long kpfn) +{ + return ksm_merge_across_nodes ? 0 : NUMA(pfn_to_nid(kpfn)); +} + 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) { + hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { if (rmap_item->hlist.next) ksm_pages_sharing--; else ksm_pages_shared--; - ksm_drop_anon_vma(rmap_item); + put_anon_vma(rmap_item->anon_vma); rmap_item->address &= PAGE_MASK; cond_resched(); } - rb_erase(&stable_node->node, &root_stable_tree); + if (stable_node->head == &migrate_nodes) + list_del(&stable_node->list); + else + rb_erase(&stable_node->node, + root_stable_tree + NUMA(stable_node->nid)); free_stable_node(stable_node); } @@ -466,6 +520,7 @@ static void remove_node_from_stable_tree(struct stable_node *stable_node) * 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. + * But beware, the stable node's page might be being migrated. * * 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 @@ -476,40 +531,77 @@ static void remove_node_from_stable_tree(struct stable_node *stable_node) * 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 stable_node *stable_node) +static struct page *get_ksm_page(struct stable_node *stable_node, bool lock_it) { struct page *page; void *expected_mapping; + unsigned long kpfn; - 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)) +again: + kpfn = ACCESS_ONCE(stable_node->kpfn); + page = pfn_to_page(kpfn); + + /* + * page is computed from kpfn, so on most architectures reading + * page->mapping is naturally ordered after reading node->kpfn, + * but on Alpha we need to be more careful. + */ + smp_read_barrier_depends(); + if (ACCESS_ONCE(page->mapping) != expected_mapping) goto stale; - if (page->mapping != expected_mapping) { + + /* + * We cannot do anything with the page while its refcount is 0. + * Usually 0 means free, or tail of a higher-order page: in which + * case this node is no longer referenced, and should be freed; + * however, it might mean that the page is under page_freeze_refs(). + * 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. + */ + while (!get_page_unless_zero(page)) { + /* + * Another check for page->mapping != expected_mapping would + * work here too. We have chosen the !PageSwapCache test to + * optimize the common case, when the page is or is about to + * be freed: PageSwapCache is cleared (under spin_lock_irq) + * in the freeze_refs section of __remove_mapping(); but Anon + * page->mapping reset to NULL later, in free_pages_prepare(). + */ + if (!PageSwapCache(page)) + goto stale; + cpu_relax(); + } + + if (ACCESS_ONCE(page->mapping) != expected_mapping) { put_page(page); goto stale; } - rcu_read_unlock(); + + if (lock_it) { + lock_page(page); + if (ACCESS_ONCE(page->mapping) != expected_mapping) { + unlock_page(page); + put_page(page); + goto stale; + } + } return page; + stale: - rcu_read_unlock(); + /* + * We come here from above when page->mapping or !PageSwapCache + * suggests that the node is stale; but it might be under migration. + * We need smp_rmb(), matching the smp_wmb() in ksm_migrate_page(), + * before checking whether node->kpfn has been changed. + */ + smp_rmb(); + if (ACCESS_ONCE(stable_node->kpfn) != kpfn) + goto again; remove_node_from_stable_tree(stable_node); return NULL; } @@ -525,11 +617,10 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) struct page *page; stable_node = rmap_item->head; - page = get_ksm_page(stable_node); + page = get_ksm_page(stable_node, true); if (!page) goto out; - lock_page(page); hlist_del(&rmap_item->hlist); unlock_page(page); put_page(page); @@ -539,7 +630,7 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) else ksm_pages_shared--; - ksm_drop_anon_vma(rmap_item); + put_anon_vma(rmap_item->anon_vma); rmap_item->address &= PAGE_MASK; } else if (rmap_item->address & UNSTABLE_FLAG) { @@ -554,8 +645,8 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); BUG_ON(age > 1); if (!age) - rb_erase(&rmap_item->node, &root_unstable_tree); - + rb_erase(&rmap_item->node, + root_unstable_tree + NUMA(rmap_item->nid)); ksm_pages_unshared--; rmap_item->address &= PAGE_MASK; } @@ -575,7 +666,7 @@ static void remove_trailing_rmap_items(struct mm_slot *mm_slot, } /* - * Though it's very tempting to unmerge in_stable_tree(rmap_item)s rather + * Though it's very tempting to unmerge rmap_items from stable tree rather * than check every pte of a given vma, the locking doesn't quite work for * that - an rmap_item is assigned to the stable tree after inserting ksm * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing @@ -608,6 +699,71 @@ static int unmerge_ksm_pages(struct vm_area_struct *vma, /* * Only called through the sysfs control interface: */ +static int remove_stable_node(struct stable_node *stable_node) +{ + struct page *page; + int err; + + page = get_ksm_page(stable_node, true); + if (!page) { + /* + * get_ksm_page did remove_node_from_stable_tree itself. + */ + return 0; + } + + if (WARN_ON_ONCE(page_mapped(page))) { + /* + * This should not happen: but if it does, just refuse to let + * merge_across_nodes be switched - there is no need to panic. + */ + err = -EBUSY; + } else { + /* + * The stable node did not yet appear stale to get_ksm_page(), + * since that allows for an unmapped ksm page to be recognized + * right up until it is freed; but the node is safe to remove. + * This page might be in a pagevec waiting to be freed, + * or it might be PageSwapCache (perhaps under writeback), + * or it might have been removed from swapcache a moment ago. + */ + set_page_stable_node(page, NULL); + remove_node_from_stable_tree(stable_node); + err = 0; + } + + unlock_page(page); + put_page(page); + return err; +} + +static int remove_all_stable_nodes(void) +{ + struct stable_node *stable_node; + struct list_head *this, *next; + int nid; + int err = 0; + + for (nid = 0; nid < ksm_nr_node_ids; nid++) { + while (root_stable_tree[nid].rb_node) { + stable_node = rb_entry(root_stable_tree[nid].rb_node, + struct stable_node, node); + if (remove_stable_node(stable_node)) { + err = -EBUSY; + break; /* proceed to next nid */ + } + cond_resched(); + } + } + list_for_each_safe(this, next, &migrate_nodes) { + stable_node = list_entry(this, struct stable_node, list); + if (remove_stable_node(stable_node)) + err = -EBUSY; + cond_resched(); + } + return err; +} + static int unmerge_and_remove_all_rmap_items(void) { struct mm_slot *mm_slot; @@ -641,7 +797,7 @@ static int unmerge_and_remove_all_rmap_items(void) ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next, struct mm_slot, mm_list); if (ksm_test_exit(mm)) { - hlist_del(&mm_slot->link); + hash_del(&mm_slot->link); list_del(&mm_slot->mm_list); spin_unlock(&ksm_mmlist_lock); @@ -655,6 +811,8 @@ static int unmerge_and_remove_all_rmap_items(void) } } + /* Clean up stable nodes, but don't worry if some are still busy */ + remove_all_stable_nodes(); ksm_scan.seqnr = 0; return 0; @@ -670,9 +828,9 @@ error: static u32 calc_checksum(struct page *page) { u32 checksum; - void *addr = kmap_atomic(page, KM_USER0); + void *addr = kmap_atomic(page); checksum = jhash2(addr, PAGE_SIZE / 4, 17); - kunmap_atomic(addr, KM_USER0); + kunmap_atomic(addr); return checksum; } @@ -681,11 +839,11 @@ static int memcmp_pages(struct page *page1, struct page *page2) char *addr1, *addr2; int ret; - addr1 = kmap_atomic(page1, KM_USER0); - addr2 = kmap_atomic(page2, KM_USER1); + addr1 = kmap_atomic(page1); + addr2 = kmap_atomic(page2); ret = memcmp(addr1, addr2, PAGE_SIZE); - kunmap_atomic(addr2, KM_USER1); - kunmap_atomic(addr1, KM_USER0); + kunmap_atomic(addr2); + kunmap_atomic(addr1); return ret; } @@ -703,14 +861,22 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page, spinlock_t *ptl; int swapped; int err = -EFAULT; + unsigned long mmun_start; /* For mmu_notifiers */ + unsigned long mmun_end; /* For mmu_notifiers */ addr = page_address_in_vma(page, vma); if (addr == -EFAULT) goto out; + BUG_ON(PageTransCompound(page)); + + mmun_start = addr; + mmun_end = addr + PAGE_SIZE; + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); + ptep = page_check_address(page, mm, addr, &ptl, 0); if (!ptep) - goto out; + goto out_mn; if (pte_write(*ptep) || pte_dirty(*ptep)) { pte_t entry; @@ -718,7 +884,7 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page, swapped = PageSwapCache(page); flush_cache_page(vma, addr, page_to_pfn(page)); /* - * Ok this is tricky, when get_user_pages_fast() run it doesnt + * Ok this is tricky, when get_user_pages_fast() run it doesn't * take any lock, therefore the check that we are going to make * with the pagecount against the mapcount is racey and * O_DIRECT can happen right after the check. @@ -745,6 +911,8 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page, out_unlock: pte_unmap_unlock(ptep, ptl); +out_mn: + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); out: return err; } @@ -762,34 +930,30 @@ static int replace_page(struct vm_area_struct *vma, struct page *page, struct page *kpage, pte_t orig_pte) { struct mm_struct *mm = vma->vm_mm; - pgd_t *pgd; - pud_t *pud; pmd_t *pmd; pte_t *ptep; spinlock_t *ptl; unsigned long addr; int err = -EFAULT; + unsigned long mmun_start; /* For mmu_notifiers */ + unsigned long mmun_end; /* For mmu_notifiers */ addr = page_address_in_vma(page, vma); if (addr == -EFAULT) goto out; - pgd = pgd_offset(mm, addr); - if (!pgd_present(*pgd)) + pmd = mm_find_pmd(mm, addr); + if (!pmd) goto out; - pud = pud_offset(pgd, addr); - if (!pud_present(*pud)) - goto out; - - pmd = pmd_offset(pud, addr); - if (!pmd_present(*pmd)) - goto out; + mmun_start = addr; + mmun_end = addr + PAGE_SIZE; + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); if (!pte_same(*ptep, orig_pte)) { pte_unmap_unlock(ptep, ptl); - goto out; + goto out_mn; } get_page(kpage); @@ -800,14 +964,45 @@ static int replace_page(struct vm_area_struct *vma, struct page *page, set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot)); page_remove_rmap(page); + if (!page_mapped(page)) + try_to_free_swap(page); put_page(page); pte_unmap_unlock(ptep, ptl); err = 0; +out_mn: + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); out: return err; } +static int page_trans_compound_anon_split(struct page *page) +{ + int ret = 0; + struct page *transhuge_head = page_trans_compound_anon(page); + if (transhuge_head) { + /* Get the reference on the head to split it. */ + if (get_page_unless_zero(transhuge_head)) { + /* + * Recheck we got the reference while the head + * was still anonymous. + */ + if (PageAnon(transhuge_head)) + ret = split_huge_page(transhuge_head); + else + /* + * Retry later if split_huge_page run + * from under us. + */ + ret = 1; + put_page(transhuge_head); + } else + /* Retry later if split_huge_page run from under us. */ + ret = 1; + } + return ret; +} + /* * try_to_merge_one_page - take two pages and merge them into one * @vma: the vma that holds the pte pointing to page @@ -828,6 +1023,9 @@ static int try_to_merge_one_page(struct vm_area_struct *vma, if (!(vma->vm_flags & VM_MERGEABLE)) goto out; + if (PageTransCompound(page) && page_trans_compound_anon_split(page)) + goto out; + BUG_ON(PageTransCompound(page)); if (!PageAnon(page)) goto out; @@ -899,8 +1097,12 @@ static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, if (err) goto out; + /* Unstable nid is in union with stable anon_vma: remove first */ + remove_rmap_item_from_tree(rmap_item); + /* Must get reference to anon_vma while still holding mmap_sem */ - hold_anon_vma(rmap_item, vma->anon_vma); + rmap_item->anon_vma = vma->anon_vma; + get_anon_vma(vma->anon_vma); out: up_read(&mm->mmap_sem); return err; @@ -948,42 +1150,99 @@ static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, */ static struct page *stable_tree_search(struct page *page) { - struct rb_node *node = root_stable_tree.rb_node; + int nid; + struct rb_root *root; + struct rb_node **new; + struct rb_node *parent; struct stable_node *stable_node; + struct stable_node *page_node; - stable_node = page_stable_node(page); - if (stable_node) { /* ksm page forked */ + page_node = page_stable_node(page); + if (page_node && page_node->head != &migrate_nodes) { + /* ksm page forked */ get_page(page); return page; } - while (node) { + nid = get_kpfn_nid(page_to_pfn(page)); + root = root_stable_tree + nid; +again: + new = &root->rb_node; + parent = NULL; + + while (*new) { struct page *tree_page; int ret; cond_resched(); - stable_node = rb_entry(node, struct stable_node, node); - tree_page = get_ksm_page(stable_node); + stable_node = rb_entry(*new, struct stable_node, node); + tree_page = get_ksm_page(stable_node, false); if (!tree_page) return NULL; ret = memcmp_pages(page, tree_page); + put_page(tree_page); - if (ret < 0) { - put_page(tree_page); - node = node->rb_left; - } else if (ret > 0) { - put_page(tree_page); - node = node->rb_right; - } else - return tree_page; + parent = *new; + if (ret < 0) + new = &parent->rb_left; + else if (ret > 0) + new = &parent->rb_right; + else { + /* + * Lock and unlock the stable_node's page (which + * might already have been migrated) so that page + * migration is sure to notice its raised count. + * It would be more elegant to return stable_node + * than kpage, but that involves more changes. + */ + tree_page = get_ksm_page(stable_node, true); + if (tree_page) { + unlock_page(tree_page); + if (get_kpfn_nid(stable_node->kpfn) != + NUMA(stable_node->nid)) { + put_page(tree_page); + goto replace; + } + return tree_page; + } + /* + * There is now a place for page_node, but the tree may + * have been rebalanced, so re-evaluate parent and new. + */ + if (page_node) + goto again; + return NULL; + } } - return NULL; + if (!page_node) + return NULL; + + list_del(&page_node->list); + DO_NUMA(page_node->nid = nid); + rb_link_node(&page_node->node, parent, new); + rb_insert_color(&page_node->node, root); + get_page(page); + return page; + +replace: + if (page_node) { + list_del(&page_node->list); + DO_NUMA(page_node->nid = nid); + rb_replace_node(&stable_node->node, &page_node->node, root); + get_page(page); + } else { + rb_erase(&stable_node->node, root); + page = NULL; + } + stable_node->head = &migrate_nodes; + list_add(&stable_node->list, stable_node->head); + return page; } /* - * stable_tree_insert - insert rmap_item pointing to new ksm page + * stable_tree_insert - insert stable tree node pointing to new ksm page * into the stable tree. * * This function returns the stable tree node just allocated on success, @@ -991,17 +1250,25 @@ static struct page *stable_tree_search(struct page *page) */ static struct stable_node *stable_tree_insert(struct page *kpage) { - struct rb_node **new = &root_stable_tree.rb_node; + int nid; + unsigned long kpfn; + struct rb_root *root; + struct rb_node **new; struct rb_node *parent = NULL; struct stable_node *stable_node; + kpfn = page_to_pfn(kpage); + nid = get_kpfn_nid(kpfn); + root = root_stable_tree + nid; + new = &root->rb_node; + while (*new) { struct page *tree_page; int ret; cond_resched(); stable_node = rb_entry(*new, struct stable_node, node); - tree_page = get_ksm_page(stable_node); + tree_page = get_ksm_page(stable_node, false); if (!tree_page) return NULL; @@ -1027,13 +1294,12 @@ static struct stable_node *stable_tree_insert(struct page *kpage) if (!stable_node) return NULL; - 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); + stable_node->kpfn = kpfn; set_page_stable_node(kpage, stable_node); + DO_NUMA(stable_node->nid = nid); + rb_link_node(&stable_node->node, parent, new); + rb_insert_color(&stable_node->node, root); return stable_node; } @@ -1056,10 +1322,15 @@ static struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, struct page *page, struct page **tree_pagep) - { - struct rb_node **new = &root_unstable_tree.rb_node; + struct rb_node **new; + struct rb_root *root; struct rb_node *parent = NULL; + int nid; + + nid = get_kpfn_nid(page_to_pfn(page)); + root = root_unstable_tree + nid; + new = &root->rb_node; while (*new) { struct rmap_item *tree_rmap_item; @@ -1089,6 +1360,15 @@ struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, } else if (ret > 0) { put_page(tree_page); new = &parent->rb_right; + } else if (!ksm_merge_across_nodes && + page_to_nid(tree_page) != nid) { + /* + * If tree_page has been migrated to another NUMA node, + * it will be flushed out and put in the right unstable + * tree next time: only merge with it when across_nodes. + */ + put_page(tree_page); + return NULL; } else { *tree_pagep = tree_page; return tree_rmap_item; @@ -1097,8 +1377,9 @@ struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, rmap_item->address |= UNSTABLE_FLAG; rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); + DO_NUMA(rmap_item->nid = nid); rb_link_node(&rmap_item->node, parent, new); - rb_insert_color(&rmap_item->node, &root_unstable_tree); + rb_insert_color(&rmap_item->node, root); ksm_pages_unshared++; return NULL; @@ -1140,10 +1421,29 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) unsigned int checksum; int err; - remove_rmap_item_from_tree(rmap_item); + stable_node = page_stable_node(page); + if (stable_node) { + if (stable_node->head != &migrate_nodes && + get_kpfn_nid(stable_node->kpfn) != NUMA(stable_node->nid)) { + rb_erase(&stable_node->node, + root_stable_tree + NUMA(stable_node->nid)); + stable_node->head = &migrate_nodes; + list_add(&stable_node->list, stable_node->head); + } + if (stable_node->head != &migrate_nodes && + rmap_item->head == stable_node) + return; + } /* We first start with searching the page inside the stable tree */ kpage = stable_tree_search(page); + if (kpage == page && rmap_item->head == stable_node) { + put_page(kpage); + return; + } + + remove_rmap_item_from_tree(rmap_item); + if (kpage) { err = try_to_merge_with_ksm_page(rmap_item, page, kpage); if (!err) { @@ -1177,14 +1477,11 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) kpage = try_to_merge_two_pages(rmap_item, page, tree_rmap_item, tree_page); put_page(tree_page); - /* - * As soon as we merge this page, we want to remove the - * rmap_item of the page we have merged with from the unstable - * tree, and insert it instead as new node in the stable tree. - */ if (kpage) { - remove_rmap_item_from_tree(tree_rmap_item); - + /* + * The pages were successfully merged: insert new + * node in the stable tree and add both rmap_items. + */ lock_page(kpage); stable_node = stable_tree_insert(kpage); if (stable_node) { @@ -1241,18 +1538,59 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page) struct mm_slot *slot; struct vm_area_struct *vma; struct rmap_item *rmap_item; + int nid; if (list_empty(&ksm_mm_head.mm_list)) return NULL; slot = ksm_scan.mm_slot; if (slot == &ksm_mm_head) { - root_unstable_tree = RB_ROOT; + /* + * A number of pages can hang around indefinitely on per-cpu + * pagevecs, raised page count preventing write_protect_page + * from merging them. Though it doesn't really matter much, + * it is puzzling to see some stuck in pages_volatile until + * other activity jostles them out, and they also prevented + * LTP's KSM test from succeeding deterministically; so drain + * them here (here rather than on entry to ksm_do_scan(), + * so we don't IPI too often when pages_to_scan is set low). + */ + lru_add_drain_all(); + + /* + * Whereas stale stable_nodes on the stable_tree itself + * get pruned in the regular course of stable_tree_search(), + * those moved out to the migrate_nodes list can accumulate: + * so prune them once before each full scan. + */ + if (!ksm_merge_across_nodes) { + struct stable_node *stable_node; + struct list_head *this, *next; + struct page *page; + + list_for_each_safe(this, next, &migrate_nodes) { + stable_node = list_entry(this, + struct stable_node, list); + page = get_ksm_page(stable_node, false); + if (page) + put_page(page); + cond_resched(); + } + } + + for (nid = 0; nid < ksm_nr_node_ids; nid++) + root_unstable_tree[nid] = RB_ROOT; spin_lock(&ksm_mmlist_lock); slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); ksm_scan.mm_slot = slot; spin_unlock(&ksm_mmlist_lock); + /* + * Although we tested list_empty() above, a racing __ksm_exit + * of the last mm on the list may have removed it since then. + */ + if (slot == &ksm_mm_head) + return NULL; next_mm: ksm_scan.address = 0; ksm_scan.rmap_list = &slot->rmap_list; @@ -1277,7 +1615,13 @@ next_mm: if (ksm_test_exit(mm)) break; *page = follow_page(vma, ksm_scan.address, FOLL_GET); - if (!IS_ERR_OR_NULL(*page) && PageAnon(*page)) { + if (IS_ERR_OR_NULL(*page)) { + ksm_scan.address += PAGE_SIZE; + cond_resched(); + continue; + } + if (PageAnon(*page) || + page_trans_compound_anon(*page)) { flush_anon_page(vma, *page, ksm_scan.address); flush_dcache_page(*page); rmap_item = get_next_rmap_item(slot, @@ -1291,8 +1635,7 @@ next_mm: up_read(&mm->mmap_sem); return rmap_item; } - if (!IS_ERR_OR_NULL(*page)) - put_page(*page); + put_page(*page); ksm_scan.address += PAGE_SIZE; cond_resched(); } @@ -1321,7 +1664,7 @@ next_mm: * or when all VM_MERGEABLE areas have been unmapped (and * mmap_sem then protects against race with MADV_MERGEABLE). */ - hlist_del(&slot->link); + hash_del(&slot->link); list_del(&slot->mm_list); spin_unlock(&ksm_mmlist_lock); @@ -1352,13 +1695,12 @@ static void ksm_do_scan(unsigned int scan_npages) struct rmap_item *rmap_item; struct page *uninitialized_var(page); - while (scan_npages--) { + while (scan_npages-- && likely(!freezing(current))) { cond_resched(); rmap_item = scan_get_next_rmap_item(&page); if (!rmap_item) return; - if (!PageKsm(page) || !in_stable_tree(rmap_item)) - cmp_and_merge_page(page, rmap_item); + cmp_and_merge_page(page, rmap_item); put_page(page); } } @@ -1370,19 +1712,23 @@ static int ksmd_should_run(void) static int ksm_scan_thread(void *nothing) { + set_freezable(); set_user_nice(current, 5); while (!kthread_should_stop()) { mutex_lock(&ksm_thread_mutex); + wait_while_offlining(); if (ksmd_should_run()) ksm_do_scan(ksm_thread_pages_to_scan); mutex_unlock(&ksm_thread_mutex); + try_to_freeze(); + if (ksmd_should_run()) { schedule_timeout_interruptible( msecs_to_jiffies(ksm_thread_sleep_millisecs)); } else { - wait_event_interruptible(ksm_thread_wait, + wait_event_freezable(ksm_thread_wait, ksmd_should_run() || kthread_should_stop()); } } @@ -1402,10 +1748,14 @@ 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_NONLINEAR | VM_MIXEDMAP | VM_SAO)) + VM_HUGETLB | VM_NONLINEAR | VM_MIXEDMAP)) return 0; /* just ignore the advice */ +#ifdef VM_SAO + if (*vm_flags & VM_SAO) + return 0; +#endif + if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { err = __ksm_enter(mm); if (err) @@ -1447,11 +1797,19 @@ int __ksm_enter(struct mm_struct *mm) spin_lock(&ksm_mmlist_lock); insert_to_mm_slots_hash(mm, mm_slot); /* - * Insert just behind the scanning cursor, to let the area settle + * When KSM_RUN_MERGE (or KSM_RUN_STOP), + * insert just behind the scanning cursor, to let the area settle * down a little; when fork is followed by immediate exec, we don't * want ksmd to waste time setting up and tearing down an rmap_list. + * + * But when KSM_RUN_UNMERGE, it's important to insert ahead of its + * scanning cursor, otherwise KSM pages in newly forked mms will be + * missed: then we might as well insert at the end of the list. */ - list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); + if (ksm_run & KSM_RUN_UNMERGE) + list_add_tail(&mm_slot->mm_list, &ksm_mm_head.mm_list); + else + list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); spin_unlock(&ksm_mmlist_lock); set_bit(MMF_VM_MERGEABLE, &mm->flags); @@ -1481,7 +1839,7 @@ void __ksm_exit(struct mm_struct *mm) mm_slot = get_mm_slot(mm); if (mm_slot && ksm_scan.mm_slot != mm_slot) { if (!mm_slot->rmap_list) { - hlist_del(&mm_slot->link); + hash_del(&mm_slot->link); list_del(&mm_slot->mm_list); easy_to_free = 1; } else { @@ -1501,158 +1859,64 @@ void __ksm_exit(struct mm_struct *mm) } } -struct page *ksm_does_need_to_copy(struct page *page, +struct page *ksm_might_need_to_copy(struct page *page, struct vm_area_struct *vma, unsigned long address) { + struct anon_vma *anon_vma = page_anon_vma(page); struct page *new_page; + if (PageKsm(page)) { + if (page_stable_node(page) && + !(ksm_run & KSM_RUN_UNMERGE)) + return page; /* no need to copy it */ + } else if (!anon_vma) { + return page; /* no need to copy it */ + } else if (anon_vma->root == vma->anon_vma->root && + page->index == linear_page_index(vma, address)) { + return page; /* still no need to copy it */ + } + if (!PageUptodate(page)) + return page; /* let do_swap_page report the error */ + 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); } 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 anon_vma_chain *vmac; - struct vm_area_struct *vma; - - anon_vma_lock(anon_vma); - list_for_each_entry(vmac, &anon_vma->head, same_anon_vma) { - vma = vmac->vma; - 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; - } - anon_vma_unlock(anon_vma); - 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) +int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc) { 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 anon_vma_chain *vmac; - struct vm_area_struct *vma; - - anon_vma_lock(anon_vma); - list_for_each_entry(vmac, &anon_vma->head, same_anon_vma) { - vma = vmac->vma; - 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)) { - anon_vma_unlock(anon_vma); - goto out; - } - } - anon_vma_unlock(anon_vma); - } - 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_PAGE(!PageKsm(page), page); - VM_BUG_ON(!PageKsm(page)); - VM_BUG_ON(!PageLocked(page)); + /* + * Rely on the page lock to protect against concurrent modifications + * to that page's node of the stable tree. + */ + VM_BUG_ON_PAGE(!PageLocked(page), page); stable_node = page_stable_node(page); if (!stable_node) return ret; again: - hlist_for_each_entry(rmap_item, hlist, &stable_node->hlist, hlist) { + hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { struct anon_vma *anon_vma = rmap_item->anon_vma; struct anon_vma_chain *vmac; struct vm_area_struct *vma; - anon_vma_lock(anon_vma); - list_for_each_entry(vmac, &anon_vma->head, same_anon_vma) { + anon_vma_lock_read(anon_vma); + anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root, + 0, ULONG_MAX) { vma = vmac->vma; if (rmap_item->address < vma->vm_start || rmap_item->address >= vma->vm_end) @@ -1666,13 +1930,21 @@ again: if ((rmap_item->mm == vma->vm_mm) == search_new_forks) continue; - ret = rmap_one(page, vma, rmap_item->address, arg); + if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) + continue; + + ret = rwc->rmap_one(page, vma, + rmap_item->address, rwc->arg); if (ret != SWAP_AGAIN) { - anon_vma_unlock(anon_vma); + anon_vma_unlock_read(anon_vma); + goto out; + } + if (rwc->done && rwc->done(page)) { + anon_vma_unlock_read(anon_vma); goto out; } } - anon_vma_unlock(anon_vma); + anon_vma_unlock_read(anon_vma); } if (!search_new_forks++) goto again; @@ -1680,71 +1952,128 @@ out: return ret; } +#ifdef CONFIG_MIGRATION 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); + VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage); + VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); + VM_BUG_ON_PAGE(newpage->mapping != oldpage->mapping, newpage); stable_node = page_stable_node(newpage); if (stable_node) { - VM_BUG_ON(stable_node->kpfn != page_to_pfn(oldpage)); + VM_BUG_ON_PAGE(stable_node->kpfn != page_to_pfn(oldpage), oldpage); stable_node->kpfn = page_to_pfn(newpage); + /* + * newpage->mapping was set in advance; now we need smp_wmb() + * to make sure that the new stable_node->kpfn is visible + * to get_ksm_page() before it can see that oldpage->mapping + * has gone stale (or that PageSwapCache has been cleared). + */ + smp_wmb(); + set_page_stable_node(oldpage, NULL); } } #endif /* CONFIG_MIGRATION */ #ifdef CONFIG_MEMORY_HOTREMOVE -static struct stable_node *ksm_check_stable_tree(unsigned long start_pfn, - unsigned long end_pfn) +static int just_wait(void *word) { - struct rb_node *node; + schedule(); + return 0; +} - for (node = rb_first(&root_stable_tree); node; node = rb_next(node)) { - struct stable_node *stable_node; +static void wait_while_offlining(void) +{ + while (ksm_run & KSM_RUN_OFFLINE) { + mutex_unlock(&ksm_thread_mutex); + wait_on_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE), + just_wait, TASK_UNINTERRUPTIBLE); + mutex_lock(&ksm_thread_mutex); + } +} - stable_node = rb_entry(node, struct stable_node, node); +static void ksm_check_stable_tree(unsigned long start_pfn, + unsigned long end_pfn) +{ + struct stable_node *stable_node; + struct list_head *this, *next; + struct rb_node *node; + int nid; + + for (nid = 0; nid < ksm_nr_node_ids; nid++) { + node = rb_first(root_stable_tree + nid); + while (node) { + stable_node = rb_entry(node, struct stable_node, node); + if (stable_node->kpfn >= start_pfn && + stable_node->kpfn < end_pfn) { + /* + * Don't get_ksm_page, page has already gone: + * which is why we keep kpfn instead of page* + */ + remove_node_from_stable_tree(stable_node); + node = rb_first(root_stable_tree + nid); + } else + node = rb_next(node); + cond_resched(); + } + } + list_for_each_safe(this, next, &migrate_nodes) { + stable_node = list_entry(this, struct stable_node, list); if (stable_node->kpfn >= start_pfn && stable_node->kpfn < end_pfn) - return stable_node; + remove_node_from_stable_tree(stable_node); + cond_resched(); } - 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. + * Prevent ksm_do_scan(), unmerge_and_remove_all_rmap_items() + * and remove_all_stable_nodes() while memory is going offline: + * it is unsafe for them to touch the stable tree at this time. + * But unmerge_ksm_pages(), rmap lookups and other entry points + * which do not need the ksm_thread_mutex are all safe. */ mutex_lock(&ksm_thread_mutex); + ksm_run |= KSM_RUN_OFFLINE; + mutex_unlock(&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. + * pages which have been offlined: prune those from the tree, + * otherwise get_ksm_page() might later try to access a + * non-existent struct page. */ - while ((stable_node = ksm_check_stable_tree(mn->start_pfn, - mn->start_pfn + mn->nr_pages)) != NULL) - remove_node_from_stable_tree(stable_node); + ksm_check_stable_tree(mn->start_pfn, + mn->start_pfn + mn->nr_pages); /* fallthrough */ case MEM_CANCEL_OFFLINE: + mutex_lock(&ksm_thread_mutex); + ksm_run &= ~KSM_RUN_OFFLINE; mutex_unlock(&ksm_thread_mutex); + + smp_mb(); /* wake_up_bit advises this */ + wake_up_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE)); break; } return NOTIFY_OK; } +#else +static void wait_while_offlining(void) +{ +} #endif /* CONFIG_MEMORY_HOTREMOVE */ #ifdef CONFIG_SYSFS @@ -1771,7 +2100,7 @@ static ssize_t sleep_millisecs_store(struct kobject *kobj, unsigned long msecs; int err; - err = strict_strtoul(buf, 10, &msecs); + err = kstrtoul(buf, 10, &msecs); if (err || msecs > UINT_MAX) return -EINVAL; @@ -1794,7 +2123,7 @@ static ssize_t pages_to_scan_store(struct kobject *kobj, int err; unsigned long nr_pages; - err = strict_strtoul(buf, 10, &nr_pages); + err = kstrtoul(buf, 10, &nr_pages); if (err || nr_pages > UINT_MAX) return -EINVAL; @@ -1807,7 +2136,7 @@ KSM_ATTR(pages_to_scan); static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return sprintf(buf, "%u\n", ksm_run); + return sprintf(buf, "%lu\n", ksm_run); } static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, @@ -1816,7 +2145,7 @@ static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, int err; unsigned long flags; - err = strict_strtoul(buf, 10, &flags); + err = kstrtoul(buf, 10, &flags); if (err || flags > UINT_MAX) return -EINVAL; if (flags > KSM_RUN_UNMERGE) @@ -1830,12 +2159,13 @@ static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, */ mutex_lock(&ksm_thread_mutex); + wait_while_offlining(); if (ksm_run != flags) { ksm_run = flags; if (flags & KSM_RUN_UNMERGE) { - current->flags |= PF_OOM_ORIGIN; + set_current_oom_origin(); err = unmerge_and_remove_all_rmap_items(); - current->flags &= ~PF_OOM_ORIGIN; + clear_current_oom_origin(); if (err) { ksm_run = KSM_RUN_STOP; count = err; @@ -1851,6 +2181,64 @@ static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, } KSM_ATTR(run); +#ifdef CONFIG_NUMA +static ssize_t merge_across_nodes_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%u\n", ksm_merge_across_nodes); +} + +static ssize_t merge_across_nodes_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int err; + unsigned long knob; + + err = kstrtoul(buf, 10, &knob); + if (err) + return err; + if (knob > 1) + return -EINVAL; + + mutex_lock(&ksm_thread_mutex); + wait_while_offlining(); + if (ksm_merge_across_nodes != knob) { + if (ksm_pages_shared || remove_all_stable_nodes()) + err = -EBUSY; + else if (root_stable_tree == one_stable_tree) { + struct rb_root *buf; + /* + * This is the first time that we switch away from the + * default of merging across nodes: must now allocate + * a buffer to hold as many roots as may be needed. + * Allocate stable and unstable together: + * MAXSMP NODES_SHIFT 10 will use 16kB. + */ + buf = kcalloc(nr_node_ids + nr_node_ids, sizeof(*buf), + GFP_KERNEL); + /* Let us assume that RB_ROOT is NULL is zero */ + if (!buf) + err = -ENOMEM; + else { + root_stable_tree = buf; + root_unstable_tree = buf + nr_node_ids; + /* Stable tree is empty but not the unstable */ + root_unstable_tree[0] = one_unstable_tree[0]; + } + } + if (!err) { + ksm_merge_across_nodes = knob; + ksm_nr_node_ids = knob ? 1 : nr_node_ids; + } + } + mutex_unlock(&ksm_thread_mutex); + + return err ? err : count; +} +KSM_ATTR(merge_across_nodes); +#endif + static ssize_t pages_shared_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { @@ -1905,6 +2293,9 @@ static struct attribute *ksm_attrs[] = { &pages_unshared_attr.attr, &pages_volatile_attr.attr, &full_scans_attr.attr, +#ifdef CONFIG_NUMA + &merge_across_nodes_attr.attr, +#endif NULL, }; @@ -1943,10 +2334,7 @@ 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. - */ + /* There is no significance to this priority 100 */ hotplug_memory_notifier(ksm_memory_callback, 100); #endif return 0; @@ -1956,4 +2344,4 @@ out_free: out: return err; } -module_init(ksm_init) +subsys_initcall(ksm_init); |