#include <linux/wait.h>
#include <linux/slab.h>
#include <linux/rbtree.h>
+#include <linux/memory.h>
#include <linux/mmu_notifier.h>
#include <linux/swap.h>
#include <linux/ksm.h>
#include <asm/tlbflush.h>
+#include "internal.h"
/*
* A few notes about the KSM scanning process,
* struct mm_slot - ksm information per mm that is being scanned
* @link: link to the mm_slots hash list
* @mm_list: link into the mm_slots list, rooted in ksm_mm_head
- * @rmap_list: head for this mm_slot's list of rmap_items
+ * @rmap_list: head for this mm_slot's singly-linked list of rmap_items
* @mm: the mm that this information is valid for
*/
struct mm_slot {
struct hlist_node link;
struct list_head mm_list;
- struct list_head rmap_list;
+ struct rmap_item *rmap_list;
struct mm_struct *mm;
};
* struct ksm_scan - cursor for scanning
* @mm_slot: the current mm_slot we are scanning
* @address: the next address inside that to be scanned
- * @rmap_item: the current rmap that we are scanning inside the rmap_list
+ * @rmap_list: link to the next rmap to be scanned in the rmap_list
* @seqnr: count of completed full scans (needed when removing unstable node)
*
* There is only the one ksm_scan instance of this cursor structure.
struct ksm_scan {
struct mm_slot *mm_slot;
unsigned long address;
- struct rmap_item *rmap_item;
+ struct rmap_item **rmap_list;
unsigned long seqnr;
};
+/**
+ * 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
- * @link: link into mm_slot's rmap_list (rmap_list is per mm)
+ * @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
* @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 list_head link;
+ struct rmap_item *rmap_list;
+ 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;
};
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 */
/* 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;
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;
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;
}
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 */
bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
% MM_SLOTS_HASH_HEADS];
mm_slot->mm = mm;
- INIT_LIST_HEAD(&mm_slot->rmap_list);
hlist_add_head(&mm_slot->link, bucket);
}
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,
return (ret & VM_FAULT_OOM) ? -ENOMEM : 0;
}
-static void break_cow(struct mm_struct *mm, unsigned long addr)
+static void break_cow(struct rmap_item *rmap_item)
{
+ struct mm_struct *mm = rmap_item->mm;
+ 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;
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;
}
/*
*/
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
ksm_pages_unshared--;
rmap_item->address &= PAGE_MASK;
}
-
+out:
cond_resched(); /* we're called from many long loops */
}
static void remove_trailing_rmap_items(struct mm_slot *mm_slot,
- struct list_head *cur)
+ struct rmap_item **rmap_list)
{
- struct rmap_item *rmap_item;
-
- while (cur != &mm_slot->rmap_list) {
- rmap_item = list_entry(cur, struct rmap_item, link);
- cur = cur->next;
+ while (*rmap_list) {
+ struct rmap_item *rmap_item = *rmap_list;
+ *rmap_list = rmap_item->rmap_list;
remove_rmap_item_from_tree(rmap_item);
- list_del(&rmap_item->link);
free_rmap_item(rmap_item);
}
}
goto error;
}
- remove_trailing_rmap_items(mm_slot, mm_slot->rmap_list.next);
+ remove_trailing_rmap_items(mm_slot, &mm_slot->rmap_list);
spin_lock(&ksm_mmlist_lock);
ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next,
* Check that no O_DIRECT or similar I/O is in progress on the
* page
*/
- if ((page_mapcount(page) + 2 + swapped) != page_count(page)) {
+ if (page_mapcount(page) + 1 + swapped != page_count(page)) {
set_pte_at_notify(mm, addr, ptep, entry);
goto out_unlock;
}
/**
* replace_page - replace page in vma by new ksm page
- * @vma: vma that holds the pte pointing to oldpage
- * @oldpage: the page we are replacing by newpage
- * @newpage: the ksm page we replace oldpage by
+ * @vma: vma that holds the pte pointing to page
+ * @page: the page we are replacing by kpage
+ * @kpage: the ksm page we replace page by
* @orig_pte: the original value of the pte
*
* Returns 0 on success, -EFAULT on failure.
*/
-static int replace_page(struct vm_area_struct *vma, struct page *oldpage,
- struct page *newpage, pte_t orig_pte)
+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;
pte_t *ptep;
spinlock_t *ptl;
unsigned long addr;
- pgprot_t prot;
int err = -EFAULT;
- prot = vm_get_page_prot(vma->vm_flags & ~VM_WRITE);
-
- addr = page_address_in_vma(oldpage, vma);
+ addr = page_address_in_vma(page, vma);
if (addr == -EFAULT)
goto out;
goto out;
}
- get_page(newpage);
- page_add_ksm_rmap(newpage);
+ get_page(kpage);
+ page_add_anon_rmap(kpage, vma, addr);
flush_cache_page(vma, addr, pte_pfn(*ptep));
ptep_clear_flush(vma, addr, ptep);
- set_pte_at_notify(mm, addr, ptep, mk_pte(newpage, prot));
+ set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
- page_remove_rmap(oldpage);
- put_page(oldpage);
+ page_remove_rmap(page);
+ put_page(page);
pte_unmap_unlock(ptep, ptl);
err = 0;
/*
* try_to_merge_one_page - take two pages and merge them into one
- * @vma: the vma that hold the pte pointing into oldpage
- * @oldpage: the page that we want to replace with newpage
- * @newpage: the page that we want to map instead of oldpage
- *
- * Note:
- * oldpage should be a PageAnon page, while newpage should be a PageKsm page,
- * or a newly allocated kernel page which page_add_ksm_rmap will make PageKsm.
+ * @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 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.
*/
static int try_to_merge_one_page(struct vm_area_struct *vma,
- struct page *oldpage,
- struct page *newpage)
+ struct page *page, struct page *kpage)
{
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(oldpage))
+ if (!PageAnon(page))
goto out;
- get_page(newpage);
- get_page(oldpage);
-
/*
* We need the page lock to read a stable PageSwapCache in
* write_protect_page(). We use trylock_page() instead of
* prefer to continue scanning and merging different pages,
* then come back to this page when it is unlocked.
*/
- if (!trylock_page(oldpage))
- goto out_putpage;
+ if (!trylock_page(page))
+ goto out;
/*
* If this anonymous page is mapped only here, its pte may need
* to be write-protected. If it's mapped elsewhere, all of its
* 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, oldpage, &orig_pte)) {
- unlock_page(oldpage);
- goto out_putpage;
+ 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);
}
- unlock_page(oldpage);
- if (pages_identical(oldpage, newpage))
- err = replace_page(vma, oldpage, newpage, 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 */
+ }
+ }
-out_putpage:
- put_page(oldpage);
- put_page(newpage);
+ unlock_page(page);
out:
return err;
}
/*
* try_to_merge_with_ksm_page - like try_to_merge_two_pages,
* but no new kernel page is allocated: kpage must already be a ksm page.
+ *
+ * This function returns 0 if the pages were merged, -EFAULT otherwise.
*/
-static int try_to_merge_with_ksm_page(struct mm_struct *mm1,
- unsigned long addr1,
- struct page *page1,
- struct page *kpage)
+static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item,
+ struct page *page, struct page *kpage)
{
+ struct mm_struct *mm = rmap_item->mm;
struct vm_area_struct *vma;
int err = -EFAULT;
- down_read(&mm1->mmap_sem);
- if (ksm_test_exit(mm1))
+ down_read(&mm->mmap_sem);
+ if (ksm_test_exit(mm))
+ goto out;
+ vma = find_vma(mm, rmap_item->address);
+ if (!vma || vma->vm_start > rmap_item->address)
goto out;
- vma = find_vma(mm1, addr1);
- if (!vma || vma->vm_start > addr1)
+ err = try_to_merge_one_page(vma, page, kpage);
+ if (err)
goto out;
- err = try_to_merge_one_page(vma, page1, kpage);
+ /* Must get reference to anon_vma while still holding mmap_sem */
+ hold_anon_vma(rmap_item, vma->anon_vma);
out:
- up_read(&mm1->mmap_sem);
+ up_read(&mm->mmap_sem);
return err;
}
* try_to_merge_two_pages - take two identical pages and prepare them
* to be merged into one page.
*
- * This function returns 0 if we successfully mapped two identical pages
- * into one page, -EFAULT otherwise.
+ * 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 int try_to_merge_two_pages(struct mm_struct *mm1, unsigned long addr1,
- struct page *page1, struct mm_struct *mm2,
- unsigned long addr2, struct page *page2)
+static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item,
+ struct page *page,
+ struct rmap_item *tree_rmap_item,
+ struct page *tree_page)
{
- 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 err;
-
- kpage = alloc_page(GFP_HIGHUSER);
- if (!kpage)
- return err;
-
- down_read(&mm1->mmap_sem);
- if (ksm_test_exit(mm1)) {
- up_read(&mm1->mmap_sem);
- goto out;
- }
- vma = find_vma(mm1, addr1);
- if (!vma || vma->vm_start > addr1) {
- up_read(&mm1->mmap_sem);
- goto out;
- }
-
- copy_user_highpage(kpage, page1, addr1, vma);
- err = try_to_merge_one_page(vma, page1, kpage);
- up_read(&mm1->mmap_sem);
+ int err;
+ err = try_to_merge_with_ksm_page(rmap_item, page, NULL);
if (!err) {
- err = try_to_merge_with_ksm_page(mm2, addr2, page2, kpage);
+ err = try_to_merge_with_ksm_page(tree_rmap_item,
+ tree_page, page);
/*
* If that fails, we have a ksm page with only one pte
* pointing to it: so break it.
*/
if (err)
- break_cow(mm1, addr1);
+ break_cow(rmap_item);
}
-out:
- put_page(kpage);
- return err;
+ return err ? NULL : page;
}
/*
- * stable_tree_search - search page inside the stable tree
- * @page: the page that we are searching identical pages to.
- * @page2: pointer into identical page that we are holding inside the stable
- * tree that we have found.
- * @rmap_item: the reverse mapping item
+ * stable_tree_search - search for page inside the stable tree
*
* 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 **page2,
- struct rmap_item *rmap_item)
+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();
- page2[0] = get_ksm_page(tree_rmap_item);
- if (page2[0])
- 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, page2[0]);
+ ret = memcmp_pages(page, tree_page);
if (ret < 0) {
- put_page(page2[0]);
+ put_page(tree_page);
node = node->rb_left;
} else if (ret > 0) {
- put_page(page2[0]);
+ put_page(tree_page);
node = node->rb_right;
- } else {
- return tree_rmap_item;
- }
+ } else
+ return tree_page;
}
return NULL;
* stable_tree_insert - insert rmap_item pointing to new ksm page
* into the stable tree.
*
- * @page: the page that we are searching identical page to inside the stable
- * tree.
- * @rmap_item: pointer to the reverse mapping item.
- *
- * 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 *page,
- 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(page, tree_page);
+ ret = memcmp_pages(kpage, tree_page);
put_page(tree_page);
parent = *new;
}
}
- 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;
}
/*
- * unstable_tree_search_insert - search and insert items into the unstable tree.
- *
- * @page: the page that we are going to search for identical page or to insert
- * into the unstable tree
- * @page2: pointer into identical page that was found inside the unstable tree
- * @rmap_item: the reverse mapping item of page
+ * unstable_tree_search_insert - search for identical page,
+ * else insert rmap_item into the unstable tree.
*
* This function searches for a page in the unstable tree identical to the
* page currently being scanned; and if no identical page is found in the
* This function does both searching and inserting, because they share
* the same walking algorithm in an rbtree.
*/
-static struct rmap_item *unstable_tree_search_insert(struct page *page,
- struct page **page2,
- struct rmap_item *rmap_item)
+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 *parent = NULL;
while (*new) {
struct rmap_item *tree_rmap_item;
+ struct page *tree_page;
int ret;
cond_resched();
tree_rmap_item = rb_entry(*new, struct rmap_item, node);
- page2[0] = get_mergeable_page(tree_rmap_item);
- if (!page2[0])
+ tree_page = get_mergeable_page(tree_rmap_item);
+ if (!tree_page)
return NULL;
/*
- * Don't substitute an unswappable ksm page
- * just for one good swappable forked page.
+ * Don't substitute a ksm page for a forked page.
*/
- if (page == page2[0]) {
- put_page(page2[0]);
+ if (page == tree_page) {
+ put_page(tree_page);
return NULL;
}
- ret = memcmp_pages(page, page2[0]);
+ ret = memcmp_pages(page, tree_page);
parent = *new;
if (ret < 0) {
- put_page(page2[0]);
+ put_page(tree_page);
new = &parent->rb_left;
} else if (ret > 0) {
- put_page(page2[0]);
+ put_page(tree_page);
new = &parent->rb_right;
} else {
+ *tree_pagep = tree_page;
return tree_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);
* 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++;
}
/*
*/
static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
{
- struct page *page2[1];
struct rmap_item *tree_rmap_item;
+ struct page *tree_page = NULL;
+ struct stable_node *stable_node;
+ struct page *kpage;
unsigned int checksum;
int err;
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, page2, rmap_item);
- if (tree_rmap_item) {
- if (page == page2[0]) /* forked */
- err = 0;
- else
- err = try_to_merge_with_ksm_page(rmap_item->mm,
- rmap_item->address,
- page, page2[0]);
- put_page(page2[0]);
-
+ 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->mm, rmap_item->address);
-
- /*
- * 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) {
return;
}
- tree_rmap_item = unstable_tree_search_insert(page, page2, rmap_item);
+ tree_rmap_item =
+ unstable_tree_search_insert(rmap_item, page, &tree_page);
if (tree_rmap_item) {
- err = try_to_merge_two_pages(rmap_item->mm,
- rmap_item->address, page,
- tree_rmap_item->mm,
- tree_rmap_item->address, page2[0]);
+ 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 (!err) {
+ 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(page2[0], tree_rmap_item))
- stable_tree_append(rmap_item, tree_rmap_item);
- else {
- break_cow(tree_rmap_item->mm,
- tree_rmap_item->address);
- break_cow(rmap_item->mm, rmap_item->address);
+ if (!stable_node) {
+ break_cow(tree_rmap_item);
+ break_cow(rmap_item);
}
}
-
- put_page(page2[0]);
}
}
static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot,
- struct list_head *cur,
+ struct rmap_item **rmap_list,
unsigned long addr)
{
struct rmap_item *rmap_item;
- while (cur != &mm_slot->rmap_list) {
- rmap_item = list_entry(cur, struct rmap_item, link);
+ while (*rmap_list) {
+ rmap_item = *rmap_list;
if ((rmap_item->address & PAGE_MASK) == addr)
return rmap_item;
if (rmap_item->address > addr)
break;
- cur = cur->next;
+ *rmap_list = rmap_item->rmap_list;
remove_rmap_item_from_tree(rmap_item);
- list_del(&rmap_item->link);
free_rmap_item(rmap_item);
}
/* It has already been zeroed */
rmap_item->mm = mm_slot->mm;
rmap_item->address = addr;
- list_add_tail(&rmap_item->link, cur);
+ rmap_item->rmap_list = *rmap_list;
+ *rmap_list = rmap_item;
}
return rmap_item;
}
spin_unlock(&ksm_mmlist_lock);
next_mm:
ksm_scan.address = 0;
- ksm_scan.rmap_item = list_entry(&slot->rmap_list,
- struct rmap_item, link);
+ ksm_scan.rmap_list = &slot->rmap_list;
}
mm = slot->mm;
flush_anon_page(vma, *page, ksm_scan.address);
flush_dcache_page(*page);
rmap_item = get_next_rmap_item(slot,
- ksm_scan.rmap_item->link.next,
- ksm_scan.address);
+ ksm_scan.rmap_list, ksm_scan.address);
if (rmap_item) {
- ksm_scan.rmap_item = rmap_item;
+ ksm_scan.rmap_list =
+ &rmap_item->rmap_list;
ksm_scan.address += PAGE_SIZE;
} else
put_page(*page);
if (ksm_test_exit(mm)) {
ksm_scan.address = 0;
- ksm_scan.rmap_item = list_entry(&slot->rmap_list,
- struct rmap_item, link);
+ ksm_scan.rmap_list = &slot->rmap_list;
}
/*
* Nuke all the rmap_items that are above this current rmap:
* because there were no VM_MERGEABLE vmas with such addresses.
*/
- remove_trailing_rmap_items(slot, ksm_scan.rmap_item->link.next);
+ remove_trailing_rmap_items(slot, ksm_scan.rmap_list);
spin_lock(&ksm_mmlist_lock);
ksm_scan.mm_slot = list_entry(slot->mm_list.next,
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->mm, rmap_item->address);
- remove_rmap_item_from_tree(rmap_item);
- rmap_item->oldchecksum = calc_checksum(page);
- }
put_page(page);
}
}
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)) {
spin_lock(&ksm_mmlist_lock);
mm_slot = get_mm_slot(mm);
if (mm_slot && ksm_scan.mm_slot != mm_slot) {
- if (list_empty(&mm_slot->rmap_list)) {
+ if (!mm_slot->rmap_list) {
hlist_del(&mm_slot->link);
list_del(&mm_slot->mm_list);
easy_to_free = 1;
}
}
+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 anon_vma_chain *vmac;
+ struct vm_area_struct *vma;
+
+ spin_lock(&anon_vma->lock);
+ 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;
+ }
+ 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 anon_vma_chain *vmac;
+ struct vm_area_struct *vma;
+
+ spin_lock(&anon_vma->lock);
+ 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)) {
+ 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 anon_vma_chain *vmac;
+ struct vm_area_struct *vma;
+
+ spin_lock(&anon_vma->lock);
+ 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 = 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.
/*
* 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);
}
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)
{
&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,
struct task_struct *ksm_thread;
int err;
- ksm_max_kernel_pages = totalram_pages / 4;
-
err = ksm_slab_init();
if (err)
goto out;
#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:
Code Review / linux-2.6.git / blobdiff