if (unlikely(!anon_vma))
goto out_enomem_free_avc;
allocated = anon_vma;
+ /*
+ * This VMA had no anon_vma yet. This anon_vma is
+ * the root of any anon_vma tree that might form.
+ */
+ anon_vma->root = anon_vma;
}
- spin_lock(&anon_vma->lock);
+ anon_vma_lock(anon_vma);
/* page_table_lock to protect against threads */
spin_lock(&mm->page_table_lock);
if (likely(!vma->anon_vma)) {
avc->anon_vma = anon_vma;
avc->vma = vma;
list_add(&avc->same_vma, &vma->anon_vma_chain);
- list_add(&avc->same_anon_vma, &anon_vma->head);
+ list_add_tail(&avc->same_anon_vma, &anon_vma->head);
allocated = NULL;
avc = NULL;
}
spin_unlock(&mm->page_table_lock);
- spin_unlock(&anon_vma->lock);
+ anon_vma_unlock(anon_vma);
if (unlikely(allocated))
anon_vma_free(allocated);
avc->anon_vma = anon_vma;
list_add(&avc->same_vma, &vma->anon_vma_chain);
- spin_lock(&anon_vma->lock);
+ anon_vma_lock(anon_vma);
list_add_tail(&avc->same_anon_vma, &anon_vma->head);
- spin_unlock(&anon_vma->lock);
+ anon_vma_unlock(anon_vma);
}
/*
avc = anon_vma_chain_alloc();
if (!avc)
goto out_error_free_anon_vma;
- anon_vma_chain_link(vma, avc, anon_vma);
+
+ /*
+ * The root anon_vma's spinlock is the lock actually used when we
+ * lock any of the anon_vmas in this anon_vma tree.
+ */
+ anon_vma->root = pvma->anon_vma->root;
+ /*
+ * With KSM refcounts, an anon_vma can stay around longer than the
+ * process it belongs to. The root anon_vma needs to be pinned
+ * until this anon_vma is freed, because the lock lives in the root.
+ */
+ get_anon_vma(anon_vma->root);
/* Mark this anon_vma as the one where our new (COWed) pages go. */
vma->anon_vma = anon_vma;
+ anon_vma_chain_link(vma, avc, anon_vma);
return 0;
if (!anon_vma)
return;
- spin_lock(&anon_vma->lock);
+ anon_vma_lock(anon_vma);
list_del(&anon_vma_chain->same_anon_vma);
/* We must garbage collect the anon_vma if it's empty */
empty = list_empty(&anon_vma->head) && !anonvma_external_refcount(anon_vma);
- spin_unlock(&anon_vma->lock);
+ anon_vma_unlock(anon_vma);
- if (empty)
+ if (empty) {
+ /* We no longer need the root anon_vma */
+ if (anon_vma->root != anon_vma)
+ drop_anon_vma(anon_vma->root);
anon_vma_free(anon_vma);
+ }
}
void unlink_anon_vmas(struct vm_area_struct *vma)
{
struct anon_vma_chain *avc, *next;
- /* Unlink each anon_vma chained to the VMA. */
+ /*
+ * Unlink each anon_vma chained to the VMA. This list is ordered
+ * from newest to oldest, ensuring the root anon_vma gets freed last.
+ */
list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
anon_vma_unlink(avc);
list_del(&avc->same_vma);
goto out;
anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
- spin_lock(&anon_vma->lock);
+ anon_vma_lock(anon_vma);
return anon_vma;
out:
rcu_read_unlock();
void page_unlock_anon_vma(struct anon_vma *anon_vma)
{
- spin_unlock(&anon_vma->lock);
+ anon_vma_unlock(anon_vma);
rcu_read_unlock();
}
*/
unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
{
- if (PageAnon(page))
- ;
- else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
+ if (PageAnon(page)) {
+ if (vma->anon_vma->root != page_anon_vma(page)->root)
+ return -EFAULT;
+ } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
if (!vma->vm_file ||
vma->vm_file->f_mapping != page->mapping)
return -EFAULT;
* If the page isn't exclusively mapped into this vma,
* we must use the _oldest_ possible anon_vma for the
* page mapping!
- *
- * So take the last AVC chain entry in the vma, which is
- * the deepest ancestor, and use the anon_vma from that.
*/
if (!exclusive) {
- struct anon_vma_chain *avc;
- avc = list_entry(vma->anon_vma_chain.prev, struct anon_vma_chain, same_vma);
- anon_vma = avc->anon_vma;
+ if (PageAnon(page))
+ return;
+ anon_vma = anon_vma->root;
+ } else {
+ /*
+ * In this case, swapped-out-but-not-discarded swap-cache
+ * is remapped. So, no need to update page->mapping here.
+ * We convice anon_vma poitned by page->mapping is not obsolete
+ * because vma->anon_vma is necessary to be a family of it.
+ */
+ if (PageAnon(page))
+ return;
}
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
* are initially only visible via the pagetables, and the pte is locked
* over the call to page_add_new_anon_rmap.
*/
+ BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
BUG_ON(page->index != linear_page_index(vma, address));
#endif
}
*/
void page_add_anon_rmap(struct page *page,
struct vm_area_struct *vma, unsigned long address)
+{
+ do_page_add_anon_rmap(page, vma, address, 0);
+}
+
+/*
+ * Special version of the above for do_swap_page, which often runs
+ * into pages that are exclusively owned by the current process.
+ * Everybody else should continue to use page_add_anon_rmap above.
+ */
+void do_page_add_anon_rmap(struct page *page,
+ struct vm_area_struct *vma, unsigned long address, int exclusive)
{
int first = atomic_inc_and_test(&page->_mapcount);
if (first)
VM_BUG_ON(!PageLocked(page));
VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
if (first)
- __page_set_anon_rmap(page, vma, address, 0);
+ __page_set_anon_rmap(page, vma, address, exclusive);
else
__page_check_anon_rmap(page, vma, address);
}
return try_to_unmap_file(page, TTU_MUNLOCK);
}
+#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
+/*
+ * Drop an anon_vma refcount, freeing the anon_vma and anon_vma->root
+ * if necessary. Be careful to do all the tests under the lock. Once
+ * we know we are the last user, nobody else can get a reference and we
+ * can do the freeing without the lock.
+ */
+void drop_anon_vma(struct anon_vma *anon_vma)
+{
+ BUG_ON(atomic_read(&anon_vma->external_refcount) <= 0);
+ if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->root->lock)) {
+ struct anon_vma *root = anon_vma->root;
+ int empty = list_empty(&anon_vma->head);
+ int last_root_user = 0;
+ int root_empty = 0;
+
+ /*
+ * The refcount on a non-root anon_vma got dropped. Drop
+ * the refcount on the root and check if we need to free it.
+ */
+ if (empty && anon_vma != root) {
+ BUG_ON(atomic_read(&root->external_refcount) <= 0);
+ last_root_user = atomic_dec_and_test(&root->external_refcount);
+ root_empty = list_empty(&root->head);
+ }
+ anon_vma_unlock(anon_vma);
+
+ if (empty) {
+ anon_vma_free(anon_vma);
+ if (root_empty && last_root_user)
+ anon_vma_free(root);
+ }
+ }
+}
+#endif
+
#ifdef CONFIG_MIGRATION
/*
* rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file():
anon_vma = page_anon_vma(page);
if (!anon_vma)
return ret;
- spin_lock(&anon_vma->lock);
+ anon_vma_lock(anon_vma);
list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
struct vm_area_struct *vma = avc->vma;
unsigned long address = vma_address(page, vma);
if (ret != SWAP_AGAIN)
break;
}
- spin_unlock(&anon_vma->lock);
+ anon_vma_unlock(anon_vma);
return ret;
}
git.samba.org / sfrench / cifs-2.6.git / blobdiff