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-rw-r--r--mm/rmap.c156
1 files changed, 130 insertions, 26 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index 5cb47111f79e..be34094e4595 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -62,6 +62,7 @@
#include "internal.h"
static struct kmem_cache *anon_vma_cachep;
+static struct kmem_cache *anon_vma_chain_cachep;
static inline struct anon_vma *anon_vma_alloc(void)
{
@@ -73,6 +74,16 @@ void anon_vma_free(struct anon_vma *anon_vma)
kmem_cache_free(anon_vma_cachep, anon_vma);
}
+static inline struct anon_vma_chain *anon_vma_chain_alloc(void)
+{
+ return kmem_cache_alloc(anon_vma_chain_cachep, GFP_KERNEL);
+}
+
+void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
+{
+ kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
+}
+
/**
* anon_vma_prepare - attach an anon_vma to a memory region
* @vma: the memory region in question
@@ -103,18 +114,23 @@ void anon_vma_free(struct anon_vma *anon_vma)
int anon_vma_prepare(struct vm_area_struct *vma)
{
struct anon_vma *anon_vma = vma->anon_vma;
+ struct anon_vma_chain *avc;
might_sleep();
if (unlikely(!anon_vma)) {
struct mm_struct *mm = vma->vm_mm;
struct anon_vma *allocated;
+ avc = anon_vma_chain_alloc();
+ if (!avc)
+ goto out_enomem;
+
anon_vma = find_mergeable_anon_vma(vma);
allocated = NULL;
if (!anon_vma) {
anon_vma = anon_vma_alloc();
if (unlikely(!anon_vma))
- return -ENOMEM;
+ goto out_enomem_free_avc;
allocated = anon_vma;
}
spin_lock(&anon_vma->lock);
@@ -123,53 +139,113 @@ int anon_vma_prepare(struct vm_area_struct *vma)
spin_lock(&mm->page_table_lock);
if (likely(!vma->anon_vma)) {
vma->anon_vma = anon_vma;
- list_add_tail(&vma->anon_vma_node, &anon_vma->head);
+ 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);
allocated = NULL;
}
spin_unlock(&mm->page_table_lock);
spin_unlock(&anon_vma->lock);
- if (unlikely(allocated))
+ if (unlikely(allocated)) {
anon_vma_free(allocated);
+ anon_vma_chain_free(avc);
+ }
}
return 0;
+
+ out_enomem_free_avc:
+ anon_vma_chain_free(avc);
+ out_enomem:
+ return -ENOMEM;
}
-void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next)
+static void anon_vma_chain_link(struct vm_area_struct *vma,
+ struct anon_vma_chain *avc,
+ struct anon_vma *anon_vma)
{
- BUG_ON(vma->anon_vma != next->anon_vma);
- list_del(&next->anon_vma_node);
+ avc->vma = vma;
+ avc->anon_vma = anon_vma;
+ list_add(&avc->same_vma, &vma->anon_vma_chain);
+
+ spin_lock(&anon_vma->lock);
+ list_add_tail(&avc->same_anon_vma, &anon_vma->head);
+ spin_unlock(&anon_vma->lock);
}
-void __anon_vma_link(struct vm_area_struct *vma)
+/*
+ * Attach the anon_vmas from src to dst.
+ * Returns 0 on success, -ENOMEM on failure.
+ */
+int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
{
- struct anon_vma *anon_vma = vma->anon_vma;
+ struct anon_vma_chain *avc, *pavc;
+
+ list_for_each_entry(pavc, &src->anon_vma_chain, same_vma) {
+ avc = anon_vma_chain_alloc();
+ if (!avc)
+ goto enomem_failure;
+ anon_vma_chain_link(dst, avc, pavc->anon_vma);
+ }
+ return 0;
- if (anon_vma)
- list_add_tail(&vma->anon_vma_node, &anon_vma->head);
+ enomem_failure:
+ unlink_anon_vmas(dst);
+ return -ENOMEM;
}
-void anon_vma_link(struct vm_area_struct *vma)
+/*
+ * Attach vma to its own anon_vma, as well as to the anon_vmas that
+ * the corresponding VMA in the parent process is attached to.
+ * Returns 0 on success, non-zero on failure.
+ */
+int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
{
- struct anon_vma *anon_vma = vma->anon_vma;
+ struct anon_vma_chain *avc;
+ struct anon_vma *anon_vma;
- if (anon_vma) {
- spin_lock(&anon_vma->lock);
- list_add_tail(&vma->anon_vma_node, &anon_vma->head);
- spin_unlock(&anon_vma->lock);
- }
+ /* Don't bother if the parent process has no anon_vma here. */
+ if (!pvma->anon_vma)
+ return 0;
+
+ /*
+ * First, attach the new VMA to the parent VMA's anon_vmas,
+ * so rmap can find non-COWed pages in child processes.
+ */
+ if (anon_vma_clone(vma, pvma))
+ return -ENOMEM;
+
+ /* Then add our own anon_vma. */
+ anon_vma = anon_vma_alloc();
+ if (!anon_vma)
+ goto out_error;
+ avc = anon_vma_chain_alloc();
+ if (!avc)
+ goto out_error_free_anon_vma;
+ anon_vma_chain_link(vma, avc, anon_vma);
+ /* Mark this anon_vma as the one where our new (COWed) pages go. */
+ vma->anon_vma = anon_vma;
+
+ return 0;
+
+ out_error_free_anon_vma:
+ anon_vma_free(anon_vma);
+ out_error:
+ return -ENOMEM;
}
-void anon_vma_unlink(struct vm_area_struct *vma)
+static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain)
{
- struct anon_vma *anon_vma = vma->anon_vma;
+ struct anon_vma *anon_vma = anon_vma_chain->anon_vma;
int empty;
+ /* If anon_vma_fork fails, we can get an empty anon_vma_chain. */
if (!anon_vma)
return;
spin_lock(&anon_vma->lock);
- list_del(&vma->anon_vma_node);
+ 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) && !ksm_refcount(anon_vma);
@@ -179,6 +255,18 @@ void anon_vma_unlink(struct vm_area_struct *vma)
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. */
+ list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
+ anon_vma_unlink(avc);
+ list_del(&avc->same_vma);
+ anon_vma_chain_free(avc);
+ }
+}
+
static void anon_vma_ctor(void *data)
{
struct anon_vma *anon_vma = data;
@@ -192,6 +280,7 @@ void __init anon_vma_init(void)
{
anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
+ anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
}
/*
@@ -240,6 +329,18 @@ vma_address(struct page *page, struct vm_area_struct *vma)
/* page should be within @vma mapping range */
return -EFAULT;
}
+ if (unlikely(vma->vm_flags & VM_LOCK_RMAP)) {
+ /*
+ * This VMA is being unlinked or is not yet linked into the
+ * VMA tree. Do not try to follow this rmap. This race
+ * condition can result in page_referenced() ignoring a
+ * reference or in try_to_unmap() failing to unmap a page.
+ * The VMA cannot be freed under us because we hold the
+ * anon_vma->lock, which the munmap code takes while
+ * unlinking the anon_vmas from the VMA.
+ */
+ return -EFAULT;
+ }
return address;
}
@@ -396,7 +497,7 @@ static int page_referenced_anon(struct page *page,
{
unsigned int mapcount;
struct anon_vma *anon_vma;
- struct vm_area_struct *vma;
+ struct anon_vma_chain *avc;
int referenced = 0;
anon_vma = page_lock_anon_vma(page);
@@ -404,7 +505,8 @@ static int page_referenced_anon(struct page *page,
return referenced;
mapcount = page_mapcount(page);
- list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
+ 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 (address == -EFAULT)
continue;
@@ -1025,14 +1127,15 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
{
struct anon_vma *anon_vma;
- struct vm_area_struct *vma;
+ struct anon_vma_chain *avc;
int ret = SWAP_AGAIN;
anon_vma = page_lock_anon_vma(page);
if (!anon_vma)
return ret;
- list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
+ 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 (address == -EFAULT)
continue;
@@ -1223,7 +1326,7 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
struct vm_area_struct *, unsigned long, void *), void *arg)
{
struct anon_vma *anon_vma;
- struct vm_area_struct *vma;
+ struct anon_vma_chain *avc;
int ret = SWAP_AGAIN;
/*
@@ -1238,7 +1341,8 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
if (!anon_vma)
return ret;
spin_lock(&anon_vma->lock);
- list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
+ 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 (address == -EFAULT)
continue;

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