dect/linux-2.6
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Merge branch 'anon_vma-locking'

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* anon_vma-locking:
  mm: avoid anon_vma_chain allocation under anon_vma lock
  mm: avoid repeated anon_vma lock/unlock sequences in unlink_anon_vmas()
  mm: avoid repeated anon_vma lock/unlock sequences in anon_vma_clone()
This commit is contained in:
Linus Torvalds 2011-06-17 21:01:21 -07:00
commit 95559f2ca1
1 changed files with 75 additions and 31 deletions
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106
mm/rmap.c
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@ -112,9 +112,9 @@ static inline 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)
static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
{
return kmem_cache_alloc(anon_vma_chain_cachep, GFP_KERNEL);
return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
}
static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
@ -159,7 +159,7 @@ int anon_vma_prepare(struct vm_area_struct *vma)
struct mm_struct *mm = vma->vm_mm;
struct anon_vma *allocated;
avc = anon_vma_chain_alloc();
avc = anon_vma_chain_alloc(GFP_KERNEL);
if (!avc)
goto out_enomem;
@ -200,6 +200,32 @@ int anon_vma_prepare(struct vm_area_struct *vma)
return -ENOMEM;
}
/*
* This is a useful helper function for locking the anon_vma root as
* we traverse the vma->anon_vma_chain, looping over anon_vma's that
* have the same vma.
*
* Such anon_vma's should have the same root, so you'd expect to see
* just a single mutex_lock for the whole traversal.
*/
static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
{
struct anon_vma *new_root = anon_vma->root;
if (new_root != root) {
if (WARN_ON_ONCE(root))
mutex_unlock(&root->mutex);
root = new_root;
mutex_lock(&root->mutex);
}
return root;
}
static inline void unlock_anon_vma_root(struct anon_vma *root)
{
if (root)
mutex_unlock(&root->mutex);
}
static void anon_vma_chain_link(struct vm_area_struct *vma,
struct anon_vma_chain *avc,
struct anon_vma *anon_vma)
@ -208,13 +234,11 @@ static void anon_vma_chain_link(struct vm_area_struct *vma,
avc->anon_vma = anon_vma;
list_add(&avc->same_vma, &vma->anon_vma_chain);
anon_vma_lock(anon_vma);
/*
* It's critical to add new vmas to the tail of the anon_vma,
* see comment in huge_memory.c:__split_huge_page().
*/
list_add_tail(&avc->same_anon_vma, &anon_vma->head);
anon_vma_unlock(anon_vma);
}
/*
@ -224,13 +248,24 @@ static void anon_vma_chain_link(struct vm_area_struct *vma,
int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
{
struct anon_vma_chain *avc, *pavc;
struct anon_vma *root = NULL;
list_for_each_entry_reverse(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);
struct anon_vma *anon_vma;
avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
if (unlikely(!avc)) {
unlock_anon_vma_root(root);
root = NULL;
avc = anon_vma_chain_alloc(GFP_KERNEL);
if (!avc)
goto enomem_failure;
}
anon_vma = pavc->anon_vma;
root = lock_anon_vma_root(root, anon_vma);
anon_vma_chain_link(dst, avc, anon_vma);
}
unlock_anon_vma_root(root);
return 0;
enomem_failure:
@ -263,7 +298,7 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
anon_vma = anon_vma_alloc();
if (!anon_vma)
goto out_error;
avc = anon_vma_chain_alloc();
avc = anon_vma_chain_alloc(GFP_KERNEL);
if (!avc)
goto out_error_free_anon_vma;
@ -280,7 +315,9 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
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_lock(anon_vma);
anon_vma_chain_link(vma, avc, anon_vma);
anon_vma_unlock(anon_vma);
return 0;
@ -291,36 +328,43 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
return -ENOMEM;
}
static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain)
{
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;
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);
anon_vma_unlock(anon_vma);
if (empty)
put_anon_vma(anon_vma);
}
void unlink_anon_vmas(struct vm_area_struct *vma)
{
struct anon_vma_chain *avc, *next;
struct anon_vma *root = NULL;
/*
* 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);
struct anon_vma *anon_vma = avc->anon_vma;
root = lock_anon_vma_root(root, anon_vma);
list_del(&avc->same_anon_vma);
/*
* Leave empty anon_vmas on the list - we'll need
* to free them outside the lock.
*/
if (list_empty(&anon_vma->head))
continue;
list_del(&avc->same_vma);
anon_vma_chain_free(avc);
}
unlock_anon_vma_root(root);
/*
* Iterate the list once more, it now only contains empty and unlinked
* anon_vmas, destroy them. Could not do before due to __put_anon_vma()
* needing to acquire the anon_vma->root->mutex.
*/
list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
struct anon_vma *anon_vma = avc->anon_vma;
put_anon_vma(anon_vma);
list_del(&avc->same_vma);
anon_vma_chain_free(avc);
}