Merge branch 'anon_vma-locking'
* 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:
commit
95559f2ca1
1 changed files with 75 additions and 31 deletions
106
mm/rmap.c
106
mm/rmap.c
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@ -112,9 +112,9 @@ static inline void anon_vma_free(struct anon_vma *anon_vma)
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kmem_cache_free(anon_vma_cachep, anon_vma);
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}
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static inline struct anon_vma_chain *anon_vma_chain_alloc(void)
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static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
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{
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return kmem_cache_alloc(anon_vma_chain_cachep, GFP_KERNEL);
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return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
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}
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static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
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@ -159,7 +159,7 @@ int anon_vma_prepare(struct vm_area_struct *vma)
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struct mm_struct *mm = vma->vm_mm;
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struct anon_vma *allocated;
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avc = anon_vma_chain_alloc();
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avc = anon_vma_chain_alloc(GFP_KERNEL);
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if (!avc)
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goto out_enomem;
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@ -200,6 +200,32 @@ int anon_vma_prepare(struct vm_area_struct *vma)
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return -ENOMEM;
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}
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/*
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* This is a useful helper function for locking the anon_vma root as
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* we traverse the vma->anon_vma_chain, looping over anon_vma's that
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* have the same vma.
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*
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* Such anon_vma's should have the same root, so you'd expect to see
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* just a single mutex_lock for the whole traversal.
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*/
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static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
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{
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struct anon_vma *new_root = anon_vma->root;
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if (new_root != root) {
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if (WARN_ON_ONCE(root))
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mutex_unlock(&root->mutex);
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root = new_root;
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mutex_lock(&root->mutex);
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}
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return root;
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}
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static inline void unlock_anon_vma_root(struct anon_vma *root)
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{
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if (root)
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mutex_unlock(&root->mutex);
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}
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static void anon_vma_chain_link(struct vm_area_struct *vma,
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struct anon_vma_chain *avc,
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struct anon_vma *anon_vma)
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@ -208,13 +234,11 @@ static void anon_vma_chain_link(struct vm_area_struct *vma,
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avc->anon_vma = anon_vma;
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list_add(&avc->same_vma, &vma->anon_vma_chain);
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anon_vma_lock(anon_vma);
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/*
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* It's critical to add new vmas to the tail of the anon_vma,
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* see comment in huge_memory.c:__split_huge_page().
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*/
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list_add_tail(&avc->same_anon_vma, &anon_vma->head);
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anon_vma_unlock(anon_vma);
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}
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/*
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@ -224,13 +248,24 @@ static void anon_vma_chain_link(struct vm_area_struct *vma,
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int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
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{
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struct anon_vma_chain *avc, *pavc;
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struct anon_vma *root = NULL;
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list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
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avc = anon_vma_chain_alloc();
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if (!avc)
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goto enomem_failure;
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anon_vma_chain_link(dst, avc, pavc->anon_vma);
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struct anon_vma *anon_vma;
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avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
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if (unlikely(!avc)) {
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unlock_anon_vma_root(root);
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root = NULL;
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avc = anon_vma_chain_alloc(GFP_KERNEL);
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if (!avc)
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goto enomem_failure;
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}
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anon_vma = pavc->anon_vma;
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root = lock_anon_vma_root(root, anon_vma);
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anon_vma_chain_link(dst, avc, anon_vma);
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}
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unlock_anon_vma_root(root);
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return 0;
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enomem_failure:
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@ -263,7 +298,7 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
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anon_vma = anon_vma_alloc();
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if (!anon_vma)
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goto out_error;
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avc = anon_vma_chain_alloc();
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avc = anon_vma_chain_alloc(GFP_KERNEL);
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if (!avc)
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goto out_error_free_anon_vma;
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@ -280,7 +315,9 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
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get_anon_vma(anon_vma->root);
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/* Mark this anon_vma as the one where our new (COWed) pages go. */
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vma->anon_vma = anon_vma;
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anon_vma_lock(anon_vma);
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anon_vma_chain_link(vma, avc, anon_vma);
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anon_vma_unlock(anon_vma);
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return 0;
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@ -291,36 +328,43 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
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return -ENOMEM;
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}
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static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain)
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{
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struct anon_vma *anon_vma = anon_vma_chain->anon_vma;
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int empty;
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/* If anon_vma_fork fails, we can get an empty anon_vma_chain. */
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if (!anon_vma)
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return;
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anon_vma_lock(anon_vma);
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list_del(&anon_vma_chain->same_anon_vma);
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/* We must garbage collect the anon_vma if it's empty */
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empty = list_empty(&anon_vma->head);
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anon_vma_unlock(anon_vma);
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if (empty)
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put_anon_vma(anon_vma);
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}
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void unlink_anon_vmas(struct vm_area_struct *vma)
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{
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struct anon_vma_chain *avc, *next;
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struct anon_vma *root = NULL;
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/*
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* Unlink each anon_vma chained to the VMA. This list is ordered
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* from newest to oldest, ensuring the root anon_vma gets freed last.
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*/
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list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
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anon_vma_unlink(avc);
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struct anon_vma *anon_vma = avc->anon_vma;
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root = lock_anon_vma_root(root, anon_vma);
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list_del(&avc->same_anon_vma);
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/*
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* Leave empty anon_vmas on the list - we'll need
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* to free them outside the lock.
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*/
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if (list_empty(&anon_vma->head))
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continue;
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list_del(&avc->same_vma);
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anon_vma_chain_free(avc);
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}
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unlock_anon_vma_root(root);
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/*
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* Iterate the list once more, it now only contains empty and unlinked
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* anon_vmas, destroy them. Could not do before due to __put_anon_vma()
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* needing to acquire the anon_vma->root->mutex.
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*/
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list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
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struct anon_vma *anon_vma = avc->anon_vma;
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put_anon_vma(anon_vma);
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list_del(&avc->same_vma);
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anon_vma_chain_free(avc);
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}
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