X-Git-Url: http://drtracing.org/?a=blobdiff_plain;f=mm%2Frmap.c;h=27dfd3b82b0f39cfcd38ff8b2a02c55151651f30;hb=7553e8f2d5161a2b7a9b7a9f37be1b77e735552f;hp=6bada99cd61c51cf98e36728b0ba646bd1410580;hpb=437cb0dbd104a1564e0e78f0d486b97677f80909;p=deliverable%2Flinux.git diff --git a/mm/rmap.c b/mm/rmap.c index 6bada99cd61c..27dfd3b82b0f 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -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); } @@ -352,6 +396,11 @@ void __init anon_vma_init(void) * The page might have been remapped to a different anon_vma or the anon_vma * returned may already be freed (and even reused). * + * In case it was remapped to a different anon_vma, the new anon_vma will be a + * child of the old anon_vma, and the anon_vma lifetime rules will therefore + * ensure that any anon_vma obtained from the page will still be valid for as + * long as we observe page_mapped() [ hence all those page_mapped() tests ]. + * * All users of this function must be very careful when walking the anon_vma * chain and verify that the page in question is indeed mapped in it * [ something equivalent to page_mapped_in_vma() ]. @@ -421,7 +470,7 @@ struct anon_vma *page_lock_anon_vma(struct page *page) /* * If the page is still mapped, then this anon_vma is still * its anon_vma, and holding the mutex ensures that it will - * not go away, see __put_anon_vma(). + * not go away, see anon_vma_free(). */ if (!page_mapped(page)) { mutex_unlock(&root_anon_vma->mutex);