[PATCH 4/5] always lock the root (oldest) anon_vma
in [Kernel]
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From: Rik van Riel on 12 May 2010 13:50 Subject: always lock the root (oldest) anon_vma Always (and only) lock the root (oldest) anon_vma whenever we do something in an anon_vma. The recently introduced anon_vma scalability is due to the rmap code scanning only the VMAs that need to be scanned. Many common operations still took the anon_vma lock on the root anon_vma, so always taking that lock is not expected to introduce any scalability issues. However, always taking the same lock does mean we only need to take one lock, which means rmap_walk on pages from any anon_vma in the vma is excluded from occurring during an munmap, expand_stack or other operation that needs to exclude rmap_walk and similar functions. Also add the proper locking to vma_adjust. Signed-off-by: Rik van Riel <riel(a)redhat.com> --- include/linux/rmap.h | 8 ++++---- mm/ksm.c | 2 +- mm/mmap.c | 6 +++++- 3 files changed, 10 insertions(+), 6 deletions(-) diff --git a/include/linux/rmap.h b/include/linux/rmap.h index 457ae1e..33ffe14 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -95,24 +95,24 @@ static inline void vma_lock_anon_vma(struct vm_area_struct *vma) { struct anon_vma *anon_vma = vma->anon_vma; if (anon_vma) - spin_lock(&anon_vma->lock); + spin_lock(&anon_vma->root->lock); } static inline void vma_unlock_anon_vma(struct vm_area_struct *vma) { struct anon_vma *anon_vma = vma->anon_vma; if (anon_vma) - spin_unlock(&anon_vma->lock); + spin_unlock(&anon_vma->root->lock); } static inline void anon_vma_lock(struct anon_vma *anon_vma) { - spin_lock(&anon_vma->lock); + spin_lock(&anon_vma->root->lock); } static inline void anon_vma_unlock(struct anon_vma *anon_vma) { - spin_unlock(&anon_vma->lock); + spin_unlock(&anon_vma->root->lock); } /* diff --git a/mm/ksm.c b/mm/ksm.c index d488012..7ca0dd7 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -325,7 +325,7 @@ static void drop_anon_vma(struct rmap_item *rmap_item) { struct anon_vma *anon_vma = rmap_item->anon_vma; - if (atomic_dec_and_lock(&anon_vma->ksm_refcount, &anon_vma->lock)) { + if (atomic_dec_and_lock(&anon_vma->ksm_refcount, &anon_vma->root->lock)) { int empty = list_empty(&anon_vma->head); anon_vma_unlock(anon_vma); if (empty) diff --git a/mm/mmap.c b/mm/mmap.c index f70bc65..b7dfe30 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -553,6 +553,8 @@ again: remove_next = 1 + (end > next->vm_end); } } + vma_lock_anon_vma(vma); + if (file) { mapping = file->f_mapping; if (!(vma->vm_flags & VM_NONLINEAR)) @@ -600,6 +602,8 @@ again: remove_next = 1 + (end > next->vm_end); flush_dcache_mmap_unlock(mapping); } + vma_unlock_anon_vma(vma); + if (remove_next) { /* * vma_merge has merged next into vma, and needs @@ -2471,7 +2475,7 @@ static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma) * The LSB of head.next can't change from under us * because we hold the mm_all_locks_mutex. */ - spin_lock_nest_lock(&anon_vma->lock, &mm->mmap_sem); + spin_lock_nest_lock(&anon_vma->root->lock, &mm->mmap_sem); /* * We can safely modify head.next after taking the * anon_vma->lock. If some other vma in this mm shares -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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