Btrfs: Switch the extent buffer rbtree into a radix tree
This patch reduces the CPU time spent in the extent buffer search by using the radix tree instead of the rbtree and using the rcu lock instead of the spin lock. I did a quick test by the benchmark tool[1] and found the patch improve the file creation/deletion performance problem that I have reported[2]. Before applying this patch: Create files: Total files: 50000 Total time: 0.971531 Average time: 0.000019 Delete files: Total files: 50000 Total time: 1.366761 Average time: 0.000027 After applying this patch: Create files: Total files: 50000 Total time: 0.927455 Average time: 0.000019 Delete files: Total files: 50000 Total time: 1.292280 Average time: 0.000026 [1] http://marc.info/?l=linux-btrfs&m=128212635122920&q=p3 [2] http://marc.info/?l=linux-btrfs&m=128212635122920&w=2 Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>hifive-unleashed-5.1
Miao Xie
Chris Mason
parent
897ca6e9b4
commit
19fe0a8b78
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@ -104,7 +104,7 @@ void extent_io_tree_init(struct extent_io_tree *tree,
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struct address_space *mapping, gfp_t mask)
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{
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tree->state = RB_ROOT;
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tree->buffer = RB_ROOT;
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INIT_RADIX_TREE(&tree->buffer, GFP_ATOMIC);
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tree->ops = NULL;
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tree->dirty_bytes = 0;
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spin_lock_init(&tree->lock);
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@ -235,50 +235,6 @@ static inline struct rb_node *tree_search(struct extent_io_tree *tree,
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return ret;
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}
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static struct extent_buffer *buffer_tree_insert(struct extent_io_tree *tree,
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u64 offset, struct rb_node *node)
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{
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struct rb_root *root = &tree->buffer;
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struct rb_node **p = &root->rb_node;
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struct rb_node *parent = NULL;
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struct extent_buffer *eb;
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while (*p) {
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parent = *p;
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eb = rb_entry(parent, struct extent_buffer, rb_node);
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if (offset < eb->start)
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p = &(*p)->rb_left;
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else if (offset > eb->start)
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p = &(*p)->rb_right;
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else
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return eb;
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}
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rb_link_node(node, parent, p);
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rb_insert_color(node, root);
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return NULL;
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}
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static struct extent_buffer *buffer_search(struct extent_io_tree *tree,
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u64 offset)
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{
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struct rb_root *root = &tree->buffer;
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struct rb_node *n = root->rb_node;
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struct extent_buffer *eb;
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while (n) {
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eb = rb_entry(n, struct extent_buffer, rb_node);
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if (offset < eb->start)
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n = n->rb_left;
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else if (offset > eb->start)
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n = n->rb_right;
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else
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return eb;
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}
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return NULL;
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}
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static void merge_cb(struct extent_io_tree *tree, struct extent_state *new,
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struct extent_state *other)
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{
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@ -3082,6 +3038,7 @@ static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree,
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eb->len = len;
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spin_lock_init(&eb->lock);
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init_waitqueue_head(&eb->lock_wq);
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INIT_RCU_HEAD(&eb->rcu_head);
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#if LEAK_DEBUG
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spin_lock_irqsave(&leak_lock, flags);
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@ -3150,16 +3107,16 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
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struct page *p;
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struct address_space *mapping = tree->mapping;
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int uptodate = 1;
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int ret;
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spin_lock(&tree->buffer_lock);
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eb = buffer_search(tree, start);
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if (eb) {
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atomic_inc(&eb->refs);
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spin_unlock(&tree->buffer_lock);
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rcu_read_lock();
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eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);
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if (eb && atomic_inc_not_zero(&eb->refs)) {
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rcu_read_unlock();
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mark_page_accessed(eb->first_page);
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return eb;
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}
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spin_unlock(&tree->buffer_lock);
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rcu_read_unlock();
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eb = __alloc_extent_buffer(tree, start, len, mask);
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if (!eb)
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@ -3198,17 +3155,25 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
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if (uptodate)
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set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
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ret = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
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if (ret)
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goto free_eb;
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spin_lock(&tree->buffer_lock);
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exists = buffer_tree_insert(tree, start, &eb->rb_node);
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if (exists) {
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ret = radix_tree_insert(&tree->buffer, start >> PAGE_CACHE_SHIFT, eb);
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if (ret == -EEXIST) {
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exists = radix_tree_lookup(&tree->buffer,
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start >> PAGE_CACHE_SHIFT);
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/* add one reference for the caller */
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atomic_inc(&exists->refs);
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spin_unlock(&tree->buffer_lock);
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radix_tree_preload_end();
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goto free_eb;
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}
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/* add one reference for the tree */
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atomic_inc(&eb->refs);
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spin_unlock(&tree->buffer_lock);
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radix_tree_preload_end();
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return eb;
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free_eb:
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@ -3224,16 +3189,16 @@ struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree,
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{
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struct extent_buffer *eb;
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spin_lock(&tree->buffer_lock);
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eb = buffer_search(tree, start);
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if (eb)
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atomic_inc(&eb->refs);
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spin_unlock(&tree->buffer_lock);
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if (eb)
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rcu_read_lock();
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eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);
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if (eb && atomic_inc_not_zero(&eb->refs)) {
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rcu_read_unlock();
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mark_page_accessed(eb->first_page);
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return eb;
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}
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rcu_read_unlock();
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return eb;
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return NULL;
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}
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void free_extent_buffer(struct extent_buffer *eb)
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@ -3863,6 +3828,14 @@ void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
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}
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}
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static inline void btrfs_release_extent_buffer_rcu(struct rcu_head *head)
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{
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struct extent_buffer *eb =
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container_of(head, struct extent_buffer, rcu_head);
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btrfs_release_extent_buffer(eb);
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}
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int try_release_extent_buffer(struct extent_io_tree *tree, struct page *page)
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{
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u64 start = page_offset(page);
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@ -3870,23 +3843,30 @@ int try_release_extent_buffer(struct extent_io_tree *tree, struct page *page)
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int ret = 1;
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spin_lock(&tree->buffer_lock);
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eb = buffer_search(tree, start);
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eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);
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if (!eb)
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goto out;
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if (atomic_read(&eb->refs) > 1) {
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ret = 0;
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goto out;
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}
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if (test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags)) {
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ret = 0;
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goto out;
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}
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rb_erase(&eb->rb_node, &tree->buffer);
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/* at this point we can safely release the extent buffer */
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btrfs_release_extent_buffer(eb);
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/*
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* set @eb->refs to 0 if it is already 1, and then release the @eb.
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* Or go back.
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*/
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if (atomic_cmpxchg(&eb->refs, 1, 0) != 1) {
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ret = 0;
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goto out;
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}
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radix_tree_delete(&tree->buffer, start >> PAGE_CACHE_SHIFT);
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out:
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spin_unlock(&tree->buffer_lock);
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/* at this point we can safely release the extent buffer */
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if (atomic_read(&eb->refs) == 0)
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call_rcu(&eb->rcu_head, btrfs_release_extent_buffer_rcu);
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return ret;
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}
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@ -85,7 +85,7 @@ struct extent_io_ops {
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struct extent_io_tree {
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struct rb_root state;
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struct rb_root buffer;
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struct radix_tree_root buffer;
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struct address_space *mapping;
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u64 dirty_bytes;
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spinlock_t lock;
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@ -123,7 +123,7 @@ struct extent_buffer {
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unsigned long bflags;
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atomic_t refs;
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struct list_head leak_list;
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struct rb_node rb_node;
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struct rcu_head rcu_head;
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/* the spinlock is used to protect most operations */
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spinlock_t lock;
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