Btrfs: Index extent buffers in an rbtree
Before, extent buffers were a temporary object, meant to map a number of pages
at once and collect operations on them.
But, a few extra fields have crept in, and they are also the best place to
store a per-tree block lock field as well. This commit puts the extent
buffers into an rbtree, and ensures a single extent buffer for each
tree block.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index d4a63ae..32bb4ed 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -91,29 +91,16 @@
struct address_space *mapping, gfp_t mask)
{
tree->state.rb_node = NULL;
+ tree->buffer.rb_node = NULL;
tree->ops = NULL;
tree->dirty_bytes = 0;
spin_lock_init(&tree->lock);
- spin_lock_init(&tree->lru_lock);
+ spin_lock_init(&tree->buffer_lock);
tree->mapping = mapping;
- INIT_LIST_HEAD(&tree->buffer_lru);
- tree->lru_size = 0;
tree->last = NULL;
}
EXPORT_SYMBOL(extent_io_tree_init);
-void extent_io_tree_empty_lru(struct extent_io_tree *tree)
-{
- struct extent_buffer *eb;
- while(!list_empty(&tree->buffer_lru)) {
- eb = list_entry(tree->buffer_lru.next, struct extent_buffer,
- lru);
- list_del_init(&eb->lru);
- free_extent_buffer(eb);
- }
-}
-EXPORT_SYMBOL(extent_io_tree_empty_lru);
-
struct extent_state *alloc_extent_state(gfp_t mask)
{
struct extent_state *state;
@@ -245,6 +232,50 @@
return ret;
}
+static struct extent_buffer *buffer_tree_insert(struct extent_io_tree *tree,
+ u64 offset, struct rb_node *node)
+{
+ struct rb_root *root = &tree->buffer;
+ struct rb_node ** p = &root->rb_node;
+ struct rb_node * parent = NULL;
+ struct extent_buffer *eb;
+
+ while(*p) {
+ parent = *p;
+ eb = rb_entry(parent, struct extent_buffer, rb_node);
+
+ if (offset < eb->start)
+ p = &(*p)->rb_left;
+ else if (offset > eb->start)
+ p = &(*p)->rb_right;
+ else
+ return eb;
+ }
+
+ rb_link_node(node, parent, p);
+ rb_insert_color(node, root);
+ return NULL;
+}
+
+static struct extent_buffer *buffer_search(struct extent_io_tree *tree,
+ u64 offset)
+{
+ struct rb_root *root = &tree->buffer;
+ struct rb_node * n = root->rb_node;
+ struct extent_buffer *eb;
+
+ while(n) {
+ eb = rb_entry(n, struct extent_buffer, rb_node);
+ if (offset < eb->start)
+ n = n->rb_left;
+ else if (offset > eb->start)
+ n = n->rb_right;
+ else
+ return eb;
+ }
+ return NULL;
+}
+
/*
* utility function to look for merge candidates inside a given range.
* Any extents with matching state are merged together into a single
@@ -1817,9 +1848,8 @@
{
if (!PagePrivate(page)) {
SetPagePrivate(page);
- WARN_ON(!page->mapping->a_ops->invalidatepage);
- set_page_private(page, EXTENT_PAGE_PRIVATE);
page_cache_get(page);
+ set_page_private(page, EXTENT_PAGE_PRIVATE);
}
}
@@ -2627,51 +2657,6 @@
return sector;
}
-static int add_lru(struct extent_io_tree *tree, struct extent_buffer *eb)
-{
- if (list_empty(&eb->lru)) {
- extent_buffer_get(eb);
- list_add(&eb->lru, &tree->buffer_lru);
- tree->lru_size++;
- if (tree->lru_size >= BUFFER_LRU_MAX) {
- struct extent_buffer *rm;
- rm = list_entry(tree->buffer_lru.prev,
- struct extent_buffer, lru);
- tree->lru_size--;
- list_del_init(&rm->lru);
- free_extent_buffer(rm);
- }
- } else
- list_move(&eb->lru, &tree->buffer_lru);
- return 0;
-}
-static struct extent_buffer *find_lru(struct extent_io_tree *tree,
- u64 start, unsigned long len)
-{
- struct list_head *lru = &tree->buffer_lru;
- struct list_head *cur = lru->next;
- struct extent_buffer *eb;
-
- if (list_empty(lru))
- return NULL;
-
- do {
- eb = list_entry(cur, struct extent_buffer, lru);
- if (eb->start == start && eb->len == len) {
- extent_buffer_get(eb);
- return eb;
- }
- cur = cur->next;
- } while (cur != lru);
- return NULL;
-}
-
-static inline unsigned long num_extent_pages(u64 start, u64 len)
-{
- return ((start + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT) -
- (start >> PAGE_CACHE_SHIFT);
-}
-
static inline struct page *extent_buffer_page(struct extent_buffer *eb,
unsigned long i)
{
@@ -2688,44 +2673,10 @@
return p;
}
-int release_extent_buffer_tail_pages(struct extent_buffer *eb)
+static inline unsigned long num_extent_pages(u64 start, u64 len)
{
- unsigned long num_pages = num_extent_pages(eb->start, eb->len);
- struct page *page;
- unsigned long i;
-
- if (num_pages == 1)
- return 0;
- for (i = 1; i < num_pages; i++) {
- page = extent_buffer_page(eb, i);
- page_cache_release(page);
- }
- return 0;
-}
-
-
-int invalidate_extent_lru(struct extent_io_tree *tree, u64 start,
- unsigned long len)
-{
- struct list_head *lru = &tree->buffer_lru;
- struct list_head *cur = lru->next;
- struct extent_buffer *eb;
- int found = 0;
-
- spin_lock(&tree->lru_lock);
- if (list_empty(lru))
- goto out;
-
- do {
- eb = list_entry(cur, struct extent_buffer, lru);
- if (eb->start <= start && eb->start + eb->len > start) {
- eb->flags &= ~EXTENT_UPTODATE;
- }
- cur = cur->next;
- } while (cur != lru);
-out:
- spin_unlock(&tree->lru_lock);
- return found;
+ return ((start + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT) -
+ (start >> PAGE_CACHE_SHIFT);
}
static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree,
@@ -2736,15 +2687,7 @@
struct extent_buffer *eb = NULL;
unsigned long flags;
- spin_lock(&tree->lru_lock);
- eb = find_lru(tree, start, len);
- spin_unlock(&tree->lru_lock);
- if (eb) {
- return eb;
- }
-
eb = kmem_cache_zalloc(extent_buffer_cache, mask);
- INIT_LIST_HEAD(&eb->lru);
eb->start = start;
eb->len = len;
spin_lock_irqsave(&leak_lock, flags);
@@ -2773,17 +2716,24 @@
unsigned long i;
unsigned long index = start >> PAGE_CACHE_SHIFT;
struct extent_buffer *eb;
+ struct extent_buffer *exists = NULL;
struct page *p;
struct address_space *mapping = tree->mapping;
int uptodate = 1;
+ spin_lock(&tree->buffer_lock);
+ eb = buffer_search(tree, start);
+ if (eb) {
+ atomic_inc(&eb->refs);
+ spin_unlock(&tree->buffer_lock);
+ return eb;
+ }
+ spin_unlock(&tree->buffer_lock);
+
eb = __alloc_extent_buffer(tree, start, len, mask);
if (!eb)
return NULL;
- if (eb->flags & EXTENT_BUFFER_FILLED)
- goto lru_add;
-
if (page0) {
eb->first_page = page0;
i = 1;
@@ -2800,7 +2750,7 @@
p = find_or_create_page(mapping, index, mask | __GFP_HIGHMEM);
if (!p) {
WARN_ON(1);
- goto fail;
+ goto free_eb;
}
set_page_extent_mapped(p);
mark_page_accessed(p);
@@ -2818,25 +2768,28 @@
eb->flags |= EXTENT_UPTODATE;
eb->flags |= EXTENT_BUFFER_FILLED;
-lru_add:
- spin_lock(&tree->lru_lock);
- add_lru(tree, eb);
- spin_unlock(&tree->lru_lock);
+ spin_lock(&tree->buffer_lock);
+ exists = buffer_tree_insert(tree, start, &eb->rb_node);
+ if (exists) {
+ /* add one reference for the caller */
+ atomic_inc(&exists->refs);
+ spin_unlock(&tree->buffer_lock);
+ goto free_eb;
+ }
+ spin_unlock(&tree->buffer_lock);
+
+ /* add one reference for the tree */
+ atomic_inc(&eb->refs);
return eb;
-fail:
- spin_lock(&tree->lru_lock);
- list_del_init(&eb->lru);
- spin_unlock(&tree->lru_lock);
+free_eb:
if (!atomic_dec_and_test(&eb->refs))
- return NULL;
- for (index = 1; index < i; index++) {
+ return exists;
+ for (index = 1; index < i; index++)
page_cache_release(extent_buffer_page(eb, index));
- }
- if (i > 0)
- page_cache_release(extent_buffer_page(eb, 0));
+ page_cache_release(extent_buffer_page(eb, 0));
__free_extent_buffer(eb);
- return NULL;
+ return exists;
}
EXPORT_SYMBOL(alloc_extent_buffer);
@@ -2844,89 +2797,27 @@
u64 start, unsigned long len,
gfp_t mask)
{
- unsigned long num_pages = num_extent_pages(start, len);
- unsigned long i;
- unsigned long index = start >> PAGE_CACHE_SHIFT;
struct extent_buffer *eb;
- struct page *p;
- struct address_space *mapping = tree->mapping;
- int uptodate = 1;
- eb = __alloc_extent_buffer(tree, start, len, mask);
- if (!eb)
- return NULL;
+ spin_lock(&tree->buffer_lock);
+ eb = buffer_search(tree, start);
+ if (eb)
+ atomic_inc(&eb->refs);
+ spin_unlock(&tree->buffer_lock);
- if (eb->flags & EXTENT_BUFFER_FILLED)
- goto lru_add;
-
- for (i = 0; i < num_pages; i++, index++) {
- p = find_get_page(mapping, index);
- if (!p) {
- goto fail;
- }
- if (TestSetPageLocked(p)) {
- page_cache_release(p);
- goto fail;
- }
-
- set_page_extent_mapped(p);
- mark_page_accessed(p);
-
- if (i == 0) {
- eb->first_page = p;
- set_page_extent_head(p, len);
- } else {
- set_page_private(p, EXTENT_PAGE_PRIVATE);
- }
-
- if (!PageUptodate(p))
- uptodate = 0;
- unlock_page(p);
- }
- if (uptodate)
- eb->flags |= EXTENT_UPTODATE;
- eb->flags |= EXTENT_BUFFER_FILLED;
-
-lru_add:
- spin_lock(&tree->lru_lock);
- add_lru(tree, eb);
- spin_unlock(&tree->lru_lock);
return eb;
-fail:
- spin_lock(&tree->lru_lock);
- list_del_init(&eb->lru);
- spin_unlock(&tree->lru_lock);
- if (!atomic_dec_and_test(&eb->refs))
- return NULL;
- for (index = 1; index < i; index++) {
- page_cache_release(extent_buffer_page(eb, index));
- }
- if (i > 0)
- page_cache_release(extent_buffer_page(eb, 0));
- __free_extent_buffer(eb);
- return NULL;
}
EXPORT_SYMBOL(find_extent_buffer);
void free_extent_buffer(struct extent_buffer *eb)
{
- unsigned long i;
- unsigned long num_pages;
-
if (!eb)
return;
if (!atomic_dec_and_test(&eb->refs))
return;
- WARN_ON(!list_empty(&eb->lru));
- num_pages = num_extent_pages(eb->start, eb->len);
-
- for (i = 1; i < num_pages; i++) {
- page_cache_release(extent_buffer_page(eb, i));
- }
- page_cache_release(extent_buffer_page(eb, 0));
- __free_extent_buffer(eb);
+ WARN_ON(1);
}
EXPORT_SYMBOL(free_extent_buffer);
@@ -3583,3 +3474,35 @@
}
}
EXPORT_SYMBOL(memmove_extent_buffer);
+
+int try_release_extent_buffer(struct extent_io_tree *tree, struct page *page)
+{
+ u64 start = page_offset(page);
+ struct extent_buffer *eb;
+ int ret = 1;
+ unsigned long i;
+ unsigned long num_pages;
+
+ spin_lock(&tree->buffer_lock);
+ eb = buffer_search(tree, start);
+ if (!eb)
+ goto out;
+
+ if (atomic_read(&eb->refs) > 1) {
+ ret = 0;
+ goto out;
+ }
+ /* at this point we can safely release the extent buffer */
+ num_pages = num_extent_pages(eb->start, eb->len);
+ for (i = 0; i < num_pages; i++) {
+ struct page *page = extent_buffer_page(eb, i);
+ page_cache_release(page);
+ }
+ rb_erase(&eb->rb_node, &tree->buffer);
+ __free_extent_buffer(eb);
+out:
+ spin_unlock(&tree->buffer_lock);
+ return ret;
+}
+EXPORT_SYMBOL(try_release_extent_buffer);
+