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Btrfs: Leaf reference cache update
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This changes the reference cache to make a single cache per root
instead of one cache per transaction, and to key by the byte number
of the disk block instead of the keys inside.

This makes it much less likely to have cache misses if a snapshot
or something has an extra reference on a higher node or a leaf while
the first transaction that added the leaf into the cache is dropping.

Some throttling is added to functions that free blocks heavily so they
wait for old transactions to drop.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
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Chris Mason committed Sep 25, 2008
1 parent 31153d8 commit 017e536
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Showing 8 changed files with 61 additions and 109 deletions.
11 changes: 10 additions & 1 deletion fs/btrfs/ctree.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -594,7 +594,6 @@ struct btrfs_fs_info {

spinlock_t ref_cache_lock;
u64 total_ref_cache_size;
u64 running_ref_cache_size;

u64 avail_data_alloc_bits;
u64 avail_metadata_alloc_bits;
Expand All @@ -606,10 +605,18 @@ struct btrfs_fs_info {
void *bdev_holder;
};

struct btrfs_leaf_ref_tree {
struct rb_root root;
struct btrfs_leaf_ref *last;
struct list_head list;
spinlock_t lock;
};

/*
* in ram representation of the tree. extent_root is used for all allocations
* and for the extent tree extent_root root.
*/
struct dirty_root;
struct btrfs_root {
struct extent_buffer *node;

Expand All @@ -618,6 +625,8 @@ struct btrfs_root {

struct extent_buffer *commit_root;
struct btrfs_leaf_ref_tree *ref_tree;
struct btrfs_leaf_ref_tree ref_tree_struct;
struct dirty_root *dirty_root;

struct btrfs_root_item root_item;
struct btrfs_key root_key;
Expand Down
8 changes: 5 additions & 3 deletions fs/btrfs/disk-io.c
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,7 @@
#include "print-tree.h"
#include "async-thread.h"
#include "locking.h"
#include "ref-cache.h"

#if 0
static int check_tree_block(struct btrfs_root *root, struct extent_buffer *buf)
Expand Down Expand Up @@ -737,6 +738,10 @@ static int __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
spin_lock_init(&root->node_lock);
spin_lock_init(&root->orphan_lock);
mutex_init(&root->objectid_mutex);

btrfs_leaf_ref_tree_init(&root->ref_tree_struct);
root->ref_tree = &root->ref_tree_struct;

memset(&root->root_key, 0, sizeof(root->root_key));
memset(&root->root_item, 0, sizeof(root->root_item));
memset(&root->defrag_progress, 0, sizeof(root->defrag_progress));
Expand Down Expand Up @@ -1176,9 +1181,6 @@ static int transaction_kthread(void *arg)
goto sleep;
}

printk("btrfs: running reference cache size %Lu\n",
root->fs_info->running_ref_cache_size);

now = get_seconds();
if (now < cur->start_time || now - cur->start_time < 30) {
mutex_unlock(&root->fs_info->trans_mutex);
Expand Down
18 changes: 6 additions & 12 deletions fs/btrfs/extent-tree.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1004,8 +1004,6 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
goto out;
}

btrfs_item_key_to_cpu(buf, &ref->key, 0);

ref->bytenr = buf->start;
ref->owner = btrfs_header_owner(buf);
ref->generation = btrfs_header_generation(buf);
Expand Down Expand Up @@ -2387,19 +2385,15 @@ static void noinline reada_walk_down(struct btrfs_root *root,
}
}

/*
* we want to avoid as much random IO as we can with the alloc mutex
* held, so drop the lock and do the lookup, then do it again with the
* lock held.
*/
int drop_snap_lookup_refcount(struct btrfs_root *root, u64 start, u64 len,
u32 *refs)
{
int ret;
mutex_unlock(&root->fs_info->alloc_mutex);
lookup_extent_ref(NULL, root, start, len, refs);
ret = lookup_extent_ref(NULL, root, start, len, refs);
cond_resched();
mutex_lock(&root->fs_info->alloc_mutex);
return lookup_extent_ref(NULL, root, start, len, refs);
return ret;
}

/*
Expand Down Expand Up @@ -2468,11 +2462,11 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
BUG_ON(ret);
continue;
}

if (*level == 1) {
struct btrfs_key key;
btrfs_node_key_to_cpu(cur, &key, path->slots[*level]);
ref = btrfs_lookup_leaf_ref(root, &key);
ref = btrfs_lookup_leaf_ref(root, bytenr);
if (ref) {
ret = drop_leaf_ref(trans, root, ref);
BUG_ON(ret);
Expand All @@ -2482,7 +2476,6 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
break;
}
}

next = btrfs_find_tree_block(root, bytenr, blocksize);
if (!next || !btrfs_buffer_uptodate(next, ptr_gen)) {
free_extent_buffer(next);
Expand Down Expand Up @@ -2672,6 +2665,7 @@ int btrfs_drop_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root
ret = -EAGAIN;
break;
}
wake_up(&root->fs_info->transaction_throttle);
}
for (i = 0; i <= orig_level; i++) {
if (path->nodes[i]) {
Expand Down
2 changes: 1 addition & 1 deletion fs/btrfs/file.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -347,7 +347,7 @@ static int noinline dirty_and_release_pages(struct btrfs_trans_handle *trans,
btrfs_update_inode(trans, root, inode);
}
failed:
err = btrfs_end_transaction_throttle(trans, root);
err = btrfs_end_transaction(trans, root);
out_unlock:
unlock_extent(io_tree, start_pos, end_of_last_block, GFP_NOFS);
return err;
Expand Down
8 changes: 4 additions & 4 deletions fs/btrfs/inode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2482,7 +2482,7 @@ static int btrfs_create(struct inode *dir, struct dentry *dentry,
btrfs_update_inode_block_group(trans, dir);
out_unlock:
nr = trans->blocks_used;
btrfs_end_transaction_throttle(trans, root);
btrfs_end_transaction(trans, root);
fail:
if (drop_inode) {
inode_dec_link_count(inode);
Expand Down Expand Up @@ -2535,7 +2535,7 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
drop_inode = 1;

nr = trans->blocks_used;
btrfs_end_transaction_throttle(trans, root);
btrfs_end_transaction(trans, root);
fail:
if (drop_inode) {
inode_dec_link_count(inode);
Expand Down Expand Up @@ -2609,7 +2609,7 @@ static int btrfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)

out_fail:
nr = trans->blocks_used;
btrfs_end_transaction_throttle(trans, root);
btrfs_end_transaction(trans, root);

out_unlock:
if (drop_on_err)
Expand Down Expand Up @@ -3548,7 +3548,7 @@ static int btrfs_symlink(struct inode *dir, struct dentry *dentry,

out_unlock:
nr = trans->blocks_used;
btrfs_end_transaction_throttle(trans, root);
btrfs_end_transaction(trans, root);
out_fail:
if (drop_inode) {
inode_dec_link_count(inode);
Expand Down
71 changes: 15 additions & 56 deletions fs/btrfs/ref-cache.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,7 @@ struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(int nr_extents)
if (ref) {
memset(ref, 0, sizeof(*ref));
atomic_set(&ref->usage, 1);
INIT_LIST_HEAD(&ref->list);
}
return ref;
}
Expand All @@ -44,40 +45,21 @@ void btrfs_free_leaf_ref(struct btrfs_leaf_ref *ref)
}
}

static int comp_keys(struct btrfs_key *k1, struct btrfs_key *k2)
{
if (k1->objectid > k2->objectid)
return 1;
if (k1->objectid < k2->objectid)
return -1;
if (k1->type > k2->type)
return 1;
if (k1->type < k2->type)
return -1;
if (k1->offset > k2->offset)
return 1;
if (k1->offset < k2->offset)
return -1;
return 0;
}

static struct rb_node *tree_insert(struct rb_root *root, struct btrfs_key *key,
static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
struct rb_node *node)
{
struct rb_node ** p = &root->rb_node;
struct rb_node * parent = NULL;
struct btrfs_leaf_ref *entry;
int ret;

while(*p) {
parent = *p;
entry = rb_entry(parent, struct btrfs_leaf_ref, rb_node);
WARN_ON(!entry->in_tree);

ret = comp_keys(key, &entry->key);
if (ret < 0)
if (bytenr < entry->bytenr)
p = &(*p)->rb_left;
else if (ret > 0)
else if (bytenr > entry->bytenr)
p = &(*p)->rb_right;
else
return parent;
Expand All @@ -90,20 +72,18 @@ static struct rb_node *tree_insert(struct rb_root *root, struct btrfs_key *key,
return NULL;
}

static struct rb_node *tree_search(struct rb_root *root, struct btrfs_key *key)
static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
{
struct rb_node * n = root->rb_node;
struct btrfs_leaf_ref *entry;
int ret;

while(n) {
entry = rb_entry(n, struct btrfs_leaf_ref, rb_node);
WARN_ON(!entry->in_tree);

ret = comp_keys(key, &entry->key);
if (ret < 0)
if (bytenr < entry->bytenr)
n = n->rb_left;
else if (ret > 0)
else if (bytenr > entry->bytenr)
n = n->rb_right;
else
return n;
Expand All @@ -122,11 +102,11 @@ int btrfs_remove_leaf_refs(struct btrfs_root *root)

spin_lock(&tree->lock);
while(!btrfs_leaf_ref_tree_empty(tree)) {
tree->last = NULL;
rb = rb_first(&tree->root);
ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
rb_erase(&ref->rb_node, &tree->root);
ref->in_tree = 0;
list_del_init(&ref->list);

spin_unlock(&tree->lock);

Expand All @@ -140,7 +120,7 @@ int btrfs_remove_leaf_refs(struct btrfs_root *root)
}

struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
struct btrfs_key *key)
u64 bytenr)
{
struct rb_node *rb;
struct btrfs_leaf_ref *ref = NULL;
Expand All @@ -150,15 +130,9 @@ struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
return NULL;

spin_lock(&tree->lock);
if (tree->last && comp_keys(key, &tree->last->key) == 0) {
ref = tree->last;
} else {
rb = tree_search(&tree->root, key);
if (rb) {
ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
tree->last = ref;
}
}
rb = tree_search(&tree->root, bytenr);
if (rb)
ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
if (ref)
atomic_inc(&ref->usage);
spin_unlock(&tree->lock);
Expand All @@ -171,21 +145,17 @@ int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
struct rb_node *rb;
size_t size = btrfs_leaf_ref_size(ref->nritems);
struct btrfs_leaf_ref_tree *tree = root->ref_tree;
struct btrfs_transaction *trans = root->fs_info->running_transaction;

spin_lock(&tree->lock);
rb = tree_insert(&tree->root, &ref->key, &ref->rb_node);
rb = tree_insert(&tree->root, ref->bytenr, &ref->rb_node);
if (rb) {
ret = -EEXIST;
} else {
spin_lock(&root->fs_info->ref_cache_lock);
root->fs_info->total_ref_cache_size += size;
if (trans && tree->generation == trans->transid)
root->fs_info->running_ref_cache_size += size;
spin_unlock(&root->fs_info->ref_cache_lock);

tree->last = ref;
atomic_inc(&ref->usage);
list_add_tail(&ref->list, &tree->list);
}
spin_unlock(&tree->lock);
return ret;
Expand All @@ -195,28 +165,17 @@ int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
{
size_t size = btrfs_leaf_ref_size(ref->nritems);
struct btrfs_leaf_ref_tree *tree = root->ref_tree;
struct btrfs_transaction *trans = root->fs_info->running_transaction;

BUG_ON(!ref->in_tree);
spin_lock(&tree->lock);

spin_lock(&root->fs_info->ref_cache_lock);
root->fs_info->total_ref_cache_size -= size;
if (trans && tree->generation == trans->transid)
root->fs_info->running_ref_cache_size -= size;
spin_unlock(&root->fs_info->ref_cache_lock);

if (tree->last == ref) {
struct rb_node *next = rb_next(&ref->rb_node);
if (next) {
tree->last = rb_entry(next, struct btrfs_leaf_ref,
rb_node);
} else
tree->last = NULL;
}

rb_erase(&ref->rb_node, &tree->root);
ref->in_tree = 0;
list_del_init(&ref->list);

spin_unlock(&tree->lock);

Expand Down
18 changes: 8 additions & 10 deletions fs/btrfs/ref-cache.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,8 @@
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*/
#ifndef __REFCACHE__
#define __REFCACHE__

struct btrfs_extent_info {
u64 bytenr;
Expand All @@ -25,22 +27,16 @@ struct btrfs_extent_info {

struct btrfs_leaf_ref {
struct rb_node rb_node;
struct btrfs_key key;
int in_tree;
atomic_t usage;

u64 bytenr;
u64 owner;
u64 generation;
int nritems;
struct btrfs_extent_info extents[];
};

struct btrfs_leaf_ref_tree {
struct rb_root root;
struct btrfs_leaf_ref *last;
u64 generation;
spinlock_t lock;
struct list_head list;
struct btrfs_extent_info extents[];
};

static inline size_t btrfs_leaf_ref_size(int nr_extents)
Expand All @@ -53,7 +49,7 @@ static inline void btrfs_leaf_ref_tree_init(struct btrfs_leaf_ref_tree *tree)
{
tree->root.rb_node = NULL;
tree->last = NULL;
tree->generation = 0;
INIT_LIST_HEAD(&tree->list);
spin_lock_init(&tree->lock);
}

Expand All @@ -66,7 +62,9 @@ void btrfs_leaf_ref_tree_init(struct btrfs_leaf_ref_tree *tree);
struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(int nr_extents);
void btrfs_free_leaf_ref(struct btrfs_leaf_ref *ref);
struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
struct btrfs_key *key);
u64 bytenr);
int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref);
int btrfs_remove_leaf_refs(struct btrfs_root *root);
int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref);

#endif
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