Btrfs: implement memory reclaim for leaf reference cache
The memory reclaiming issue happens when snapshot exists. In that
case, some cache entries may not be used during old snapshot dropping,
so they will remain in the cache until umount.
The patch adds a field to struct btrfs_leaf_ref to record create time. Besides,
the patch makes all dead roots of a given snapshot linked together in order of
create time. After a old snapshot was completely dropped, we check the dead
root list and remove all cache entries created before the oldest dead root in
the list.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ref-cache.c b/fs/btrfs/ref-cache.c
index ec95877..272b989 100644
--- a/fs/btrfs/ref-cache.c
+++ b/fs/btrfs/ref-cache.c
@@ -21,12 +21,18 @@
#include "ref-cache.h"
#include "transaction.h"
-struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(int nr_extents)
+struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(struct btrfs_root *root,
+ int nr_extents)
{
struct btrfs_leaf_ref *ref;
+ size_t size = btrfs_leaf_ref_size(nr_extents);
- ref = kmalloc(btrfs_leaf_ref_size(nr_extents), GFP_NOFS);
+ ref = kmalloc(size, GFP_NOFS);
if (ref) {
+ spin_lock(&root->fs_info->ref_cache_lock);
+ root->fs_info->total_ref_cache_size += size;
+ spin_unlock(&root->fs_info->ref_cache_lock);
+
memset(ref, 0, sizeof(*ref));
atomic_set(&ref->usage, 1);
INIT_LIST_HEAD(&ref->list);
@@ -34,14 +40,20 @@
return ref;
}
-void btrfs_free_leaf_ref(struct btrfs_leaf_ref *ref)
+void btrfs_free_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
{
if (!ref)
return;
WARN_ON(atomic_read(&ref->usage) == 0);
if (atomic_dec_and_test(&ref->usage)) {
+ size_t size = btrfs_leaf_ref_size(ref->nritems);
+
BUG_ON(ref->in_tree);
kfree(ref);
+
+ spin_lock(&root->fs_info->ref_cache_lock);
+ root->fs_info->total_ref_cache_size -= size;
+ spin_unlock(&root->fs_info->ref_cache_lock);
}
}
@@ -64,7 +76,7 @@
else
return parent;
}
-
+
entry = rb_entry(node, struct btrfs_leaf_ref, rb_node);
entry->in_tree = 1;
rb_link_node(node, parent, p);
@@ -91,9 +103,8 @@
return NULL;
}
-int btrfs_remove_leaf_refs(struct btrfs_root *root)
+int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen)
{
- struct rb_node *rb;
struct btrfs_leaf_ref *ref = NULL;
struct btrfs_leaf_ref_tree *tree = root->ref_tree;
@@ -101,17 +112,18 @@
return 0;
spin_lock(&tree->lock);
- while(!btrfs_leaf_ref_tree_empty(tree)) {
- rb = rb_first(&tree->root);
- ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
+ while(!list_empty(&tree->list)) {
+ ref = list_entry(tree->list.next, struct btrfs_leaf_ref, list);
+ BUG_ON(!ref->in_tree);
+ if (ref->root_gen > max_root_gen)
+ break;
+
rb_erase(&ref->rb_node, &tree->root);
ref->in_tree = 0;
list_del_init(&ref->list);
spin_unlock(&tree->lock);
-
- btrfs_free_leaf_ref(ref);
-
+ btrfs_free_leaf_ref(root, ref);
cond_resched();
spin_lock(&tree->lock);
}
@@ -143,7 +155,6 @@
{
int ret = 0;
struct rb_node *rb;
- size_t size = btrfs_leaf_ref_size(ref->nritems);
struct btrfs_leaf_ref_tree *tree = root->ref_tree;
spin_lock(&tree->lock);
@@ -151,9 +162,6 @@
if (rb) {
ret = -EEXIST;
} else {
- spin_lock(&root->fs_info->ref_cache_lock);
- root->fs_info->total_ref_cache_size += size;
- spin_unlock(&root->fs_info->ref_cache_lock);
atomic_inc(&ref->usage);
list_add_tail(&ref->list, &tree->list);
}
@@ -163,15 +171,10 @@
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;
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;
- spin_unlock(&root->fs_info->ref_cache_lock);
rb_erase(&ref->rb_node, &tree->root);
ref->in_tree = 0;
@@ -179,7 +182,6 @@
spin_unlock(&tree->lock);
- btrfs_free_leaf_ref(ref);
+ btrfs_free_leaf_ref(root, ref);
return 0;
}
-