Btrfs: Add a leaf reference cache

Much of the IO done while dropping snapshots is done looking up
leaves in the filesystem trees to see if they point to any extents and
to drop the references on any extents found.

This creates a cache so that IO isn't required.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 49 insertions, 18 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 768b0d223e6..543e5ee4033 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -24,6 +24,7 @@
 #include "disk-io.h"
 #include "transaction.h"
 #include "locking.h"
+#include "ref-cache.h"
 
 static int total_trans = 0;
 extern struct kmem_cache *btrfs_trans_handle_cachep;
@@ -31,6 +32,13 @@ extern struct kmem_cache *btrfs_transaction_cachep;
 
 #define BTRFS_ROOT_TRANS_TAG 0
 
+struct dirty_root {
+	struct list_head list;
+	struct btrfs_root *root;
+	struct btrfs_root *latest_root;
+	struct btrfs_leaf_ref_tree ref_tree;
+};
+
 static noinline void put_transaction(struct btrfs_transaction *transaction)
 {
 	WARN_ON(transaction->use_count == 0);
@@ -84,6 +92,7 @@ static noinline int join_transaction(struct btrfs_root *root)
 
 static noinline int record_root_in_trans(struct btrfs_root *root)
 {
+	struct dirty_root *dirty;
 	u64 running_trans_id = root->fs_info->running_transaction->transid;
 	if (root->ref_cows && root->last_trans < running_trans_id) {
 		WARN_ON(root == root->fs_info->extent_root);
@@ -91,7 +100,25 @@ static noinline int record_root_in_trans(struct btrfs_root *root)
 			radix_tree_tag_set(&root->fs_info->fs_roots_radix,
 				   (unsigned long)root->root_key.objectid,
 				   BTRFS_ROOT_TRANS_TAG);
+
+			dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
+			BUG_ON(!dirty);
+			dirty->root = kmalloc(sizeof(*dirty->root), GFP_NOFS);
+			BUG_ON(!dirty->root);
+
+			dirty->latest_root = root;
+			INIT_LIST_HEAD(&dirty->list);
+			btrfs_leaf_ref_tree_init(&dirty->ref_tree);
+			dirty->ref_tree.generation = running_trans_id;
+
 			root->commit_root = btrfs_root_node(root);
+			root->ref_tree = &dirty->ref_tree;
+
+			memcpy(dirty->root, root, sizeof(*root));
+			spin_lock_init(&dirty->root->node_lock);
+			mutex_init(&dirty->root->objectid_mutex);
+			dirty->root->node = root->commit_root;
+			dirty->root->commit_root = NULL;
 		} else {
 			WARN_ON(1);
 		}
@@ -310,12 +337,6 @@ int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans,
 	return 0;
 }
 
-struct dirty_root {
-	struct list_head list;
-	struct btrfs_root *root;
-	struct btrfs_root *latest_root;
-};
-
 int btrfs_add_dead_root(struct btrfs_root *root,
 			struct btrfs_root *latest,
 			struct list_head *dead_list)
@@ -325,8 +346,10 @@ int btrfs_add_dead_root(struct btrfs_root *root,
 	dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
 	if (!dirty)
 		return -ENOMEM;
+	btrfs_leaf_ref_tree_init(&dirty->ref_tree);
 	dirty->root = root;
 	dirty->latest_root = latest;
+	root->ref_tree = NULL;
 	list_add(&dirty->list, dead_list);
 	return 0;
 }
@@ -354,11 +377,23 @@ static noinline int add_dirty_roots(struct btrfs_trans_handle *trans,
 			radix_tree_tag_clear(radix,
 				     (unsigned long)root->root_key.objectid,
 				     BTRFS_ROOT_TRANS_TAG);
+
+			BUG_ON(!root->ref_tree);
+			dirty = container_of(root->ref_tree, struct dirty_root,
+					     ref_tree);
+
 			if (root->commit_root == root->node) {
 				WARN_ON(root->node->start !=
 					btrfs_root_bytenr(&root->root_item));
+
+				BUG_ON(!btrfs_leaf_ref_tree_empty(
+							root->ref_tree));
 				free_extent_buffer(root->commit_root);
 				root->commit_root = NULL;
+				root->ref_tree = NULL;
+				
+				kfree(dirty->root);
+				kfree(dirty);
 
 				/* make sure to update the root on disk
 				 * so we get any updates to the block used
@@ -370,23 +405,12 @@ static noinline int add_dirty_roots(struct btrfs_trans_handle *trans,
 						&root->root_item);
 				continue;
 			}
-			dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
-			BUG_ON(!dirty);
-			dirty->root = kmalloc(sizeof(*dirty->root), GFP_NOFS);
-			BUG_ON(!dirty->root);
 
 			memset(&root->root_item.drop_progress, 0,
 			       sizeof(struct btrfs_disk_key));
 			root->root_item.drop_level = 0;
-
-			memcpy(dirty->root, root, sizeof(*root));
-			dirty->root->node = root->commit_root;
-			dirty->latest_root = root;
-			spin_lock_init(&dirty->root->node_lock);
-			mutex_init(&dirty->root->objectid_mutex);
-
 			root->commit_root = NULL;
-
+			root->ref_tree = NULL;
 			root->root_key.offset = root->fs_info->generation;
 			btrfs_set_root_bytenr(&root->root_item,
 					      root->node->start);
@@ -409,6 +433,7 @@ static noinline int add_dirty_roots(struct btrfs_trans_handle *trans,
 				list_add(&dirty->list, list);
 			} else {
 				WARN_ON(1);
+				free_extent_buffer(dirty->root->node);
 				kfree(dirty->root);
 				kfree(dirty);
 			}
@@ -514,6 +539,8 @@ static noinline int drop_dirty_roots(struct btrfs_root *tree_root,
 		ret = btrfs_end_transaction(trans, tree_root);
 		BUG_ON(ret);
 
+		btrfs_remove_leaf_refs(dirty->root);
+
 		free_extent_buffer(dirty->root->node);
 		kfree(dirty->root);
 		kfree(dirty);
@@ -698,6 +725,10 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 			      &dirty_fs_roots);
 	BUG_ON(ret);
 
+	spin_lock(&root->fs_info->ref_cache_lock);
+	root->fs_info->running_ref_cache_size = 0;
+	spin_unlock(&root->fs_info->ref_cache_lock);
+
 	ret = btrfs_commit_tree_roots(trans, root);
 	BUG_ON(ret);