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, 14 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index d60923967347..4f0e1d06c384 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -716,6 +716,7 @@ static int __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
         root->node = NULL;
         root->inode = NULL;
         root->commit_root = NULL;
+        root->ref_tree = NULL;
         root->sectorsize = sectorsize;
         root->nodesize = nodesize;
         root->leafsize = leafsize;
@@ -1165,12 +1166,19 @@ static int transaction_kthread(void *arg)
                 vfs_check_frozen(root->fs_info->sb, SB_FREEZE_WRITE);
                 mutex_lock(&root->fs_info->transaction_kthread_mutex);
 
+                printk("btrfs: total reference cache size %Lu\n",
+                        root->fs_info->total_ref_cache_size);
+
                 mutex_lock(&root->fs_info->trans_mutex);
                 cur = root->fs_info->running_transaction;
                 if (!cur) {
                         mutex_unlock(&root->fs_info->trans_mutex);
                         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);
@@ -1233,6 +1241,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         spin_lock_init(&fs_info->hash_lock);
         spin_lock_init(&fs_info->delalloc_lock);
         spin_lock_init(&fs_info->new_trans_lock);
+        spin_lock_init(&fs_info->ref_cache_lock);
 
         init_completion(&fs_info->kobj_unregister);
         fs_info->tree_root = tree_root;
@@ -1699,6 +1708,11 @@ int close_ctree(struct btrfs_root *root)
                 printk("btrfs: at unmount delalloc count %Lu\n",
                        fs_info->delalloc_bytes);
         }
+        if (fs_info->total_ref_cache_size) {
+                printk("btrfs: at umount reference cache size %Lu\n",
+                        fs_info->total_ref_cache_size);
+        }
+        
         if (fs_info->extent_root->node)
                 free_extent_buffer(fs_info->extent_root->node);