Btrfs: avoid tree log commit when there are no changes

[linux-2.6-block.git] / fs / btrfs / tree-log.c

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 6d9ec285644d285a00ab9e581c7e63843edd4beb..0a1bde26896338d918de06d258f3dd752aadbdd1 100644 (file)
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -1980,6 +1980,7 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
        int ret;
        struct btrfs_root *log = root->log_root;
        struct btrfs_root *log_root_tree = root->fs_info->log_root_tree;
+       u64 log_transid = 0;
 
        mutex_lock(&root->log_mutex);
        index1 = root->log_transid % 2;
@@ -2018,6 +2019,7 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
        btrfs_set_root_node(&log->root_item, log->node);
 
        root->log_batch = 0;
+       log_transid = root->log_transid;
        root->log_transid++;
        log->log_transid = root->log_transid;
        root->log_start_pid = 0;
@@ -2095,6 +2097,11 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
        write_ctree_super(trans, root->fs_info->tree_root, 1);
        ret = 0;
 
+       mutex_lock(&root->log_mutex);
+       if (root->last_log_commit < log_transid)
+               root->last_log_commit = log_transid;
+       mutex_unlock(&root->log_mutex);
+
 out_wake_log_root:
        atomic_set(&log_root_tree->log_commit[index2], 0);
        smp_mb();
@@ -2862,6 +2869,21 @@ out:
        return ret;
 }
 
+static int inode_in_log(struct btrfs_trans_handle *trans,
+                struct inode *inode)
+{
+       struct btrfs_root *root = BTRFS_I(inode)->root;
+       int ret = 0;
+
+       mutex_lock(&root->log_mutex);
+       if (BTRFS_I(inode)->logged_trans == trans->transid &&
+           BTRFS_I(inode)->last_sub_trans <= root->last_log_commit)
+               ret = 1;
+       mutex_unlock(&root->log_mutex);
+       return ret;
+}
+
+
 /*
  * helper function around btrfs_log_inode to make sure newly created
  * parent directories also end up in the log.  A minimal inode and backref
@@ -2901,6 +2923,11 @@ int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
        if (ret)
                goto end_no_trans;
 
+       if (inode_in_log(trans, inode)) {
+               ret = BTRFS_NO_LOG_SYNC;
+               goto end_no_trans;
+       }
+
        start_log_trans(trans, root);
 
        ret = btrfs_log_inode(trans, root, inode, inode_only);