Btrfs: avoid tree log commit when there are no changes

[net-next-2.6.git] / fs / btrfs / file.c

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 53fb1c997f0e96c76913def6c57d0b7c95216b98..4599113ed72ea4d71fdf4a0160b3beccbb83ec5b 100644 (file)
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1087,8 +1087,10 @@ out_nolock:
                                        btrfs_end_transaction(trans, root);
                                else
                                        btrfs_commit_transaction(trans, root);
-                       } else {
+                       } else if (ret != BTRFS_NO_LOG_SYNC) {
                                btrfs_commit_transaction(trans, root);
+                       } else {
+                               btrfs_end_transaction(trans, root);
                        }
                }
                if (file->f_flags & O_DIRECT) {
@@ -1138,6 +1140,13 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
        int ret = 0;
        struct btrfs_trans_handle *trans;
 
+
+       /* we wait first, since the writeback may change the inode */
+       root->log_batch++;
+       /* the VFS called filemap_fdatawrite for us */
+       btrfs_wait_ordered_range(inode, 0, (u64)-1);
+       root->log_batch++;
+
        /*
         * check the transaction that last modified this inode
         * and see if its already been committed
@@ -1145,6 +1154,11 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
        if (!BTRFS_I(inode)->last_trans)
                goto out;
 
+       /*
+        * if the last transaction that changed this file was before
+        * the current transaction, we can bail out now without any
+        * syncing
+        */
        mutex_lock(&root->fs_info->trans_mutex);
        if (BTRFS_I(inode)->last_trans <=
            root->fs_info->last_trans_committed) {
@@ -1154,13 +1168,6 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
        }
        mutex_unlock(&root->fs_info->trans_mutex);
 
-       root->log_batch++;
-       filemap_fdatawrite(inode->i_mapping);
-       btrfs_wait_ordered_range(inode, 0, (u64)-1);
-       root->log_batch++;
-
-       if (datasync && !(inode->i_state & I_DIRTY_PAGES))
-               goto out;
        /*
         * ok we haven't committed the transaction yet, lets do a commit
         */
@@ -1189,14 +1196,18 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
         */
        mutex_unlock(&dentry->d_inode->i_mutex);
 
-       if (ret > 0) {
-               ret = btrfs_commit_transaction(trans, root);
-       } else {
-               ret = btrfs_sync_log(trans, root);
-               if (ret == 0)
-                       ret = btrfs_end_transaction(trans, root);
-               else
+       if (ret != BTRFS_NO_LOG_SYNC) {
+               if (ret > 0) {
                        ret = btrfs_commit_transaction(trans, root);
+               } else {
+                       ret = btrfs_sync_log(trans, root);
+                       if (ret == 0)
+                               ret = btrfs_end_transaction(trans, root);
+                       else
+                               ret = btrfs_commit_transaction(trans, root);
+               }
+       } else {
+               ret = btrfs_end_transaction(trans, root);
        }
        mutex_lock(&dentry->d_inode->i_mutex);
 out: