Btrfs: Dir fsync optimizations

Drop i_mutex during the commit

Don't bother doing the fsync at all unless the dir is marked as dirtied
and needing fsync in this transaction.  For directories, this means
that someone has unlinked a file from the dir without fsyncing the
file.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/btrfs_inode.h

@@ -56,6 +56,9 @@ struct btrfs_inode {
 	 * transid that last logged this inode
 	 */
 	u64 logged_trans;
+
+	/* trans that last made a change that should be fully fsync'd */
+	u64 log_dirty_trans;
 	u64 delalloc_bytes;
 	u64 disk_i_size;
 	u32 flags;

fs/btrfs/file.c

@@ -1061,7 +1061,9 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
 	}
 	mutex_unlock(&root->fs_info->trans_mutex);
 
+	root->fs_info->tree_log_batch++;
 	filemap_fdatawait(inode->i_mapping);
+	root->fs_info->tree_log_batch++;
 
 	/*
 	 * ok we haven't committed the transaction yet, lets do a commit
@@ -1076,14 +1078,29 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
 	}
 
 	ret = btrfs_log_dentry_safe(trans, root, file->f_dentry);
-	if (ret < 0)
+	if (ret < 0) {
 		goto out;
+	}
+
+	/* we've logged all the items and now have a consistent
+	 * version of the file in the log.  It is possible that
+	 * someone will come in and modify the file, but that's
+	 * fine because the log is consistent on disk, and we
+	 * have references to all of the file's extents
+	 *
+	 * It is possible that someone will come in and log the
+	 * file again, but that will end up using the synchronization
+	 * inside btrfs_sync_log to keep things safe.
+	 */
+	mutex_unlock(&file->f_dentry->d_inode->i_mutex);
+
 	if (ret > 0) {
 		ret = btrfs_commit_transaction(trans, root);
 	} else {
 		btrfs_sync_log(trans, root);
 		ret = btrfs_end_transaction(trans, root);
 	}
+	mutex_lock(&file->f_dentry->d_inode->i_mutex);
 out:
 	return ret > 0 ? EIO : ret;
 }

fs/btrfs/inode.c

@@ -1187,7 +1187,9 @@ int btrfs_unlink_inode(struct btrfs_trans_handle *trans,
 
 	ret = btrfs_del_inode_ref_in_log(trans, root, name, name_len,
 					 inode, dir->i_ino);
-	BUG_ON(ret);
+	BUG_ON(ret != 0 && ret != -ENOENT);
+	if (ret != -ENOENT)
+		BTRFS_I(dir)->log_dirty_trans = trans->transid;
 
 	ret = btrfs_del_dir_entries_in_log(trans, root, name, name_len,
 					   dir, index);
@@ -1790,6 +1792,7 @@ static noinline void init_btrfs_i(struct inode *inode)
 	bi->disk_i_size = 0;
 	bi->flags = 0;
 	bi->index_cnt = (u64)-1;
+	bi->log_dirty_trans = 0;
 	extent_map_tree_init(&BTRFS_I(inode)->extent_tree, GFP_NOFS);
 	extent_io_tree_init(&BTRFS_I(inode)->io_tree,
 			     inode->i_mapping, GFP_NOFS);

fs/btrfs/tree-log.c

@@ -1973,10 +1973,10 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 	atomic_set(&log->fs_info->tree_log_commit, 1);
 
 	while(1) {
+		batch = log->fs_info->tree_log_batch;
 		mutex_unlock(&log->fs_info->tree_log_mutex);
 		schedule_timeout_uninterruptible(1);
 		mutex_lock(&log->fs_info->tree_log_mutex);
-		batch = log->fs_info->tree_log_batch;
 
 		while(atomic_read(&log->fs_info->tree_log_writers)) {
 			DEFINE_WAIT(wait);
@@ -2189,8 +2189,6 @@ int btrfs_del_inode_ref_in_log(struct btrfs_trans_handle *trans,
 	mutex_unlock(&BTRFS_I(inode)->log_mutex);
 	end_log_trans(root);
 
-	if (ret == 0 || ret == -ENOENT)
-		return 0;
 	return ret;
 }
 
@@ -2620,9 +2618,11 @@ static int __btrfs_log_inode(struct btrfs_trans_handle *trans,
 		else
 			break;
 	}
-	if (inode_only == LOG_INODE_ALL && S_ISDIR(inode->i_mode)) {
+	if (inode_only == LOG_INODE_ALL && S_ISDIR(inode->i_mode) &&
+	    BTRFS_I(inode)->log_dirty_trans >= trans->transid) {
 		btrfs_release_path(root, path);
 		btrfs_release_path(log, dst_path);
+		BTRFS_I(inode)->log_dirty_trans = 0;
 		ret = log_directory_changes(trans, root, inode, path, dst_path);
 		BUG_ON(ret);
 	}