Btrfs: fix unprotected ->log_batch

We forget to protect ->log_batch when syncing a file, this patch fix
this problem by atomic operation. And ->log_batch is used to check
if there are parallel sync operations or not, so it is unnecessary to
reset it to 0 after the sync operation of the current log tree complete.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>

fs/btrfs/ctree.h

@@ -1491,9 +1491,9 @@ struct btrfs_root {
 	wait_queue_head_t log_commit_wait[2];
 	atomic_t log_writers;
 	atomic_t log_commit[2];
+	atomic_t log_batch;
 	unsigned long log_transid;
 	unsigned long last_log_commit;
-	unsigned long log_batch;
 	pid_t log_start_pid;
 	bool log_multiple_pids;
 

fs/btrfs/disk-io.c

@@ -1168,8 +1168,8 @@ static void __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
 	atomic_set(&root->log_commit[0], 0);
 	atomic_set(&root->log_commit[1], 0);
 	atomic_set(&root->log_writers, 0);
+	atomic_set(&root->log_batch, 0);
 	atomic_set(&root->orphan_inodes, 0);
-	root->log_batch = 0;
 	root->log_transid = 0;
 	root->last_log_commit = 0;
 	extent_io_tree_init(&root->dirty_log_pages,

fs/btrfs/file.c

@@ -1551,9 +1551,9 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 	 * ordered range does a filemape_write_and_wait_range which is why we
 	 * don't do it above like other file systems.
 	 */
-	root->log_batch++;
+	atomic_inc(&root->log_batch);
 	btrfs_wait_ordered_range(inode, start, end);
-	root->log_batch++;
+	atomic_inc(&root->log_batch);
 
 	/*
 	 * check the transaction that last modified this inode

fs/btrfs/tree-log.c

@@ -147,7 +147,7 @@ static int start_log_trans(struct btrfs_trans_handle *trans,
 			root->log_multiple_pids = true;
 		}
 
-		root->log_batch++;
+		atomic_inc(&root->log_batch);
 		atomic_inc(&root->log_writers);
 		mutex_unlock(&root->log_mutex);
 		return 0;
@@ -166,7 +166,7 @@ static int start_log_trans(struct btrfs_trans_handle *trans,
 			err = ret;
 	}
 	mutex_unlock(&root->fs_info->tree_log_mutex);
-	root->log_batch++;
+	atomic_inc(&root->log_batch);
 	atomic_inc(&root->log_writers);
 	mutex_unlock(&root->log_mutex);
 	return err;
@@ -2036,7 +2036,7 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 	if (atomic_read(&root->log_commit[(index1 + 1) % 2]))
 		wait_log_commit(trans, root, root->log_transid - 1);
 	while (1) {
-		unsigned long batch = root->log_batch;
+		int batch = atomic_read(&root->log_batch);
 		/* when we're on an ssd, just kick the log commit out */
 		if (!btrfs_test_opt(root, SSD) && root->log_multiple_pids) {
 			mutex_unlock(&root->log_mutex);
@@ -2044,7 +2044,7 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 			mutex_lock(&root->log_mutex);
 		}
 		wait_for_writer(trans, root);
-		if (batch == root->log_batch)
+		if (batch == atomic_read(&root->log_batch))
 			break;
 	}
 
@@ -2073,7 +2073,6 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 
 	btrfs_set_root_node(&log->root_item, log->node);
 
-	root->log_batch = 0;
 	root->log_transid++;
 	log->log_transid = root->log_transid;
 	root->log_start_pid = 0;
@@ -2086,7 +2085,7 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 	mutex_unlock(&root->log_mutex);
 
 	mutex_lock(&log_root_tree->log_mutex);
-	log_root_tree->log_batch++;
+	atomic_inc(&log_root_tree->log_batch);
 	atomic_inc(&log_root_tree->log_writers);
 	mutex_unlock(&log_root_tree->log_mutex);
 
@@ -2156,7 +2155,6 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 	btrfs_set_super_log_root_level(root->fs_info->super_for_commit,
 				btrfs_header_level(log_root_tree->node));
 
-	log_root_tree->log_batch = 0;
 	log_root_tree->log_transid++;
 	smp_mb();