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>

1 files changed, 5 insertions, 7 deletions

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index f9b0fc911661..038a5229404a 100644
--- a/fs/btrfs/tree-log.c
+++ b/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();