Btrfs: don't start a new transaction when starting sync

If there is no running transaction in the fs, we needn't start a new one when
we want to start sync.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 5022e62..7b1f614 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3065,16 +3065,22 @@ static noinline long btrfs_ioctl_start_sync(struct btrfs_root *root,
        u64 transid;
        int ret;
 
-       trans = btrfs_start_transaction(root, 0);
-       if (IS_ERR(trans))
-               return PTR_ERR(trans);
+       trans = btrfs_attach_transaction(root);
+       if (IS_ERR(trans)) {
+               if (PTR_ERR(trans) != -ENOENT)
+                       return PTR_ERR(trans);
+
+               /* No running transaction, don't bother */
+               transid = root->fs_info->last_trans_committed;
+               goto out;
+       }
        transid = trans->transid;
        ret = btrfs_commit_transaction_async(trans, root, 0);
        if (ret) {
                btrfs_end_transaction(trans, root);
                return ret;
        }
-
+out:
        if (argp)
                if (copy_to_user(argp, &transid, sizeof(transid)))
                        return -EFAULT;

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index bcc6b65..8db401f 100644 (file)
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1307,9 +1307,10 @@ static void do_async_commit(struct work_struct *work)
         * We've got freeze protection passed with the transaction.
         * Tell lockdep about it.
         */
-       rwsem_acquire_read(
-               &ac->root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
-               0, 1, _THIS_IP_);
+       if (ac->newtrans->type < TRANS_JOIN_NOLOCK)
+               rwsem_acquire_read(
+                    &ac->root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
+                    0, 1, _THIS_IP_);
 
        current->journal_info = ac->newtrans;
 
@@ -1347,8 +1348,10 @@ int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans,
         * Tell lockdep we've released the freeze rwsem, since the
         * async commit thread will be the one to unlock it.
         */
-       rwsem_release(&root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
-                     1, _THIS_IP_);
+       if (trans->type < TRANS_JOIN_NOLOCK)
+               rwsem_release(
+                       &root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
+                       1, _THIS_IP_);
 
        schedule_delayed_work(&ac->work, 0);