Btrfs: check file pointer in btrfs_sync_file

fsync can be called by NFS with a null file pointer, and btrfs was
oopsing in this case.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 3e8023efaff7..872f104576e5 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1222,7 +1222,7 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
         /*
          * ok we haven't committed the transaction yet, lets do a commit
          */
-        if (file->private_data)
+        if (file && file->private_data)
                 btrfs_ioctl_trans_end(file);
 
         trans = btrfs_start_transaction(root, 1);
@@ -1231,7 +1231,7 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
                 goto out;
         }
 
-        ret = btrfs_log_dentry_safe(trans, root, file->f_dentry);
+        ret = btrfs_log_dentry_safe(trans, root, dentry);
         if (ret < 0)
                 goto out;
 
@@ -1245,7 +1245,7 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
          * 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);
+        mutex_unlock(&dentry->d_inode->i_mutex);
 
         if (ret > 0) {
                 ret = btrfs_commit_transaction(trans, root);
@@ -1253,7 +1253,7 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
                 btrfs_sync_log(trans, root);
                 ret = btrfs_end_transaction(trans, root);
         }
-        mutex_lock(&file->f_dentry->d_inode->i_mutex);
+        mutex_lock(&dentry->d_inode->i_mutex);
 out:
         return ret > 0 ? EIO : ret;
 }