ovl: add ovl_fsync()

Implement stacked fsync().

Don't sync if lower (noticed by Amir Goldstein).

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 53d95c9..8adddee 100644 (file)
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -233,10 +233,33 @@ out_unlock:
        return ret;
 }
 
+static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
+{
+       struct fd real;
+       const struct cred *old_cred;
+       int ret;
+
+       ret = ovl_real_fdget(file, &real);
+       if (ret)
+               return ret;
+
+       /* Don't sync lower file for fear of receiving EROFS error */
+       if (file_inode(real.file) == ovl_inode_upper(file_inode(file))) {
+               old_cred = ovl_override_creds(file_inode(file)->i_sb);
+               ret = vfs_fsync_range(real.file, start, end, datasync);
+               revert_creds(old_cred);
+       }
+
+       fdput(real);
+
+       return ret;
+}
+
 const struct file_operations ovl_file_operations = {
        .open           = ovl_open,
        .release        = ovl_release,
        .llseek         = ovl_llseek,
        .read_iter      = ovl_read_iter,
        .write_iter     = ovl_write_iter,
+       .fsync          = ovl_fsync,
 };