ovl: add ovl_mmap()

Implement stacked mmap.

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

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 8adddee..4c8bf77 100644 (file)
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -255,6 +255,37 @@ static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
        return ret;
 }
 
+static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
+{
+       struct file *realfile = file->private_data;
+       const struct cred *old_cred;
+       int ret;
+
+       if (!realfile->f_op->mmap)
+               return -ENODEV;
+
+       if (WARN_ON(file != vma->vm_file))
+               return -EIO;
+
+       vma->vm_file = get_file(realfile);
+
+       old_cred = ovl_override_creds(file_inode(file)->i_sb);
+       ret = call_mmap(vma->vm_file, vma);
+       revert_creds(old_cred);
+
+       if (ret) {
+               /* Drop reference count from new vm_file value */
+               fput(realfile);
+       } else {
+               /* Drop reference count from previous vm_file value */
+               fput(file);
+       }
+
+       ovl_file_accessed(file);
+
+       return ret;
+}
+
 const struct file_operations ovl_file_operations = {
        .open           = ovl_open,
        .release        = ovl_release,
@@ -262,4 +293,5 @@ const struct file_operations ovl_file_operations = {
        .read_iter      = ovl_read_iter,
        .write_iter     = ovl_write_iter,
        .fsync          = ovl_fsync,
+       .mmap           = ovl_mmap,
 };