[PATCH 17/39] ovl: add ovl_write_iter()

[Miklos Szeredi]

Implement stacked writes.

Signed-off-by: Miklos Szeredi <mszer...@redhat.com>
---
 fs/overlayfs/file.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index bbc40a14acf8..a7af56861aa5 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -195,9 +195,48 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct 
iov_iter *iter)
        return ret;
 }
 
+static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+       struct file *file = iocb->ki_filp;
+       struct inode *inode = file_inode(file);
+       struct fd real;
+       const struct cred *old_cred;
+       ssize_t ret;
+
+       if (!iov_iter_count(iter))
+               return 0;
+
+       inode_lock(inode);
+       /* Update mode */
+       ovl_copyattr(ovl_inode_real(inode), inode);
+       ret = file_remove_privs(file);
+       if (ret)
+               goto out_unlock;
+
+       ret = ovl_real_fdget(file, &real);
+       if (ret)
+               goto out_unlock;
+
+       old_cred = ovl_override_creds(file_inode(file)->i_sb);
+       ret = vfs_iter_write(real.file, iter, &iocb->ki_pos,
+                            ovl_iocb_to_rwf(iocb));
+       revert_creds(old_cred);
+
+       /* Update size */
+       ovl_copyattr(ovl_inode_real(inode), inode);
+
+       fdput(real);
+
+out_unlock:
+       inode_unlock(inode);
+
+       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,
 };
-- 
2.14.3