io_uring: fix issue with io_write() not always undoing sb_start_write()

commit e053aaf upstream.

This is actually an older issue, but we never used to hit the -EAGAIN
path before having done sb_start_write(). Make sure that we always call
kiocb_end_write() if we need to retry the write, so that we keep the
calls to sb_start_write() etc balanced.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/io_uring.c

@@ -3720,7 +3720,12 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
 copy_iov:
 		iov_iter_restore(iter, state);
 		ret = io_setup_async_rw(req, iovec, inline_vecs, iter, false);
-		return ret ?: -EAGAIN;
+		if (!ret) {
+			if (kiocb->ki_flags & IOCB_WRITE)
+				kiocb_end_write(req);
+			return -EAGAIN;
+		}
+		return ret;
 	}
 out_free:
 	/* it's reportedly faster than delegating the null check to kfree() */