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

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>

io_uring/rw.c

@@ -945,6 +945,8 @@ int io_write(struct io_kiocb *req, unsigned int issue_flags)
 			if (rw)
 				rw->bytes_done += ret2;
 
+			if (kiocb->ki_flags & IOCB_WRITE)
+				kiocb_end_write(req);
 			return ret ? ret : -EAGAIN;
 		}
 done:
@@ -953,7 +955,12 @@ int io_write(struct io_kiocb *req, unsigned int issue_flags)
 copy_iov:
 		iov_iter_restore(&s->iter, &s->iter_state);
 		ret = io_setup_async_rw(req, iovec, s, false);
-		return ret ?: -EAGAIN;
+		if (!ret) {
+			if (kiocb->ki_flags & IOCB_WRITE)
+				kiocb_end_write(req);
+			return -EAGAIN;
+		}
+		return ret;
 	}
 	/* it's reportedly faster than delegating the null check to kfree() */
 	if (iovec)