From 571ae76c18afb74bd492aee0ba18ee52beaa484b Mon Sep 17 00:00:00 2001
From: Florian Fischer <florian.fischer@muhq.space>
Date: Tue, 6 Jul 2021 18:32:27 +0200
Subject: [PATCH] [IO] document and adjust tests to changes in io_uring's
broken link handling
Until kernel commit cf10960426515 io_uring submitted sqe until it encountered
an invalid one. Now io_uring will catch the error on subimssion and
will cancel all sqe's contained in the link prior to the invalid one.
---
emper/io/IoContext.cpp | 9 +++++++--
tests/io/LinkFutureTest.cpp | 5 ++++-
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/emper/io/IoContext.cpp b/emper/io/IoContext.cpp
index bc5300f8..473f8924 100644
--- a/emper/io/IoContext.cpp
+++ b/emper/io/IoContext.cpp
@@ -133,13 +133,18 @@ void IoContext::submit(Future &future) {
// Because we submit every Future right away multiple prepared sqes can only
// occur for Future chains.
// If we could not submit the whole chain cancel all non submitted Futures
- // because we can not guaranty the soundness of the chain and invalidate their
- // prepared sqe
+ // because we can not guaranty the soundness of the chain have to invalidate
+ // non submitted but prepared sqes
// req1 -> invalid_req -> req3
// will submit only 2 instead of all 3 prepared sqes leaving a sqe for req3
// in the SQ but unsubmitted
// See: https://github.com/axboe/liburing/issues/186
// https://github.com/axboe/liburing/issues/92
+ //
+ // Since kernel commit cf10960426515 io_uring does no longer submit parts of a
+ // broken chains. This means that all sqes in a chain except the broken one will
+ // result in cqes with result -ECANCELD and the invalid one will
+ // generate a cqe with the appropriate error code
if (unlikely(static_cast<unsigned>(submitted) < prepared)) {
unsigned unsubmitted = io_uring_sq_ready(&ring);
Future *unsubmittedFuture = &future;
diff --git a/tests/io/LinkFutureTest.cpp b/tests/io/LinkFutureTest.cpp
index 14c15cb0..94291c21 100644
--- a/tests/io/LinkFutureTest.cpp
+++ b/tests/io/LinkFutureTest.cpp
@@ -119,7 +119,10 @@ static void failureChainCorInvCor() {
assert(res == -EBADF);
res = correctFuture1.wait();
- assert(res == (int32_t)buf.size());
+ // Since the kernel commit cf10960426515 io_uring does not
+ // submit broken links and completes any request before a
+ // invalid one as canceled.
+ assert(res == -ECANCELED || res == (int32_t)buf.size());
emper::io::closeAndWait(fd);
}
--
GitLab