[PATCH] test_aio: Skip io_uring tests when kernel disables it

From 77c0e188720213f1a99eb6dc4502a152f72500d8 Mon Sep 17 00:00:00 2001
From: HyunSu Choi <assam258@gmail.com>
Date: Mon, 8 Dec 2025 09:58:49 +0900
Subject: [PATCH] test_aio: Skip io_uring tests when kernel disables it

The test_aio module fails on systems where io_uring is disabled at
the kernel level, despite PostgreSQL being compiled with io_uring
support.  The existing have_io_uring() function only checks whether
PostgreSQL was compiled with io_uring support, but does not verify
that the kernel actually permits io_uring operations at runtime.

Many enterprise Linux distributions (e.g., RHEL 9) set
io_uring_disabled=2 by default due to security concerns.  When
io_uring is kernel-disabled, initdb fails with EPERM, causing test
bailouts.

Add io_uring_enabled() to check /proc/sys/kernel/io_uring_disabled.
Tests only run when the value is 0 (fully enabled).  We skip tests
for value 1 (requires CAP_SYS_ADMIN) as well, since checking for
that capability adds complexity and most test users lack it.  When
the sysctl file doesn't exist (kernels < 5.1), we treat it as
disabled via "|| echo 2", which is the safest approach.

The implementation follows the existing pattern for have_io_uring(),
using a simple conditional to skip the entire test block when the
feature is unavailable.  Diagnostic output is provided via note()
when tests are skipped.

This is a test-only change with no impact on server functionality.
---
 src/test/modules/test_aio/t/001_aio.pl | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 3f0453619e8..9a4ff86e78f 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -29,7 +29,7 @@ $node_worker->stop();
 # Test io_method=io_uring
 ###
 
-if (have_io_uring())
+if (have_io_uring() and io_uring_enabled())
 {
 	my $node_uring = create_node('io_uring');
 	$node_uring->start();
@@ -128,6 +128,27 @@ sub have_io_uring
 	return ($methods =~ m/io_uring/) ? 1 : 0;
 }
 
+sub io_uring_enabled
+{
+	# Check if io_uring is disabled by the kernel
+	# 0 = enabled for all users
+	# 1 = disabled for unprivileged users (requires CAP_SYS_ADMIN)
+	# 2 = disabled for all users
+	# file not exists = very old kernel (< 5.1), treat as disabled
+
+	my $io_uring_disabled = `cat /proc/sys/kernel/io_uring_disabled 2>/dev/null || echo 2`;
+	chomp($io_uring_disabled);
+
+	# Only allow when fully enabled (value is 0)
+	if ($io_uring_disabled ne '0')
+	{
+		note "io_uring is restricted or disabled (io_uring_disabled=$io_uring_disabled)";
+		return 0;
+	}
+
+	return 1;
+}
+
 sub psql_like
 {
 	local $Test::Builder::Level = $Test::Builder::Level + 1;
-- 
2.34.1