linux-kernel - [PATCH 2/2] loop: Test to detect a race condition between loop detach and open

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Message-Id: <20240521224249.7389-2-gulam.mohamed@oracle.com>
Date: Tue, 21 May 2024 22:42:49 +0000
From: Gulam Mohamed <gulam.mohamed@...cle.com>
To: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: axboe@...nel.dk, shinichiro.kawasaki@....com, chaitanyak@...dia.com,
        hch@....de
Subject: [PATCH 2/2] loop: Test to detect a race condition between loop detach and open

When one process opens a loop device partition and another process detaches
it, there will be a race condition due to which stale loop partitions are
created causing IO errors. This test will detect the race

Signed-off-by: Gulam Mohamed <gulam.mohamed@...cle.com>
---
 tests/loop/010     | 90 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/loop/010.out |  2 ++
 2 files changed, 92 insertions(+)
 create mode 100755 tests/loop/010
 create mode 100644 tests/loop/010.out

diff --git a/tests/loop/010 b/tests/loop/010
new file mode 100755
index 000000000000..ea93a120d51a
--- /dev/null
+++ b/tests/loop/010
@@ -0,0 +1,90 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-3.0+
+# Copyright (C) 2024, Oracle and/or its affiliates.
+#
+# Test to detect a race between loop detach and loop open which creates
+# stale loop partitions when one process opens the loop partition and
+# another process detaches the loop device
+#
+. tests/loop/rc
+DESCRIPTION="check stale loop partition"
+TIMED=1
+
+requires() {
+        _have_program parted
+        _have_program mkfs.xfs
+}
+
+image_file="/tmp/loopImg"
+line1="partition scan of loop0 failed (rc=-16)"
+
+function create_loop()
+{
+        while [ 1 ]
+        do
+                loop_device="$(losetup -P -f --show "${image_file}")"
+                blkid /dev/loop0p1 >> /dev/null 2>&1
+        done
+}
+
+function detach_loop()
+{
+        while [ 1 ]
+        do
+                if [ -e /dev/loop0 ]; then
+                        losetup -d /dev/loop0 > /dev/null 2>&1
+                fi
+        done
+}
+
+test() {
+	echo "Running ${TEST_NAME}"
+	local failure="/tmp/failure"
+	touch $failure
+	echo 0 > $failure
+	dmesg -c > /dev/null 2>&1
+
+	truncate -s 2G "${image_file}"
+	parted -a none -s "${image_file}" mklabel gpt
+	loop_device="$(losetup -P -f --show "${image_file}")"
+	parted -a none -s "${loop_device}" mkpart primary 64s 109051s
+	
+	udevadm settle
+        if [ ! -e "${loop_device}" ]; then
+		return 1
+        fi
+
+        mkfs.xfs -f "${loop_device}p1" > /dev/null 2>&1
+
+        losetup -d "${loop_device}" >  /dev/null 2>&1
+
+        create_loop &
+	create_pid=$!
+        detach_loop &
+	detach_pid=$!
+
+	sleep "${TIMEOUT:-180}"
+        {
+                kill -9 $create_pid
+		kill -9 $detach_pid
+                wait
+                sleep 1
+        } 2>/dev/null
+
+        losetup -D > /dev/null 2>&1
+        dmesg  | while IFS= read -r line2
+	do
+        	match=$(echo "$line2" | grep -o "$line1")
+                if [ "$line1" == "$match" ]; then
+			echo 1 > "/tmp/failure"
+			break
+                fi
+        done
+	failed=$(cat $failure)
+	if [ $failed -eq 0 ]; then
+		echo "Test complete"
+	else
+		echo "Test failed"
+	fi
+	rm -f $failure
+}
diff --git a/tests/loop/010.out b/tests/loop/010.out
new file mode 100644
index 000000000000..64a6aee00b8a
--- /dev/null
+++ b/tests/loop/010.out
@@ -0,0 +1,2 @@
+Running loop/010
+Test complete
-- 
2.39.3