selftests/damon: introduce _common.sh to host shared function

The current test scripts contain duplicated root permission checks in
multiple locations.  This patch consolidates these checks into _common.sh
to eliminate code redundancy.

Link: https://lkml.kernel.org/r/20250718064217.299300-1-lienze@kylinos.cn
Signed-off-by: Enze Li <lienze@kylinos.cn>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/damon/_common.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+check_dependencies()
+{
+	if [ $EUID -ne 0 ]
+	then
+		echo "Run as root"
+		exit $ksft_skip
+	fi
+}

tools/testing/selftests/damon/lru_sort.sh

@@ -1,14 +1,12 @@
 #!/bin/bash
 # SPDX-License-Identifier: GPL-2.0
 
+source _common.sh
+
 # Kselftest framework requirement - SKIP code is 4.
 ksft_skip=4
 
-if [ $EUID -ne 0 ]
-then
-	echo "Run as root"
-	exit $ksft_skip
-fi
+check_dependencies
 
 damon_lru_sort_enabled="/sys/module/damon_lru_sort/parameters/enabled"
 if [ ! -f "$damon_lru_sort_enabled" ]

tools/testing/selftests/damon/reclaim.sh

@@ -1,14 +1,12 @@
 #!/bin/bash
 # SPDX-License-Identifier: GPL-2.0
 
+source _common.sh
+
 # Kselftest framework requirement - SKIP code is 4.
 ksft_skip=4
 
-if [ $EUID -ne 0 ]
-then
-	echo "Run as root"
-	exit $ksft_skip
-fi
+check_dependencies
 
 damon_reclaim_enabled="/sys/module/damon_reclaim/parameters/enabled"
 if [ ! -f "$damon_reclaim_enabled" ]

tools/testing/selftests/damon/sysfs.sh

@@ -1,6 +1,8 @@
 #!/bin/bash
 # SPDX-License-Identifier: GPL-2.0
 
+source _common.sh
+
 # Kselftest frmework requirement - SKIP code is 4.
 ksft_skip=4
 
@@ -364,14 +366,5 @@ test_damon_sysfs()
 	test_kdamonds "$damon_sysfs/kdamonds"
 }
 
-check_dependencies()
-{
-	if [ $EUID -ne 0 ]
-	then
-		echo "Run as root"
-		exit $ksft_skip
-	fi
-}
-
 check_dependencies
 test_damon_sysfs "/sys/kernel/mm/damon/admin"

tools/testing/selftests/damon/sysfs_update_removed_scheme_dir.sh

@@ -1,14 +1,12 @@
 #!/bin/bash
 # SPDX-License-Identifier: GPL-2.0
 
+source _common.sh
+
 # Kselftest framework requirement - SKIP code is 4.
 ksft_skip=4
 
-if [ $EUID -ne 0 ]
-then
-	echo "Run as root"
-	exit $ksft_skip
-fi
+check_dependencies
 
 damon_sysfs="/sys/kernel/mm/damon/admin"
 if [ ! -d "$damon_sysfs" ]