selftests/bpf: Limit URLS parsing logic to actual scope in vmtest

The URLS array is only valid in the download_rootfs function and does
not need to be parsed globally in advance. At the same time, the logic
of loading rootfs is refactored to prepare vmtest for supporting local
rootfs.
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Link: https://lore.kernel.org/r/20240905081401.1894789-5-pulehui@huaweicloud.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/vmtest.sh

@@ -92,19 +92,6 @@ populate_url_map()
 	fi
 }
 
-download()
-{
-	local file="$1"
-
-	if [[ ! -v URLS[$file] ]]; then
-		echo "$file not found" >&2
-		return 1
-	fi
-
-	echo "Downloading $file..." >&2
-	curl -Lsf "${URLS[$file]}" "${@:2}"
-}
-
 newest_rootfs_version()
 {
 	{
@@ -118,16 +105,30 @@ newest_rootfs_version()
 
 download_rootfs()
 {
-	local rootfsversion="$1"
-	local dir="$2"
+	populate_url_map
+
+	local rootfsversion="$(newest_rootfs_version)"
+	local file="${ARCH}/libbpf-vmtest-rootfs-$rootfsversion.tar.zst"
+
+	if [[ ! -v URLS[$file] ]]; then
+		echo "$file not found" >&2
+		return 1
+	fi
+
+	echo "Downloading $file..." >&2
+	curl -Lsf "${URLS[$file]}" "${@:2}"
+}
+
+load_rootfs()
+{
+	local dir="$1"
 
 	if ! which zstd &> /dev/null; then
 		echo 'Could not find "zstd" on the system, please install zstd'
 		exit 1
 	fi
 
-	download "${ARCH}/libbpf-vmtest-rootfs-$rootfsversion.tar.zst" |
-		zstd -d | sudo tar -C "$dir" -x
+	download_rootfs | zstd -d | sudo tar -C "$dir" -x
 }
 
 recompile_kernel()
@@ -227,7 +228,7 @@ create_vm_image()
 	mkfs.ext4 -q "${rootfs_img}"
 
 	mount_image
-	download_rootfs "$(newest_rootfs_version)" "${mount_dir}"
+	load_rootfs "${mount_dir}"
 	unmount_image
 }
 
@@ -402,8 +403,6 @@ main()
 		make_command="${make_command} KBUILD_OUTPUT=${KBUILD_OUTPUT}"
 	fi
 
-	populate_url_map
-
 	local rootfs_img="${OUTPUT_DIR}/${ROOTFS_IMAGE}"
 	local mount_dir="${OUTPUT_DIR}/${MOUNT_DIR}"