Merge "libdm: Add a helper function for creating placeholder devices." (3460b752) · Commits · e / os / android_system_core

fs_mgr/libdm/dm.cpp

+24 −0

Original line number	Diff line number	Diff line
		@@ -20,6 +20,7 @@
		#include <sys/ioctl.h>
		#include <sys/sysmacros.h>
		#include <sys/types.h>
		#include <sys/utsname.h>

		#include <chrono>
		#include <functional>
		@@ -711,5 +712,28 @@ std::map<std::string, std::string> DeviceMapper::FindDmPartitions() {
		return dm_block_devices;
		}

		bool DeviceMapper::CreatePlaceholderDevice(const std::string& name) {
		if (!CreateEmptyDevice(name)) {
		return false;
		}

		struct utsname uts;
		unsigned int major, minor;
		if (uname(&uts) != 0 \|\| sscanf(uts.release, "%u.%u", &major, &minor) != 2) {
		LOG(ERROR) << "Could not parse the kernel version from uname";
		return true;
		}

		// On Linux 5.15+, there is no uevent until DM_TABLE_LOAD.
		if (major > 5 \|\| (major == 5 && minor >= 15)) {
		DmTable table;
		table.Emplace<DmTargetError>(0, 1);
		if (!LoadTable(name, table)) {
		return false;
		}
		}
		return true;
		}

		} // namespace dm
		} // namespace android

+6 −0

Original line number	Diff line number	Diff line
		@@ -292,6 +292,12 @@ class DeviceMapper final : public IDeviceMapper {
		// Returns mapping <partition-name, /dev/block/dm-x>
		std::map<std::string, std::string> FindDmPartitions();

		// Create a placeholder device. This is useful for ensuring that a uevent is in the pipeline,
		// to reduce the amount of time a future WaitForDevice will block. On kernels < 5.15, this
		// simply calls CreateEmptyDevice. On 5.15 and higher, it also loads (but does not activate)
		// a placeholder table containing dm-error.
		bool CreatePlaceholderDevice(const std::string& name);

		private:
		// Maximum possible device mapper targets registered in the kernel.
		// This is only used to read the list of targets from kernel so we allocate