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Commit 5e9e74be authored by David Anderson's avatar David Anderson
Browse files

libdm: Implement GetDmDevicePathByName(). 

This change implements the ability to get the path of a block device
given a device-mapper device name. In addition, dmctl now has a
"getpath" command to perform this query, as a shortcut for searching
through /sys/block/*/dm/name.

Bug: 110035986
Test: N/A
Change-Id: I9ebd824fa800004f591fc02fc1b1950e0c7fba65
parent 8ddd1055

fs_mgr/libdm/dm.cpp

+12 −2
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include "libdm/dm.h"



#include <sys/ioctl.h>

#include <sys/sysmacros.h>

#include <sys/types.h>



#include <android-base/macros.h>
@@ -258,8 +259,17 @@ bool DeviceMapper::GetAvailableDevices(std::vector<DmBlockDevice>* devices) { 


// Accepts a device mapper device name (like system_a, vendor_b etc) and

// returns the path to it's device node (or symlink to the device node)

std::string DeviceMapper::GetDmDevicePathByName(const std::string& /* name */) {

    return "";

bool DeviceMapper::GetDmDevicePathByName(const std::string& name, std::string* path) {

    struct dm_ioctl io;

    InitIo(&io, name);

    if (ioctl(fd_, DM_DEV_STATUS, &io) < 0) {

        PLOG(ERROR) << "DM_DEV_STATUS failed for " << name;

        return false;

    }



    uint32_t dev_num = minor(io.dev);

    *path = "/dev/block/dm-" + std::to_string(dev_num);

    return true;

}



// private methods of DeviceMapper

fs_mgr/libdm/include/libdm/dm.h

+3 −2
Original line number Diff line number Diff line
@@ -104,8 +104,9 @@ class DeviceMapper final { 
    bool GetAvailableDevices(std::vector<DmBlockDevice>* devices);



    // Returns the path to the device mapper device node in '/dev' corresponding to

    // 'name'.

    std::string GetDmDevicePathByName(const std::string& name);

    // 'name'. If the device does not exist, false is returned, and the path

    // parameter is not set.

    bool GetDmDevicePathByName(const std::string& name, std::string* path);



    // The only way to create a DeviceMapper object.

    static DeviceMapper& Instance();

fs_mgr/tools/dmctl.cpp

+20 −0
Original line number Diff line number Diff line
@@ -49,6 +49,7 @@ static int Usage(void) { 
    std::cerr << "  create <dm-name> [-ro] <targets...>" << std::endl;

    std::cerr << "  delete <dm-name>" << std::endl;

    std::cerr << "  list <devices | targets>" << std::endl;

    std::cerr << "  getpath <dm-name>" << std::endl;

    std::cerr << "  help" << std::endl;

    std::cerr << std::endl;

    std::cerr << "Target syntax:" << std::endl;
@@ -241,11 +242,30 @@ static int HelpCmdHandler(int /* argc */, char** /* argv */) { 
    return 0;

}



static int GetPathCmdHandler(int argc, char** argv) {

    if (argc != 1) {

        std::cerr << "Invalid arguments, see \'dmctl help\'" << std::endl;

        return -EINVAL;

    }



    DeviceMapper& dm = DeviceMapper::Instance();

    std::string path;

    if (!dm.GetDmDevicePathByName(argv[0], &path)) {

        std::cerr << "Could not query path of device \"" << argv[0] << "\"." << std::endl;

        return -EINVAL;

    }

    std::cout << path << std::endl;

    return 0;

}



static std::map<std::string, std::function<int(int, char**)>> cmdmap = {

        // clang-format off

        {"create", DmCreateCmdHandler},

        {"delete", DmDeleteCmdHandler},

        {"list", DmListCmdHandler},

        {"help", HelpCmdHandler},

        {"getpath", GetPathCmdHandler},

        // clang-format on

};



int main(int argc, char** argv) {