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Commit d106f1e2 authored by David Anderson's avatar David Anderson
Browse files

libdm: Add helpers for getting the device number of a dm device. 

device-mapper will accept a "major:minor" string in place of a path for
any target parameter that specifies another block devie. This is useful
to have a helper for, since it lets us avoid a call to WaitForFile().

Bug: 134536978
Test: manual test
Change-Id: I13fd6699dd5d405bfa676830825b006b7810aa0f
parent 3215fd93

fs_mgr/libdm/Android.bp

+1 −0
Original line number Diff line number Diff line
@@ -46,6 +46,7 @@ cc_test { 
    static_libs: [

        "libdm",

        "libbase",

        "libfs_mgr",

        "liblog",

    ],

    srcs: [

fs_mgr/libdm/dm.cpp

+20 −0
Original line number Diff line number Diff line
@@ -302,6 +302,26 @@ bool DeviceMapper::GetDmDevicePathByName(const std::string& name, std::string* p 
    return true;

}



bool DeviceMapper::GetDeviceNumber(const std::string& name, dev_t* dev) {

    struct dm_ioctl io;

    InitIo(&io, name);

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

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

        return false;

    }

    *dev = io.dev;

    return true;

}



bool DeviceMapper::GetDeviceString(const std::string& name, std::string* dev) {

    dev_t num;

    if (!GetDeviceNumber(name, &num)) {

        return false;

    }

    *dev = std::to_string(major(num)) + ":" + std::to_string(minor(num));

    return true;

}



bool DeviceMapper::GetTableStatus(const std::string& name, std::vector<TargetInfo>* table) {

    return GetTable(name, 0, table);

}

fs_mgr/libdm/dm_test.cpp

+12 −3
Original line number Diff line number Diff line
@@ -132,8 +132,8 @@ TEST(libdm, DmLinear) { 
    // Define a 2-sector device, with each sector mapping to the first sector

    // of one of our loop devices.

    DmTable table;

    ASSERT_TRUE(table.AddTarget(make_unique<DmTargetLinear>(0, 1, loop_a.device(), 0)));

    ASSERT_TRUE(table.AddTarget(make_unique<DmTargetLinear>(1, 1, loop_b.device(), 0)));

    ASSERT_TRUE(table.Emplace<DmTargetLinear>(0, 1, loop_a.device(), 0));

    ASSERT_TRUE(table.Emplace<DmTargetLinear>(1, 1, loop_b.device(), 0));

    ASSERT_TRUE(table.valid());



    TempDevice dev("libdm-test-dm-linear", table);
@@ -141,6 +141,16 @@ TEST(libdm, DmLinear) { 
    ASSERT_FALSE(dev.path().empty());

    ASSERT_TRUE(dev.WaitForUdev());



    auto& dm = DeviceMapper::Instance();



    dev_t dev_number;

    ASSERT_TRUE(dm.GetDeviceNumber(dev.name(), &dev_number));

    ASSERT_NE(dev_number, 0);



    std::string dev_string;

    ASSERT_TRUE(dm.GetDeviceString(dev.name(), &dev_string));

    ASSERT_FALSE(dev_string.empty());



    // Note: a scope is needed to ensure that there are no open descriptors

    // when we go to close the device.

    {
@@ -157,7 +167,6 @@ TEST(libdm, DmLinear) { 
    }



    // Test GetTableStatus.

    DeviceMapper& dm = DeviceMapper::Instance();

    vector<DeviceMapper::TargetInfo> targets;

    ASSERT_TRUE(dm.GetTableStatus(dev.name(), &targets));

    ASSERT_EQ(targets.size(), 2);

fs_mgr/libdm/include/libdm/dm.h

+8 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <fcntl.h>

#include <linux/dm-ioctl.h>

#include <linux/kdev_t.h>

#include <linux/types.h>

#include <stdint.h>

#include <sys/sysmacros.h>

#include <unistd.h>
@@ -111,6 +112,13 @@ class DeviceMapper final { 
    // parameter is not set.

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



    // Returns the dev_t for the named device-mapper node.

    bool GetDeviceNumber(const std::string& name, dev_t* dev);



    // Returns a major:minor string for the named device-mapper node, that can

    // be used as inputs to DmTargets that take a block device.

    bool GetDeviceString(const std::string& name, std::string* dev);



    // The only way to create a DeviceMapper object.

    static DeviceMapper& Instance();