Use DM layer directly to manage private DM volumes

Abolish cryptfs_revert_ext_volume, handle in caller. This allows us to
use DeleteDeviceIfExists, avoiding a spurious error message.

Test: create private volume on Cuttlefish, eject, check logs
Bug: 147814592
Change-Id: I836d8bd11b29e32da0863aaa75144543bb9cab9c

cryptfs.cpp

@@ -1939,14 +1939,6 @@ int cryptfs_setup_ext_volume(const char* label, const char* real_blkdev, const K
                                  real_blkdev, out_crypto_blkdev, label, flags);
 }
 
-/*
- * Called by vold when it's asked to unmount an encrypted external
- * storage volume.
- */
-int cryptfs_revert_ext_volume(const char* label) {
-    return delete_crypto_blk_dev(label);
-}
-
 int cryptfs_crypto_complete(void) {
     return do_crypto_complete("/data");
 }

cryptfs.h

@@ -66,7 +66,6 @@ int cryptfs_changepw(int type, const char* newpw);
 int cryptfs_enable_default(int no_ui);
 int cryptfs_setup_ext_volume(const char* label, const char* real_blkdev,
                              const android::vold::KeyBuffer& key, std::string* out_crypto_blkdev);
-int cryptfs_revert_ext_volume(const char* label);
 int cryptfs_getfield(const char* fieldname, char* value, int len);
 int cryptfs_setfield(const char* fieldname, const char* value);
 int cryptfs_mount_default_encrypted(void);

model/PrivateVolume.cpp

@@ -25,6 +25,7 @@
 #include <android-base/logging.h>
 #include <android-base/stringprintf.h>
 #include <cutils/fs.h>
+#include <libdm/dm.h>
 #include <private/android_filesystem_config.h>
 
 #include <fcntl.h>
@@ -66,7 +67,11 @@ status_t PrivateVolume::doCreate() {
     }
 
     // Recover from stale vold by tearing down any old mappings
-    cryptfs_revert_ext_volume(getId().c_str());
+    auto& dm = dm::DeviceMapper::Instance();
+    if (!dm.DeleteDeviceIfExists(getId())) {
+        PLOG(ERROR) << "Cannot remove dm device " << getId();
+        return -EIO;
+    }
 
     // TODO: figure out better SELinux labels for private volumes
 
@@ -80,8 +85,10 @@ status_t PrivateVolume::doCreate() {
 }
 
 status_t PrivateVolume::doDestroy() {
-    if (cryptfs_revert_ext_volume(getId().c_str())) {
-        LOG(ERROR) << getId() << " failed to revert cryptfs";
+    auto& dm = dm::DeviceMapper::Instance();
+    if (!dm.DeleteDevice(getId())) {
+        PLOG(ERROR) << "Cannot remove dm device " << getId();
+        return -EIO;
     }
     return DestroyDeviceNode(mRawDevPath);
 }