commit cba1c44df88255ef3305fcbcf243a2f6a4dbf7a3
author Paul Lawrence <paullawrence@google.com> Mon Jun 01 12:58:04 2020 -0700
committer Eric Biggers <ebiggers@google.com> Tue Jun 09 09:20:24 2020 -0700
tree 9130f38d3dfd25f73ee2dff2e95a5d0e7d60edf8
parent 2d7f4879b57db3cf036541e448dcbe266b66ea1a

Set block size in dm-bow

Fix block-level checkpointing to work correctly when used in combination with
512 byte hardware sectors and metadata encryption with dm-default-key v2.

Bug: 153512828
Test: Parameter is passed to dm-bow based on first_api_level
Change-Id: Ic0a071221559271db20b06b2f17459b5b041e02d
Merged-In: Ic0a071221559271db20b06b2f17459b5b041e02d

fs_mgr/fs_mgr.cpp

diff --git a/fs_mgr/fs_mgr.cpp b/fs_mgr/fs_mgr.cpp
index b8385d3..19abe78 100644
--- a/fs_mgr/fs_mgr.cpp
+++ b/fs_mgr/fs_mgr.cpp
@@ -1120,8 +1120,28 @@
                 }
 
                 android::dm::DmTable table;
-                if (!table.AddTarget(std::make_unique<android::dm::DmTargetBow>(
-                            0, size, entry->blk_device))) {
+                auto bowTarget =
+                        std::make_unique<android::dm::DmTargetBow>(0, size, entry->blk_device);
+
+                // dm-bow uses the first block as a log record, and relocates the real first block
+                // elsewhere. For metadata encrypted devices, dm-bow sits below dm-default-key, and
+                // for post Android Q devices dm-default-key uses a block size of 4096 always.
+                // So if dm-bow's block size, which by default is the block size of the underlying
+                // hardware, is less than dm-default-key's, blocks will get broken up and I/O will
+                // fail as it won't be data_unit_size aligned.
+                // However, since it is possible there is an already shipping non
+                // metadata-encrypted device with smaller blocks, we must not change this for
+                // devices shipped with Q or earlier unless they explicitly selected dm-default-key
+                // v2
+                constexpr unsigned int pre_gki_level = __ANDROID_API_Q__;
+                unsigned int options_format_version = android::base::GetUintProperty<unsigned int>(
+                        "ro.crypto.dm_default_key.options_format.version",
+                        (android::fscrypt::GetFirstApiLevel() <= pre_gki_level ? 1 : 2));
+                if (options_format_version > 1) {
+                    bowTarget->SetBlockSize(4096);
+                }
+
+                if (!table.AddTarget(std::move(bowTarget))) {
                     LERROR << "Failed to add bow target";
                     return false;
                 }

fs_mgr/libdm/dm_target.cpp

diff --git a/fs_mgr/libdm/dm_target.cpp b/fs_mgr/libdm/dm_target.cpp
index a594198..250cb82 100644
--- a/fs_mgr/libdm/dm_target.cpp
+++ b/fs_mgr/libdm/dm_target.cpp
@@ -120,6 +120,11 @@
     return keyid_ + " " + block_device_;
 }
 
+std::string DmTargetBow::GetParameterString() const {
+    if (!block_size_) return target_string_;
+    return target_string_ + " 1 block_size:" + std::to_string(block_size_);
+}
+
 std::string DmTargetSnapshot::name() const {
     if (mode_ == SnapshotStorageMode::Merge) {
         return "snapshot-merge";

fs_mgr/libdm/include/libdm/dm_target.h

diff --git a/fs_mgr/libdm/include/libdm/dm_target.h b/fs_mgr/libdm/include/libdm/dm_target.h
index 57096ce..f986cfe 100644
--- a/fs_mgr/libdm/include/libdm/dm_target.h
+++ b/fs_mgr/libdm/include/libdm/dm_target.h
@@ -175,11 +175,14 @@
     DmTargetBow(uint64_t start, uint64_t length, const std::string& target_string)
         : DmTarget(start, length), target_string_(target_string) {}
 
+    void SetBlockSize(uint32_t block_size) { block_size_ = block_size; }
+
     std::string name() const override { return "bow"; }
-    std::string GetParameterString() const override { return target_string_; }
+    std::string GetParameterString() const override;
 
   private:
     std::string target_string_;
+    uint32_t block_size_ = 0;
 };
 
 enum class SnapshotStorageMode {