From ed1a7d5fafd98049777c2c26349984ae31563a86 Mon Sep 17 00:00:00 2001
From: Daniel Zheng <zhengdaniel@google.com>
Date: Tue, 12 Sep 2023 14:37:44 -0700
Subject: [PATCH 1/2] Add v3 Cow Header

Adding Version 3 of CowHeader. This will inherit from original
CowHeader and add a compression field. We are no longer supporting
different compressions per operation so having this one field is enough.

Test: cow_api_test
Change-Id: If88dceda139807cc5e647b706ddeb2b3e83c024f
---
 fs_mgr/libsnapshot/include/libsnapshot/cow_format.h | 12 ++++++++++++
 fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp    |  4 ++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h b/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
index bfa8f6bea..b271dad6c 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
@@ -91,6 +91,18 @@ struct CowHeader {
 
     // Scratch space used during merge
     uint32_t buffer_size;
+
+} __attribute__((packed));
+
+struct CowHeaderV3 : public CowHeader {
+    // Location of sequence buffer in COW.
+    uint64_t sequence_buffer_offset;
+    // Size, in bytes, of the CowResumePoint buffer.
+    uint32_t resume_buffer_size;
+    // Size, in bytes, of the CowOperation buffer.
+    uint32_t op_buffer_size;
+    // Compression Algorithm
+    uint32_t compression_algorithm;
 } __attribute__((packed));
 
 // This structure is the same size of a normal Operation, but is repurposed for the footer.
diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp
index e51dbde63..a6f449faa 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp
@@ -243,7 +243,7 @@ bool CowWriterV2::OpenForWrite() {
 
     // Headers are not complete, but this ensures the file is at the right
     // position.
-    if (!android::base::WriteFully(fd_, &header_, sizeof(header_))) {
+    if (!android::base::WriteFully(fd_, &header_, sizeof(CowHeader))) {
         PLOG(ERROR) << "write failed";
         return false;
     }
@@ -262,7 +262,7 @@ bool CowWriterV2::OpenForWrite() {
         return false;
     }
 
-    if (lseek(fd_.get(), sizeof(header_) + header_.buffer_size, SEEK_SET) < 0) {
+    if (lseek(fd_.get(), sizeof(CowHeader) + header_.buffer_size, SEEK_SET) < 0) {
         PLOG(ERROR) << "lseek failed";
         return false;
     }

From bb45742ba141ad149c3960854ff32074390a9f5a Mon Sep 17 00:00:00 2001
From: Daniel Zheng <zhengdaniel@google.com>
Date: Tue, 10 Oct 2023 13:19:56 -0700
Subject: [PATCH 2/2] Move Cow Header child writer

v2 writer and v3 writer will write different versions of the header.
It's better to have each writer hold it's own header.

Test: th
Change-Id: Ibe310d58b830950ad556aabcd0c1009483fc8d86
---
 fs_mgr/libsnapshot/libsnapshot_cow/writer_base.h | 1 -
 fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.h   | 1 +
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/writer_base.h b/fs_mgr/libsnapshot/libsnapshot_cow/writer_base.h
index cdf622268..709b248e6 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/writer_base.h
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/writer_base.h
@@ -63,7 +63,6 @@ class CowWriterBase : public ICowWriter {
     bool ValidateNewBlock(uint64_t new_block);
 
     CowOptions options_;
-    CowHeader header_{};
 
     android::base::unique_fd fd_;
     bool is_dev_null_ = false;
diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.h b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.h
index ce97b0182..24170ebbd 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.h
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.h
@@ -63,6 +63,7 @@ class CowWriterV2 : public CowWriterBase {
 
   private:
     CowFooter footer_{};
+    CowHeader header_{};
     CowCompression compression_;
     // in the case that we are using one thread for compression, we can store and re-use the same
     // compressor