libsnapshot:snapuserd: Add 2MB scratch space in COW file
Add 2MB scratch space in the COW file. This is a preparation
patch for read-ahead patch. This just add the buffer
space right after the header. Bump up the version number
in the header in order to distiguish between older and newer
COW formats.
No operation is done on this buffer with this patch-set.
Scratch space option is disabled by default.
Bug: 183863613
Test: 1: Create Full OTA with the new COW format.
2: Incremental OTA with older COW format.
3: vts_libsnapshot_test
Signed-off-by: Akilesh Kailash <akailash@google.com>
Change-Id: I42a535a48ec22adb893dfe6f86a4f51650e1f88a
diff --git a/fs_mgr/libsnapshot/cow_reader.cpp b/fs_mgr/libsnapshot/cow_reader.cpp
index 7199b38..c2e4f89 100644
--- a/fs_mgr/libsnapshot/cow_reader.cpp
+++ b/fs_mgr/libsnapshot/cow_reader.cpp
@@ -94,11 +94,6 @@
<< "Expected: " << kCowMagicNumber;
return false;
}
- if (header_.header_size != sizeof(CowHeader)) {
- LOG(ERROR) << "Header size unknown, read " << header_.header_size << ", expected "
- << sizeof(CowHeader);
- return false;
- }
if (header_.footer_size != sizeof(CowFooter)) {
LOG(ERROR) << "Footer size unknown, read " << header_.footer_size << ", expected "
<< sizeof(CowFooter);
@@ -123,8 +118,7 @@
return false;
}
- if ((header_.major_version != kCowVersionMajor) ||
- (header_.minor_version != kCowVersionMinor)) {
+ if ((header_.major_version > kCowVersionMajor) || (header_.minor_version != kCowVersionMinor)) {
LOG(ERROR) << "Header version mismatch";
LOG(ERROR) << "Major version: " << header_.major_version
<< "Expected: " << kCowVersionMajor;
@@ -137,10 +131,25 @@
}
bool CowReader::ParseOps(std::optional<uint64_t> label) {
- uint64_t pos = lseek(fd_.get(), sizeof(header_), SEEK_SET);
- if (pos != sizeof(header_)) {
- PLOG(ERROR) << "lseek ops failed";
- return false;
+ uint64_t pos;
+
+ // Skip the scratch space
+ if (header_.major_version >= 2 && (header_.buffer_size > 0)) {
+ LOG(DEBUG) << " Scratch space found of size: " << header_.buffer_size;
+ size_t init_offset = header_.header_size + header_.buffer_size;
+ pos = lseek(fd_.get(), init_offset, SEEK_SET);
+ if (pos != init_offset) {
+ PLOG(ERROR) << "lseek ops failed";
+ return false;
+ }
+ } else {
+ pos = lseek(fd_.get(), header_.header_size, SEEK_SET);
+ if (pos != header_.header_size) {
+ PLOG(ERROR) << "lseek ops failed";
+ return false;
+ }
+ // Reading a v1 version of COW which doesn't have buffer_size.
+ header_.buffer_size = 0;
}
auto ops_buffer = std::make_shared<std::vector<CowOperation>>();
@@ -470,7 +479,7 @@
bool CowReader::GetRawBytes(uint64_t offset, void* buffer, size_t len, size_t* read) {
// Validate the offset, taking care to acknowledge possible overflow of offset+len.
- if (offset < sizeof(header_) || offset >= fd_size_ - sizeof(CowFooter) || len >= fd_size_ ||
+ if (offset < header_.header_size || offset >= fd_size_ - sizeof(CowFooter) || len >= fd_size_ ||
offset + len > fd_size_ - sizeof(CowFooter)) {
LOG(ERROR) << "invalid data offset: " << offset << ", " << len << " bytes";
return false;
diff --git a/fs_mgr/libsnapshot/cow_writer.cpp b/fs_mgr/libsnapshot/cow_writer.cpp
index c51336d..51c00a9 100644
--- a/fs_mgr/libsnapshot/cow_writer.cpp
+++ b/fs_mgr/libsnapshot/cow_writer.cpp
@@ -94,6 +94,7 @@
header_.block_size = options_.block_size;
header_.num_merge_ops = 0;
header_.cluster_ops = options_.cluster_ops;
+ header_.buffer_size = 0;
footer_ = {};
footer_.op.data_length = 64;
footer_.op.type = kCowFooterOp;
@@ -166,7 +167,7 @@
}
void CowWriter::InitPos() {
- next_op_pos_ = sizeof(header_);
+ next_op_pos_ = sizeof(header_) + header_.buffer_size;
cluster_size_ = header_.cluster_ops * sizeof(CowOperation);
if (header_.cluster_ops) {
next_data_pos_ = next_op_pos_ + cluster_size_;
@@ -190,6 +191,10 @@
return false;
}
+ if (options_.scratch_space) {
+ header_.buffer_size = BUFFER_REGION_DEFAULT_SIZE;
+ }
+
// Headers are not complete, but this ensures the file is at the right
// position.
if (!android::base::WriteFully(fd_, &header_, sizeof(header_))) {
@@ -197,7 +202,27 @@
return false;
}
+ if (options_.scratch_space) {
+ // Initialize the scratch space
+ std::string data(header_.buffer_size, 0);
+ if (!android::base::WriteFully(fd_, data.data(), header_.buffer_size)) {
+ PLOG(ERROR) << "writing scratch space failed";
+ return false;
+ }
+ }
+
+ if (!Sync()) {
+ LOG(ERROR) << "Header sync failed";
+ return false;
+ }
+
+ if (lseek(fd_.get(), sizeof(header_) + header_.buffer_size, SEEK_SET) < 0) {
+ PLOG(ERROR) << "lseek failed";
+ return false;
+ }
+
InitPos();
+
return true;
}
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h b/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
index e93254e..060d363 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
@@ -21,11 +21,14 @@
namespace snapshot {
static constexpr uint64_t kCowMagicNumber = 0x436f77634f572121ULL;
-static constexpr uint32_t kCowVersionMajor = 1;
+static constexpr uint32_t kCowVersionMajor = 2;
static constexpr uint32_t kCowVersionMinor = 0;
static constexpr uint32_t kCowVersionManifest = 1;
+static constexpr uint32_t BLOCK_SZ = 4096;
+static constexpr uint32_t BLOCK_SHIFT = (__builtin_ffs(BLOCK_SZ) - 1);
+
// This header appears as the first sequence of bytes in the COW. All fields
// in the layout are little-endian encoded. The on-disk layout is:
//
@@ -70,6 +73,9 @@
// Tracks merge operations completed
uint64_t num_merge_ops;
+
+ // Scratch space used during merge
+ uint32_t buffer_size;
} __attribute__((packed));
// This structure is the same size of a normal Operation, but is repurposed for the footer.
@@ -151,6 +157,9 @@
CowFooterData data;
} __attribute__((packed));
+// 2MB Scratch space used for read-ahead
+static constexpr uint64_t BUFFER_REGION_DEFAULT_SIZE = (1ULL << 21);
+
std::ostream& operator<<(std::ostream& os, CowOperation const& arg);
int64_t GetNextOpOffset(const CowOperation& op, uint32_t cluster_size);
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/cow_writer.h b/fs_mgr/libsnapshot/include/libsnapshot/cow_writer.h
index a9d85bf..c764190 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/cow_writer.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/cow_writer.h
@@ -36,6 +36,8 @@
// Number of CowOperations in a cluster. 0 for no clustering. Cannot be 1.
uint32_t cluster_ops = 200;
+
+ bool scratch_space = false;
};
// Interface for writing to a snapuserd COW. All operations are ordered; merges
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/snapuserd_kernel.h b/fs_mgr/libsnapshot/include/libsnapshot/snapuserd_kernel.h
index 2b6c8ef..6bb7a39 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/snapuserd_kernel.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/snapuserd_kernel.h
@@ -47,9 +47,6 @@
static constexpr uint32_t CHUNK_SIZE = 8;
static constexpr uint32_t CHUNK_SHIFT = (__builtin_ffs(CHUNK_SIZE) - 1);
-static constexpr uint32_t BLOCK_SZ = 4096;
-static constexpr uint32_t BLOCK_SHIFT = (__builtin_ffs(BLOCK_SZ) - 1);
-
#define DIV_ROUND_UP(n, d) (((n) + (d)-1) / (d))
// This structure represents the kernel COW header.
diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index c504355..8de622a 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -2941,7 +2941,13 @@
return Return::Error();
}
- CowWriter writer(CowOptions{.compression = it->second.compression_algorithm()});
+ CowOptions options;
+ if (device()->IsTestDevice()) {
+ options.scratch_space = false;
+ }
+ options.compression = it->second.compression_algorithm();
+
+ CowWriter writer(options);
if (!writer.Initialize(fd) || !writer.Finalize()) {
LOG(ERROR) << "Could not initialize COW device for " << target_partition->name();
return Return::Error();
@@ -3050,6 +3056,10 @@
CowOptions cow_options;
cow_options.compression = status.compression_algorithm();
cow_options.max_blocks = {status.device_size() / cow_options.block_size};
+ // Disable scratch space for vts tests
+ if (device()->IsTestDevice()) {
+ cow_options.scratch_space = false;
+ }
// Currently we don't support partial snapshots, since partition_cow_creator
// never creates this scenario.
diff --git a/fs_mgr/libsnapshot/snapshot_reader_test.cpp b/fs_mgr/libsnapshot/snapshot_reader_test.cpp
index 4202d22..9373059 100644
--- a/fs_mgr/libsnapshot/snapshot_reader_test.cpp
+++ b/fs_mgr/libsnapshot/snapshot_reader_test.cpp
@@ -150,6 +150,7 @@
CowOptions options;
options.compression = "gz";
options.max_blocks = {kBlockCount};
+ options.scratch_space = false;
unique_fd cow_fd(dup(cow_->fd));
ASSERT_GE(cow_fd, 0);
diff --git a/fs_mgr/libsnapshot/snapshot_test.cpp b/fs_mgr/libsnapshot/snapshot_test.cpp
index 8fae00b..337d410 100644
--- a/fs_mgr/libsnapshot/snapshot_test.cpp
+++ b/fs_mgr/libsnapshot/snapshot_test.cpp
@@ -12,6 +12,7 @@
// See the License for the specific language governing permissions and
// limitations under the License.
+#include <libsnapshot/cow_format.h>
#include <libsnapshot/snapshot.h>
#include <fcntl.h>
@@ -327,6 +328,7 @@
auto dynamic_partition_metadata = manifest.mutable_dynamic_partition_metadata();
dynamic_partition_metadata->set_vabc_enabled(IsCompressionEnabled());
+ dynamic_partition_metadata->set_cow_version(android::snapshot::kCowVersionMajor);
auto group = dynamic_partition_metadata->add_groups();
group->set_name("group");
@@ -841,6 +843,7 @@
auto dynamic_partition_metadata = manifest_.mutable_dynamic_partition_metadata();
dynamic_partition_metadata->set_vabc_enabled(IsCompressionEnabled());
+ dynamic_partition_metadata->set_cow_version(android::snapshot::kCowVersionMajor);
// Create a fake update package metadata.
// Not using full name "system", "vendor", "product" because these names collide with the
