Merge "snapuserd: Lock the buffer during snapshot-merge" into main (e10fc836) · Commits · e / os / android_system_core

fs_mgr/libsnapshot/snapuserd/user-space-merge/merge_worker.cpp

+16 −0

Original line number	Diff line number	Diff line
		@@ -233,6 +233,11 @@ bool MergeWorker::MergeOrderedOpsAsync() {
		return false;
		}

		std::optional<std::lock_guard<std::mutex>> buffer_lock;
		// Acquire the buffer lock at this point so that RA thread
		// doesn't step into this buffer. See b/377819507
		buffer_lock.emplace(snapuserd_->GetBufferLock());

		snapuserd_->SetMergeInProgress(ra_block_index_);

		loff_t offset = 0;
		@@ -383,6 +388,9 @@ bool MergeWorker::MergeOrderedOpsAsync() {
		// Mark the block as merge complete
		snapuserd_->SetMergeCompleted(ra_block_index_);

		// Release the buffer lock
		buffer_lock.reset();

		// Notify RA thread that the merge thread is ready to merge the next
		// window
		snapuserd_->NotifyRAForMergeReady();
		@@ -415,6 +423,11 @@ bool MergeWorker::MergeOrderedOps() {
		return false;
		}

		std::optional<std::lock_guard<std::mutex>> buffer_lock;
		// Acquire the buffer lock at this point so that RA thread
		// doesn't step into this buffer. See b/377819507
		buffer_lock.emplace(snapuserd_->GetBufferLock());

		snapuserd_->SetMergeInProgress(ra_block_index_);

		loff_t offset = 0;
		@@ -468,6 +481,9 @@ bool MergeWorker::MergeOrderedOps() {
		// Mark the block as merge complete
		snapuserd_->SetMergeCompleted(ra_block_index_);

		// Release the buffer lock
		buffer_lock.reset();

		// Notify RA thread that the merge thread is ready to merge the next
		// window
		snapuserd_->NotifyRAForMergeReady();

+4 −0

Original line number	Diff line number	Diff line
		@@ -186,6 +186,7 @@ class SnapshotHandler : public std::enable_shared_from_this<SnapshotHandler> {

		bool IsIouringSupported();
		bool CheckPartitionVerification();
		std::mutex& GetBufferLock() { return buffer_lock_; }

		private:
		bool ReadMetadata();
		@@ -216,6 +217,9 @@ class SnapshotHandler : public std::enable_shared_from_this<SnapshotHandler> {
		std::mutex lock_;
		std::condition_variable cv;

		// Lock the buffer used for snapshot-merge
		std::mutex buffer_lock_;

		void* mapped_addr_;
		size_t total_mapped_addr_length_;

+23 −16

Original line number	Diff line number	Diff line
		@@ -706,6 +706,12 @@ bool ReadAhead::ReadAheadIOStart() {
		return false;
		}

		// Acquire buffer lock before doing memcpy to the scratch buffer. Although,
		// by now snapshot-merge thread shouldn't be working on this scratch space
		// but we take additional measure to ensure that the buffer is not being
		// used by the merge thread at this point. see b/377819507
		{
		std::lock_guard<std::mutex> buffer_lock(snapuserd_->GetBufferLock());
		// Copy the data to scratch space
		memcpy(metadata_buffer_, ra_temp_meta_buffer_.get(), snapuserd_->GetBufferMetadataSize());
		memcpy(read_ahead_buffer_, ra_temp_buffer_.get(), total_blocks_merged_ * BLOCK_SZ);
		@@ -724,6 +730,7 @@ bool ReadAhead::ReadAheadIOStart() {

		total_ra_blocks_completed_ += total_blocks_merged_;
		snapuserd_->SetMergedBlockCountForNextCommit(total_blocks_merged_);
		}

		// Flush the scratch data - Technically, we should flush only for overlapping
		// blocks; However, since this region is mmap'ed, the dirty pages can still