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Merge "snapuserd: Lock the buffer during snapshot-merge" into main

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This commit is contained in:
Akilesh Kailash 2024-11-22 04:55:53 +00:00 • committed by Gerrit Code Review
commit e10fc8369a
3 changed files with 41 additions and 14 deletions
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16
fs_mgr/libsnapshot/snapuserd/user-space-merge/merge_worker.cpp
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@ -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
fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.h
View file

@ -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_;

35
fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_readahead.cpp
View file

@ -706,25 +706,32 @@ bool ReadAhead::ReadAheadIOStart() {
return false;
}
// 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);
// 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);
loff_t offset = 0;
std::unordered_map<uint64_t, void*>& read_ahead_buffer_map = snapuserd_->GetReadAheadMap();
read_ahead_buffer_map.clear();
loff_t offset = 0;
std::unordered_map<uint64_t, void*>& read_ahead_buffer_map = snapuserd_->GetReadAheadMap();
read_ahead_buffer_map.clear();
for (size_t block_index = 0; block_index < blocks_.size(); block_index++) {
void* bufptr = static_cast<void*>((char*)read_ahead_buffer_ + offset);
uint64_t new_block = blocks_[block_index];
for (size_t block_index = 0; block_index < blocks_.size(); block_index++) {
void* bufptr = static_cast<void*>((char*)read_ahead_buffer_ + offset);
uint64_t new_block = blocks_[block_index];
read_ahead_buffer_map[new_block] = bufptr;
offset += BLOCK_SZ;
read_ahead_buffer_map[new_block] = bufptr;
offset += BLOCK_SZ;
}
total_ra_blocks_completed_ += total_blocks_merged_;
snapuserd_->SetMergedBlockCountForNextCommit(total_blocks_merged_);
}
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
// get flushed to disk at any random point in time. Instead, make sure