rocksdb/table/block_fetcher.cc
Akanksha Mahajan 78641c0930 Fix segfault in FilePrefetchBuffer with async_io enabled (#9777)
Summary:
If FilePrefetchBuffer object is destroyed and then later Poll() calls callback on object which has been destroyed, it gives segfault on accessing destroyed object. It was caught after adding unit tests that tests Posix implementation of ReadAsync and Poll APIs.
This PR also updates and fixes existing IOURing tests which were not running locally because RocksDbIOUringEnable function wasn't defined and IOUring was disabled for those tests

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9777

Test Plan: Added new unit test

Reviewed By: anand1976

Differential Revision: D35254002

Pulled By: akankshamahajan15

fbshipit-source-id: 68e80054ffb14ae25c255920ebc6548ca5f130a1
2022-04-06 21:02:55 -07:00

344 lines
13 KiB
C++

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include "table/block_fetcher.h"
#include <cinttypes>
#include <string>
#include "logging/logging.h"
#include "memory/memory_allocator.h"
#include "monitoring/perf_context_imp.h"
#include "rocksdb/compression_type.h"
#include "rocksdb/env.h"
#include "table/block_based/block.h"
#include "table/block_based/block_based_table_reader.h"
#include "table/block_based/block_type.h"
#include "table/block_based/reader_common.h"
#include "table/format.h"
#include "table/persistent_cache_helper.h"
#include "util/compression.h"
#include "util/stop_watch.h"
namespace ROCKSDB_NAMESPACE {
inline void BlockFetcher::ProcessTrailerIfPresent() {
if (footer_.GetBlockTrailerSize() > 0) {
assert(footer_.GetBlockTrailerSize() == BlockBasedTable::kBlockTrailerSize);
if (read_options_.verify_checksums) {
io_status_ = status_to_io_status(VerifyBlockChecksum(
footer_.checksum_type(), slice_.data(), block_size_,
file_->file_name(), handle_.offset()));
}
compression_type_ =
BlockBasedTable::GetBlockCompressionType(slice_.data(), block_size_);
} else {
// E.g. plain table or cuckoo table
compression_type_ = kNoCompression;
}
}
inline bool BlockFetcher::TryGetUncompressBlockFromPersistentCache() {
if (cache_options_.persistent_cache &&
!cache_options_.persistent_cache->IsCompressed()) {
Status status = PersistentCacheHelper::LookupUncompressedPage(
cache_options_, handle_, contents_);
if (status.ok()) {
// uncompressed page is found for the block handle
return true;
} else {
// uncompressed page is not found
if (ioptions_.logger && !status.IsNotFound()) {
assert(!status.ok());
ROCKS_LOG_INFO(ioptions_.logger,
"Error reading from persistent cache. %s",
status.ToString().c_str());
}
}
}
return false;
}
inline bool BlockFetcher::TryGetFromPrefetchBuffer() {
if (prefetch_buffer_ != nullptr) {
IOOptions opts;
IOStatus io_s = file_->PrepareIOOptions(read_options_, opts);
if (io_s.ok()) {
bool read_from_prefetch_buffer = false;
if (read_options_.async_io) {
read_from_prefetch_buffer = prefetch_buffer_->TryReadFromCacheAsync(
opts, file_, handle_.offset(), block_size_with_trailer_, &slice_,
&io_s, read_options_.rate_limiter_priority, for_compaction_);
} else {
read_from_prefetch_buffer = prefetch_buffer_->TryReadFromCache(
opts, file_, handle_.offset(), block_size_with_trailer_, &slice_,
&io_s, read_options_.rate_limiter_priority, for_compaction_);
}
if (read_from_prefetch_buffer) {
ProcessTrailerIfPresent();
if (!io_status_.ok()) {
return true;
}
got_from_prefetch_buffer_ = true;
used_buf_ = const_cast<char*>(slice_.data());
}
}
if (!io_s.ok()) {
io_status_ = io_s;
return true;
}
}
return got_from_prefetch_buffer_;
}
inline bool BlockFetcher::TryGetCompressedBlockFromPersistentCache() {
if (cache_options_.persistent_cache &&
cache_options_.persistent_cache->IsCompressed()) {
// lookup uncompressed cache mode p-cache
std::unique_ptr<char[]> raw_data;
io_status_ = status_to_io_status(PersistentCacheHelper::LookupRawPage(
cache_options_, handle_, &raw_data, block_size_with_trailer_));
if (io_status_.ok()) {
heap_buf_ = CacheAllocationPtr(raw_data.release());
used_buf_ = heap_buf_.get();
slice_ = Slice(heap_buf_.get(), block_size_);
ProcessTrailerIfPresent();
return true;
} else if (!io_status_.IsNotFound() && ioptions_.logger) {
assert(!io_status_.ok());
ROCKS_LOG_INFO(ioptions_.logger,
"Error reading from persistent cache. %s",
io_status_.ToString().c_str());
}
}
return false;
}
inline void BlockFetcher::PrepareBufferForBlockFromFile() {
// cache miss read from device
if ((do_uncompress_ || ioptions_.allow_mmap_reads) &&
block_size_with_trailer_ < kDefaultStackBufferSize) {
// If we've got a small enough hunk of data, read it in to the
// trivially allocated stack buffer instead of needing a full malloc()
//
// `GetBlockContents()` cannot return this data as its lifetime is tied to
// this `BlockFetcher`'s lifetime. That is fine because this is only used
// in cases where we do not expect the `GetBlockContents()` result to be the
// same buffer we are assigning here. If we guess incorrectly, there will be
// a heap allocation and memcpy in `GetBlockContents()` to obtain the final
// result. Considering we are eliding a heap allocation here by using the
// stack buffer, the cost of guessing incorrectly here is one extra memcpy.
//
// When `do_uncompress_` is true, we expect the uncompression step will
// allocate heap memory for the final result. However this expectation will
// be wrong if the block turns out to already be uncompressed, which we
// won't know for sure until after reading it.
//
// When `ioptions_.allow_mmap_reads` is true, we do not expect the file
// reader to use the scratch buffer at all, but instead return a pointer
// into the mapped memory. This expectation will be wrong when using a
// file reader that does not implement mmap reads properly.
used_buf_ = &stack_buf_[0];
} else if (maybe_compressed_ && !do_uncompress_) {
compressed_buf_ = AllocateBlock(block_size_with_trailer_,
memory_allocator_compressed_);
used_buf_ = compressed_buf_.get();
} else {
heap_buf_ =
AllocateBlock(block_size_with_trailer_, memory_allocator_);
used_buf_ = heap_buf_.get();
}
}
inline void BlockFetcher::InsertCompressedBlockToPersistentCacheIfNeeded() {
if (io_status_.ok() && read_options_.fill_cache &&
cache_options_.persistent_cache &&
cache_options_.persistent_cache->IsCompressed()) {
// insert to raw cache
PersistentCacheHelper::InsertRawPage(cache_options_, handle_, used_buf_,
block_size_with_trailer_);
}
}
inline void BlockFetcher::InsertUncompressedBlockToPersistentCacheIfNeeded() {
if (io_status_.ok() && !got_from_prefetch_buffer_ &&
read_options_.fill_cache && cache_options_.persistent_cache &&
!cache_options_.persistent_cache->IsCompressed()) {
// insert to uncompressed cache
PersistentCacheHelper::InsertUncompressedPage(cache_options_, handle_,
*contents_);
}
}
inline void BlockFetcher::CopyBufferToHeapBuf() {
assert(used_buf_ != heap_buf_.get());
heap_buf_ = AllocateBlock(block_size_with_trailer_, memory_allocator_);
memcpy(heap_buf_.get(), used_buf_, block_size_with_trailer_);
#ifndef NDEBUG
num_heap_buf_memcpy_++;
#endif
}
inline void BlockFetcher::CopyBufferToCompressedBuf() {
assert(used_buf_ != compressed_buf_.get());
compressed_buf_ = AllocateBlock(block_size_with_trailer_,
memory_allocator_compressed_);
memcpy(compressed_buf_.get(), used_buf_, block_size_with_trailer_);
#ifndef NDEBUG
num_compressed_buf_memcpy_++;
#endif
}
// Entering this method means the block is not compressed or do not need to be
// uncompressed. The block can be in one of the following buffers:
// 1. prefetch buffer if prefetch is enabled and the block is prefetched before
// 2. stack_buf_ if block size is smaller than the stack_buf_ size and block
// is not compressed
// 3. heap_buf_ if the block is not compressed
// 4. compressed_buf_ if the block is compressed
// 5. direct_io_buf_ if direct IO is enabled
// After this method, if the block is compressed, it should be in
// compressed_buf_, otherwise should be in heap_buf_.
inline void BlockFetcher::GetBlockContents() {
if (slice_.data() != used_buf_) {
// the slice content is not the buffer provided
*contents_ = BlockContents(Slice(slice_.data(), block_size_));
} else {
// page can be either uncompressed or compressed, the buffer either stack
// or heap provided. Refer to https://github.com/facebook/rocksdb/pull/4096
if (got_from_prefetch_buffer_ || used_buf_ == &stack_buf_[0]) {
CopyBufferToHeapBuf();
} else if (used_buf_ == compressed_buf_.get()) {
if (compression_type_ == kNoCompression &&
memory_allocator_ != memory_allocator_compressed_) {
CopyBufferToHeapBuf();
} else {
heap_buf_ = std::move(compressed_buf_);
}
} else if (direct_io_buf_.get() != nullptr) {
if (compression_type_ == kNoCompression) {
CopyBufferToHeapBuf();
} else {
CopyBufferToCompressedBuf();
heap_buf_ = std::move(compressed_buf_);
}
}
*contents_ = BlockContents(std::move(heap_buf_), block_size_);
}
#ifndef NDEBUG
contents_->is_raw_block = true;
#endif
}
IOStatus BlockFetcher::ReadBlockContents() {
if (TryGetUncompressBlockFromPersistentCache()) {
compression_type_ = kNoCompression;
#ifndef NDEBUG
contents_->is_raw_block = true;
#endif // NDEBUG
return IOStatus::OK();
}
if (TryGetFromPrefetchBuffer()) {
if (!io_status_.ok()) {
return io_status_;
}
} else if (!TryGetCompressedBlockFromPersistentCache()) {
IOOptions opts;
io_status_ = file_->PrepareIOOptions(read_options_, opts);
// Actual file read
if (io_status_.ok()) {
if (file_->use_direct_io()) {
PERF_TIMER_GUARD(block_read_time);
io_status_ = file_->Read(
opts, handle_.offset(), block_size_with_trailer_, &slice_, nullptr,
&direct_io_buf_, read_options_.rate_limiter_priority);
PERF_COUNTER_ADD(block_read_count, 1);
used_buf_ = const_cast<char*>(slice_.data());
} else {
PrepareBufferForBlockFromFile();
PERF_TIMER_GUARD(block_read_time);
io_status_ = file_->Read(opts, handle_.offset(),
block_size_with_trailer_, &slice_, used_buf_,
nullptr, read_options_.rate_limiter_priority);
PERF_COUNTER_ADD(block_read_count, 1);
#ifndef NDEBUG
if (slice_.data() == &stack_buf_[0]) {
num_stack_buf_memcpy_++;
} else if (slice_.data() == heap_buf_.get()) {
num_heap_buf_memcpy_++;
} else if (slice_.data() == compressed_buf_.get()) {
num_compressed_buf_memcpy_++;
}
#endif
}
}
// TODO: introduce dedicated perf counter for range tombstones
switch (block_type_) {
case BlockType::kFilter:
PERF_COUNTER_ADD(filter_block_read_count, 1);
break;
case BlockType::kCompressionDictionary:
PERF_COUNTER_ADD(compression_dict_block_read_count, 1);
break;
case BlockType::kIndex:
PERF_COUNTER_ADD(index_block_read_count, 1);
break;
// Nothing to do here as we don't have counters for the other types.
default:
break;
}
PERF_COUNTER_ADD(block_read_byte, block_size_with_trailer_);
if (!io_status_.ok()) {
return io_status_;
}
if (slice_.size() != block_size_with_trailer_) {
return IOStatus::Corruption("truncated block read from " +
file_->file_name() + " offset " +
ToString(handle_.offset()) + ", expected " +
ToString(block_size_with_trailer_) +
" bytes, got " + ToString(slice_.size()));
}
ProcessTrailerIfPresent();
if (io_status_.ok()) {
InsertCompressedBlockToPersistentCacheIfNeeded();
} else {
return io_status_;
}
}
if (do_uncompress_ && compression_type_ != kNoCompression) {
PERF_TIMER_GUARD(block_decompress_time);
// compressed page, uncompress, update cache
UncompressionContext context(compression_type_);
UncompressionInfo info(context, uncompression_dict_, compression_type_);
io_status_ = status_to_io_status(UncompressBlockContents(
info, slice_.data(), block_size_, contents_, footer_.format_version(),
ioptions_, memory_allocator_));
#ifndef NDEBUG
num_heap_buf_memcpy_++;
#endif
compression_type_ = kNoCompression;
} else {
GetBlockContents();
}
InsertUncompressedBlockToPersistentCacheIfNeeded();
return io_status_;
}
} // namespace ROCKSDB_NAMESPACE