1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 #include "net/disk_cache/block_files.h"
7 #include "base/atomicops.h"
8 #include "base/files/file_path.h"
9 #include "base/metrics/histogram.h"
10 #include "base/strings/string_util.h"
11 #include "base/strings/stringprintf.h"
12 #include "base/threading/thread_checker.h"
13 #include "base/time/time.h"
14 #include "net/disk_cache/cache_util.h"
15 #include "net/disk_cache/file_lock.h"
16 #include "net/disk_cache/stress_support.h"
17 #include "net/disk_cache/trace.h"
19 using base::TimeTicks;
23 const char* kBlockName = "data_";
25 // This array is used to perform a fast lookup of the nibble bit pattern to the
26 // type of entry that can be stored there (number of consecutive blocks).
27 const char s_types[16] = {4, 3, 2, 2, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0};
29 // Returns the type of block (number of consecutive blocks that can be stored)
30 // for a given nibble of the bitmap.
31 inline int GetMapBlockType(uint8 value) {
33 return s_types[value];
38 namespace disk_cache {
40 BlockHeader::BlockHeader() : header_(NULL) {
43 BlockHeader::BlockHeader(BlockFileHeader* header) : header_(header) {
46 BlockHeader::BlockHeader(MappedFile* file)
47 : header_(reinterpret_cast<BlockFileHeader*>(file->buffer())) {
50 BlockHeader::BlockHeader(const BlockHeader& other) : header_(other.header_) {
53 BlockHeader::~BlockHeader() {
56 bool BlockHeader::CreateMapBlock(int size, int* index) {
57 DCHECK(size > 0 && size <= kMaxNumBlocks);
59 for (int i = size; i <= kMaxNumBlocks; i++) {
60 if (header_->empty[i - 1]) {
71 TimeTicks start = TimeTicks::Now();
72 // We are going to process the map on 32-block chunks (32 bits), and on every
73 // chunk, iterate through the 8 nibbles where the new block can be located.
74 int current = header_->hints[target - 1];
75 for (int i = 0; i < header_->max_entries / 32; i++, current++) {
76 if (current == header_->max_entries / 32)
78 uint32 map_block = header_->allocation_map[current];
80 for (int j = 0; j < 8; j++, map_block >>= 4) {
81 if (GetMapBlockType(map_block) != target)
84 disk_cache::FileLock lock(header_);
85 int index_offset = j * 4 + 4 - target;
86 *index = current * 32 + index_offset;
87 STRESS_DCHECK(*index / 4 == (*index + size - 1) / 4);
88 uint32 to_add = ((1 << size) - 1) << index_offset;
89 header_->num_entries++;
91 // Note that there is no race in the normal sense here, but if we enforce
92 // the order of memory accesses between num_entries and allocation_map, we
93 // can assert that even if we crash here, num_entries will never be less
94 // than the actual number of used blocks.
95 base::subtle::MemoryBarrier();
96 header_->allocation_map[current] |= to_add;
98 header_->hints[target - 1] = current;
99 header_->empty[target - 1]--;
100 STRESS_DCHECK(header_->empty[target - 1] >= 0);
101 if (target != size) {
102 header_->empty[target - size - 1]++;
104 HISTOGRAM_TIMES("DiskCache.CreateBlock", TimeTicks::Now() - start);
109 // It is possible to have an undetected corruption (for example when the OS
110 // crashes), fix it here.
111 LOG(ERROR) << "Failing CreateMapBlock";
112 FixAllocationCounters();
116 void BlockHeader::DeleteMapBlock(int index, int size) {
117 if (size < 0 || size > kMaxNumBlocks) {
121 TimeTicks start = TimeTicks::Now();
122 int byte_index = index / 8;
123 uint8* byte_map = reinterpret_cast<uint8*>(header_->allocation_map);
124 uint8 map_block = byte_map[byte_index];
129 // See what type of block will be available after we delete this one.
130 int bits_at_end = 4 - size - index % 4;
131 uint8 end_mask = (0xf << (4 - bits_at_end)) & 0xf;
132 bool update_counters = (map_block & end_mask) == 0;
133 uint8 new_value = map_block & ~(((1 << size) - 1) << (index % 4));
134 int new_type = GetMapBlockType(new_value);
136 disk_cache::FileLock lock(header_);
137 STRESS_DCHECK((((1 << size) - 1) << (index % 8)) < 0x100);
138 uint8 to_clear = ((1 << size) - 1) << (index % 8);
139 STRESS_DCHECK((byte_map[byte_index] & to_clear) == to_clear);
140 byte_map[byte_index] &= ~to_clear;
142 if (update_counters) {
144 header_->empty[bits_at_end - 1]--;
145 header_->empty[new_type - 1]++;
146 STRESS_DCHECK(header_->empty[bits_at_end - 1] >= 0);
148 base::subtle::MemoryBarrier();
149 header_->num_entries--;
150 STRESS_DCHECK(header_->num_entries >= 0);
151 HISTOGRAM_TIMES("DiskCache.DeleteBlock", TimeTicks::Now() - start);
154 // Note that this is a simplified version of DeleteMapBlock().
155 bool BlockHeader::UsedMapBlock(int index, int size) {
156 if (size < 0 || size > kMaxNumBlocks)
159 int byte_index = index / 8;
160 uint8* byte_map = reinterpret_cast<uint8*>(header_->allocation_map);
161 uint8 map_block = byte_map[byte_index];
166 STRESS_DCHECK((((1 << size) - 1) << (index % 8)) < 0x100);
167 uint8 to_clear = ((1 << size) - 1) << (index % 8);
168 return ((byte_map[byte_index] & to_clear) == to_clear);
171 void BlockHeader::FixAllocationCounters() {
172 for (int i = 0; i < kMaxNumBlocks; i++) {
173 header_->hints[i] = 0;
174 header_->empty[i] = 0;
177 for (int i = 0; i < header_->max_entries / 32; i++) {
178 uint32 map_block = header_->allocation_map[i];
180 for (int j = 0; j < 8; j++, map_block >>= 4) {
181 int type = GetMapBlockType(map_block);
183 header_->empty[type -1]++;
188 bool BlockHeader::NeedToGrowBlockFile(int block_count) const {
189 bool have_space = false;
190 int empty_blocks = 0;
191 for (int i = 0; i < kMaxNumBlocks; i++) {
192 empty_blocks += header_->empty[i] * (i + 1);
193 if (i >= block_count - 1 && header_->empty[i])
197 if (header_->next_file && (empty_blocks < kMaxBlocks / 10)) {
198 // This file is almost full but we already created another one, don't use
199 // this file yet so that it is easier to find empty blocks when we start
200 // using this file again.
206 bool BlockHeader::CanAllocate(int block_count) const {
207 DCHECK_GT(block_count, 0);
208 for (int i = block_count - 1; i < kMaxNumBlocks; i++) {
209 if (header_->empty[i])
216 int BlockHeader::EmptyBlocks() const {
217 int empty_blocks = 0;
218 for (int i = 0; i < kMaxNumBlocks; i++) {
219 empty_blocks += header_->empty[i] * (i + 1);
220 if (header_->empty[i] < 0)
226 int BlockHeader::MinimumAllocations() const {
227 return header_->empty[kMaxNumBlocks - 1];
230 int BlockHeader::Capacity() const {
231 return header_->max_entries;
234 bool BlockHeader::ValidateCounters() const {
235 if (header_->max_entries < 0 || header_->max_entries > kMaxBlocks ||
236 header_->num_entries < 0)
239 int empty_blocks = EmptyBlocks();
240 if (empty_blocks + header_->num_entries > header_->max_entries)
246 int BlockHeader::FileId() const {
247 return header_->this_file;
250 int BlockHeader::NextFileId() const {
251 return header_->next_file;
254 int BlockHeader::Size() const {
255 return static_cast<int>(sizeof(*header_));
258 BlockFileHeader* BlockHeader::Header() {
262 // ------------------------------------------------------------------------
264 BlockFiles::BlockFiles(const base::FilePath& path)
265 : init_(false), zero_buffer_(NULL), path_(path) {
268 BlockFiles::~BlockFiles() {
270 delete[] zero_buffer_;
274 bool BlockFiles::Init(bool create_files) {
279 thread_checker_.reset(new base::ThreadChecker);
281 block_files_.resize(kFirstAdditionalBlockFile);
282 for (int i = 0; i < kFirstAdditionalBlockFile; i++) {
284 if (!CreateBlockFile(i, static_cast<FileType>(i + 1), true))
287 if (!OpenBlockFile(i))
290 // Walk this chain of files removing empty ones.
291 if (!RemoveEmptyFile(static_cast<FileType>(i + 1)))
299 MappedFile* BlockFiles::GetFile(Addr address) {
300 DCHECK(thread_checker_->CalledOnValidThread());
301 DCHECK_GE(block_files_.size(),
302 static_cast<size_t>(kFirstAdditionalBlockFile));
303 DCHECK(address.is_block_file() || !address.is_initialized());
304 if (!address.is_initialized())
307 int file_index = address.FileNumber();
308 if (static_cast<unsigned int>(file_index) >= block_files_.size() ||
309 !block_files_[file_index]) {
310 // We need to open the file
311 if (!OpenBlockFile(file_index))
314 DCHECK_GE(block_files_.size(), static_cast<unsigned int>(file_index));
315 return block_files_[file_index];
318 bool BlockFiles::CreateBlock(FileType block_type, int block_count,
319 Addr* block_address) {
320 DCHECK(thread_checker_->CalledOnValidThread());
321 DCHECK_NE(block_type, EXTERNAL);
322 DCHECK_NE(block_type, BLOCK_FILES);
323 DCHECK_NE(block_type, BLOCK_ENTRIES);
324 DCHECK_NE(block_type, BLOCK_EVICTED);
325 if (block_count < 1 || block_count > kMaxNumBlocks)
331 MappedFile* file = FileForNewBlock(block_type, block_count);
335 ScopedFlush flush(file);
336 BlockHeader file_header(file);
339 if (!file_header.CreateMapBlock(block_count, &index))
342 Addr address(block_type, block_count, file_header.FileId(), index);
343 block_address->set_value(address.value());
344 Trace("CreateBlock 0x%x", address.value());
348 void BlockFiles::DeleteBlock(Addr address, bool deep) {
349 DCHECK(thread_checker_->CalledOnValidThread());
350 if (!address.is_initialized() || address.is_separate_file())
354 zero_buffer_ = new char[Addr::BlockSizeForFileType(BLOCK_4K) * 4];
355 memset(zero_buffer_, 0, Addr::BlockSizeForFileType(BLOCK_4K) * 4);
357 MappedFile* file = GetFile(address);
361 Trace("DeleteBlock 0x%x", address.value());
363 size_t size = address.BlockSize() * address.num_blocks();
364 size_t offset = address.start_block() * address.BlockSize() +
367 file->Write(zero_buffer_, size, offset);
369 BlockHeader file_header(file);
370 file_header.DeleteMapBlock(address.start_block(), address.num_blocks());
373 if (!file_header.Header()->num_entries) {
374 // This file is now empty. Let's try to delete it.
375 FileType type = Addr::RequiredFileType(file_header.Header()->entry_size);
376 if (Addr::BlockSizeForFileType(RANKINGS) ==
377 file_header.Header()->entry_size) {
380 RemoveEmptyFile(type); // Ignore failures.
384 void BlockFiles::CloseFiles() {
386 DCHECK(thread_checker_->CalledOnValidThread());
389 for (unsigned int i = 0; i < block_files_.size(); i++) {
390 if (block_files_[i]) {
391 block_files_[i]->Release();
392 block_files_[i] = NULL;
395 block_files_.clear();
398 void BlockFiles::ReportStats() {
399 DCHECK(thread_checker_->CalledOnValidThread());
400 int used_blocks[kFirstAdditionalBlockFile];
401 int load[kFirstAdditionalBlockFile];
402 for (int i = 0; i < kFirstAdditionalBlockFile; i++) {
403 GetFileStats(i, &used_blocks[i], &load[i]);
405 UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_0", used_blocks[0]);
406 UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_1", used_blocks[1]);
407 UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_2", used_blocks[2]);
408 UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_3", used_blocks[3]);
410 UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_0", load[0], 101);
411 UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_1", load[1], 101);
412 UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_2", load[2], 101);
413 UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_3", load[3], 101);
416 bool BlockFiles::IsValid(Addr address) {
420 if (!address.is_initialized() || address.is_separate_file())
423 MappedFile* file = GetFile(address);
427 BlockHeader header(file);
428 bool rv = header.UsedMapBlock(address.start_block(), address.num_blocks());
431 static bool read_contents = false;
433 scoped_ptr<char[]> buffer;
434 buffer.reset(new char[Addr::BlockSizeForFileType(BLOCK_4K) * 4]);
435 size_t size = address.BlockSize() * address.num_blocks();
436 size_t offset = address.start_block() * address.BlockSize() +
438 bool ok = file->Read(buffer.get(), size, offset);
446 bool BlockFiles::CreateBlockFile(int index, FileType file_type, bool force) {
447 base::FilePath name = Name(index);
449 force ? base::PLATFORM_FILE_CREATE_ALWAYS : base::PLATFORM_FILE_CREATE;
450 flags |= base::PLATFORM_FILE_WRITE | base::PLATFORM_FILE_EXCLUSIVE_WRITE;
452 scoped_refptr<File> file(new File(
453 base::CreatePlatformFile(name, flags, NULL, NULL)));
454 if (!file->IsValid())
457 BlockFileHeader header;
458 memset(&header, 0, sizeof(header));
459 header.magic = kBlockMagic;
460 header.version = kBlockVersion2;
461 header.entry_size = Addr::BlockSizeForFileType(file_type);
462 header.this_file = static_cast<int16>(index);
463 DCHECK(index <= kint16max && index >= 0);
465 return file->Write(&header, sizeof(header), 0);
468 bool BlockFiles::OpenBlockFile(int index) {
469 if (block_files_.size() - 1 < static_cast<unsigned int>(index)) {
471 int to_add = index - static_cast<int>(block_files_.size()) + 1;
472 block_files_.resize(block_files_.size() + to_add);
475 base::FilePath name = Name(index);
476 scoped_refptr<MappedFile> file(new MappedFile());
478 if (!file->Init(name, kBlockHeaderSize)) {
479 LOG(ERROR) << "Failed to open " << name.value();
483 size_t file_len = file->GetLength();
484 if (file_len < static_cast<size_t>(kBlockHeaderSize)) {
485 LOG(ERROR) << "File too small " << name.value();
489 BlockHeader file_header(file.get());
490 BlockFileHeader* header = file_header.Header();
491 if (kBlockMagic != header->magic || kBlockVersion2 != header->version) {
492 LOG(ERROR) << "Invalid file version or magic " << name.value();
496 if (header->updating || !file_header.ValidateCounters()) {
497 // Last instance was not properly shutdown, or counters are out of sync.
498 if (!FixBlockFileHeader(file.get())) {
499 LOG(ERROR) << "Unable to fix block file " << name.value();
504 if (static_cast<int>(file_len) <
505 header->max_entries * header->entry_size + kBlockHeaderSize) {
506 LOG(ERROR) << "File too small " << name.value();
511 // Load the links file into memory with a single read.
512 scoped_ptr<char[]> buf(new char[file_len]);
513 if (!file->Read(buf.get(), file_len, 0))
517 ScopedFlush flush(file.get());
518 DCHECK(!block_files_[index]);
519 file.swap(&block_files_[index]);
523 bool BlockFiles::GrowBlockFile(MappedFile* file, BlockFileHeader* header) {
524 if (kMaxBlocks == header->max_entries)
527 ScopedFlush flush(file);
528 DCHECK(!header->empty[3]);
529 int new_size = header->max_entries + 1024;
530 if (new_size > kMaxBlocks)
531 new_size = kMaxBlocks;
533 int new_size_bytes = new_size * header->entry_size + sizeof(*header);
535 if (!file->SetLength(new_size_bytes)) {
536 // Most likely we are trying to truncate the file, so the header is wrong.
537 if (header->updating < 10 && !FixBlockFileHeader(file)) {
538 // If we can't fix the file increase the lock guard so we'll pick it on
539 // the next start and replace it.
540 header->updating = 100;
543 return (header->max_entries >= new_size);
546 FileLock lock(header);
547 header->empty[3] = (new_size - header->max_entries) / 4; // 4 blocks entries
548 header->max_entries = new_size;
553 MappedFile* BlockFiles::FileForNewBlock(FileType block_type, int block_count) {
554 COMPILE_ASSERT(RANKINGS == 1, invalid_file_type);
555 MappedFile* file = block_files_[block_type - 1];
556 BlockHeader file_header(file);
558 TimeTicks start = TimeTicks::Now();
559 while (file_header.NeedToGrowBlockFile(block_count)) {
560 if (kMaxBlocks == file_header.Header()->max_entries) {
561 file = NextFile(file);
564 file_header = BlockHeader(file);
568 if (!GrowBlockFile(file, file_header.Header()))
572 HISTOGRAM_TIMES("DiskCache.GetFileForNewBlock", TimeTicks::Now() - start);
576 MappedFile* BlockFiles::NextFile(MappedFile* file) {
577 ScopedFlush flush(file);
578 BlockFileHeader* header = reinterpret_cast<BlockFileHeader*>(file->buffer());
579 int new_file = header->next_file;
581 // RANKINGS is not reported as a type for small entries, but we may be
582 // extending the rankings block file.
583 FileType type = Addr::RequiredFileType(header->entry_size);
584 if (header->entry_size == Addr::BlockSizeForFileType(RANKINGS))
587 new_file = CreateNextBlockFile(type);
591 FileLock lock(header);
592 header->next_file = new_file;
595 // Only the block_file argument is relevant for what we want.
596 Addr address(BLOCK_256, 1, new_file, 0);
597 return GetFile(address);
600 int BlockFiles::CreateNextBlockFile(FileType block_type) {
601 for (int i = kFirstAdditionalBlockFile; i <= kMaxBlockFile; i++) {
602 if (CreateBlockFile(i, block_type, false))
608 // We walk the list of files for this particular block type, deleting the ones
610 bool BlockFiles::RemoveEmptyFile(FileType block_type) {
611 MappedFile* file = block_files_[block_type - 1];
612 BlockFileHeader* header = reinterpret_cast<BlockFileHeader*>(file->buffer());
614 while (header->next_file) {
615 // Only the block_file argument is relevant for what we want.
616 Addr address(BLOCK_256, 1, header->next_file, 0);
617 MappedFile* next_file = GetFile(address);
621 BlockFileHeader* next_header =
622 reinterpret_cast<BlockFileHeader*>(next_file->buffer());
623 if (!next_header->num_entries) {
624 DCHECK_EQ(next_header->entry_size, header->entry_size);
625 // Delete next_file and remove it from the chain.
626 int file_index = header->next_file;
627 header->next_file = next_header->next_file;
628 DCHECK(block_files_.size() >= static_cast<unsigned int>(file_index));
631 // We get a new handle to the file and release the old one so that the
632 // file gets unmmaped... so we can delete it.
633 base::FilePath name = Name(file_index);
634 scoped_refptr<File> this_file(new File(false));
635 this_file->Init(name);
636 block_files_[file_index]->Release();
637 block_files_[file_index] = NULL;
639 int failure = DeleteCacheFile(name) ? 0 : 1;
640 UMA_HISTOGRAM_COUNTS("DiskCache.DeleteFailed2", failure);
642 LOG(ERROR) << "Failed to delete " << name.value() << " from the cache.";
646 header = next_header;
652 // Note that we expect to be called outside of a FileLock... however, we cannot
653 // DCHECK on header->updating because we may be fixing a crash.
654 bool BlockFiles::FixBlockFileHeader(MappedFile* file) {
655 ScopedFlush flush(file);
656 BlockHeader file_header(file);
657 int file_size = static_cast<int>(file->GetLength());
658 if (file_size < file_header.Size())
659 return false; // file_size > 2GB is also an error.
661 const int kMinBlockSize = 36;
662 const int kMaxBlockSize = 4096;
663 BlockFileHeader* header = file_header.Header();
664 if (header->entry_size < kMinBlockSize ||
665 header->entry_size > kMaxBlockSize || header->num_entries < 0)
668 // Make sure that we survive crashes.
669 header->updating = 1;
670 int expected = header->entry_size * header->max_entries + file_header.Size();
671 if (file_size != expected) {
672 int max_expected = header->entry_size * kMaxBlocks + file_header.Size();
673 if (file_size < expected || header->empty[3] || file_size > max_expected) {
675 LOG(ERROR) << "Unexpected file size";
678 // We were in the middle of growing the file.
679 int num_entries = (file_size - file_header.Size()) / header->entry_size;
680 header->max_entries = num_entries;
683 file_header.FixAllocationCounters();
684 int empty_blocks = file_header.EmptyBlocks();
685 if (empty_blocks + header->num_entries > header->max_entries)
686 header->num_entries = header->max_entries - empty_blocks;
688 if (!file_header.ValidateCounters())
691 header->updating = 0;
695 // We are interested in the total number of blocks used by this file type, and
696 // the max number of blocks that we can store (reported as the percentage of
697 // used blocks). In order to find out the number of used blocks, we have to
698 // substract the empty blocks from the total blocks for each file in the chain.
699 void BlockFiles::GetFileStats(int index, int* used_count, int* load) {
704 if (!block_files_[index] && !OpenBlockFile(index))
707 BlockFileHeader* header =
708 reinterpret_cast<BlockFileHeader*>(block_files_[index]->buffer());
710 max_blocks += header->max_entries;
711 int used = header->max_entries;
712 for (int i = 0; i < kMaxNumBlocks; i++) {
713 used -= header->empty[i] * (i + 1);
718 if (!header->next_file)
720 index = header->next_file;
723 *load = *used_count * 100 / max_blocks;
726 base::FilePath BlockFiles::Name(int index) {
727 // The file format allows for 256 files.
728 DCHECK(index < 256 && index >= 0);
729 std::string tmp = base::StringPrintf("%s%d", kBlockName, index);
730 return path_.AppendASCII(tmp);
733 } // namespace disk_cache