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/trace.h"
18 using base::TimeTicks;
22 const char* kBlockName = "data_";
24 // This array is used to perform a fast lookup of the nibble bit pattern to the
25 // type of entry that can be stored there (number of consecutive blocks).
26 const char s_types[16] = {4, 3, 2, 2, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0};
28 // Returns the type of block (number of consecutive blocks that can be stored)
29 // for a given nibble of the bitmap.
30 inline int GetMapBlockType(uint8 value) {
32 return s_types[value];
37 namespace disk_cache {
39 BlockHeader::BlockHeader() : header_(NULL) {
42 BlockHeader::BlockHeader(BlockFileHeader* header) : header_(header) {
45 BlockHeader::BlockHeader(MappedFile* file)
46 : header_(reinterpret_cast<BlockFileHeader*>(file->buffer())) {
49 BlockHeader::BlockHeader(const BlockHeader& other) : header_(other.header_) {
52 BlockHeader::~BlockHeader() {
55 bool BlockHeader::CreateMapBlock(int size, int* index) {
56 DCHECK(size > 0 && size <= kMaxNumBlocks);
58 for (int i = size; i <= kMaxNumBlocks; i++) {
59 if (header_->empty[i - 1]) {
70 TimeTicks start = TimeTicks::Now();
71 // We are going to process the map on 32-block chunks (32 bits), and on every
72 // chunk, iterate through the 8 nibbles where the new block can be located.
73 int current = header_->hints[target - 1];
74 for (int i = 0; i < header_->max_entries / 32; i++, current++) {
75 if (current == header_->max_entries / 32)
77 uint32 map_block = header_->allocation_map[current];
79 for (int j = 0; j < 8; j++, map_block >>= 4) {
80 if (GetMapBlockType(map_block) != target)
83 disk_cache::FileLock lock(header_);
84 int index_offset = j * 4 + 4 - target;
85 *index = current * 32 + index_offset;
86 DLOG_IF(ERROR, *index / 4 != (*index + size - 1) / 4) << "Bit mismatch";
87 uint32 to_add = ((1 << size) - 1) << index_offset;
88 header_->num_entries++;
90 // Note that there is no race in the normal sense here, but if we enforce
91 // the order of memory accesses between num_entries and allocation_map, we
92 // can assert that even if we crash here, num_entries will never be less
93 // than the actual number of used blocks.
94 base::subtle::MemoryBarrier();
95 header_->allocation_map[current] |= to_add;
97 header_->hints[target - 1] = current;
98 header_->empty[target - 1]--;
99 DCHECK_GE(header_->empty[target - 1], 0);
100 if (target != size) {
101 header_->empty[target - size - 1]++;
103 HISTOGRAM_TIMES("DiskCache.CreateBlock", TimeTicks::Now() - start);
108 // It is possible to have an undetected corruption (for example when the OS
109 // crashes), fix it here.
110 LOG(ERROR) << "Failing CreateMapBlock";
111 FixAllocationCounters();
115 void BlockHeader::DeleteMapBlock(int index, int size) {
116 if (size < 0 || size > kMaxNumBlocks) {
120 TimeTicks start = TimeTicks::Now();
121 int byte_index = index / 8;
122 uint8* byte_map = reinterpret_cast<uint8*>(header_->allocation_map);
123 uint8 map_block = byte_map[byte_index];
128 // See what type of block will be available after we delete this one.
129 int bits_at_end = 4 - size - index % 4;
130 uint8 end_mask = (0xf << (4 - bits_at_end)) & 0xf;
131 bool update_counters = (map_block & end_mask) == 0;
132 uint8 new_value = map_block & ~(((1 << size) - 1) << (index % 4));
133 int new_type = GetMapBlockType(new_value);
135 disk_cache::FileLock lock(header_);
136 DCHECK((((1 << size) - 1) << (index % 8)) < 0x100);
137 uint8 to_clear = ((1 << size) - 1) << (index % 8);
138 DCHECK((byte_map[byte_index] & to_clear) == to_clear);
139 byte_map[byte_index] &= ~to_clear;
141 if (update_counters) {
143 header_->empty[bits_at_end - 1]--;
144 header_->empty[new_type - 1]++;
145 DCHECK_GE(header_->empty[bits_at_end - 1], 0);
147 base::subtle::MemoryBarrier();
148 header_->num_entries--;
149 DCHECK_GE(header_->num_entries, 0);
150 HISTOGRAM_TIMES("DiskCache.DeleteBlock", TimeTicks::Now() - start);
153 // Note that this is a simplified version of DeleteMapBlock().
154 bool BlockHeader::UsedMapBlock(int index, int size) {
155 if (size < 0 || size > kMaxNumBlocks)
158 int byte_index = index / 8;
159 uint8* byte_map = reinterpret_cast<uint8*>(header_->allocation_map);
160 uint8 map_block = byte_map[byte_index];
165 DCHECK((((1 << size) - 1) << (index % 8)) < 0x100);
166 uint8 to_clear = ((1 << size) - 1) << (index % 8);
167 return ((byte_map[byte_index] & to_clear) == to_clear);
170 void BlockHeader::FixAllocationCounters() {
171 for (int i = 0; i < kMaxNumBlocks; i++) {
172 header_->hints[i] = 0;
173 header_->empty[i] = 0;
176 for (int i = 0; i < header_->max_entries / 32; i++) {
177 uint32 map_block = header_->allocation_map[i];
179 for (int j = 0; j < 8; j++, map_block >>= 4) {
180 int type = GetMapBlockType(map_block);
182 header_->empty[type -1]++;
187 bool BlockHeader::NeedToGrowBlockFile(int block_count) const {
188 bool have_space = false;
189 int empty_blocks = 0;
190 for (int i = 0; i < kMaxNumBlocks; i++) {
191 empty_blocks += header_->empty[i] * (i + 1);
192 if (i >= block_count - 1 && header_->empty[i])
196 if (header_->next_file && (empty_blocks < kMaxBlocks / 10)) {
197 // This file is almost full but we already created another one, don't use
198 // this file yet so that it is easier to find empty blocks when we start
199 // using this file again.
205 bool BlockHeader::CanAllocate(int block_count) const {
206 DCHECK_GT(block_count, 0);
207 for (int i = block_count - 1; i < kMaxNumBlocks; i++) {
208 if (header_->empty[i])
215 int BlockHeader::EmptyBlocks() const {
216 int empty_blocks = 0;
217 for (int i = 0; i < kMaxNumBlocks; i++) {
218 empty_blocks += header_->empty[i] * (i + 1);
219 if (header_->empty[i] < 0)
225 int BlockHeader::MinimumAllocations() const {
226 return header_->empty[kMaxNumBlocks - 1];
229 int BlockHeader::Capacity() const {
230 return header_->max_entries;
233 bool BlockHeader::ValidateCounters() const {
234 if (header_->max_entries < 0 || header_->max_entries > kMaxBlocks ||
235 header_->num_entries < 0)
238 int empty_blocks = EmptyBlocks();
239 if (empty_blocks + header_->num_entries > header_->max_entries)
245 int BlockHeader::FileId() const {
246 return header_->this_file;
249 int BlockHeader::NextFileId() const {
250 return header_->next_file;
253 int BlockHeader::Size() const {
254 return static_cast<int>(sizeof(*header_));
257 BlockFileHeader* BlockHeader::Header() {
261 // ------------------------------------------------------------------------
263 BlockFiles::BlockFiles(const base::FilePath& path)
264 : init_(false), zero_buffer_(NULL), path_(path) {
267 BlockFiles::~BlockFiles() {
269 delete[] zero_buffer_;
273 bool BlockFiles::Init(bool create_files) {
278 thread_checker_.reset(new base::ThreadChecker);
280 block_files_.resize(kFirstAdditionalBlockFile);
281 for (int i = 0; i < kFirstAdditionalBlockFile; i++) {
283 if (!CreateBlockFile(i, static_cast<FileType>(i + 1), true))
286 if (!OpenBlockFile(i))
289 // Walk this chain of files removing empty ones.
290 if (!RemoveEmptyFile(static_cast<FileType>(i + 1)))
298 MappedFile* BlockFiles::GetFile(Addr address) {
299 DCHECK(thread_checker_->CalledOnValidThread());
300 DCHECK_GE(block_files_.size(),
301 static_cast<size_t>(kFirstAdditionalBlockFile));
302 DCHECK(address.is_block_file() || !address.is_initialized());
303 if (!address.is_initialized())
306 int file_index = address.FileNumber();
307 if (static_cast<unsigned int>(file_index) >= block_files_.size() ||
308 !block_files_[file_index]) {
309 // We need to open the file
310 if (!OpenBlockFile(file_index))
313 DCHECK_GE(block_files_.size(), static_cast<unsigned int>(file_index));
314 return block_files_[file_index];
317 bool BlockFiles::CreateBlock(FileType block_type, int block_count,
318 Addr* block_address) {
319 DCHECK(thread_checker_->CalledOnValidThread());
320 DCHECK_NE(block_type, EXTERNAL);
321 DCHECK_NE(block_type, BLOCK_FILES);
322 DCHECK_NE(block_type, BLOCK_ENTRIES);
323 DCHECK_NE(block_type, BLOCK_EVICTED);
324 if (block_count < 1 || block_count > kMaxNumBlocks)
330 MappedFile* file = FileForNewBlock(block_type, block_count);
334 ScopedFlush flush(file);
335 BlockHeader file_header(file);
338 if (!file_header.CreateMapBlock(block_count, &index))
341 Addr address(block_type, block_count, file_header.FileId(), index);
342 block_address->set_value(address.value());
343 Trace("CreateBlock 0x%x", address.value());
347 void BlockFiles::DeleteBlock(Addr address, bool deep) {
348 DCHECK(thread_checker_->CalledOnValidThread());
349 if (!address.is_initialized() || address.is_separate_file())
353 zero_buffer_ = new char[Addr::BlockSizeForFileType(BLOCK_4K) * 4];
354 memset(zero_buffer_, 0, Addr::BlockSizeForFileType(BLOCK_4K) * 4);
356 MappedFile* file = GetFile(address);
360 Trace("DeleteBlock 0x%x", address.value());
362 size_t size = address.BlockSize() * address.num_blocks();
363 size_t offset = address.start_block() * address.BlockSize() +
366 file->Write(zero_buffer_, size, offset);
368 BlockHeader file_header(file);
369 file_header.DeleteMapBlock(address.start_block(), address.num_blocks());
372 if (!file_header.Header()->num_entries) {
373 // This file is now empty. Let's try to delete it.
374 FileType type = Addr::RequiredFileType(file_header.Header()->entry_size);
375 if (Addr::BlockSizeForFileType(RANKINGS) ==
376 file_header.Header()->entry_size) {
379 RemoveEmptyFile(type); // Ignore failures.
383 void BlockFiles::CloseFiles() {
385 DCHECK(thread_checker_->CalledOnValidThread());
388 for (unsigned int i = 0; i < block_files_.size(); i++) {
389 if (block_files_[i]) {
390 block_files_[i]->Release();
391 block_files_[i] = NULL;
394 block_files_.clear();
397 void BlockFiles::ReportStats() {
398 DCHECK(thread_checker_->CalledOnValidThread());
399 int used_blocks[kFirstAdditionalBlockFile];
400 int load[kFirstAdditionalBlockFile];
401 for (int i = 0; i < kFirstAdditionalBlockFile; i++) {
402 GetFileStats(i, &used_blocks[i], &load[i]);
404 UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_0", used_blocks[0]);
405 UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_1", used_blocks[1]);
406 UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_2", used_blocks[2]);
407 UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_3", used_blocks[3]);
409 UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_0", load[0], 101);
410 UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_1", load[1], 101);
411 UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_2", load[2], 101);
412 UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_3", load[3], 101);
415 bool BlockFiles::IsValid(Addr address) {
419 if (!address.is_initialized() || address.is_separate_file())
422 MappedFile* file = GetFile(address);
426 BlockHeader header(file);
427 bool rv = header.UsedMapBlock(address.start_block(), address.num_blocks());
430 static bool read_contents = false;
432 scoped_ptr<char[]> buffer;
433 buffer.reset(new char[Addr::BlockSizeForFileType(BLOCK_4K) * 4]);
434 size_t size = address.BlockSize() * address.num_blocks();
435 size_t offset = address.start_block() * address.BlockSize() +
437 bool ok = file->Read(buffer.get(), size, offset);
445 bool BlockFiles::CreateBlockFile(int index, FileType file_type, bool force) {
446 base::FilePath name = Name(index);
448 force ? base::PLATFORM_FILE_CREATE_ALWAYS : base::PLATFORM_FILE_CREATE;
449 flags |= base::PLATFORM_FILE_WRITE | base::PLATFORM_FILE_EXCLUSIVE_WRITE;
451 scoped_refptr<File> file(new File(
452 base::CreatePlatformFile(name, flags, NULL, NULL)));
453 if (!file->IsValid())
456 BlockFileHeader header;
457 memset(&header, 0, sizeof(header));
458 header.magic = kBlockMagic;
459 header.version = kBlockVersion2;
460 header.entry_size = Addr::BlockSizeForFileType(file_type);
461 header.this_file = static_cast<int16>(index);
462 DCHECK(index <= kint16max && index >= 0);
464 return file->Write(&header, sizeof(header), 0);
467 bool BlockFiles::OpenBlockFile(int index) {
468 if (block_files_.size() - 1 < static_cast<unsigned int>(index)) {
470 int to_add = index - static_cast<int>(block_files_.size()) + 1;
471 block_files_.resize(block_files_.size() + to_add);
474 base::FilePath name = Name(index);
475 scoped_refptr<MappedFile> file(new MappedFile());
477 if (!file->Init(name, kBlockHeaderSize)) {
478 LOG(ERROR) << "Failed to open " << name.value();
482 size_t file_len = file->GetLength();
483 if (file_len < static_cast<size_t>(kBlockHeaderSize)) {
484 LOG(ERROR) << "File too small " << name.value();
488 BlockHeader file_header(file.get());
489 BlockFileHeader* header = file_header.Header();
490 if (kBlockMagic != header->magic || kBlockVersion2 != header->version) {
491 LOG(ERROR) << "Invalid file version or magic " << name.value();
495 if (header->updating || !file_header.ValidateCounters()) {
496 // Last instance was not properly shutdown, or counters are out of sync.
497 if (!FixBlockFileHeader(file.get())) {
498 LOG(ERROR) << "Unable to fix block file " << name.value();
503 if (static_cast<int>(file_len) <
504 header->max_entries * header->entry_size + kBlockHeaderSize) {
505 LOG(ERROR) << "File too small " << name.value();
510 // Load the links file into memory with a single read.
511 scoped_ptr<char[]> buf(new char[file_len]);
512 if (!file->Read(buf.get(), file_len, 0))
516 ScopedFlush flush(file.get());
517 DCHECK(!block_files_[index]);
518 file.swap(&block_files_[index]);
522 bool BlockFiles::GrowBlockFile(MappedFile* file, BlockFileHeader* header) {
523 if (kMaxBlocks == header->max_entries)
526 ScopedFlush flush(file);
527 DCHECK(!header->empty[3]);
528 int new_size = header->max_entries + 1024;
529 if (new_size > kMaxBlocks)
530 new_size = kMaxBlocks;
532 int new_size_bytes = new_size * header->entry_size + sizeof(*header);
534 if (!file->SetLength(new_size_bytes)) {
535 // Most likely we are trying to truncate the file, so the header is wrong.
536 if (header->updating < 10 && !FixBlockFileHeader(file)) {
537 // If we can't fix the file increase the lock guard so we'll pick it on
538 // the next start and replace it.
539 header->updating = 100;
542 return (header->max_entries >= new_size);
545 FileLock lock(header);
546 header->empty[3] = (new_size - header->max_entries) / 4; // 4 blocks entries
547 header->max_entries = new_size;
552 MappedFile* BlockFiles::FileForNewBlock(FileType block_type, int block_count) {
553 COMPILE_ASSERT(RANKINGS == 1, invalid_file_type);
554 MappedFile* file = block_files_[block_type - 1];
555 BlockHeader file_header(file);
557 TimeTicks start = TimeTicks::Now();
558 while (file_header.NeedToGrowBlockFile(block_count)) {
559 if (kMaxBlocks == file_header.Header()->max_entries) {
560 file = NextFile(file);
563 file_header = BlockHeader(file);
567 if (!GrowBlockFile(file, file_header.Header()))
571 HISTOGRAM_TIMES("DiskCache.GetFileForNewBlock", TimeTicks::Now() - start);
575 MappedFile* BlockFiles::NextFile(MappedFile* file) {
576 ScopedFlush flush(file);
577 BlockFileHeader* header = reinterpret_cast<BlockFileHeader*>(file->buffer());
578 int new_file = header->next_file;
580 // RANKINGS is not reported as a type for small entries, but we may be
581 // extending the rankings block file.
582 FileType type = Addr::RequiredFileType(header->entry_size);
583 if (header->entry_size == Addr::BlockSizeForFileType(RANKINGS))
586 new_file = CreateNextBlockFile(type);
590 FileLock lock(header);
591 header->next_file = new_file;
594 // Only the block_file argument is relevant for what we want.
595 Addr address(BLOCK_256, 1, new_file, 0);
596 return GetFile(address);
599 int BlockFiles::CreateNextBlockFile(FileType block_type) {
600 for (int i = kFirstAdditionalBlockFile; i <= kMaxBlockFile; i++) {
601 if (CreateBlockFile(i, block_type, false))
607 // We walk the list of files for this particular block type, deleting the ones
609 bool BlockFiles::RemoveEmptyFile(FileType block_type) {
610 MappedFile* file = block_files_[block_type - 1];
611 BlockFileHeader* header = reinterpret_cast<BlockFileHeader*>(file->buffer());
613 while (header->next_file) {
614 // Only the block_file argument is relevant for what we want.
615 Addr address(BLOCK_256, 1, header->next_file, 0);
616 MappedFile* next_file = GetFile(address);
620 BlockFileHeader* next_header =
621 reinterpret_cast<BlockFileHeader*>(next_file->buffer());
622 if (!next_header->num_entries) {
623 DCHECK_EQ(next_header->entry_size, header->entry_size);
624 // Delete next_file and remove it from the chain.
625 int file_index = header->next_file;
626 header->next_file = next_header->next_file;
627 DCHECK(block_files_.size() >= static_cast<unsigned int>(file_index));
630 // We get a new handle to the file and release the old one so that the
631 // file gets unmmaped... so we can delete it.
632 base::FilePath name = Name(file_index);
633 scoped_refptr<File> this_file(new File(false));
634 this_file->Init(name);
635 block_files_[file_index]->Release();
636 block_files_[file_index] = NULL;
638 int failure = DeleteCacheFile(name) ? 0 : 1;
639 UMA_HISTOGRAM_COUNTS("DiskCache.DeleteFailed2", failure);
641 LOG(ERROR) << "Failed to delete " << name.value() << " from the cache.";
645 header = next_header;
651 // Note that we expect to be called outside of a FileLock... however, we cannot
652 // DCHECK on header->updating because we may be fixing a crash.
653 bool BlockFiles::FixBlockFileHeader(MappedFile* file) {
654 ScopedFlush flush(file);
655 BlockHeader file_header(file);
656 int file_size = static_cast<int>(file->GetLength());
657 if (file_size < file_header.Size())
658 return false; // file_size > 2GB is also an error.
660 const int kMinBlockSize = 36;
661 const int kMaxBlockSize = 4096;
662 BlockFileHeader* header = file_header.Header();
663 if (header->entry_size < kMinBlockSize ||
664 header->entry_size > kMaxBlockSize || header->num_entries < 0)
667 // Make sure that we survive crashes.
668 header->updating = 1;
669 int expected = header->entry_size * header->max_entries + file_header.Size();
670 if (file_size != expected) {
671 int max_expected = header->entry_size * kMaxBlocks + file_header.Size();
672 if (file_size < expected || header->empty[3] || file_size > max_expected) {
674 LOG(ERROR) << "Unexpected file size";
677 // We were in the middle of growing the file.
678 int num_entries = (file_size - file_header.Size()) / header->entry_size;
679 header->max_entries = num_entries;
682 file_header.FixAllocationCounters();
683 int empty_blocks = file_header.EmptyBlocks();
684 if (empty_blocks + header->num_entries > header->max_entries)
685 header->num_entries = header->max_entries - empty_blocks;
687 if (!file_header.ValidateCounters())
690 header->updating = 0;
694 // We are interested in the total number of blocks used by this file type, and
695 // the max number of blocks that we can store (reported as the percentage of
696 // used blocks). In order to find out the number of used blocks, we have to
697 // substract the empty blocks from the total blocks for each file in the chain.
698 void BlockFiles::GetFileStats(int index, int* used_count, int* load) {
703 if (!block_files_[index] && !OpenBlockFile(index))
706 BlockFileHeader* header =
707 reinterpret_cast<BlockFileHeader*>(block_files_[index]->buffer());
709 max_blocks += header->max_entries;
710 int used = header->max_entries;
711 for (int i = 0; i < kMaxNumBlocks; i++) {
712 used -= header->empty[i] * (i + 1);
717 if (!header->next_file)
719 index = header->next_file;
722 *load = *used_count * 100 / max_blocks;
725 base::FilePath BlockFiles::Name(int index) {
726 // The file format allows for 256 files.
727 DCHECK(index < 256 && index >= 0);
728 std::string tmp = base::StringPrintf("%s%d", kBlockName, index);
729 return path_.AppendASCII(tmp);
732 } // namespace disk_cache