Disk Cache: Delete chained block files when they become empty....

net/disk_cache/block_files.cc

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/disk_cache/block_files.h"
 
 #include "base/file_util.h"
 #include "base/histogram.h"
 #include "base/string_util.h"
 #include "base/time.h"
+#include "net/disk_cache/cache_util.h"
 #include "net/disk_cache/file_lock.h"
 
 using base::Time;
 
 namespace {
 
 const wchar_t* kBlockName = L"data_";
 
 // This array is used to perform a fast lookup of the nibble bit pattern to the
 // type of entry that can be stored there (number of consecutive blocks).
@@ skipping 108 matching lines @@
 
     for (int j = 0; j < 8; j++, map_block >>= 4) {
       int type = GetMapBlockType(map_block);
       if (type)
         header->empty[type -1]++;
     }
   }
 }
 
 // Returns true if the current block file should not be used as-is to store more
-// records. |block_count| is the number of blocks to allocate, and
-// |use_next_file| is set to true on return if we should use the next file in
-// the chain, even though we could find empty space on the current file.
+// records. |block_count| is the number of blocks to allocate.
 bool NeedToGrowBlockFile(const disk_cache::BlockFileHeader* header,
-                         int block_count, bool* use_next_file) {
-  if ((header->max_entries > disk_cache::kMaxBlocks * 9 / 10) &&
-      header->next_file) {
+                         int block_count) {
+  bool have_space = false;
+  int empty_blocks = 0;
+  for (int i = 0; i < disk_cache::kMaxNumBlocks; i++) {
+    empty_blocks += header->empty[i] * (i + 1);
+    if (i >= block_count - 1 && header->empty[i])
+      have_space = true;
+  }
+
+  if (header->next_file && (empty_blocks < disk_cache::kMaxBlocks / 10)) {
     // This file is almost full but we already created another one, don't use
     // this file yet so that it is easier to find empty blocks when we start
     // using this file again.
-    *use_next_file = true;
     return true;
   }
-  *use_next_file = false;
-  for (int i = block_count; i <= disk_cache::kMaxNumBlocks; i++) {
-    if (header->empty[i - 1])
-      return false;
-  }
-  return true;
+  return !have_space;
 }
 
 }  // namespace
 
 namespace disk_cache {
 
 BlockFiles::~BlockFiles() {
   if (zero_buffer_)
     delete[] zero_buffer_;
   CloseFiles();
 }
 
 bool BlockFiles::Init(bool create_files) {
   DCHECK(!init_);
   if (init_)
     return false;
 
   block_files_.resize(kFirstAdditionlBlockFile);
   for (int i = 0; i < kFirstAdditionlBlockFile; i++) {
     if (create_files)
       if (!CreateBlockFile(i, static_cast<FileType>(i + 1), true))
         return false;
 
     if (!OpenBlockFile(i))
       return false;
+
+    // Walk this chain of files removing empty ones.
+    RemoveEmptyFile(static_cast<FileType>(i + 1));
   }
 
   init_ = true;
   return true;
 }
 
 void BlockFiles::CloseFiles() {
   init_ = false;
   for (unsigned int i = 0; i < block_files_.size(); i++) {
     if (block_files_[i]) {
@@ skipping 112 matching lines @@
 
   return true;
 }
 
 MappedFile* BlockFiles::FileForNewBlock(FileType block_type, int block_count) {
   COMPILE_ASSERT(RANKINGS == 1, invalid_fily_type);
   MappedFile* file = block_files_[block_type - 1];
   BlockFileHeader* header = reinterpret_cast<BlockFileHeader*>(file->buffer());
 
   Time start = Time::Now();
-  bool use_next_file;
-  while (NeedToGrowBlockFile(header, block_count, &use_next_file)) {
-    if (use_next_file || kMaxBlocks == header->max_entries) {
+  while (NeedToGrowBlockFile(header, block_count)) {
+    if (kMaxBlocks == header->max_entries) {
       file = NextFile(file);
       if (!file)
         return NULL;
       header = reinterpret_cast<BlockFileHeader*>(file->buffer());
       continue;
     }
 
     if (!GrowBlockFile(file, header))
       return NULL;
     break;
@@ skipping 26 matching lines @@
 }
 
 int BlockFiles::CreateNextBlockFile(FileType block_type) {
   for (int i = kFirstAdditionlBlockFile; i <= kMaxBlockFile; i++) {
     if (CreateBlockFile(i, block_type, false))
       return i;
   }
   return 0;
 }
 
+// We walk the list of files for this particular block type, deleting the ones
+// that are empty.
+void BlockFiles::RemoveEmptyFile(FileType block_type) {
+  MappedFile* file = block_files_[block_type - 1];
+  BlockFileHeader* header = reinterpret_cast<BlockFileHeader*>(file->buffer());
+
+  while (header->next_file) {
+    // Only the block_file argument is relevant for what we want.
+    Addr address(BLOCK_256, 1, header->next_file, 0);
+    MappedFile* next_file = GetFile(address);
+    if (!next_file)
+      return;
+
+    BlockFileHeader* next_header =
+        reinterpret_cast<BlockFileHeader*>(next_file->buffer());
+    if (!next_header->num_entries) {
+      DCHECK_EQ(next_header->entry_size, header->entry_size);
+      // Delete next_file and remove it from the chain.
+      int file_index = header->next_file;
+      header->next_file = next_header->next_file;
+      DCHECK(block_files_.size() >= static_cast<unsigned int>(file_index));
+      block_files_[file_index]->Release();
+      block_files_[file_index] = NULL;
+
+      std::wstring name = Name(file_index);
+      int failure = DeleteCacheFile(name) ? 0 : 1;
+      UMA_HISTOGRAM_COUNTS("DiskCache.DeleteFailed2", failure);
+      if (failure)
+        LOG(ERROR) << "Failed to delete " << name << " from the cache.";
+      continue;
+    }
+
+    header = next_header;
+    file = next_file;
+  }
+}
+
 bool BlockFiles::CreateBlock(FileType block_type, int block_count,
                              Addr* block_address) {
   if (block_type < RANKINGS || block_type > BLOCK_4K ||
       block_count < 1 || block_count > 4)
     return false;
   if (!init_)
     return false;
 
   MappedFile* file = FileForNewBlock(block_type, block_count);
   if (!file)
@@ skipping 32 matching lines @@
     return;
 
   size_t size = address.BlockSize() * address.num_blocks();
   size_t offset = address.start_block() * address.BlockSize() +
                   kBlockHeaderSize;
   if (deep)
     file->Write(zero_buffer_, size, offset);
 
   BlockFileHeader* header = reinterpret_cast<BlockFileHeader*>(file->buffer());
   DeleteMapBlock(address.start_block(), address.num_blocks(), header);
+  if (!header->num_entries) {
+    // This file is now empty. Let's try to delete it.
+    FileType type = Addr::RequiredFileType(header->entry_size);
+    if (Addr::BlockSizeForFileType(RANKINGS) == header->entry_size)
+      type = RANKINGS;
+    RemoveEmptyFile(type);
+  }
 }
 
 bool BlockFiles::FixBlockFileHeader(MappedFile* file) {
   BlockFileHeader* header = reinterpret_cast<BlockFileHeader*>(file->buffer());
   int file_size = static_cast<int>(file->GetLength());
   if (file_size < static_cast<int>(sizeof(*header)))
     return false;  // file_size > 2GB is also an error.
 
   int expected = header->entry_size * header->max_entries + sizeof(*header);
   if (file_size != expected) {
     int max_expected = header->entry_size * kMaxBlocks + sizeof(*header);
     if (file_size < expected || header->empty[3] || file_size > max_expected) {
       NOTREACHED();
       LOG(ERROR) << "Unexpected file size";
       return false;
     }
     // We were in the middle of growing the file.
     int num_entries = (file_size - sizeof(*header)) / header->entry_size;
     header->max_entries = num_entries;
   }
 
   FixAllocationCounters(header);
   header->updating = 0;
   return true;
 }
 
 }  // namespace disk_cache