1 //
2 // Copyright (C) 2015 The Android Open Source Project
3 //
4 // Licensed under the Apache License, Version 2.0 (the "License");
5 // you may not use this file except in compliance with the License.
6 // You may obtain a copy of the License at
7 //
8 // http://www.apache.org/licenses/LICENSE-2.0
9 //
10 // Unless required by applicable law or agreed to in writing, software
11 // distributed under the License is distributed on an "AS IS" BASIS,
12 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 // See the License for the specific language governing permissions and
14 // limitations under the License.
15 //
16
17 #include "update_engine/payload_generator/block_mapping.h"
18
19 #include <fcntl.h>
20 #include <sys/stat.h>
21 #include <sys/types.h>
22
23 #include <functional>
24 #include <string>
25 #include <vector>
26
27 #include "update_engine/common/utils.h"
28
29 using std::string;
30 using std::vector;
31
32 namespace {
33
HashValue(const brillo::Blob & blob)34 size_t HashValue(const brillo::Blob& blob) {
35 std::hash<string> hash_fn;
36 return hash_fn(string(blob.begin(), blob.end()));
37 }
38
39 } // namespace
40
41 namespace chromeos_update_engine {
42
AddBlock(const brillo::Blob & block_data)43 BlockMapping::BlockId BlockMapping::AddBlock(const brillo::Blob& block_data) {
44 return AddBlock(-1, 0, block_data);
45 }
46
AddDiskBlock(int fd,off_t byte_offset)47 BlockMapping::BlockId BlockMapping::AddDiskBlock(int fd, off_t byte_offset) {
48 brillo::Blob blob(block_size_);
49 ssize_t bytes_read = 0;
50 if (!utils::PReadAll(fd, blob.data(), block_size_, byte_offset, &bytes_read))
51 return -1;
52 if (static_cast<size_t>(bytes_read) != block_size_)
53 return -1;
54 return AddBlock(fd, byte_offset, blob);
55 }
56
AddManyDiskBlocks(int fd,off_t initial_byte_offset,size_t num_blocks,vector<BlockId> * block_ids)57 bool BlockMapping::AddManyDiskBlocks(int fd,
58 off_t initial_byte_offset,
59 size_t num_blocks,
60 vector<BlockId>* block_ids) {
61 bool ret = true;
62 block_ids->resize(num_blocks);
63 for (size_t block = 0; block < num_blocks; block++) {
64 (*block_ids)[block] = AddDiskBlock(
65 fd, initial_byte_offset + block * block_size_);
66 ret = ret && (*block_ids)[block] != -1;
67 }
68 return ret;
69 }
70
AddBlock(int fd,off_t byte_offset,const brillo::Blob & block_data)71 BlockMapping::BlockId BlockMapping::AddBlock(int fd,
72 off_t byte_offset,
73 const brillo::Blob& block_data) {
74 if (block_data.size() != block_size_)
75 return -1;
76 size_t h = HashValue(block_data);
77
78 // We either reuse a UniqueBlock or create a new one. If we need a new
79 // UniqueBlock it could also be part of a new or existing bucket (if there is
80 // a hash collision).
81 vector<UniqueBlock> *bucket = nullptr;
82
83 auto mapping_it = mapping_.find(h);
84 if (mapping_it == mapping_.end()) {
85 bucket = &mapping_[h];
86 } else {
87 for (UniqueBlock& existing_block : mapping_it->second) {
88 bool equals = false;
89 if (!existing_block.CompareData(block_data, &equals))
90 return -1;
91 if (equals)
92 return existing_block.block_id;
93 }
94 bucket = &mapping_it->second;
95 }
96
97 // No existing block was found at this point, so we create and fill in a new
98 // one.
99 bucket->emplace_back();
100 UniqueBlock *new_ublock = &bucket->back();
101
102 new_ublock->times_read = 1;
103 new_ublock->fd = fd;
104 new_ublock->byte_offset = byte_offset;
105 new_ublock->block_id = used_block_ids++;
106 // We need to cache blocks that are not referencing any disk location.
107 if (fd == -1)
108 new_ublock->block_data = block_data;
109
110 return new_ublock->block_id;
111 }
112
CompareData(const brillo::Blob & other_block,bool * equals)113 bool BlockMapping::UniqueBlock::CompareData(const brillo::Blob& other_block,
114 bool* equals) {
115 if (!block_data.empty()) {
116 *equals = block_data == other_block;
117 return true;
118 }
119 const size_t block_size = other_block.size();
120 brillo::Blob blob(block_size);
121 ssize_t bytes_read = 0;
122 if (!utils::PReadAll(fd, blob.data(), block_size, byte_offset, &bytes_read))
123 return false;
124 if (static_cast<size_t>(bytes_read) != block_size)
125 return false;
126 *equals = blob == other_block;
127
128 // We increase the number of times we had to read this block from disk and
129 // we cache this block based on that. This caching method is optimized for
130 // the common use case of having two partitions that share blocks between them
131 // but have few repeated blocks inside each partition, such as the block
132 // with all zeros or duplicated files.
133 times_read++;
134 if (times_read > 3)
135 block_data = std::move(blob);
136 return true;
137 }
138
MapPartitionBlocks(const string & old_part,const string & new_part,size_t old_size,size_t new_size,size_t block_size,vector<BlockMapping::BlockId> * old_block_ids,vector<BlockMapping::BlockId> * new_block_ids)139 bool MapPartitionBlocks(const string& old_part,
140 const string& new_part,
141 size_t old_size,
142 size_t new_size,
143 size_t block_size,
144 vector<BlockMapping::BlockId>* old_block_ids,
145 vector<BlockMapping::BlockId>* new_block_ids) {
146 BlockMapping mapping(block_size);
147 if (mapping.AddBlock(brillo::Blob(block_size, '\0')) != 0)
148 return false;
149 int old_fd = HANDLE_EINTR(open(old_part.c_str(), O_RDONLY));
150 int new_fd = HANDLE_EINTR(open(new_part.c_str(), O_RDONLY));
151 ScopedFdCloser old_fd_closer(&old_fd);
152 ScopedFdCloser new_fd_closer(&new_fd);
153
154 TEST_AND_RETURN_FALSE(mapping.AddManyDiskBlocks(
155 old_fd, 0, old_size / block_size, old_block_ids));
156 TEST_AND_RETURN_FALSE(mapping.AddManyDiskBlocks(
157 new_fd, 0, new_size / block_size, new_block_ids));
158 return true;
159 }
160
161 } // namespace chromeos_update_engine
162