1 /*
2 * Copyright (C) 2017 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 "FileDeviceUtils.h"
18
19 #include <stdio.h>
20 #include <stdlib.h>
21 #include <errno.h>
22 #include <sys/types.h>
23 #include <sys/stat.h>
24 #include <fcntl.h>
25 #include <linux/fs.h>
26 #include <linux/fiemap.h>
27 #include <mntent.h>
28
29 #include <android-base/file.h>
30 #include <android-base/logging.h>
31 #include <android-base/unique_fd.h>
32
33 namespace {
34
35 std::unique_ptr<struct fiemap> alloc_fiemap(uint32_t extent_count);
36
37 }
38
39 namespace android {
40 namespace vold {
41
42 // Given a file path, look for the corresponding block device in /proc/mount
BlockDeviceForPath(const std::string & path)43 std::string BlockDeviceForPath(const std::string &path)
44 {
45 std::unique_ptr<FILE, int(*)(FILE*)> mnts(setmntent("/proc/mounts", "re"), endmntent);
46 if (!mnts) {
47 PLOG(ERROR) << "Unable to open /proc/mounts";
48 return "";
49 }
50 std::string result;
51 size_t best_length = 0;
52 struct mntent *mnt; // getmntent returns a thread local, so it's safe.
53 while ((mnt = getmntent(mnts.get())) != nullptr) {
54 auto l = strlen(mnt->mnt_dir);
55 if (l > best_length &&
56 path.size() > l &&
57 path[l] == '/' &&
58 path.compare(0, l, mnt->mnt_dir) == 0) {
59 result = mnt->mnt_fsname;
60 best_length = l;
61 }
62 }
63 if (result.empty()) {
64 LOG(ERROR) <<"Didn't find a mountpoint to match path " << path;
65 return "";
66 }
67 LOG(DEBUG) << "For path " << path << " block device is " << result;
68 return result;
69 }
70
PathFiemap(const std::string & path,uint32_t extent_count)71 std::unique_ptr<struct fiemap> PathFiemap(const std::string &path, uint32_t extent_count)
72 {
73 android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(
74 path.c_str(), O_RDONLY | O_CLOEXEC, 0)));
75 if (fd == -1) {
76 if (errno == ENOENT) {
77 PLOG(DEBUG) << "Unable to open " << path;
78 } else {
79 PLOG(ERROR) << "Unable to open " << path;
80 }
81 return nullptr;
82 }
83 auto fiemap = alloc_fiemap(extent_count);
84 if (ioctl(fd.get(), FS_IOC_FIEMAP, fiemap.get()) != 0) {
85 PLOG(ERROR) << "Unable to FIEMAP " << path;
86 return nullptr;
87 }
88 auto mapped = fiemap->fm_mapped_extents;
89 if (mapped < 1 || mapped > extent_count) {
90 LOG(ERROR) << "Extent count not in bounds 1 <= " << mapped << " <= " << extent_count
91 << " in " << path;
92 return nullptr;
93 }
94 return fiemap;
95 }
96
97 } // namespace vold
98 } // namespace android
99
100 namespace {
101
alloc_fiemap(uint32_t extent_count)102 std::unique_ptr<struct fiemap> alloc_fiemap(uint32_t extent_count)
103 {
104 size_t allocsize = offsetof(struct fiemap, fm_extents[extent_count]);
105 std::unique_ptr<struct fiemap> res(new (::operator new (allocsize)) struct fiemap);
106 memset(res.get(), 0, allocsize);
107 res->fm_start = 0;
108 res->fm_length = UINT64_MAX;
109 res->fm_flags = 0;
110 res->fm_extent_count = extent_count;
111 res->fm_mapped_extents = 0;
112 return res;
113 }
114
115 }
116