109 lines
3.3 KiB
C++
109 lines
3.3 KiB
C++
/*
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* Copyright (C) 2017 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "FileDeviceUtils.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <linux/fiemap.h>
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#include <linux/fs.h>
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#include <mntent.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <android-base/file.h>
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#include <android-base/logging.h>
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#include <android-base/unique_fd.h>
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namespace {
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std::unique_ptr<struct fiemap> alloc_fiemap(uint32_t extent_count);
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}
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namespace android {
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namespace vold {
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// Given a file path, look for the corresponding block device in /proc/mount
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std::string BlockDeviceForPath(const std::string& path) {
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std::unique_ptr<FILE, int (*)(FILE*)> mnts(setmntent("/proc/mounts", "re"), endmntent);
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if (!mnts) {
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PLOG(ERROR) << "Unable to open /proc/mounts";
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return "";
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}
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std::string result;
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size_t best_length = 0;
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struct mntent* mnt; // getmntent returns a thread local, so it's safe.
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while ((mnt = getmntent(mnts.get())) != nullptr) {
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auto l = strlen(mnt->mnt_dir);
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if (l > best_length && path.size() > l && path[l] == '/' &&
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path.compare(0, l, mnt->mnt_dir) == 0) {
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result = mnt->mnt_fsname;
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best_length = l;
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}
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}
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if (result.empty()) {
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LOG(ERROR) << "Didn't find a mountpoint to match path " << path;
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return "";
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}
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return result;
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}
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std::unique_ptr<struct fiemap> PathFiemap(const std::string& path, uint32_t extent_count) {
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android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(path.c_str(), O_RDONLY | O_CLOEXEC, 0)));
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if (fd == -1) {
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if (errno == ENOENT) {
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PLOG(DEBUG) << "Unable to open " << path;
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} else {
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PLOG(ERROR) << "Unable to open " << path;
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}
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return nullptr;
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}
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auto fiemap = alloc_fiemap(extent_count);
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if (ioctl(fd.get(), FS_IOC_FIEMAP, fiemap.get()) != 0) {
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PLOG(ERROR) << "Unable to FIEMAP " << path;
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return nullptr;
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}
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auto mapped = fiemap->fm_mapped_extents;
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if (mapped < 1 || mapped > extent_count) {
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LOG(ERROR) << "Extent count not in bounds 1 <= " << mapped << " <= " << extent_count
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<< " in " << path;
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return nullptr;
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}
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return fiemap;
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}
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} // namespace vold
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} // namespace android
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namespace {
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std::unique_ptr<struct fiemap> alloc_fiemap(uint32_t extent_count) {
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size_t allocsize = offsetof(struct fiemap, fm_extents[extent_count]);
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std::unique_ptr<struct fiemap> res(new (::operator new(allocsize)) struct fiemap);
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memset(res.get(), 0, allocsize);
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res->fm_start = 0;
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res->fm_length = UINT64_MAX;
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res->fm_flags = 0;
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res->fm_extent_count = extent_count;
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res->fm_mapped_extents = 0;
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return res;
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}
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} // namespace
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