blob: 14b217ca897e21a97b9ffe77b4ab701cc589c45d [file] [log] [blame]
/*
* Copyright (C) 2021 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/stringprintf.h>
#include <android-base/strings.h>
#include <dirent.h>
#include <libdm/dm.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <sys/types.h>
#include "blockdev.h"
using android::base::Basename;
using android::base::ErrnoError;
using android::base::Error;
using android::base::Result;
using android::base::ResultError;
using android::base::StartsWith;
using android::base::StringPrintf;
using android::base::unique_fd;
using android::dm::DeviceMapper;
// Return the parent device of a partition. Converts e.g. "sda26" into "sda".
static std::string PartitionParent(const std::string& blockdev) {
if (blockdev.find('/') != std::string::npos) {
LOG(ERROR) << __func__ << ": invalid argument " << blockdev;
return blockdev;
}
auto dir = std::unique_ptr<DIR, decltype(&closedir)>{opendir("/sys/class/block"), closedir};
if (!dir) {
return blockdev;
}
for (struct dirent* ent = readdir(dir.get()); ent; ent = readdir(dir.get())) {
if (ent->d_name[0] == '.') {
continue;
}
std::string path = StringPrintf("/sys/class/block/%s/%s", ent->d_name, blockdev.c_str());
struct stat statbuf;
if (stat(path.c_str(), &statbuf) >= 0) {
return ent->d_name;
}
}
return blockdev;
}
// Convert a major:minor pair into a block device name.
static std::string BlockdevName(dev_t dev) {
auto dir = std::unique_ptr<DIR, decltype(&closedir)>{opendir("/dev/block"), closedir};
if (!dir) {
return {};
}
for (struct dirent* ent = readdir(dir.get()); ent; ent = readdir(dir.get())) {
if (ent->d_name[0] == '.') {
continue;
}
const std::string path = std::string("/dev/block/") + ent->d_name;
struct stat statbuf;
if (stat(path.c_str(), &statbuf) >= 0 && dev == statbuf.st_rdev) {
return ent->d_name;
}
}
return {};
}
// Trim whitespace from the end of a string.
static void rtrim(std::string& s) {
s.erase(s.find_last_not_of('\n') + 1, s.length());
}
// For file `file_path`, retrieve the block device backing the filesystem on
// which the file exists and return the queue depth of the block device.
static Result<uint32_t> BlockDeviceQueueDepth(const std::string& file_path) {
struct stat statbuf;
int res = stat(file_path.c_str(), &statbuf);
if (res < 0) {
return ErrnoError() << "stat(" << file_path << ")";
}
std::string blockdev = "/dev/block/" + BlockdevName(statbuf.st_dev);
LOG(DEBUG) << __func__ << ": " << file_path << " -> " << blockdev;
if (blockdev.empty()) {
const std::string err_msg =
StringPrintf("Failed to convert %u:%u (path %s)", major(statbuf.st_dev),
minor(statbuf.st_dev), file_path.c_str());
return ResultError(err_msg, 0);
}
auto& dm = DeviceMapper::Instance();
for (;;) {
std::optional<std::string> child = dm.GetParentBlockDeviceByPath(blockdev);
if (!child) {
break;
}
LOG(DEBUG) << __func__ << ": " << blockdev << " -> " << *child;
blockdev = *child;
}
std::optional<std::string> maybe_blockdev = android::dm::ExtractBlockDeviceName(blockdev);
if (!maybe_blockdev) {
return ResultError("Failed to remove /dev/block/ prefix from " + blockdev, 0);
}
blockdev = PartitionParent(*maybe_blockdev);
LOG(DEBUG) << __func__ << ": "
<< "Partition parent: " << blockdev;
const std::string nr_tags_path =
StringPrintf("/sys/class/block/%s/mq/0/nr_tags", blockdev.c_str());
std::string nr_tags;
if (!android::base::ReadFileToString(nr_tags_path, &nr_tags)) {
return ResultError("Failed to read " + nr_tags_path, 0);
}
rtrim(nr_tags);
LOG(DEBUG) << __func__ << ": " << file_path << " is backed by /dev/" << blockdev
<< " and that block device supports queue depth " << nr_tags;
return strtol(nr_tags.c_str(), NULL, 0);
}
// Set 'nr_requests' of `loop_device_path` to the queue depth of the block
// device backing `file_path`.
Result<void> ConfigureQueueDepth(const std::string& loop_device_path,
const std::string& file_path) {
if (!StartsWith(loop_device_path, "/dev/")) {
return Error() << "Invalid argument " << loop_device_path;
}
const std::string loop_device_name = Basename(loop_device_path);
const Result<uint32_t> qd = BlockDeviceQueueDepth(file_path);
if (!qd.ok()) {
LOG(DEBUG) << __func__ << ": "
<< "BlockDeviceQueueDepth() returned " << qd.error();
return ResultError(qd.error());
}
const std::string nr_requests = StringPrintf("%u", *qd);
const std::string sysfs_path =
StringPrintf("/sys/class/block/%s/queue/nr_requests", loop_device_name.c_str());
unique_fd sysfs_fd(open(sysfs_path.c_str(), O_RDWR | O_CLOEXEC));
if (sysfs_fd == -1) {
return ErrnoError() << "Failed to open " << sysfs_path;
}
const int res = write(sysfs_fd.get(), nr_requests.data(), nr_requests.length());
if (res < 0) {
return ErrnoError() << "Failed to write to " << sysfs_path;
}
return {};
}