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Move GetMountedEntryForUserdata to fs_mgr.h 

Logic of unwinding dm-device stack to figure out what entry was used to
mount userdata turned out to be a little bit more involved, and it
shouldn't be part of libfstab

This CL just moves code around and cleans API a little bit, actual fix
will be in the follow-up CL.

Test: atest CtsFsMgrTest
Test: atest CtsUserspaceRebootHostSideTestCases
Bug: 148612148
Change-Id: If0f8a765dba63adb0e6a711eb81fffdcabea3480
This commit is contained in:
Nikita Ioffe 2020-03-06 15:55:20 +00:00
parent 70b6a95619
commit 8f50cfc28d
5 changed files with 88 additions and 92 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

85
fs_mgr/fs_mgr.cpp
View File

@ -96,6 +96,7 @@
using android::base::Basename;
using android::base::GetBoolProperty;
using android::base::Readlink;
using android::base::Realpath;
using android::base::SetProperty;
using android::base::StartsWith;
@ -1588,6 +1589,79 @@ static bool fs_mgr_unmount_all_data_mounts(const std::string& block_device) {
}
}
static std::string ResolveBlockDevice(const std::string& block_device) {
if (!StartsWith(block_device, "/dev/block/")) {
LWARNING << block_device << " is not a block device";
return block_device;
}
std::string name = block_device.substr(5);
if (!StartsWith(name, "block/dm-")) {
// Not a dm-device, but might be a symlink. Optimistically try to readlink.
std::string result;
if (Readlink(block_device, &result)) {
return result;
} else if (errno == EINVAL) {
// After all, it wasn't a symlink.
return block_device;
} else {
LERROR << "Failed to readlink " << block_device;
return "";
}
}
// It's a dm-device, let's find what's inside!
std::string sys_dir = "/sys/" + name;
while (true) {
std::string slaves_dir = sys_dir + "/slaves";
std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(slaves_dir.c_str()), closedir);
if (!dir) {
LERROR << "Failed to open " << slaves_dir;
return "";
}
std::string sub_device_name = "";
for (auto entry = readdir(dir.get()); entry; entry = readdir(dir.get())) {
if (entry->d_type != DT_LNK) continue;
if (!sub_device_name.empty()) {
LERROR << "Too many slaves in " << slaves_dir;
return "";
}
sub_device_name = entry->d_name;
}
if (sub_device_name.empty()) {
LERROR << "No slaves in " << slaves_dir;
return "";
}
if (!StartsWith(sub_device_name, "dm-")) {
// Not a dm-device! We can stop now.
return "/dev/block/" + sub_device_name;
}
// Still a dm-device, keep digging.
sys_dir = "/sys/block/" + sub_device_name;
}
}
FstabEntry* fs_mgr_get_mounted_entry_for_userdata(Fstab* fstab, const FstabEntry& mounted_entry) {
std::string resolved_block_device = ResolveBlockDevice(mounted_entry.blk_device);
if (resolved_block_device.empty()) {
return nullptr;
}
LINFO << "/data is mounted on " << resolved_block_device;
for (auto& entry : *fstab) {
if (entry.mount_point != "/data") {
continue;
}
std::string block_device;
if (!Readlink(entry.blk_device, &block_device)) {
LWARNING << "Failed to readlink " << entry.blk_device;
block_device = entry.blk_device;
}
if (block_device == resolved_block_device) {
return &entry;
}
}
LERROR << "Didn't find entry that was used to mount /data";
return nullptr;
}
// TODO(b/143970043): return different error codes based on which step failed.
int fs_mgr_remount_userdata_into_checkpointing(Fstab* fstab) {
Fstab proc_mounts;
@ -1596,16 +1670,13 @@ int fs_mgr_remount_userdata_into_checkpointing(Fstab* fstab) {
return -1;
}
std::string block_device;
if (auto entry = GetEntryForMountPoint(&proc_mounts, "/data"); entry != nullptr) {
// Note: we don't care about a userdata wrapper here, since it's safe
// to remount on top of the bow device instead, there will be no
// conflicts.
block_device = entry->blk_device;
} else {
auto mounted_entry = GetEntryForMountPoint(&proc_mounts, "/data");
if (mounted_entry == nullptr) {
LERROR << "/data is not mounted";
return -1;
}
auto fstab_entry = GetMountedEntryForUserdata(fstab);
block_device = mounted_entry->blk_device;
auto fstab_entry = fs_mgr_get_mounted_entry_for_userdata(fstab, *mounted_entry);
if (fstab_entry == nullptr) {
LERROR << "Can't find /data in fstab";
return -1;

83
fs_mgr/fs_mgr_fstab.cpp
View File

@ -814,89 +814,6 @@ std::vector<FstabEntry*> GetEntriesForMountPoint(Fstab* fstab, const std::string
return entries;
}
static std::string ResolveBlockDevice(const std::string& block_device) {
if (!StartsWith(block_device, "/dev/block/")) {
LWARNING << block_device << " is not a block device";
return block_device;
}
std::string name = block_device.substr(5);
if (!StartsWith(name, "block/dm-")) {
// Not a dm-device, but might be a symlink. Optimistically try to readlink.
std::string result;
if (Readlink(block_device, &result)) {
return result;
} else if (errno == EINVAL) {
// After all, it wasn't a symlink.
return block_device;
} else {
LERROR << "Failed to readlink " << block_device;
return "";
}
}
// It's a dm-device, let's find what's inside!
std::string sys_dir = "/sys/" + name;
while (true) {
std::string slaves_dir = sys_dir + "/slaves";
std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(slaves_dir.c_str()), closedir);
if (!dir) {
LERROR << "Failed to open " << slaves_dir;
return "";
}
std::string sub_device_name = "";
for (auto entry = readdir(dir.get()); entry; entry = readdir(dir.get())) {
if (entry->d_type != DT_LNK) continue;
if (!sub_device_name.empty()) {
LERROR << "Too many slaves in " << slaves_dir;
return "";
}
sub_device_name = entry->d_name;
}
if (sub_device_name.empty()) {
LERROR << "No slaves in " << slaves_dir;
return "";
}
if (!StartsWith(sub_device_name, "dm-")) {
// Not a dm-device! We can stop now.
return "/dev/block/" + sub_device_name;
}
// Still a dm-device, keep digging.
sys_dir = "/sys/block/" + sub_device_name;
}
}
FstabEntry* GetMountedEntryForUserdata(Fstab* fstab) {
Fstab mounts;
if (!ReadFstabFromFile("/proc/mounts", &mounts)) {
LERROR << "Failed to read /proc/mounts";
return nullptr;
}
auto mounted_entry = GetEntryForMountPoint(&mounts, "/data");
if (mounted_entry == nullptr) {
LWARNING << "/data is not mounted";
return nullptr;
}
std::string resolved_block_device = ResolveBlockDevice(mounted_entry->blk_device);
if (resolved_block_device.empty()) {
return nullptr;
}
LINFO << "/data is mounted on " << resolved_block_device;
for (auto& entry : *fstab) {
if (entry.mount_point != "/data") {
continue;
}
std::string block_device;
if (!Readlink(entry.blk_device, &block_device)) {
LWARNING << "Failed to readlink " << entry.blk_device;
block_device = entry.blk_device;
}
if (block_device == resolved_block_device) {
return &entry;
}
}
LERROR << "Didn't find entry that was used to mount /data";
return nullptr;
}
std::set<std::string> GetBootDevices() {
// First check the kernel commandline, then try the device tree otherwise
std::string dt_file_name = get_android_dt_dir() + "/boot_devices";

4
fs_mgr/include/fs_mgr.h
View File

@ -107,6 +107,10 @@ enum FsMgrUmountStatus : int {
// it destroys verity devices from device mapper after the device is unmounted.
int fs_mgr_umount_all(android::fs_mgr::Fstab* fstab);
// Finds a entry in |fstab| that was used to mount a /data |mounted_entry| from
// /proc/mounts.
android::fs_mgr::FstabEntry* fs_mgr_get_mounted_entry_for_userdata(
android::fs_mgr::Fstab* fstab, const android::fs_mgr::FstabEntry& mounted_entry);
int fs_mgr_remount_userdata_into_checkpointing(android::fs_mgr::Fstab* fstab);
// Finds the dm_bow device on which this block device is stacked, or returns

1
fs_mgr/include_fstab/fstab/fstab.h
View File

@ -102,7 +102,6 @@ bool SkipMountingPartitions(Fstab* fstab);
FstabEntry* GetEntryForMountPoint(Fstab* fstab, const std::string& path);
// The Fstab can contain multiple entries for the same mount point with different configurations.
std::vector<FstabEntry*> GetEntriesForMountPoint(Fstab* fstab, const std::string& path);
FstabEntry* GetMountedEntryForUserdata(Fstab* fstab);
// This method builds DSU fstab entries and transfer the fstab.
//

7
fs_mgr/tests/fs_mgr_test.cpp
View File

@ -27,6 +27,7 @@
#include <android-base/file.h>
#include <android-base/properties.h>
#include <android-base/strings.h>
#include <fs_mgr.h>
#include <fstab/fstab.h>
#include <gtest/gtest.h>
@ -1001,6 +1002,10 @@ TEST(fs_mgr, UserdataMountedFromDefaultFstab) {
}
Fstab fstab;
ASSERT_TRUE(ReadDefaultFstab(&fstab)) << "Failed to read default fstab";
ASSERT_NE(nullptr, GetMountedEntryForUserdata(&fstab))
Fstab proc_mounts;
ASSERT_TRUE(ReadFstabFromFile("/proc/mounts", &proc_mounts)) << "Failed to read /proc/mounts";
auto mounted_entry = GetEntryForMountPoint(&proc_mounts, "/data");
ASSERT_NE(mounted_entry, nullptr) << "/data is not mounted";
ASSERT_NE(nullptr, fs_mgr_get_mounted_entry_for_userdata(&fstab, *mounted_entry))
<< "/data wasn't mounted from default fstab";
}