fs/Ext4.cpp

/*
 * Copyright (C) 2012 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 <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <string>
#include <vector>

#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>

#include <linux/kdev_t.h>

#include <android-base/logging.h>
#include <android-base/properties.h>
#include <android-base/stringprintf.h>
#include <cutils/properties.h>
#include <fscrypt/fscrypt.h>
#include <logwrap/logwrap.h>
#include <selinux/selinux.h>

#include "Ext4.h"
#include "FsCrypt.h"
#include "Utils.h"
#include "VoldUtil.h"

using android::base::StringPrintf;

namespace android {
namespace vold {
namespace ext4 {

static const char* kResizefsPath = "/system/bin/resize2fs";
static const char* kMkfsPath = "/system/bin/mke2fs";
static const char* kFsckPath = "/system/bin/e2fsck";

bool IsSupported() {
    return access(kMkfsPath, X_OK) == 0 && access(kFsckPath, X_OK) == 0 &&
           IsFilesystemSupported("ext4");
}

status_t Check(const std::string& source, const std::string& target) {
    // The following is shamelessly borrowed from fs_mgr.c, so it should be
    // kept in sync with any changes over there.

    const char* c_source = source.c_str();
    const char* c_target = target.c_str();

    int status;
    int ret;
    long tmpmnt_flags = MS_NOATIME | MS_NOEXEC | MS_NOSUID;
    char* tmpmnt_opts = (char*)"nomblk_io_submit,errors=remount-ro";

    /*
     * First try to mount and unmount the filesystem.  We do this because
     * the kernel is more efficient than e2fsck in running the journal and
     * processing orphaned inodes, and on at least one device with a
     * performance issue in the emmc firmware, it can take e2fsck 2.5 minutes
     * to do what the kernel does in about a second.
     *
     * After mounting and unmounting the filesystem, run e2fsck, and if an
     * error is recorded in the filesystem superblock, e2fsck will do a full
     * check.  Otherwise, it does nothing.  If the kernel cannot mount the
     * filesytsem due to an error, e2fsck is still run to do a full check
     * fix the filesystem.
     */
    ret = mount(c_source, c_target, "ext4", tmpmnt_flags, tmpmnt_opts);
    if (!ret) {
        int i;
        for (i = 0; i < 5; i++) {
            // Try to umount 5 times before continuing on.
            // Should we try rebooting if all attempts fail?
            int result = umount(c_target);
            if (result == 0) {
                break;
            }
            LOG(WARNING) << __func__ << "(): umount(" << c_target << ")=" << result << ": "
                         << strerror(errno);
            sleep(1);
        }
    }

    /*
     * Some system images do not have e2fsck for licensing reasons
     * (e.g. recent SDK system images). Detect these and skip the check.
     */
    if (access(kFsckPath, X_OK)) {
        LOG(DEBUG) << "Not running " << kFsckPath << " on " << c_source
                   << " (executable not in system image)";
    } else {
        LOG(DEBUG) << "Running " << kFsckPath << " on " << c_source;

        std::vector<std::string> cmd;
        cmd.push_back(kFsckPath);
        cmd.push_back("-y");
        cmd.push_back(c_source);

        // ext4 devices are currently always trusted
        return ForkExecvp(cmd, sFsckContext);
    }

    return 0;
}

status_t Mount(const std::string& source, const std::string& target, bool ro, bool remount,
               bool executable) {
    int rc;
    unsigned long flags;

    const char* c_source = source.c_str();
    const char* c_target = target.c_str();

    flags = MS_NOATIME | MS_NODEV | MS_NOSUID | MS_DIRSYNC;

    flags |= (executable ? 0 : MS_NOEXEC);
    flags |= (ro ? MS_RDONLY : 0);
    flags |= (remount ? MS_REMOUNT : 0);

    rc = mount(c_source, c_target, "ext4", flags, NULL);

    if (rc && errno == EROFS) {
        LOG(ERROR) << source << " appears to be a read only filesystem - retrying mount RO";
        flags |= MS_RDONLY;
        rc = mount(c_source, c_target, "ext4", flags, NULL);
    }

    return rc;
}

status_t Resize(const std::string& source, unsigned long numSectors) {
    std::vector<std::string> cmd;
    cmd.push_back(kResizefsPath);
    cmd.push_back("-f");
    cmd.push_back(source);
    cmd.push_back(StringPrintf("%lu", numSectors));

    return ForkExecvp(cmd);
}

status_t Format(const std::string& source, unsigned long numSectors, const std::string& target) {
    std::vector<std::string> cmd;
    cmd.push_back(kMkfsPath);

    cmd.push_back("-b");
    cmd.push_back("4096");

    cmd.push_back("-t");
    cmd.push_back("ext4");

    cmd.push_back("-M");
    cmd.push_back(target);

    std::string options("has_journal");
    if (android::base::GetBoolProperty("vold.has_quota", false)) {
        options += ",quota";
    }
    if (fscrypt_is_native()) {
        options += ",encrypt";
    }

    cmd.push_back("-O");
    cmd.push_back(options);

    cmd.push_back(source);

    if (numSectors) {
        cmd.push_back(StringPrintf("%lu", numSectors * (4096 / 512)));
    }

    return ForkExecvp(cmd);
}

}  // namespace ext4
}  // namespace vold
}  // namespace android