Userdata 分区 resize 功能

1. 挂载分区时添加resize功能

system/core/fs_mgr/fs_mgr.cpp

#include "cryptfs.h"
#define RESIZE2FS_BIN   "/system/bin/resize2fs"

static void resize_fs(const char *blk_device, char *fs_type, char *key_loc) {
    uint64_t device_sz;
    uint64_t device_ss;
    uint64_t device_sn;
    int status = 0;
    int ret = 0;

    android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(blk_device, O_RDONLY | O_CLOEXEC)));

    if (fd < 0) {
        PERROR << "Failed to open '" << blk_device << "'";
        return;
    }

    /* Cannot use BLKGETSIZE to get the number of sectors,
    * because need to do device_sz -= CRYPT_FOOTER_OFFSET
    */
    if ((ioctl(fd, BLKGETSIZE64, &device_sz)) == -1) {
        PERROR << "(BLKGETSIZE64) Can't get '" << blk_device << "' size";
        return;
    }

    if ((ioctl(fd, BLKSSZGET, &device_ss)) == -1) {
        PERROR << "(BLKSSZGET) Can't get '" << blk_device << "' size";
        return;
    }

    /* Format the partition using the calculated length */
    if (!strcmp(key_loc, KEY_IN_FOOTER))
        device_sz -= CRYPT_FOOTER_OFFSET;

    if (is_extfs(fs_type)) {
        if (access(RESIZE2FS_BIN, X_OK)) {
            LINFO << "Not running " << RESIZE2FS_BIN << " on " << blk_device
            << " (executable not in system image)";
        } else {
            std::string size_kb_str(android::base::StringPrintf("%" PRIu64 "K", device_sz / 1024));

            LINFO << "Running " << RESIZE2FS_BIN << " on " << blk_device;

            /* extX cmd */
            const char *resize2fs_argv[] = {
                RESIZE2FS_BIN,
                "-f",
                blk_device,
                size_kb_str.c_str()
            };

            ret = android_fork_execvp_ext(ARRAY_SIZE(resize2fs_argv),
                const_cast<char **>(resize2fs_argv),
                &status, true, LOG_KLOG,
                false, NULL, NULL, 0);

            if (ret < 0) {
                /* No need to check for error in fork, we can't really handle it now */
                LERROR << "Failed trying to run " << RESIZE2FS_BIN;
                return;
            }
        }
    }
}

static int prepare_fs_for_mount(const char* blk_device, const struct fstab_rec* rec) {
    ...
    if ((rec->fs_mgr_flags & MF_RESIZE) && !strcmp(blk_device, rec->blk_device)) {
        resize_fs(blk_device, rec->fs_type, rec->key_loc);
        check_fs(blk_device, rec->fs_type, rec->mount_point, &fs_stat);
    }
    ...
}

2. 添加fstab标签

system/core/fs_mgr/fs_mgr_fstab.cpp

static struct flag_list fs_mgr_flags[] = {
    ...
    {"resize", MF_RESIZE},
    ...
}

system/core/fs_mgr/fs_mgr_priv.h

#define MF_RESIZE         0x10000000

3. 添加相关selinux权限

system/sepolicy/private/file_contexts

/system/bin/resize2fs                           u:object_r:fsck_exec:s0

system/sepolicy/vendor/resize.te

type resize, domain;
type resize_exec, exec_type, file_type, vendor_file_type;
init_daemon_domain(resize)
allow resize resize_exec:file execute_no_trans;
allow resize devpts:chr_file { read write open getattr ioctl };
allow resize kmsg_device:chr_file { write open };
allow resize userdata_block_device:blk_file rw_file_perms;
allow resize block_device:dir search;
allow resize resize:capability sys_admin;
allow resize labeledfs:filesystem unmount;
allow resize property_socket:sock_file write;
allow resize init:unix_stream_socket connectto;
allow resize system_file:file execute_no_trans;

 4. fstab.qcom 更新如下：

/dev/block/bootdevice/by-name/userdata      /data        ext4    noatime,nosuid,nodev,barrier=1,noauto_da_alloc,discard  wait,check,encryptable=footer,quota,resize

// 添加一个 resize 属性。