fstab mount 路径 - Less Or More

使用emmc启动android系统时，android会把系统分区mount到ramkdisk文件系统的指定目录 ,ramdisk里面的fstab.emmc文件会存放需要mount的分区的路径及mount点，如下： kimihuang@kimihuang-Z87X-D3H:root$ cat fstab.emmc

#Android fstab file.
#<src>  <mnt_point> <type><mnt_flags and options>   <fs_mgr_flags>
#The filesystem that contains the filesystem checker binary (typically /system) cannot
#pecify MF_CHECK, and must come before any filesystems that do specify MF_CHECK
/dev/block/platform/soc/d800a000.emmc/by-name/system/system ext4   ro,barrier=1   wait
/dev/block/platform/soc/d800a000.emmc/by-name/cache /cache  ext4   noatime,nosuid,nodev,barrier=1,data=orderedwait,check
/dev/block/platform/soc/d800a000.emmc/by-name/userdata  /data   ext4   noatime,nosuid,nodev,barrier=1,data=ordered,noauto_da_allocwait,check
/dev/block/platform/soc/d800a000.emmc/by-name/misc  /misc   emmc   defaults   defaults
/dev/block/platform/soc/d800a000.emmc/by-name/boot  /boot   emmc   defaults   defaults
/dev/block/platform/soc/d800a000.emmc/by-name/recovery  /recovery   emmc   defaults   defaults 不同android版本的系统可能新建不同的节点，比如：

android 5.1: /dev/block/platform/soc/by-name/system

android 7.0: /dev/block/platform/soc/d800a000.emmc/by-name/system

这些by-name的节点是在android的init进程里面创建的，具体的创建文件在devices.c 或者devices.cpp.

by-name就在下面这段代码里

static char **get_block_device_symlinks(struct uevent *uevent)
{
    const char *device;
    struct platform_node *pdev;
    char *slash;
    const char *type;
    char buf[256];
    char link_path[256];
    int link_num = 0;
    char *p;

    pdev = find_platform_device(uevent->path);
    if (pdev) {
        device = pdev->name;
        type = "platform";
    } else if (!find_pci_device_prefix(uevent->path, buf, sizeof(buf))) {
        device = buf;
        type = "pci";
    } else {
        return NULL;
    }

    char **links = (char**) malloc(sizeof(char *) * 4);
    if (!links)
        return NULL;
    memset(links, 0, sizeof(char *) * 4);

    INFO("found %s device %s\n", type, device);

    snprintf(link_path, sizeof(link_path), "/dev/block/%s/%s", type, device);

    if (uevent->partition_name) {
        p = strdup(uevent->partition_name);
        sanitize(p);
        if (strcmp(uevent->partition_name, p))
            NOTICE("Linking partition '%s' as '%s'\n", uevent->partition_name, p);
        if (asprintf(&links[link_num], "%s/**by-name**/%s", link_path, p) > 0)
            link_num++;
        else
            links[link_num] = NULL;
        free(p);
    }

    if (uevent->partition_num >= 0) {
        if (asprintf(&links[link_num], "%s/by-num/p%d", link_path, uevent->partition_num) > 0)
            link_num++;
        else
            links[link_num] = NULL;
    }

    slash = strrchr(uevent->path, '/');
    if (asprintf(&links[link_num], "%s/%s", link_path, slash + 1) > 0)
        link_num++;
    else
        links[link_num] = NULL;

    return links;
}

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