- 创建一个大小为4G的文件
$ dd if=/dev/zero of=mmc.bin bs=$((1024*1024)) count=$((4 * 1024))
- 使用fdisk/cfdisk分区
将分成5个区：2个主分区和3个逻辑分区：
$ fdisk mmc.bin
Command(m for help): o
# 创建第一个分区：
Command (m for help): n
Partition type:
p primary (0 primary, 0 extended, 4 free)
e extended
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-8388607, default 2048):
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-8388607, default 8388607): +100M
# 创建第二个分区：
Command (m for help): n
Partition type:
p primary (1 primary, 0 extended, 3 free)
e extended
Select (default p): p
Partition number (1-4, default 2):
Using default value 2
First sector (206848-8388607, default 206848):
Using default value 206848
Last sector, +sectors or +size{K,M,G} (206848-8388607, default 8388607): +400M
# 创建扩展分区：
Command (m for help): n
Partition type:
p primary (2 primary, 0 extended, 2 free)
e extended
Select (default p): e
Partition number (1-4, default 3): 3
First sector (1026048-8388607, default 1026048):
Using default value 1026048
Last sector, +sectors or +size{K,M,G} (1026048-8388607, default 8388607):
# 创建逻辑分区：
Command (m for help): n
Partition type:
p primary (2 primary, 1 extended, 1 free)
l logical (numbered from 5)
Select (default p): l
Adding logical partition 5
First sector (1028096-8388607, default 1028096):
Using default value 1028096
Last sector, +sectors or +size{K,M,G} (1028096-8388607, default 8388607): +400M
- 最终的分区表如下：
Command (m for help): p Disk mmc.bin: 4294 MB, 4294967296 bytes 255 heads, 63 sectors/track, 522 cylinders, total 8388608 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x9f922a9a Device Boot Start End Blocks Id System mmc.bin1 2048 206847 102400 83 Linux mmc.bin2 206848 1026047 409600 83 Linux mmc.bin3 1026048 8388607 3681280 5 Extended mmc.bin5 1028096 1847295 409600 83 Linux mmc.bin6 1849344 2668543 409600 83 Linux mmc.bin7 2670592 8388607 2859008 83 Linux
可以看到扇区的大小为512字节，每个分区的起始位置和大小。
- 对分区进行挂载和格式化
$ sudo losetup -o $((2048*512)) --sizelimit $((102400*512)) -f --show mmc.bin /dev/loop0 ＃可以看到是挂载到了/dev/loop0上了， 下面对它进行格式化操作： $ sudo mkfs.vfat -n boot /dev/loop0 mkfs.fat 3.0.26 (2014-03-07) mkfs.fat: warning - lowercase labels might not work properly with DOS or Windows Loop device does not match a floppy size, using default hd params # 卸载，其他的分区也采用同样的操作 $ sudo losetup -d /dev/loop0 $ sudo losetup -o $((206848*512)) --sizelimit $((409600*512)) -f --show mmc.bin /dev/loop0 sudo mkfs.ext4 -L root /dev/loop0 mke2fs 1.42.9 (4-Feb-2014) Discarding device blocks: done Filesystem label=root OS type: Linux Block size=1024 (log=0) Fragment size=1024 (log=0) Stride=0 blocks, Stripe width=0 blocks 51200 inodes, 204800 blocks 10240 blocks (5.00%) reserved for the super user First data block=1 Maximum filesystem blocks=67371008 25 block groups 8192 blocks per group, 8192 fragments per group 2048 inodes per group Superblock backups stored on blocks: 8193, 24577, 40961, 57345, 73729 Allocating group tables: done Writing inode tables: done Creating journal (4096 blocks): done Writing superblocks and filesystem accounting information: done $ sudo losetup -d /dev/loop0 $ sudo losetup -o $((1028096*512)) --sizelimit $((409600*512)) -f --show mmc.bin /dev/loop0 $ sudo mkfs.ext4 -L system /dev/loop0 mke2fs 1.42.9 (4-Feb-2014) Discarding device blocks: done Filesystem label=system OS type: Linux Block size=1024 (log=0) Fragment size=1024 (log=0) Stride=0 blocks, Stripe width=0 blocks 51200 inodes, 204800 blocks 10240 blocks (5.00%) reserved for the super user First data block=1 Maximum filesystem blocks=67371008 25 block groups 8192 blocks per group, 8192 fragments per group 2048 inodes per group Superblock backups stored on blocks: 8193, 24577, 40961, 57345, 73729 Allocating group tables: done Writing inode tables: done Creating journal (4096 blocks): done Writing superblocks and filesystem accounting information: done
- 验证：
使用brilloemulator-arm @ brillo-m8-release进行验证：
$ brilloemulator-arm -m 256 -- -sd mmc.bin # 可以看到在kernel log中有如下信息： mmc0: new SDHC card at address 4567 mmcblk0: mmc0:4567 QEMU! 4.00 GiB mmcblk0: p1 p2 p3 < p5 p6 p7 >
在去挂载/dev/block/mmcblk0p2的时候，会出现如下信息：
# mount /dev/block/mmcblk0p2 /mnt/ EXT3-fs (mmcblk0p2): error: couldn't mount because of unsupported optional features (240) EXT2-fs (mmcblk0p2): error: couldn't mount because of unsupported optional features (240) EXT4-fs (mmcblk0p2): Filesystem with huge files cannot be mounted RDWR without CONFIG_LBDAF
由于kernel没有CONFIG_LBDAF而mkfs.ext4默认是enable的, 分区挂载失败了。可以通过下面的方法解决：
$ sudo losetup -o $((206848*512)) --sizelimit $((409600*512)) -f --show mmc.bin /dev/loop0 $ sudo tune2fs -O ^huge_file /dev/loop0 tune2fs 1.42.9 (4-Feb-2014) Please run e2fsck on the filesystem. $ sudo fsck.ext4 /dev/loop0 e2fsck 1.42.9 (4-Feb-2014) root was not cleanly unmounted, check forced. Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information root: 11/51200 files (0.0% non-contiguous), 12109/204800 blocks $ sudo losetup -d /dev/loop0
再去做挂载的时候，CONFIG_LBDAF相关的信息已经没有了，分区可正常挂载：
# mount /dev/block/mmcblk0p2 /mnt/ EXT3-fs (mmcblk0p2): error: couldn't mount because of unsupported optional features (240) EXT2-fs (mmcblk0p2): error: couldn't mount because of unsupported optional features (240) EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. Opts: (null) # mount /dev/root on / type ext4 (ro,seclabel,relatime,data=ordered) tmpfs on /dev type tmpfs (rw,seclabel,nosuid,relatime,mode=755) devpts on /dev/pts type devpts (rw,seclabel,relatime,mode=600) proc on /proc type proc (rw,relatime,gid=3009,hidepid=2) sysfs on /sys type sysfs (rw,seclabel,relatime) selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime) none on /acct type cgroup (rw,relatime,cpuacct) none on /sys/fs/cgroup type tmpfs (rw,seclabel,relatime,mode=750,gid=1000) tmpfs on /mnt type tmpfs (rw,seclabel,relatime,mode=755,gid=1000) none on /dev/cpuctl type cgroup (rw,relatime,cpu) none on /dev/cpuset type cgroup (rw,relatime,cpuset,noprefix,release_agent=/sbin/cpuset_release_agent) tmpfs on /storage type tmpfs (rw,seclabel,relatime,mode=755,gid=1000) /dev/block/mmcblk0p2 on /mnt type ext4 (rw,seclabel,relatime,data=ordered)
相关的参考文档在这里：
https://kuttler.eu/post/filesystem-with-huge-files-cannot-be-mounted-read-write-without-config_lbdaf/