【问题标题】：Mounting ext4 mounts as ext2 in linux 4.4.0 [RHEL]在 linux 4.4.0 [RHEL] 中将 ext4 挂载为 ext2
【发布时间】：2016-08-11 01:58:05
【问题描述】：

我执行的命令

mkfs .ext4 -F /dev/xxx0

mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
524288 inodes, 2097152 blocks
104857 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2147483648
64 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632

Allocating group tables: done
Writing inode tables: done
Writing superblocks and filesystem accounting information: done

mount -o dax /dev/xxx0 /mnt/ext4-xxx0

挂载输出

/dev/xxx0 on /mnt/ext4-xxx0 type ext2 (rw,relatime,seclabel,block_validity,barrier,dax,user_xattr,acl)

dmesg 输出

[ 2917.044866] EXT4-fs (xxx0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk
[ 2917.044869] EXT4-fs (xxx0): mounting ext2 file system using the ext4 subsystem
...
...
[ 2917.045459] EXT4-fs (xxx0): mounted filesystem without journal. Opts: dax

随后导致 fallocate 失败，因为 ext2 不支持 fos ext2。

任何建议/解决方案将不胜感激。

【问题讨论】：

默认类型是ext2，可能是搞糊涂了。使用替代语法可能值得：mke2fs -t ext4 /dev/xxx0（我个人建议 not 使用 -F - 卸载它。

标签： filesystems mount ext4 ext2

【解决方案1】：

安装时提供类型为 ext4。否则它将采用/etc/fstab 中提到的默认类型（或）类型。

# mount -o dax -t ext4 /dev/xxx0 /mnt/ext4-xxx0

【讨论】：