About Filesystem freeze/thaw in freebsd

[Mateusz Guzik]

On Wed, Feb 25, 2015 at 08:22:24PM -0700, andy zhang wrote:
> Thanks, I have already tried "UFSSUSPEND/UFSRESUME ioctls on the
> /dev/ufssuspend", and I found it actually not work. In Linux, if I send
> freeze ioctl, all write operations will be blocked unless I send thaw ioctl. 
>    While for "UFSSUSPEND/UFSRESUME ioctls", it does not work in that way.
> that is:
>    If I send UFSSUSPEND ioctl, I still can do write operations, like create
> files, etc.
> 
>    I am still looking that the code of ufssuspend, and if that really not
> works, i may implement that in my driver level. thanks for any advice.
> 

Can you show your code?

If you inspect ffs_susp_ioctl, you will see it expects fsid as an
argument.

Unless stuff got horribly broken, you can also see that proper usage
results in setting MNTK_SUSPEND flag. Then if you inspect code creating
files, writing etc. you will see it checks for that flag.

-- 
Mateusz Guzik <mjguzik gmail.com>