Re: vfs.root.mountfrom hammer?

[Michael Neumann <mneumann@xxxxxxxx>]

Matthew Dillon schrieb:
> :The following patch works perfectly:
> :
> :http://leaf.dragonflybsd.org/~mneumann/hammer-rootmount.diff
> :
> :It isn't possible to use more than one volume, but I think thats a minor 
> :problem for a hammer root mount.
> :
> :I'm also not quite sure where this line
> :
> :	mp->mnt_flag &= ~MNT_RDONLY; /* mount R/W */
> :..
> :best belongs to. Right now it has the effect that every hammer root mount
> :is read/write. I'm also not 100% sure if I did it right to create the root vnode 
> :(which is required in hammer_install_volume, otherwise nlookup seems to fail).
> :...
> :  Michael
> :
>
>     Normally the root mount is mounted read-only until after the
>     filesystem check.  But with HAMMER there's a problem doing that
>     in that it may cause crash recovery to fail (if the dirty buffers
>     created from the crash recovery don't fit in kernel memory).  A
>     read-write mount is probably needed so I think for now we have to
>     keep that code and force it to read-write.
>
>     There's a second problem in that I think you are still calling that
>     copyin() on the static volume buffer.
>   
I conditionalized that until I tried to reduce the patch as much as 
possible. I noticed that the copyin just works fine, so
I removed the condition :)

>     It looks like you should be able to get rid of that static buffer
>     and just make the volume array point directly to mnt_stat.f_mntfromname,
>   
I don't think that works because f_mntfromname contains e.g. "ad4s1d" 
and I think to lookup the device we
need a "/dev/ad4s1d". So I have to prepend a /dev/. That's why I used 
the static buffer. I don't like that static buffer
either.
>     then conditionalize the copyins.  HAMMER doesn't override the field
>     until after the volumes have been installed.
>
>     Your current patch is also issuing copyin()'s on the constructed kernel
>     buffer, which is not legal.  I'm not sure why it was still able to
>     complete the root mount :-)
>   
Yeah, it works perfectly. Strange ;-)

>     In anycase, would you like to make those fixes or should I?
>   

I can make them and commit it. Feel free to clean up my mistakes then ;-)

Regards,

 Michael