[RFC] [PATCH] VM & VFS changes

[Don Lewis]

On  1 Jun, Andre Guibert de Bruet wrote:
> 
> On Wed, 1 Jun 2005, Alexander Leidinger wrote:
> 
>> Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
>>
>>> Maybe the simplest solution is also the best:  keep track of the
>>> dependencies and do the cleanup leaf->root on the resulting tree.

It might not even be necessary to use a tree.  It might be possible to
just use a list like vfs_unmountall().

>> How many userland processes have to be running and consuming memory which
>> isn't available as physical RAM at this point in the shutdown sequence?
>>
>> Wouldn't a loop like the following be enough?
>> while swap
>>     umount unbusy-FS
>>     swap-off swap
>>
>> This assumes that swap-off doesn't turns off the swap if it isn't able to put
>> everything back into other swap or physical RAM areas.
> 
> I would think that one would want to disable swapping before the unmount 
> of filesystems for the very fact you could have vnode-backed swapspace in 
> use.


This order doesn't work either because you might only have 128 MB of
RAM, but 1 GB of data in /tmp, which is stored on a swap-backed memory
disk.  In this case you'll have to unmount /tmp and toss the md contents
before you disable swap.