update for shared path checker context

Christophe,

I made the following changes.

modified the path checker interface so that each path
checker
type could specify the size of their shared path context
area

discovery.c:get_state() now returns without setting path
state
if the path's mpp pointer is not set (IFF PP_DAEMON) else it
becomes tricky to update the path checker's ptr to the
shared
context area after the path checker has been already
initialized.

structs.c:free_multipath() now frees shared context area if
it was
allocated.


 <<multipath-tools.diff>> 

Ed
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Le vendredi 17 novembre 2006 à 11:21 -0500, Edward Goggin a
écrit :
> Christophe,
> 
> I made the following changes.
> 
> modified the path checker interface so that each path
checker
> type could specify the size of their shared path
context area
> 
> discovery.c:get_state() now returns without setting
path state
> if the path's mpp pointer is not set (IFF PP_DAEMON)
else it
> becomes tricky to update the path checker's ptr to the
shared
> context area after the path checker has been already
initialized.
> 
> structs.c:free_multipath() now frees shared context
area if it was
> allocated.
> 
Wouldn't a void** mpcontext in struct multipath instead of a
void* keep
us from resorting to those ->size_scxt fonctions ?

- mpcontext allocation is deported insode the checker, so
only the
checker needing the facility have to care.
- mpcontext freeing in free_multipath is ok, I guess

Something like the attached patch, for example.
(extreme hack to readsector0 to showcase the facility)

Regards,
cvaroqui

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On Monday, November 20, 2006 7:03 PM, Christophe Varoqui
wrote:
> To: goggin, edward
> Cc: dm-develredhat.com
> Subject: [dm-devel] Re: update for shared path checker
context
> 
> Le vendredi 17 novembre 2006 à 11:21 -0500, Edward
Goggin a écrit :
> > Christophe,
> > 
> > I made the following changes.
> > 
> > modified the path checker interface so that each
path checker
> > type could specify the size of their shared path
context area
> > 
> > discovery.c:get_state() now returns without
setting path state
> > if the path's mpp pointer is not set (IFF
PP_DAEMON) else it
> > becomes tricky to update the path checker's ptr to
the shared
> > context area after the path checker has been
already initialized.
> > 
> > structs.c:free_multipath() now frees shared
context area if it was
> > allocated.
> > 
> Wouldn't a void** mpcontext in struct multipath instead
of a 
> void* keep
> us from resorting to those ->size_scxt fonctions ?

Yes, much better idea!

> 
> - mpcontext allocation is deported insode the checker,
so only the
> checker needing the facility have to care.

OK.

> - mpcontext freeing in free_multipath is ok, I guess

Given your approach, should free mpcontext in the path
checker
free functions ...

> 
> Something like the attached patch, for example.
> (extreme hack to readsector0 to showcase the facility)

I'll try this out with the clariion inactive snapshot stuff
and let you know.

> 
> Regards,
> cvaroqui
> 
> 

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On Monday, November 20, 2006 7:03 PM, Christophe Varoui
wrote
> Something like the attached patch, for example.
> (extreme hack to readsector0 to showcase the facility)

Looks good, except for ...

.. just a simple change to multipath/main.c:update_paths()
to set the mpp field of each path so that the immediately
following call to pathinfo() will call get_state() on a
path with its  mpp field set.  This enables "multipath
-ll"
to utilize the shared context field of the multipath struct.
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