linux-kernel - Re: [PATCH 1/5] v2 Split the memory

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Date:	Fri, 16 Jul 2010 11:45:31 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Nathan Fontenot <nfont@...tin.ibm.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linuxppc-dev@...abs.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 1/5] v2 Split the memory_block structure

On Fri, 2010-07-16 at 13:23 -0500, Nathan Fontenot wrote:
> >> -    if (mem->state != from_state_req) {
> >> -            ret = -EINVAL;
> >> -            goto out;
> >> +    list_for_each_entry(mbs, &mem->sections, next) {
> >> +            if (mbs->state != from_state_req)
> >> +                    continue;
> >> +
> >> +            ret = memory_block_action(mbs, to_state);
> >> +            if (ret)
> >> +                    break;
> >> +    }
> >> +
> >> +    if (ret) {
> >> +            list_for_each_entry(mbs, &mem->sections, next) {
> >> +                    if (mbs->state == from_state_req)
> >> +                            continue;
> >> +
> >> +                    if (memory_block_action(mbs, to_state))
> >> +                            printk(KERN_ERR "Could not re-enable memory "
> >> +                                   "section %lx\n", mbs->phys_index);
> >> +            }
> >>      }
> > 
> > Please just use a goto here.  It's nicer looking, and much more in line
> > with what's there already.
> 
> Not sure if I follow on where you want the goto.  If you mean after the
> if (memory_block_action())...  I purposely did not have a goto here.
> Since this is in the recovery path I wanted to make sure we tried to return
> every memory section to the original state. 

Looking at it a little closer, I see what you're doing now.

First of all, should memory_block_action() get a new name since it isn
not taking 'memory_block_section's?

The thing I would have liked to see is to have that error handling block
out of the way a bit.  But, the function is small, and there's not _too_
much code in there, so what you have is probably the best way to do it.

Minor nit: Please pull the memory_block_action() out of the if() and do
the:

> >> +            ret = memory_block_action(mbs, to_state);
> >> +            if (ret)
> >> +                    break;

thing like above.  It makes it much more obvious that the loop is
related to the top one.  I was thinking if it made sense to have a
helper function to go through and do that list walk, so you could do:

	ret = set_all_states(mem->sections, to_state);
	if (ret)
		set_all_states(mem->sections, old_state);

But I think you'd need to pass in a bit more information, so it probably
isn't worth doing that, either.

-- Dave

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