Re: [PATCH] x86: split e820 reserved entries record to late v4 - fix

[Linus Torvalds <torvalds@linux-foundation.org>]

On Fri, 29 Aug 2008, Yinghai Lu wrote:
>
> try to insert_resource second time, by expand the resource...

I would hold off on this unless it's shown to actually be needed. And _if_ 
it is needed, I would just make a new function for doing this all: 
"insert_resource_expand_to_fit()"

That said, I think the insert_resource()/__insert_resource() change is 
pretty ok. However, it doesn't follow the rules, and is racy. The rules 
for resources are:

 - the "internal" version (with the "__" prepended) is static to 
   resource.c, because it must not be called from outside, which is in 
   turn because:

 - it must be called with the lock taken by the caller, because otherwise 
   returning a "struct resource *" is racy - the resource is not protected
   by anything!

So the "insert_resource_expand_to_fit()" thing would look something like 
this:

	void insert_resource_expand_to_fit(struct resource *root, struct resource *new)
	{
		write_lock(&resource_lock);
		while (new->start && new->parent) {
			struct resource *conflict;

			conflict = __insert_resource(root, new);
			if (!conflict)
				break;
			if (conflict->start < new->start)
				new->start = conflict->start;
			if (conflict->end > new->end)
				new->end = conflict->end;
		}
		write_unlock(&resource_lock);
	}

but the above is obviously _totally_ untested.

		Linus