Re: [RFC 3/8] slub: Add isolate() and migrate() methods

[Matthew Wilcox <willy@infradead.org>]

On Fri, Dec 29, 2017 at 10:42:46PM -0800, Matthew Wilcox wrote:
> Is this the right approach?  I could imagine there being more ops in
> the future.  I suspect we should bite the bullet now and do:

I thought of a cute additional slab operation we could define, print().
We could do something like this ...

        struct page *page = virt_to_head_page(ptr);
        if (!PageSlab(page))
                return false;
        slab = page->slab_cache;
        if (!(slab->flags & SLAB_FLAGS_OPS) || !slab->ops->print)
                return false;
        slab->ops->print(ptr);
        return true;

and get nice debugging output like we have for VM_BUG_ON_PAGE, only
for any type that's implemented a slab operations vec.  Of course, this
won't replace VM_BUG_ON_PAGE because struct pages aren't slab-allocated
(but could we pretend they are?)

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