Messages in this thread | | | Date | Tue, 11 Apr 2017 13:03:01 -0500 (CDT) | From | Christoph Lameter <> | Subject | Re: [PATCH] mm: Add additional consistency check |
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On Tue, 11 Apr 2017, Michal Hocko wrote:
> > > > There is a flag SLAB_DEBUG_OBJECTS that is available for this check. > > Which is way too late, at least for the kfree path. page->slab_cache > on anything else than PageSlab is just a garbage. And my understanding > of the patch objective is to stop those from happening.
We are looking here at SLAB. SLUB code can legitimately have a compound page there because large allocations fallback to the page allocator.
Garbage would be attempting to free a page that has !PageSLAB set but also is no compound page. That condition is already checked in kfree() with a BUG_ON() and that BUG_ON has been there for a long time. Certainly we can make SLAB consistent if there is no check there already. Slab just attempts a free on that object which will fail too.
So we are already handling that condition. Why change things? Add a BUG_ON if you want to make SLAB consistent.
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