On Tue, Apr 10, 2018 at 09:21:20AM -0500, Christopher Lameter wrote: > On Tue, 10 Apr 2018, Matthew Wilcox wrote: > > > __GFP_ZERO requests that the object be initialised to all-zeroes, > > while the purpose of a constructor is to initialise an object to a > > particular pattern. We cannot do both. Add a warning to catch any > > users who mistakenly pass a __GFP_ZERO flag when allocating a slab with > > a constructor. > > Can we move this check out of the critical paths and check for > a ctor and GFP_ZERO when calling the page allocator? F.e. in > allocate_slab()? Are you willing to have this kind of bug go uncaught for a while? In this specific case, __GFP_ZERO was only being passed on a few of the calls to kmem_cache_alloc. So we'd happily trash the constructed object any time we didn't allocate a page. I appreciate it's a tradeoff, and we don't want to clutter the critical path unnecessarily.
