Messages in this thread | | | Date | Fri, 2 Jun 2017 09:28:56 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH 1/9] mm: introduce kv[mz]alloc helpers |
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On Fri 02-06-17 07:17:22, Sasha Levin wrote: > On Mon, Mar 06, 2017 at 11:30:24AM +0100, Michal Hocko wrote: > > +void *kvmalloc_node(size_t size, gfp_t flags, int node) > > +{ > > + gfp_t kmalloc_flags = flags; > > + void *ret; > > + > > + /* > > + * vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables) > > + * so the given set of flags has to be compatible. > > + */ > > + WARN_ON_ONCE((flags & GFP_KERNEL) != GFP_KERNEL); > > Hm, there are quite a few locations in the kernel that do something like: > > __vmalloc(len, GFP_NOFS, PAGE_KERNEL); > > According to your patch, vmalloc can't really do GFP_NOFS, right?
Yes. It is quite likely that they will just work because the hardcoded GFP_KERNEL inside the vmalloc path is in unlikely paths (page table allocations for example) but yes they are broken. I didn't convert some places which opencode the kvmalloc with GFP_NOFS because I strongly _believe_ that the GFP_NOFS should be revisited, checked whether it is needed, documented if so and then memalloc_nofs__{save,restore} be used for the scope which is reclaim recursion unsafe. This would turn all those vmalloc users to the default GFP_KERNEL and still do the right thing. -- Michal Hocko SUSE Labs
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