Date: Fri, 29 Apr 2016 16:18:10 +0900 From: Joonsoo Kim <iamjoonsoo.kim@....com> To: Christoph Lameter <cl@...ux.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Thomas Garnier <thgarnie@...gle.com>, Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>, Kees Cook <keescook@...omium.org>, gthelen@...gle.com, labbott@...oraproject.org, kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [PATCH v4] mm: SLAB freelist randomization On Wed, Apr 27, 2016 at 10:39:29AM -0500, Christoph Lameter wrote: > On Tue, 26 Apr 2016, Andrew Morton wrote: > > > : CONFIG_FREELIST_RANDOM bugs me a bit - "freelist" is so vague. > > : CONFIG_SLAB_FREELIST_RANDOM would be better. I mean, what Kconfig > > : identifier could be used for implementing randomisation in > > : slub/slob/etc once CONFIG_FREELIST_RANDOM is used up? > > > > but this pearl appeared to pass unnoticed. > > Ok. lets add SLAB here and then use this option for the other allocators > as well. > > > > + /* If it fails, we will just use the global lists */ > > > + cachep->random_seq = kcalloc(count, sizeof(freelist_idx_t), GFP_KERNEL); > > > + if (!cachep->random_seq) > > > + return -ENOMEM; > > > > OK, no BUG. If this happens, kmem_cache_init_late() will go BUG > > instead ;) > > > > Questions for slab maintainers: > > > > What's going on with the gfp_flags in there? kmem_cache_init_late() > > passes GFP_NOWAIT into enable_cpucache(). > > > > a) why the heck does it do that? It's __init code! > > enable_cpucache() was called when a slab cache was reconfigured by writing to /proc/slabinfo. > That was changed awhile back when the memcg changes were made ot slab. So > now its ok to be made init code. > > > Finally, all callers of enable_cpucache() (and hence of > > cache_random_seq_create()) are __init, so we're unnecessarily bloating > > up vmlinux. Could someone please take a look at this as a separate > > thing? > > Hmmm. Well if that is the case then lots of stuff could be straightened > out. Joonsoo? > As I mentioned in other thread, enable_cpucache() can be called whenever kmem_cache is created. It should not be __init. Thanks.
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