Messages in this thread |  | | Date | Tue, 5 Nov 2013 15:56:19 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm: create a separate slab for page->ptl allocation |
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On Wed, 6 Nov 2013 00:42:17 +0200 "Kirill A. Shutemov" <kirill@shutemov.name> wrote:
> > > #if USE_SPLIT_PTE_PTLOCKS > > > +struct kmem_cache *page_ptl_cachep; > > > +void __init ptlock_cache_init(void) > > > +{ > > > + if (sizeof(spinlock_t) > sizeof(long)) > > > + page_ptl_cachep = kmem_cache_create("page->ptl", > > > + sizeof(spinlock_t), 0, SLAB_PANIC, NULL); > > > +} > > > > Confused. If (sizeof(spinlock_t) > sizeof(long)) happens to be false > > then the kernel will later crash. It would be better to use BUILD_BUG_ON() > > here, if that works. Otherwise BUG_ON. > > if (sizeof(spinlock_t) > sizeof(long)) is false, we don't need dynamicly > allocate page->ptl. It's embedded to struct page itself. __ptlock_alloc() > never called in this case.
OK. Please add a comment explaining this so the next reader doesn't get tripped up like I was.
Really the function shouldn't exist in this case. It is __init so the sin is not terrible, but can this be arranged?
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