mm/vmalloc: query dynamic DEBUG_PAGEALLOC setting
As CONFIG_DEBUG_PAGEALLOC can be enabled/disabled via kernel parameters we can optimize some cases by checking the enablement state. This is follow-up work for Christian's Optimize CONFIG_DEBUG_PAGEALLOC: https://lkml.org/lkml/2016/1/27/194 Remaining work is to make sparc to be aware of this but it looks not easy for me so I skip that in this series. This patch (of 5): We can disable debug_pagealloc processing even if the code is complied with CONFIG_DEBUG_PAGEALLOC. This patch changes the code to query whether it is enabled or not in runtime. [akpm@linux-foundation.org: update comment, per David. Adjust comment to use 80 cols] Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: David Rientjes <rientjes@google.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Takashi Iwai <tiwai@suse.com> Cc: Chris Metcalf <cmetcalf@ezchip.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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mm/vmalloc.c
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mm/vmalloc.c
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@ -531,22 +531,21 @@ static void unmap_vmap_area(struct vmap_area *va)
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static void vmap_debug_free_range(unsigned long start, unsigned long end)
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{
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/*
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* Unmap page tables and force a TLB flush immediately if
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* CONFIG_DEBUG_PAGEALLOC is set. This catches use after free
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* bugs similarly to those in linear kernel virtual address
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* space after a page has been freed.
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* Unmap page tables and force a TLB flush immediately if pagealloc
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* debugging is enabled. This catches use after free bugs similarly to
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* those in linear kernel virtual address space after a page has been
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* freed.
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*
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* All the lazy freeing logic is still retained, in order to
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* minimise intrusiveness of this debugging feature.
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* All the lazy freeing logic is still retained, in order to minimise
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* intrusiveness of this debugging feature.
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*
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* This is going to be *slow* (linear kernel virtual address
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* debugging doesn't do a broadcast TLB flush so it is a lot
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* faster).
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* This is going to be *slow* (linear kernel virtual address debugging
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* doesn't do a broadcast TLB flush so it is a lot faster).
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*/
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#ifdef CONFIG_DEBUG_PAGEALLOC
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if (debug_pagealloc_enabled()) {
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vunmap_page_range(start, end);
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flush_tlb_kernel_range(start, end);
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#endif
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}
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}
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/*
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