linux-kernel - [PATCH v2 1/5] mm/vmalloc: query dynamic DEBUG

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Date:	Thu, 11 Feb 2016 13:04:57 +0900
From:	js1304@...il.com
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	David Rientjes <rientjes@...gle.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Takashi Iwai <tiwai@...e.com>,
	Chris Metcalf <cmetcalf@...hip.com>,
	Christoph Lameter <cl@...ux.com>, linux-api@...r.kernel.org,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: [PATCH v2 1/5] mm/vmalloc: query dynamic DEBUG_PAGEALLOC setting

From: Joonsoo Kim <iamjoonsoo.kim@....com>

We can disable debug_pagealloc processing even if the code is compiled
with CONFIG_DEBUG_PAGEALLOC. This patch changes the code to query
whether it is enabled or not in runtime.

v2: update comment, per David.
adjust comment to use 80 cols, per Andrew.

Reviewed-by: Christian Borntraeger <borntraeger@...ibm.com>
Acked-by: David Rientjes <rientjes@...gle.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
---
 mm/vmalloc.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index fb42a5b..d4b2e34 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -531,22 +531,21 @@ static void unmap_vmap_area(struct vmap_area *va)
 static void vmap_debug_free_range(unsigned long start, unsigned long end)
 {
 	/*
-	 * Unmap page tables and force a TLB flush immediately if
-	 * CONFIG_DEBUG_PAGEALLOC is set. This catches use after free
-	 * bugs similarly to those in linear kernel virtual address
-	 * space after a page has been freed.
+	 * Unmap page tables and force a TLB flush immediately if pagealloc
+	 * debugging is enabled.  This catches use after free bugs similarly to
+	 * those in linear kernel virtual address space after a page has been
+	 * freed.
 	 *
-	 * All the lazy freeing logic is still retained, in order to
-	 * minimise intrusiveness of this debugging feature.
+	 * All the lazy freeing logic is still retained, in order to minimise
+	 * intrusiveness of this debugging feature.
 	 *
-	 * This is going to be *slow* (linear kernel virtual address
-	 * debugging doesn't do a broadcast TLB flush so it is a lot
-	 * faster).
+	 * This is going to be *slow* (linear kernel virtual address debugging
+	 * doesn't do a broadcast TLB flush so it is a lot faster).
 	 */
-#ifdef CONFIG_DEBUG_PAGEALLOC
-	vunmap_page_range(start, end);
-	flush_tlb_kernel_range(start, end);
-#endif
+	if (debug_pagealloc_enabled()) {
+		vunmap_page_range(start, end);
+		flush_tlb_kernel_range(start, end);
+	}
 }
 
 /*
-- 
1.9.1