mm/debug-pagealloc: make debug-pagealloc boottime configurable

Now, we have prepared to avoid using debug-pagealloc in boottime.  So
introduce new kernel-parameter to disable debug-pagealloc in boottime, and
makes related functions to be disabled in this case.

Only non-intuitive part is change of guard page functions.  Because guard
page is effective only if debug-pagealloc is enabled, turning off
according to debug-pagealloc is reasonable thing to do.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Dave Hansen <dave@sr71.net>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Jungsoo Son <jungsoo.son@lge.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

9 files changed, 57 insertions, 7 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 24539d1c7d25..6f067954675b 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -829,6 +829,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         CONFIG_DEBUG_PAGEALLOC, hence this option will not help
                         tracking down these problems.
 
+        debug_pagealloc=
+                        [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
+                        parameter enables the feature at boot time. In
+                        default, it is disabled. We can avoid allocating huge
+                        chunk of memory for debug pagealloc if we don't enable
+                        it at boot time and the system will work mostly same
+                        with the kernel built without CONFIG_DEBUG_PAGEALLOC.
+                        on: enable the feature
+
         debugpat        [X86] Enable PAT debugging
 
         decnet.addr=    [HW,NET]
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index e56a307bc676..2c2022d16059 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -1514,7 +1514,7 @@ static void kernel_unmap_linear_page(unsigned long vaddr, unsigned long lmi)
                                mmu_kernel_ssize, 0);
 }
 
-void kernel_map_pages(struct page *page, int numpages, int enable)
+void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
         unsigned long flags, vaddr, lmi;
         int i;
diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index d545b1231594..50fad3801f30 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -429,7 +429,7 @@ static int change_page_attr(struct page *page, int numpages, pgprot_t prot)
 }
 
 
-void kernel_map_pages(struct page *page, int numpages, int enable)
+void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
         if (PageHighMem(page))
                 return;
diff --git a/arch/s390/mm/pageattr.c b/arch/s390/mm/pageattr.c
index 3fef3b299665..426c9d462d1c 100644
--- a/arch/s390/mm/pageattr.c
+++ b/arch/s390/mm/pageattr.c
@@ -120,7 +120,7 @@ static void ipte_range(pte_t *pte, unsigned long address, int nr)
         }
 }
 
-void kernel_map_pages(struct page *page, int numpages, int enable)
+void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
         unsigned long address;
         int nr, i, j;
diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index 2d91c62f7f5f..3ea267c53320 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -1621,7 +1621,7 @@ static void __init kernel_physical_mapping_init(void)
 }
 
 #ifdef CONFIG_DEBUG_PAGEALLOC
-void kernel_map_pages(struct page *page, int numpages, int enable)
+void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
         unsigned long phys_start = page_to_pfn(page) << PAGE_SHIFT;
         unsigned long phys_end = phys_start + (numpages * PAGE_SIZE);
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index a3a5d46605d2..dfaf2e0f5f8f 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1817,7 +1817,7 @@ static int __set_pages_np(struct page *page, int numpages)
         return __change_page_attr_set_clr(&cpa, 0);
 }
 
-void kernel_map_pages(struct page *page, int numpages, int enable)
+void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
         if (PageHighMem(page))
                 return;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 66560f1a0564..8b8d77a1532f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2061,7 +2061,22 @@ static inline void vm_stat_account(struct mm_struct *mm,
 #endif /* CONFIG_PROC_FS */
 
 #ifdef CONFIG_DEBUG_PAGEALLOC
-extern void kernel_map_pages(struct page *page, int numpages, int enable);
+extern bool _debug_pagealloc_enabled;
+extern void __kernel_map_pages(struct page *page, int numpages, int enable);
+
+static inline bool debug_pagealloc_enabled(void)
+{
+        return _debug_pagealloc_enabled;
+}
+
+static inline void
+kernel_map_pages(struct page *page, int numpages, int enable)
+{
+        if (!debug_pagealloc_enabled())
+                return;
+
+        __kernel_map_pages(page, numpages, enable);
+}
 #ifdef CONFIG_HIBERNATION
 extern bool kernel_page_present(struct page *page);
 #endif /* CONFIG_HIBERNATION */
diff --git a/mm/debug-pagealloc.c b/mm/debug-pagealloc.c
index 0072f2c53331..5bf5906ce13b 100644
--- a/mm/debug-pagealloc.c
+++ b/mm/debug-pagealloc.c
@@ -10,11 +10,17 @@ static bool page_poisoning_enabled __read_mostly;
 
 static bool need_page_poisoning(void)
 {
+        if (!debug_pagealloc_enabled())
+                return false;
+
         return true;
 }
 
 static void init_page_poisoning(void)
 {
+        if (!debug_pagealloc_enabled())
+                return;
+
         page_poisoning_enabled = true;
 }
 
@@ -119,7 +125,7 @@ static void unpoison_pages(struct page *page, int n)
                 unpoison_page(page + i);
 }
 
-void kernel_map_pages(struct page *page, int numpages, int enable)
+void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
         if (!page_poisoning_enabled)
                 return;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e0a39d328ca1..303d38516807 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -425,15 +425,35 @@ static inline void prep_zero_page(struct page *page, unsigned int order,
 
 #ifdef CONFIG_DEBUG_PAGEALLOC
 unsigned int _debug_guardpage_minorder;
+bool _debug_pagealloc_enabled __read_mostly;
 bool _debug_guardpage_enabled __read_mostly;
 
+static int __init early_debug_pagealloc(char *buf)
+{
+        if (!buf)
+                return -EINVAL;
+
+        if (strcmp(buf, "on") == 0)
+                _debug_pagealloc_enabled = true;
+
+        return 0;
+}
+early_param("debug_pagealloc", early_debug_pagealloc);
+
 static bool need_debug_guardpage(void)
 {
+        /* If we don't use debug_pagealloc, we don't need guard page */
+        if (!debug_pagealloc_enabled())
+                return false;
+
         return true;
 }
 
 static void init_debug_guardpage(void)
 {
+        if (!debug_pagealloc_enabled())
+                return;
+
         _debug_guardpage_enabled = true;
 }