[PATCH v2] mm/memory-failure.c: define page types for action_result() in one place

[Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>]

This cleanup patch moves all strings passed to action_result() into a single
array action_page_type so that a reader can easily find which kind of action
results are possible. And this patch also fixes the odd lines to be printed
out, like "unknown page state page" or "free buddy, 2nd try page".

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
---
ChangeLog v1 -> v2:
- fix DIRTY_UNEVICTABLE_LRU typo
- adding "MSG_" prefix to each enum value
- use declaration with type "enum page_type" instead of int
- define action_type_type as "static const char * const" (not "static const char *")
---
 mm/memory-failure.c | 108 +++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 77 insertions(+), 31 deletions(-)

diff --git v4.0-rc4.orig/mm/memory-failure.c v4.0-rc4/mm/memory-failure.c
index 181850a760ea..8c8c9ed0dcdf 100644
--- v4.0-rc4.orig/mm/memory-failure.c
+++ v4.0-rc4/mm/memory-failure.c
@@ -523,6 +523,52 @@ static const char *action_name[] = {
 	[RECOVERED] = "Recovered",
 };
 
+enum page_type {
+	MSG_KERNEL,
+	MSG_KERNEL_HIGH_ORDER,
+	MSG_SLAB,
+	MSG_DIFFERENT_COMPOUND,
+	MSG_POISONED_HUGE,
+	MSG_HUGE,
+	MSG_FREE_HUGE,
+	MSG_UNMAP_FAILED,
+	MSG_DIRTY_SWAPCACHE,
+	MSG_CLEAN_SWAPCACHE,
+	MSG_DIRTY_MLOCKED_LRU,
+	MSG_CLEAN_MLOCKED_LRU,
+	MSG_DIRTY_UNEVICTABLE_LRU,
+	MSG_CLEAN_UNEVICTABLE_LRU,
+	MSG_DIRTY_LRU,
+	MSG_CLEAN_LRU,
+	MSG_TRUNCATED_LRU,
+	MSG_BUDDY,
+	MSG_BUDDY_2ND,
+	MSG_UNKNOWN,
+};
+
+static const char * const action_page_type[] = {
+	[MSG_KERNEL]			= "reserved kernel page",
+	[MSG_KERNEL_HIGH_ORDER]		= "high-order kernel page",
+	[MSG_SLAB]			= "kernel slab page",
+	[MSG_DIFFERENT_COMPOUND]	= "different compound page after locking",
+	[MSG_POISONED_HUGE]		= "huge page already hardware poisoned",
+	[MSG_HUGE]			= "huge page",
+	[MSG_FREE_HUGE]			= "free huge page",
+	[MSG_UNMAP_FAILED]		= "unmapping failed page",
+	[MSG_DIRTY_SWAPCACHE]		= "dirty swapcache page",
+	[MSG_CLEAN_SWAPCACHE]		= "clean swapcache page",
+	[MSG_DIRTY_MLOCKED_LRU]		= "dirty mlocked LRU page",
+	[MSG_CLEAN_MLOCKED_LRU]		= "clean mlocked LRU page",
+	[MSG_DIRTY_UNEVICTABLE_LRU]	= "dirty unevictable LRU page",
+	[MSG_CLEAN_UNEVICTABLE_LRU]	= "clean unevictable LRU page",
+	[MSG_DIRTY_LRU]			= "dirty LRU page",
+	[MSG_CLEAN_LRU]			= "clean LRU page",
+	[MSG_TRUNCATED_LRU]		= "already truncated LRU page",
+	[MSG_BUDDY]			= "free buddy page",
+	[MSG_BUDDY_2ND]			= "free buddy page (2nd try)",
+	[MSG_UNKNOWN]			= "unknown page",
+};
+
 /*
  * XXX: It is possible that a page is isolated from LRU cache,
  * and then kept in swap cache or failed to remove from page cache.
@@ -779,10 +825,10 @@ static int me_huge_page(struct page *p, unsigned long pfn)
 static struct page_state {
 	unsigned long mask;
 	unsigned long res;
-	char *msg;
+	enum page_type type;
 	int (*action)(struct page *p, unsigned long pfn);
 } error_states[] = {
-	{ reserved,	reserved,	"reserved kernel",	me_kernel },
+	{ reserved,	reserved,	MSG_KERNEL,	me_kernel },
 	/*
 	 * free pages are specially detected outside this table:
 	 * PG_buddy pages only make a small fraction of all free pages.
@@ -793,31 +839,31 @@ static struct page_state {
 	 * currently unused objects without touching them. But just
 	 * treat it as standard kernel for now.
 	 */
-	{ slab,		slab,		"kernel slab",	me_kernel },
+	{ slab,		slab,		MSG_SLAB,	me_kernel },
 
 #ifdef CONFIG_PAGEFLAGS_EXTENDED
-	{ head,		head,		"huge",		me_huge_page },
-	{ tail,		tail,		"huge",		me_huge_page },
+	{ head,		head,		MSG_HUGE,		me_huge_page },
+	{ tail,		tail,		MSG_HUGE,		me_huge_page },
 #else
-	{ compound,	compound,	"huge",		me_huge_page },
+	{ compound,	compound,	MSG_HUGE,		me_huge_page },
 #endif
 
-	{ sc|dirty,	sc|dirty,	"dirty swapcache",	me_swapcache_dirty },
-	{ sc|dirty,	sc,		"clean swapcache",	me_swapcache_clean },
+	{ sc|dirty,	sc|dirty,	MSG_DIRTY_SWAPCACHE,	me_swapcache_dirty },
+	{ sc|dirty,	sc,		MSG_CLEAN_SWAPCACHE,	me_swapcache_clean },
 
-	{ mlock|dirty,	mlock|dirty,	"dirty mlocked LRU",	me_pagecache_dirty },
-	{ mlock|dirty,	mlock,		"clean mlocked LRU",	me_pagecache_clean },
+	{ mlock|dirty,	mlock|dirty,	MSG_DIRTY_MLOCKED_LRU,	me_pagecache_dirty },
+	{ mlock|dirty,	mlock,		MSG_CLEAN_MLOCKED_LRU,	me_pagecache_clean },
 
-	{ unevict|dirty, unevict|dirty,	"dirty unevictable LRU", me_pagecache_dirty },
-	{ unevict|dirty, unevict,	"clean unevictable LRU", me_pagecache_clean },
+	{ unevict|dirty, unevict|dirty,	MSG_DIRTY_UNEVICTABLE_LRU,	me_pagecache_dirty },
+	{ unevict|dirty, unevict,	MSG_CLEAN_UNEVICTABLE_LRU,	me_pagecache_clean },
 
-	{ lru|dirty,	lru|dirty,	"dirty LRU",	me_pagecache_dirty },
-	{ lru|dirty,	lru,		"clean LRU",	me_pagecache_clean },
+	{ lru|dirty,	lru|dirty,	MSG_DIRTY_LRU,	me_pagecache_dirty },
+	{ lru|dirty,	lru,		MSG_CLEAN_LRU,	me_pagecache_clean },
 
 	/*
 	 * Catchall entry: must be at end.
 	 */
-	{ 0,		0,		"unknown page state",	me_unknown },
+	{ 0,		0,		MSG_UNKNOWN,	me_unknown },
 };
 
 #undef dirty
@@ -837,10 +883,10 @@ static struct page_state {
  * "Dirty/Clean" indication is not 100% accurate due to the possibility of
  * setting PG_dirty outside page lock. See also comment above set_page_dirty().
  */
-static void action_result(unsigned long pfn, char *msg, int result)
+static void action_result(unsigned long pfn, enum page_type type, int result)
 {
-	pr_err("MCE %#lx: %s page recovery: %s\n",
-		pfn, msg, action_name[result]);
+	pr_err("MCE %#lx: recovery action for %s: %s\n",
+		pfn, action_page_type[type], action_name[result]);
 }
 
 static int page_action(struct page_state *ps, struct page *p,
@@ -856,11 +902,11 @@ static int page_action(struct page_state *ps, struct page *p,
 		count--;
 	if (count != 0) {
 		printk(KERN_ERR
-		       "MCE %#lx: %s page still referenced by %d users\n",
-		       pfn, ps->msg, count);
+		       "MCE %#lx: %s still referenced by %d users\n",
+		       pfn, action_page_type[ps->type], count);
 		result = FAILED;
 	}
-	action_result(pfn, ps->msg, result);
+	action_result(pfn, ps->type, result);
 
 	/* Could do more checks here if page looks ok */
 	/*
@@ -1109,7 +1155,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 	if (!(flags & MF_COUNT_INCREASED) &&
 		!get_page_unless_zero(hpage)) {
 		if (is_free_buddy_page(p)) {
-			action_result(pfn, "free buddy", DELAYED);
+			action_result(pfn, MSG_BUDDY, DELAYED);
 			return 0;
 		} else if (PageHuge(hpage)) {
 			/*
@@ -1126,12 +1172,12 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 			}
 			set_page_hwpoison_huge_page(hpage);
 			res = dequeue_hwpoisoned_huge_page(hpage);
-			action_result(pfn, "free huge",
+			action_result(pfn, MSG_FREE_HUGE,
 				      res ? IGNORED : DELAYED);
 			unlock_page(hpage);
 			return res;
 		} else {
-			action_result(pfn, "high order kernel", IGNORED);
+			action_result(pfn, MSG_KERNEL_HIGH_ORDER, IGNORED);
 			return -EBUSY;
 		}
 	}
@@ -1153,9 +1199,10 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 			 */
 			if (is_free_buddy_page(p)) {
 				if (flags & MF_COUNT_INCREASED)
-					action_result(pfn, "free buddy", DELAYED);
+					action_result(pfn, MSG_BUDDY, DELAYED);
 				else
-					action_result(pfn, "free buddy, 2nd try", DELAYED);
+					action_result(pfn, MSG_BUDDY_2ND,
+						      DELAYED);
 				return 0;
 			}
 		}
@@ -1168,7 +1215,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 	 * If this happens just bail out.
 	 */
 	if (compound_head(p) != hpage) {
-		action_result(pfn, "different compound page after locking", IGNORED);
+		action_result(pfn, MSG_DIFFERENT_COMPOUND, IGNORED);
 		res = -EBUSY;
 		goto out;
 	}
@@ -1208,8 +1255,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 	 * on the head page to show that the hugepage is hwpoisoned
 	 */
 	if (PageHuge(p) && PageTail(p) && TestSetPageHWPoison(hpage)) {
-		action_result(pfn, "hugepage already hardware poisoned",
-				IGNORED);
+		action_result(pfn, MSG_POISONED_HUGE, IGNORED);
 		unlock_page(hpage);
 		put_page(hpage);
 		return 0;
@@ -1238,7 +1284,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 	 */
 	if (hwpoison_user_mappings(p, pfn, trapno, flags, &hpage)
 	    != SWAP_SUCCESS) {
-		action_result(pfn, "unmapping failed", IGNORED);
+		action_result(pfn, MSG_UNMAP_FAILED, IGNORED);
 		res = -EBUSY;
 		goto out;
 	}
@@ -1247,7 +1293,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 	 * Torn down by someone else?
 	 */
 	if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
-		action_result(pfn, "already truncated LRU", IGNORED);
+		action_result(pfn, MSG_TRUNCATED_LRU, IGNORED);
 		res = -EBUSY;
 		goto out;
 	}
-- 
1.9.3