[PATCH 7/8] badpage: ratelimit print_bad_pte and bad_page

[Hugh Dickins <hugh@veritas.com>]

print_bad_pte() and bad_page() might each need ratelimiting - especially
for their dump_stacks, almost never of interest, yet not quite dispensible.
Correlating corruption across neighbouring entries can be very helpful,
so allow a burst of 60 reports before keeping quiet for the remainder
of that minute (or allow a steady drip of one report per second).

Signed-off-by: Hugh Dickins <hugh@veritas.com>
---

 mm/memory.c     |   23 +++++++++++++++++++++++
 mm/page_alloc.c |   26 +++++++++++++++++++++++++-
 2 files changed, 48 insertions(+), 1 deletion(-)

--- badpage6/mm/memory.c	2008-11-28 20:40:48.000000000 +0000
+++ badpage7/mm/memory.c	2008-11-28 20:40:50.000000000 +0000
@@ -383,6 +383,29 @@ static void print_bad_pte(struct vm_area
 	pmd_t *pmd = pmd_offset(pud, addr);
 	struct address_space *mapping;
 	pgoff_t index;
+	static unsigned long resume;
+	static unsigned long nr_shown;
+	static unsigned long nr_unshown;
+
+	/*
+	 * Allow a burst of 60 reports, then keep quiet for that minute;
+	 * or allow a steady drip of one report per second.
+	 */
+	if (nr_shown == 60) {
+		if (time_before(jiffies, resume)) {
+			nr_unshown++;
+			return;
+		}
+		if (nr_unshown) {
+			printk(KERN_EMERG
+				"Bad page map: %lu messages suppressed\n",
+				nr_unshown);
+			nr_unshown = 0;
+		}
+		nr_shown = 0;
+	}
+	if (nr_shown++ == 0)
+		resume = jiffies + 60 * HZ;
 
 	mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
 	index = linear_page_index(vma, addr);
--- badpage6/mm/page_alloc.c	2008-11-28 20:40:42.000000000 +0000
+++ badpage7/mm/page_alloc.c	2008-11-28 20:40:50.000000000 +0000
@@ -223,6 +223,30 @@ static inline int bad_range(struct zone 
 
 static void bad_page(struct page *page)
 {
+	static unsigned long resume;
+	static unsigned long nr_shown;
+	static unsigned long nr_unshown;
+
+	/*
+	 * Allow a burst of 60 reports, then keep quiet for that minute;
+	 * or allow a steady drip of one report per second.
+	 */
+	if (nr_shown == 60) {
+		if (time_before(jiffies, resume)) {
+			nr_unshown++;
+			goto out;
+		}
+		if (nr_unshown) {
+			printk(KERN_EMERG
+				"Bad page state: %lu messages suppressed\n",
+				nr_unshown);
+			nr_unshown = 0;
+		}
+		nr_shown = 0;
+	}
+	if (nr_shown++ == 0)
+		resume = jiffies + 60 * HZ;
+
 	printk(KERN_EMERG "Bad page state in process %s  pfn:%05lx\n",
 		current->comm, page_to_pfn(page));
 	printk(KERN_EMERG
@@ -232,7 +256,7 @@ static void bad_page(struct page *page)
 	printk(KERN_EMERG "Trying to fix it up, but a reboot is needed\n");
 
 	dump_stack();
-
+out:
 	/* Leave bad fields for debug, except PageBuddy could make trouble */
 	__ClearPageBuddy(page);
 	add_taint(TAINT_BAD_PAGE);

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