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

Hugh Dickins
2008-12-01T00:46:53Z

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);