bad_page() is cool in that it prints out a bunch of data about
the page. But, I can never remember which page flags are good
and which are bad, or whether ->index or ->mapping is required to
be NULL.
This patch allows bad/dump_page() callers to specify a string about
why they are dumping the page and adds explanation strings to a
number of places. It also adds a 'bad_flags'
argument to bad_page(), which it then dumps out separately from
the flags which are actually set.
This way, the messages will show specifically why the page was
bad, *specifically* which flags it is complaining about, if it
was a page flag combination which was the problem.
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
---
linux.git-davehans/include/linux/mm.h | 4 +
linux.git-davehans/mm/balloon_compaction.c | 4 -
linux.git-davehans/mm/memory.c | 2
linux.git-davehans/mm/memory_hotplug.c | 2
linux.git-davehans/mm/page_alloc.c | 73 +++++++++++++++++++++--------
5 files changed, 62 insertions(+), 23 deletions(-)
diff -puN include/linux/mm.h~bad-page-details include/linux/mm.h
--- linux.git/include/linux/mm.h~bad-page-details 2013-12-13 15:51:47.177206143 -0800
+++ linux.git-davehans/include/linux/mm.h 2013-12-13 15:51:47.183206407 -0800
@@ -1977,7 +1977,9 @@ extern void shake_page(struct page *p, i
extern atomic_long_t num_poisoned_pages;
extern int soft_offline_page(struct page *page, int flags);
-extern void dump_page(struct page *page);
+extern void dump_page(struct page *page, char *reason);
+extern void dump_page_badflags(struct page *page, char *reason,
+ unsigned long badflags);
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
extern void clear_huge_page(struct page *page,
diff -puN mm/balloon_compaction.c~bad-page-details mm/balloon_compaction.c
--- linux.git/mm/balloon_compaction.c~bad-page-details 2013-12-13 15:51:47.178206187 -0800
+++ linux.git-davehans/mm/balloon_compaction.c 2013-12-13 15:51:47.183206407 -0800
@@ -267,7 +267,7 @@ void balloon_page_putback(struct page *p
put_page(page);
} else {
WARN_ON(1);
- dump_page(page);
+ dump_page(page, "not movable balloon page");
}
unlock_page(page);
}
@@ -287,7 +287,7 @@ int balloon_page_migrate(struct page *ne
BUG_ON(!trylock_page(newpage));
if (WARN_ON(!__is_movable_balloon_page(page))) {
- dump_page(page);
+ dump_page(page, "not movable balloon page");
unlock_page(newpage);
return rc;
}
diff -puN mm/memory.c~bad-page-details mm/memory.c
--- linux.git/mm/memory.c~bad-page-details 2013-12-13 15:51:47.179206231 -0800
+++ linux.git-davehans/mm/memory.c 2013-12-13 15:51:47.184206451 -0800
@@ -670,7 +670,7 @@ static void print_bad_pte(struct vm_area
current->comm,
(long long)pte_val(pte), (long long)pmd_val(*pmd));
if (page)
- dump_page(page);
+ dump_page(page, "bad pte");
printk(KERN_ALERT
"addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
(void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
diff -puN mm/memory_hotplug.c~bad-page-details mm/memory_hotplug.c
--- linux.git/mm/memory_hotplug.c~bad-page-details 2013-12-13 15:51:47.180206275 -0800
+++ linux.git-davehans/mm/memory_hotplug.c 2013-12-13 15:51:47.185206495 -0800
@@ -1310,7 +1310,7 @@ do_migrate_range(unsigned long start_pfn
#ifdef CONFIG_DEBUG_VM
printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
pfn);
- dump_page(page);
+ dump_page(page, "failed to remove from LRU");
#endif
put_page(page);
/* Because we don't have big zone->lock. we should
diff -puN mm/page_alloc.c~bad-page-details mm/page_alloc.c
--- linux.git/mm/page_alloc.c~bad-page-details 2013-12-13 15:51:47.181206319 -0800
+++ linux.git-davehans/mm/page_alloc.c 2013-12-13 15:51:47.186206539 -0800
@@ -295,7 +295,7 @@ static inline int bad_range(struct zone
}
#endif
-static void bad_page(struct page *page)
+static void bad_page(struct page *page, char *reason, unsigned long bad_flags)
{
static unsigned long resume;
static unsigned long nr_shown;
@@ -329,7 +329,7 @@ static void bad_page(struct page *page)
printk(KERN_ALERT "BUG: Bad page state in process %s pfn:%05lx\n",
current->comm, page_to_pfn(page));
- dump_page(page);
+ dump_page_badflags(page, reason, bad_flags);
print_modules();
dump_stack();
@@ -383,7 +383,7 @@ static int destroy_compound_page(struct
int bad = 0;
if (unlikely(compound_order(page) != order)) {
- bad_page(page);
+ bad_page(page, "wrong compound order", 0);
bad++;
}
@@ -392,8 +392,11 @@ static int destroy_compound_page(struct
for (i = 1; i < nr_pages; i++) {
struct page *p = page + i;
- if (unlikely(!PageTail(p) || (p->first_page != page))) {
- bad_page(page);
+ if (unlikely(!PageTail(p))) {
+ bad_page(page, "PageTail not set", 0);
+ bad++;
+ } else if (unlikely(p->first_page != page)) {
+ bad_page(page, "first_page not consistent", 0);
bad++;
}
__ClearPageTail(p);
@@ -618,12 +621,23 @@ out:
static inline int free_pages_check(struct page *page)
{
- if (unlikely(page_mapcount(page) |
- (page->mapping != NULL) |
- (atomic_read(&page->_count) != 0) |
- (page->flags & PAGE_FLAGS_CHECK_AT_FREE) |
- (mem_cgroup_bad_page_check(page)))) {
- bad_page(page);
+ char *bad_reason = NULL;
+ unsigned long bad_flags = 0;
+
+ if (unlikely(page_mapcount(page)))
+ bad_reason = "nonzero mapcount";
+ if (unlikely(page->mapping != NULL))
+ bad_reason = "non-NULL mapping";
+ if (unlikely(atomic_read(&page->_count) != 0))
+ bad_reason = "nonzero _count";
+ if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_FREE)) {
+ bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
+ bad_flags = PAGE_FLAGS_CHECK_AT_FREE;
+ }
+ if (unlikely(mem_cgroup_bad_page_check(page)))
+ bad_reason = "cgroup check failed";
+ if (unlikely(bad_reason)) {
+ bad_page(page, bad_reason, bad_flags);
return 1;
}
page_cpupid_reset_last(page);
@@ -843,12 +857,23 @@ static inline void expand(struct zone *z
*/
static inline int check_new_page(struct page *page)
{
- if (unlikely(page_mapcount(page) |
- (page->mapping != NULL) |
- (atomic_read(&page->_count) != 0) |
- (page->flags & PAGE_FLAGS_CHECK_AT_PREP) |
- (mem_cgroup_bad_page_check(page)))) {
- bad_page(page);
+ char *bad_reason = NULL;
+ unsigned long bad_flags = 0;
+
+ if (unlikely(page_mapcount(page)))
+ bad_reason = "nonzero mapcount";
+ if (unlikely(page->mapping != NULL))
+ bad_reason = "non-NULL mapping";
+ if (unlikely(atomic_read(&page->_count) != 0))
+ bad_reason = "nonzero _count";
+ if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_PREP)) {
+ bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag set";
+ bad_flags = PAGE_FLAGS_CHECK_AT_PREP;
+ }
+ if (unlikely(mem_cgroup_bad_page_check(page)))
+ bad_reason = "cgroup check failed";
+ if (unlikely(bad_reason)) {
+ bad_page(page, bad_reason, bad_flags);
return 1;
}
return 0;
@@ -6458,12 +6483,24 @@ static void dump_page_flags(unsigned lon
printk(")\n");
}
-void dump_page(struct page *page)
+void dump_page_badflags(struct page *page, char *reason, unsigned long badflags)
{
printk(KERN_ALERT
"page:%p count:%d mapcount:%d mapping:%p index:%#lx\n",
page, atomic_read(&page->_count), page_mapcount(page),
page->mapping, page->index);
dump_page_flags(page->flags);
+ if (reason)
+ printk(KERN_ALERT "page dumped because: %s\n", reason);
+ if (page->flags & badflags) {
+ printk(KERN_ALERT "bad because of flags:\n");
+ dump_page_flags(page->flags & badflags);
+ }
mem_cgroup_print_bad_page(page);
}
+
+void dump_page(struct page *page, char *reason)
+{
+ dump_page_badflags(page, reason, 0);
+}
+
_
--
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