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mm: print more details for bad_page()

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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.

[akpm@linux-foundation.org: switch to pr_alert]
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dave Hansen
2014-01-23 15:52:49 -08:00
committed by Linus Torvalds
parent 12ab028be0
commit f0b791a34c
5 changed files with 61 additions and 23 deletions
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72
mm/page_alloc.c
View File

@@ -295,7 +295,7 @@ static inline int bad_range(struct zone *zone, struct page *page)
}
#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 page *page, unsigned long order)
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 page *page, unsigned long order)
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 *zone, struct page *page,
*/
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;
@@ -6494,12 +6519,23 @@ static void dump_page_flags(unsigned long flags)
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)
pr_alert("page dumped because: %s\n", reason);
if (page->flags & badflags) {
pr_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);
}