From f0b791a34cb3cffd2bbc3ca4365c9b719fa2c9f3 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Thu, 23 Jan 2014 15:52:49 -0800 Subject: [PATCH] mm: print more details for bad_page() 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 Reviewed-by: Christoph Lameter Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm.h | 4 ++- mm/balloon_compaction.c | 4 +-- mm/memory.c | 2 +- mm/memory_hotplug.c | 2 +- mm/page_alloc.c | 72 ++++++++++++++++++++++++++++++----------- 5 files changed, 61 insertions(+), 23 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index a512dd836931..03bbcb84d96e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2029,7 +2029,9 @@ extern void shake_page(struct page *p, int access); 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 --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c index 07dbc8ec46cf..6e45a5074bf0 100644 --- a/mm/balloon_compaction.c +++ b/mm/balloon_compaction.c @@ -267,7 +267,7 @@ void balloon_page_putback(struct page *page) 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 *newpage, 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 --git a/mm/memory.c b/mm/memory.c index 86487dfa5e59..71d70c082b98 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -671,7 +671,7 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr, 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 --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index cc2ab37220b7..a512a47241a4 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1309,7 +1309,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_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 --git a/mm/page_alloc.c b/mm/page_alloc.c index 533e2147d14f..1939f4446a36 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -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); +} -- 2.20.1