mm: introduce dump_page() and print symbolic flag names

- introduce dump_page() to print the page info for debugging some error
  condition.

- convert three mm users: bad_page(), print_bad_pte() and memory offline
  failure.

- print an extra field: the symbolic names of page->flags

Example dump_page() output:

[  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1 mapping:ffff88001c901791 index:0x147
[  157.525570] page flags: 0x100000000100068(uptodate|lru|active|swapbacked)

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alex Chiang <achiang@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Mel Gorman <mel@linux.vnet.ibm.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 86 insertions, 13 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7f693b272c4a..e70f21beb4b4 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1465,5 +1465,7 @@ extern void shake_page(struct page *p, int access);
 extern atomic_long_t mce_bad_pages;
 extern int soft_offline_page(struct page *page, int flags);
 
+extern void dump_page(struct page *page);
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */
diff --git a/mm/memory.c b/mm/memory.c
index 3d9130bd95d0..5b7f2002e54b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -509,12 +509,8 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
                 "BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
                 current->comm,
                 (long long)pte_val(pte), (long long)pmd_val(*pmd));
-        if (page) {
-                printk(KERN_ALERT
-                "page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
-                page, (void *)page->flags, page_count(page),
-                page_mapcount(page), page->mapping, page->index);
-        }
+        if (page)
+                dump_page(page);
         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 78e34e63c7b8..be211a582930 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -688,9 +688,9 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
                         if (page_count(page))
                                 not_managed++;
 #ifdef CONFIG_DEBUG_VM
-                        printk(KERN_INFO "removing from LRU failed"
-                                         " %lx/%d/%lx\n",
-                                pfn, page_count(page), page->flags);
+                        printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
+                               pfn);
+                        dump_page(page);
 #endif
                 }
         }
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 78ce90dd671f..d03c946d5566 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -50,6 +50,7 @@
 #include <linux/kmemleak.h>
 #include <linux/memory.h>
 #include <trace/events/kmem.h>
+#include <linux/ftrace_event.h>
 
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
@@ -288,10 +289,7 @@ 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));
-        printk(KERN_ALERT
-                "page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
-                page, (void *)page->flags, page_count(page),
-                page_mapcount(page), page->mapping, page->index);
+        dump_page(page);
 
         dump_stack();
 out:
@@ -5183,3 +5181,80 @@ bool is_free_buddy_page(struct page *page)
         return order < MAX_ORDER;
 }
 #endif
+
+static struct trace_print_flags pageflag_names[] = {
+        {1UL << PG_locked,              "locked"        },
+        {1UL << PG_error,               "error"         },
+        {1UL << PG_referenced,          "referenced"    },
+        {1UL << PG_uptodate,            "uptodate"      },
+        {1UL << PG_dirty,               "dirty"         },
+        {1UL << PG_lru,                 "lru"           },
+        {1UL << PG_active,              "active"        },
+        {1UL << PG_slab,                "slab"          },
+        {1UL << PG_owner_priv_1,        "owner_priv_1"  },
+        {1UL << PG_arch_1,              "arch_1"        },
+        {1UL << PG_reserved,            "reserved"      },
+        {1UL << PG_private,             "private"       },
+        {1UL << PG_private_2,           "private_2"     },
+        {1UL << PG_writeback,           "writeback"     },
+#ifdef CONFIG_PAGEFLAGS_EXTENDED
+        {1UL << PG_head,                "head"          },
+        {1UL << PG_tail,                "tail"          },
+#else
+        {1UL << PG_compound,            "compound"      },
+#endif
+        {1UL << PG_swapcache,           "swapcache"     },
+        {1UL << PG_mappedtodisk,        "mappedtodisk"  },
+        {1UL << PG_reclaim,             "reclaim"       },
+        {1UL << PG_buddy,               "buddy"         },
+        {1UL << PG_swapbacked,          "swapbacked"    },
+        {1UL << PG_unevictable,         "unevictable"   },
+#ifdef CONFIG_MMU
+        {1UL << PG_mlocked,             "mlocked"       },
+#endif
+#ifdef CONFIG_ARCH_USES_PG_UNCACHED
+        {1UL << PG_uncached,            "uncached"      },
+#endif
+#ifdef CONFIG_MEMORY_FAILURE
+        {1UL << PG_hwpoison,            "hwpoison"      },
+#endif
+        {-1UL,                          NULL            },
+};
+
+static void dump_page_flags(unsigned long flags)
+{
+        const char *delim = "";
+        unsigned long mask;
+        int i;
+
+        printk(KERN_ALERT "page flags: %#lx(", flags);
+
+        /* remove zone id */
+        flags &= (1UL << NR_PAGEFLAGS) - 1;
+
+        for (i = 0; pageflag_names[i].name && flags; i++) {
+
+                mask = pageflag_names[i].mask;
+                if ((flags & mask) != mask)
+                        continue;
+
+                flags &= ~mask;
+                printk("%s%s", delim, pageflag_names[i].name);
+                delim = "|";
+        }
+
+        /* check for left over flags */
+        if (flags)
+                printk("%s%#lx", delim, flags);
+
+        printk(")\n");
+}
+
+void dump_page(struct page *page)
+{
+        printk(KERN_ALERT
+               "page:%p count:%d mapcount:%d mapping:%p index:%#lx\n",
+                page, page_count(page), page_mapcount(page),
+                page->mapping, page->index);
+        dump_page_flags(page->flags);
+}