Re: [PATCH] mm: introduce dump_page() and print symbolic flag names

[AmÃrico Wang]

On Wed, Dec 16, 2009 at 08:26:40PM +0800, Wu Fengguang wrote:
>- introduce dump_page() to print the page info for debugging some error condition.

Since it is for debugging, shouldn't it be surrounded by
CONFIG_DEBUG_VM too? :-/

Thanks.


>- 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:147
>[  157.525570] page flags: 100000000100068(uptodate|lru|active|swapbacked)
>
>CC: Ingo Molnar <mingo@xxxxxxx> 
>CC: Alex Chiang <achiang@xxxxxx>
>CC: Rik van Riel <riel@xxxxxxxxxx>
>CC: Andi Kleen <andi@xxxxxxxxxxxxxx> 
>CC: Mel Gorman <mel@xxxxxxxxxxxxxxxxxx> 
>CC: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx> 
>Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
>---
> include/linux/mm.h  |    2 +
> mm/memory.c         |    8 +---
> mm/memory_hotplug.c |    6 +--
> mm/page_alloc.c     |   83 +++++++++++++++++++++++++++++++++++++++---
> 4 files changed, 86 insertions(+), 13 deletions(-)
>
>--- linux-mm.orig/mm/page_alloc.c	2009-12-11 10:01:25.000000000 +0800
>+++ linux-mm/mm/page_alloc.c	2009-12-16 20:17:18.000000000 +0800
>@@ -49,6 +49,7 @@
> #include <linux/debugobjects.h>
> #include <linux/kmemleak.h>
> #include <trace/events/kmem.h>
>+#include <linux/ftrace_event.h>
> 
> #include <asm/tlbflush.h>
> #include <asm/div64.h>
>@@ -262,10 +263,7 @@ 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:
>@@ -5106,3 +5104,80 @@ bool is_free_buddy_page(struct page *pag
> 	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);
>+}
>--- linux-mm.orig/mm/memory.c	2009-12-11 10:01:25.000000000 +0800
>+++ linux-mm/mm/memory.c	2009-12-14 19:21:22.000000000 +0800
>@@ -430,12 +430,8 @@ static void print_bad_pte(struct vm_area
> 		"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);
>--- linux-mm.orig/mm/memory_hotplug.c	2009-12-11 10:01:25.000000000 +0800
>+++ linux-mm/mm/memory_hotplug.c	2009-12-14 19:21:22.000000000 +0800
>@@ -678,9 +678,9 @@ do_migrate_range(unsigned long start_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
> 		}
> 	}
>--- linux-mm.orig/include/linux/mm.h	2009-12-11 10:01:25.000000000 +0800
>+++ linux-mm/include/linux/mm.h	2009-12-14 19:21:22.000000000 +0800
>@@ -1328,5 +1328,7 @@ extern void shake_page(struct page *p, i
> 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 */
>--
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