The page_owner mechanism is useful for dealing with memory leaks. By reading
/sys/kernel/debug/page_owner one can determine the stack traces leading to
allocations of all pages, and find e.g. a buggy driver.
This information might be also potentially useful for debugging, such as the
VM_BUG_ON_PAGE() calls to dump_page(). So let's print the stored info from
dump_page().
Example output:
page:ffffea000292f1c0 count:1 mapcount:0 mapping:ffff8800b2f6cc18 index:0x91d
flags: 0x1fffff8001002c(referenced|uptodate|lru|mappedtodisk)
page dumped because: VM_BUG_ON_PAGE(1)
page->mem_cgroup:ffff8801392c5000
page allocated via order 0, migratetype Movable, gfp_mask 0x24213ca(GFP_HIGHUSER_MOVABLE|__GFP_COLD|__GFP_NOWARN|__GFP_NORETRY)
[<ffffffff811682c4>] __alloc_pages_nodemask+0x134/0x230
[<ffffffff811b40c8>] alloc_pages_current+0x88/0x120
[<ffffffff8115e386>] __page_cache_alloc+0xe6/0x120
[<ffffffff8116ba6c>] __do_page_cache_readahead+0xdc/0x240
[<ffffffff8116bd05>] ondemand_readahead+0x135/0x260
[<ffffffff8116be9c>] page_cache_async_readahead+0x6c/0x70
[<ffffffff811604c2>] generic_file_read_iter+0x3f2/0x760
[<ffffffff811e0dc7>] __vfs_read+0xa7/0xd0
page has been migrated, last migrate reason: compaction
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Sasha Levin <sasha.levin@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
---
include/linux/page_owner.h | 9 +++++++++
mm/debug.c | 2 ++
mm/page_alloc.c | 1 +
mm/page_owner.c | 25 +++++++++++++++++++++++++
4 files changed, 37 insertions(+)
diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h
index 555893bf13d7..46f1b939948c 100644
--- a/include/linux/page_owner.h
+++ b/include/linux/page_owner.h
@@ -13,6 +13,7 @@ extern void __set_page_owner(struct page *page,
extern gfp_t __get_page_owner_gfp(struct page *page);
extern void __copy_page_owner(struct page *oldpage, struct page *newpage);
extern void __set_page_owner_migrate_reason(struct page *page, int reason);
+extern void __dump_page_owner(struct page *page);
static inline void reset_page_owner(struct page *page, unsigned int order)
{
@@ -44,6 +45,11 @@ static inline void set_page_owner_migrate_reason(struct page *page, int reason)
if (static_branch_unlikely(&page_owner_inited))
__set_page_owner_migrate_reason(page, reason);
}
+static inline void dump_page_owner(struct page *page)
+{
+ if (static_branch_unlikely(&page_owner_inited))
+ __dump_page_owner(page);
+}
#else
static inline void reset_page_owner(struct page *page, unsigned int order)
{
@@ -62,5 +68,8 @@ static inline void copy_page_owner(struct page *oldpage, struct page *newpage)
static inline void set_page_owner_migrate_reason(struct page *page, int reason)
{
}
+static inline void dump_page_owner(struct page *page)
+{
+}
#endif /* CONFIG_PAGE_OWNER */
#endif /* __LINUX_PAGE_OWNER_H */
diff --git a/mm/debug.c b/mm/debug.c
index 78dc54877075..61b1f1bb328e 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -11,6 +11,7 @@
#include <linux/memcontrol.h>
#include <trace/events/mmflags.h>
#include <linux/migrate.h>
+#include <linux/page_owner.h>
#include "internal.h"
@@ -67,6 +68,7 @@ void dump_page_badflags(struct page *page, const char *reason,
void dump_page(struct page *page, const char *reason)
{
dump_page_badflags(page, reason, 0);
+ dump_page_owner(page);
}
EXPORT_SYMBOL(dump_page);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d1f385a37b5c..e8b3cb78b5cf 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -443,6 +443,7 @@ static void bad_page(struct page *page, const char *reason,
printk(KERN_ALERT "BUG: Bad page state in process %s pfn:%05lx\n",
current->comm, page_to_pfn(page));
dump_page_badflags(page, reason, bad_flags);
+ dump_page_owner(page);
print_modules();
dump_stack();
diff --git a/mm/page_owner.c b/mm/page_owner.c
index a57068cfe52f..44ad1f00c4e1 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -183,6 +183,31 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
return -ENOMEM;
}
+void __dump_page_owner(struct page *page)
+{
+ struct page_ext *page_ext = lookup_page_ext(page);
+ struct stack_trace trace = {
+ .nr_entries = page_ext->nr_entries,
+ .entries = &page_ext->trace_entries[0],
+ };
+ gfp_t gfp_mask = page_ext->gfp_mask;
+ int mt = gfpflags_to_migratetype(gfp_mask);
+
+ if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
+ pr_alert("page_owner info is not active (free page?)\n");
+ return;
+ }
+
+ pr_alert("page allocated via order %u, migratetype %s, "
+ "gfp_mask %#x(%pGg)\n", page_ext->order,
+ migratetype_names[mt], gfp_mask, &gfp_mask);
+ print_stack_trace(&trace, 0);
+
+ if (page_ext->last_migrate_reason != -1)
+ pr_alert("page has been migrated, last migrate reason: %s\n",
+ migrate_reason_names[page_ext->last_migrate_reason]);
+}
+
static ssize_t
read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
--
2.7.0
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>