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:
[ 199.188777] page:ffffea0002900540 count:2 mapcount:0 mapping:ffff880131993e18 index:0x34e
[ 199.202832] flags: 0x1fffff80020048(uptodate|active|mappedtodisk)
[ 199.207048] page dumped because: VM_BUG_ON_PAGE(1)
[ 199.207048] page->mem_cgroup:ffff880138efdc00
[ 199.207050] page allocated via order 0, mask 0x213da, migratetype 2, trace:
[ 199.207050] [<ffffffff811622c5>] __alloc_pages_nodemask+0x175/0x900
[ 199.207057] [<ffffffff811a69c1>] alloc_pages_current+0x91/0x100
[ 199.207061] [<ffffffff81158da1>] __page_cache_alloc+0xb1/0xf0
[ 199.207066] [<ffffffff81165eeb>] __do_page_cache_readahead+0xdb/0x200
[ 199.207067] [<ffffffff81166155>] ondemand_readahead+0x145/0x270
[ 199.207069] [<ffffffff811662ec>] page_cache_async_readahead+0x6c/0x70
[ 199.207070] [<ffffffff8115a838>] generic_file_read_iter+0x378/0x590
[ 199.207074] [<ffffffff811cd2d7>] __vfs_read+0xa7/0xd0
[ 199.207074] page has been migrated, last migrate reason: 0
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
---
include/linux/page_owner.h | 9 +++++++++
mm/debug.c | 2 ++
mm/page_owner.c | 18 ++++++++++++++++++
3 files changed, 29 insertions(+)
diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h
index 555893b..46f1b93 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 8362765..93373d1 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -9,6 +9,7 @@
#include <linux/mm.h>
#include <linux/trace_events.h>
#include <linux/memcontrol.h>
+#include <linux/page_owner.h>
static const struct trace_print_flags pageflag_names[] = {
{1UL << PG_locked, "locked" },
@@ -98,6 +99,7 @@ void dump_page_badflags(struct page *page, const char *reason,
if (page->mem_cgroup)
pr_alert("page->mem_cgroup:%p\n", page->mem_cgroup);
#endif
+ dump_page_owner(page);
}
void dump_page(struct page *page, const char *reason)
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 388898f..d7e0aaf 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -183,6 +183,24 @@ 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],
+ };
+
+ pr_alert("page allocated via order %u, mask 0x%x, migratetype %d, trace:\n",
+ page_ext->order, page_ext->gfp_mask,
+ gfpflags_to_migratetype(page_ext->gfp_mask));
+ print_stack_trace(&trace, 0);
+
+ if (page_ext->last_migrate_reason != -1)
+ pr_alert("page has been migrated, last migrate reason: %d\n",
+ page_ext->last_migrate_reason);
+}
+
static ssize_t
read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
--
2.6.2
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