The patch titled
Subject: mm, page_owner, debug_pagealloc: save and dump freeing stack trace
has been added to the -mm tree. Its filename is
mm-page_owner-debug_pagealloc-save-and-dump-freeing-stack-trace.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page_owner-debug_pagealloc-save-and-dump-freeing-stack-trace.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_owner-debug_pagealloc-save-and-dump-freeing-stack-trace.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: mm, page_owner, debug_pagealloc: save and dump freeing stack trace
The debug_pagealloc functionality is useful to catch buggy page allocator
users that cause e.g. use after free or double free. When page
inconsistency is detected, debugging is often simpler by knowing the call
stack of process that last allocated and freed the page. When page_owner
is also enabled, we record the allocation stack trace, but not freeing.
This patch therefore adds recording of freeing process stack trace to page
owner info, if both page_owner and debug_pagealloc are configured and
enabled. With only page_owner enabled, this info is not useful for the
memory leak debugging use case. dump_page() is adjusted to print the
info. An example result of calling __free_pages() twice may look like
this (note the page last free stack trace):
BUG: Bad page state in process bash pfn:13d8f8
page:ffffc31984f63e00 refcount:-1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x1affff800000000()
raw: 01affff800000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 ffffffffffffffff 0000000000000000
page dumped because: nonzero _refcount
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xcc0(GFP_KERNEL)
prep_new_page+0x143/0x150
get_page_from_freelist+0x289/0x380
__alloc_pages_nodemask+0x13c/0x2d0
khugepaged+0x6e/0xc10
kthread+0xf9/0x130
ret_from_fork+0x3a/0x50
page last free stack trace:
free_pcp_prepare+0x134/0x1e0
free_unref_page+0x18/0x90
khugepaged+0x7b/0xc10
kthread+0xf9/0x130
ret_from_fork+0x3a/0x50
Modules linked in:
CPU: 3 PID: 271 Comm: bash Not tainted 5.3.0-rc4-2.g07a1a73-default+ #57
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58-prebuilt.qemu.org 04/01/2014
Call Trace:
dump_stack+0x85/0xc0
bad_page.cold+0xba/0xbf
rmqueue_pcplist.isra.0+0x6c5/0x6d0
rmqueue+0x2d/0x810
get_page_from_freelist+0x191/0x380
__alloc_pages_nodemask+0x13c/0x2d0
__get_free_pages+0xd/0x30
__pud_alloc+0x2c/0x110
copy_page_range+0x4f9/0x630
dup_mmap+0x362/0x480
dup_mm+0x68/0x110
copy_process+0x19e1/0x1b40
_do_fork+0x73/0x310
__x64_sys_clone+0x75/0x80
do_syscall_64+0x6e/0x1e0
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f10af854a10
...
Link: http://lkml.kernel.org/r/20190820131828.22684-5-vbabka@xxxxxxx
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 2
mm/Kconfig.debug | 4 -
mm/page_owner.c | 53 ++++++++++----
3 files changed, 45 insertions(+), 14 deletions(-)
--- a/Documentation/admin-guide/kernel-parameters.txt~mm-page_owner-debug_pagealloc-save-and-dump-freeing-stack-trace
+++ a/Documentation/admin-guide/kernel-parameters.txt
@@ -809,6 +809,8 @@
enables the feature at boot time. By default, it is
disabled and the system will work mostly the same as a
kernel built without CONFIG_DEBUG_PAGEALLOC.
+ Note: to get most of debug_pagealloc error reports, it's
+ useful to also enable the page_owner functionality.
on: enable the feature
debugpat [X86] Enable PAT debugging
--- a/mm/Kconfig.debug~mm-page_owner-debug_pagealloc-save-and-dump-freeing-stack-trace
+++ a/mm/Kconfig.debug
@@ -21,7 +21,9 @@ config DEBUG_PAGEALLOC
Also, the state of page tracking structures is checked more often as
pages are being allocated and freed, as unexpected state changes
often happen for same reasons as memory corruption (e.g. double free,
- use-after-free).
+ use-after-free). The error reports for these checks can be augmented
+ with stack traces of last allocation and freeing of the page, when
+ PAGE_OWNER is also selected and enabled on boot.
For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
fill the pages with poison patterns after free_pages() and verify
--- a/mm/page_owner.c~mm-page_owner-debug_pagealloc-save-and-dump-freeing-stack-trace
+++ a/mm/page_owner.c
@@ -24,6 +24,9 @@ struct page_owner {
short last_migrate_reason;
gfp_t gfp_mask;
depot_stack_handle_t handle;
+#ifdef CONFIG_DEBUG_PAGEALLOC
+ depot_stack_handle_t free_handle;
+#endif
};
static bool page_owner_disabled = true;
@@ -102,19 +105,6 @@ static inline struct page_owner *get_pag
return (void *)page_ext + page_owner_ops.offset;
}
-void __reset_page_owner(struct page *page, unsigned int order)
-{
- int i;
- struct page_ext *page_ext;
-
- for (i = 0; i < (1 << order); i++) {
- page_ext = lookup_page_ext(page + i);
- if (unlikely(!page_ext))
- continue;
- __clear_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags);
- }
-}
-
static inline bool check_recursive_alloc(unsigned long *entries,
unsigned int nr_entries,
unsigned long ip)
@@ -154,6 +144,32 @@ static noinline depot_stack_handle_t sav
return handle;
}
+void __reset_page_owner(struct page *page, unsigned int order)
+{
+ int i;
+ struct page_ext *page_ext;
+#ifdef CONFIG_DEBUG_PAGEALLOC
+ depot_stack_handle_t handle = 0;
+ struct page_owner *page_owner;
+
+ if (debug_pagealloc_enabled())
+ handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
+#endif
+
+ for (i = 0; i < (1 << order); i++) {
+ page_ext = lookup_page_ext(page + i);
+ if (unlikely(!page_ext))
+ continue;
+ __clear_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags);
+#ifdef CONFIG_DEBUG_PAGEALLOC
+ if (debug_pagealloc_enabled()) {
+ page_owner = get_page_owner(page_ext);
+ page_owner->free_handle = handle;
+ }
+#endif
+ }
+}
+
static inline void __set_page_owner_handle(struct page *page,
struct page_ext *page_ext, depot_stack_handle_t handle,
unsigned int order, gfp_t gfp_mask)
@@ -435,6 +451,17 @@ void __dump_page_owner(struct page *page
stack_trace_print(entries, nr_entries, 0);
}
+#ifdef CONFIG_DEBUG_PAGEALLOC
+ handle = READ_ONCE(page_owner->free_handle);
+ if (!handle) {
+ pr_alert("page_owner free stack trace missing\n");
+ } else {
+ nr_entries = stack_depot_fetch(handle, &entries);
+ pr_alert("page last free stack trace:\n");
+ stack_trace_print(entries, nr_entries, 0);
+ }
+#endif
+
if (page_owner->last_migrate_reason != -1)
pr_alert("page has been migrated, last migrate reason: %s\n",
migrate_reason_names[page_owner->last_migrate_reason]);
_
Patches currently in -mm which might be from vbabka@xxxxxxx are
mm-page_owner-handle-thp-splits-correctly.patch
mm-page_owner-record-page-owner-for-each-subpage.patch
mm-page_owner-keep-owner-info-when-freeing-the-page.patch
mm-page_owner-debug_pagealloc-save-and-dump-freeing-stack-trace.patch
mm-compaction-clear-total_migratefree_scanned-before-scanning-a-new-zone-fix-2.patch
mm-reclaim-cleanup-should_continue_reclaim.patch
mm-compaction-raise-compaction-priority-after-it-withdrawns.patch
