The quilt patch titled
Subject: mm,page_owner: fix recursion
has been removed from the -mm tree. Its filename was
mmpage_owner-fix-recursion.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Oscar Salvador <osalvador@xxxxxxx>
Subject: mm,page_owner: fix recursion
Date: Fri, 15 Mar 2024 23:26:10 +0100
Prior to 217b2119b9e2 ("mm,page_owner: implement the tracking of the
stacks count") the only place where page_owner could potentially go into
recursion due to its need of allocating more memory was in save_stack(),
which ends up calling into stackdepot code with the possibility of
allocating memory.
We made sure to guard against that by signaling that the current task was
already in page_owner code, so in case a recursion attempt was made, we
could catch that and return dummy_handle.
After above commit, a new place in page_owner code was introduced where we
could allocate memory, meaning we could go into recursion would we take
that path.
Make sure to signal that we are in page_owner in that codepath as well.
Move the guard code into two helpers {un}set_current_in_page_owner() and
use them prior to calling in the two functions that might allocate memory.
Link: https://lkml.kernel.org/r/20240315222610.6870-1-osalvador@xxxxxxx
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
Fixes: 217b2119b9e2 ("mm,page_owner: implement the tracking of the stacks count")
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_owner.c | 33 +++++++++++++++++++++++----------
1 file changed, 23 insertions(+), 10 deletions(-)
--- a/mm/page_owner.c~mmpage_owner-fix-recursion
+++ a/mm/page_owner.c
@@ -54,6 +54,22 @@ static depot_stack_handle_t early_handle
static void init_early_allocated_pages(void);
+static inline void set_current_in_page_owner(void)
+{
+ /*
+ * Avoid recursion.
+ *
+ * We might need to allocate more memory from page_owner code, so make
+ * sure to signal it in order to avoid recursion.
+ */
+ current->in_page_owner = 1;
+}
+
+static inline void unset_current_in_page_owner(void)
+{
+ current->in_page_owner = 0;
+}
+
static int __init early_page_owner_param(char *buf)
{
int ret = kstrtobool(buf, &page_owner_enabled);
@@ -133,23 +149,16 @@ static noinline depot_stack_handle_t sav
depot_stack_handle_t handle;
unsigned int nr_entries;
- /*
- * Avoid recursion.
- *
- * Sometimes page metadata allocation tracking requires more
- * memory to be allocated:
- * - when new stack trace is saved to stack depot
- */
if (current->in_page_owner)
return dummy_handle;
- current->in_page_owner = 1;
+ set_current_in_page_owner();
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
handle = stack_depot_save(entries, nr_entries, flags);
if (!handle)
handle = failure_handle;
+ unset_current_in_page_owner();
- current->in_page_owner = 0;
return handle;
}
@@ -164,9 +173,13 @@ static void add_stack_record_to_list(str
gfp_mask &= (GFP_ATOMIC | GFP_KERNEL);
gfp_mask |= __GFP_NOWARN;
+ set_current_in_page_owner();
stack = kmalloc(sizeof(*stack), gfp_mask);
- if (!stack)
+ if (!stack) {
+ unset_current_in_page_owner();
return;
+ }
+ unset_current_in_page_owner();
stack->stack_record = stack_record;
stack->next = NULL;
_
Patches currently in -mm which might be from osalvador@xxxxxxx are
