mm,page_owner: fix recursion

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@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Fixes: 217b2119b9e2 ("mm,page_owner: implement the tracking of the stacks count")
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Marco Elver <elver@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/page_owner.c b/mm/page_owner.c
index e7139952ffd9dee593fd51fa88a9c69d8d830cd3..d17d1351ec84af6ae4f49dc34d4c27c56bf77468 100644 (file)
--- a/mm/page_owner.c
+++ b/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 save_stack(gfp_t flags)
        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(struct stack_record *stack_record,
        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;