mm: page_owner: detect page_owner recursion via task_struct
Before the change page_owner recursion was detected via fetching
backtrace and inspecting it for current instruction pointer.
It has a few problems:
- it is slightly slow as it requires extra backtrace and a linear stack
scan of the result
- it is too late to check if backtrace fetching required memory
allocation itself (ia64's unwinder requires it).
To simplify recursion tracking let's use page_owner recursion flag in
'struct task_struct'.
The change make page_owner=on work on ia64 by avoiding infinite
recursion in:
kmalloc()
-> __set_page_owner()
-> save_stack()
-> unwind() [ia64-specific]
-> build_script()
-> kmalloc()
-> __set_page_owner() [we short-circuit here]
-> save_stack()
-> unwind() [recursion]
Link: https://lkml.kernel.org/r/20210402115342.1463781-1-slyfox@gentoo.org
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 5c941ca..9661d53 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -98,42 +98,30 @@ static inline struct page_owner *get_page_owner(struct page_ext *page_ext)
return (void *)page_ext + page_owner_ops.offset;
}
-static inline bool check_recursive_alloc(unsigned long *entries,
- unsigned int nr_entries,
- unsigned long ip)
-{
- unsigned int i;
-
- for (i = 0; i < nr_entries; i++) {
- if (entries[i] == ip)
- return true;
- }
- return false;
-}
-
static noinline depot_stack_handle_t save_stack(gfp_t flags)
{
unsigned long entries[PAGE_OWNER_STACK_DEPTH];
depot_stack_handle_t handle;
unsigned int nr_entries;
- nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
-
/*
- * We need to check recursion here because our request to
- * stackdepot could trigger memory allocation to save new
- * entry. New memory allocation would reach here and call
- * stack_depot_save_entries() again if we don't catch it. There is
- * still not enough memory in stackdepot so it would try to
- * allocate memory again and loop forever.
+ * Avoid recursion.
+ *
+ * Sometimes page metadata allocation tracking requires more
+ * memory to be allocated:
+ * - when new stack trace is saved to stack depot
+ * - when backtrace itself is calculated (ia64)
*/
- if (check_recursive_alloc(entries, nr_entries, _RET_IP_))
+ if (current->in_page_owner)
return dummy_handle;
+ current->in_page_owner = 1;
+ nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
handle = stack_depot_save(entries, nr_entries, flags);
if (!handle)
handle = failure_handle;
+ current->in_page_owner = 0;
return handle;
}