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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>
This commit is contained in:
Sergei Trofimovich 2021-04-29 22:55:08 -07:00 committed by Linus Torvalds
parent 608b5d668c
commit 8e9b16c476
2 changed files with 14 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/sched.h
View File

@ -841,6 +841,10 @@ struct task_struct {
/* Stalled due to lack of memory */
unsigned in_memstall:1;
#endif
#ifdef CONFIG_PAGE_OWNER
/* Used by page_owner=on to detect recursion in page tracking. */
unsigned in_page_owner:1;
#endif
unsigned long atomic_flags; /* Flags requiring atomic access. */

32
mm/page_owner.c
View File

@ -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;
}