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author | Sergei Trofimovich <slyfox@gentoo.org> | 2021-04-29 22:55:08 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-04-30 11:20:36 -0700 |
commit | 8e9b16c47680f6e7d6e5864a37f313f905a91cf5 (patch) | |
tree | 808c4e3b1e920e4a0c570f2eab9deec1ff14bb83 /mm/page_owner.c | |
parent | 608b5d668c8ea6734594a401c9adab4093ad9847 (diff) | |
download | lwn-8e9b16c47680f6e7d6e5864a37f313f905a91cf5.tar.gz lwn-8e9b16c47680f6e7d6e5864a37f313f905a91cf5.zip |
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>
Diffstat (limited to 'mm/page_owner.c')
-rw-r--r-- | mm/page_owner.c | 32 |
1 files changed, 10 insertions, 22 deletions
diff --git a/mm/page_owner.c b/mm/page_owner.c index 5c941ca9861d..9661d5320a07 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; } |