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perf/core: Fix impossible ring-buffer sizes warning

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The following commit:

  9dff0aa95a ("perf/core: Don't WARN() for impossible ring-buffer sizes")

results in perf recording failures with larger mmap areas:

  root@skl:/tmp# perf record -g -a
  failed to mmap with 12 (Cannot allocate memory)

The root cause is that the following condition is buggy:

	if (order_base_2(size) >= MAX_ORDER)
		goto fail;

The problem is that @size is in bytes and MAX_ORDER is in pages,
so the right test is:

	if (order_base_2(size) >= PAGE_SHIFT+MAX_ORDER)
		goto fail;

Fix it.

Reported-by: "Jin, Yao" <[email protected]>
Bisected-by: Borislav Petkov <[email protected]>
Analyzed-by: Peter Zijlstra <[email protected]>
Cc: Julien Thierry <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: <[email protected]>
Fixes: 9dff0aa95a ("perf/core: Don't WARN() for impossible ring-buffer sizes")
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Ingo Molnar 2019-02-13 07:57:02 +01:00
commit 528871b456
1 changed files with 1 additions and 1 deletions
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2
kernel/events/ring_buffer.c
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@ -734,7 +734,7 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
size = sizeof(struct ring_buffer);
size += nr_pages * sizeof(void *);
if (order_base_2(size) >= MAX_ORDER)
if (order_base_2(size) >= PAGE_SHIFT+MAX_ORDER)
goto fail;
rb = kzalloc(size, GFP_KERNEL);