Re: [PATCHv3] perf: Fix vmalloc ring buffer free function

From: Peter Zijlstra
Date: Tue Mar 12 2013 - 12:25:10 EST


Right you are..

How about something like the below; using that 0 << -1 is still 0.

---
kernel/events/ring_buffer.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 23cb34f..e72ca70 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -316,7 +316,7 @@ void rb_free(struct ring_buffer *rb)
struct page *
perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
{
- if (pgoff > (1UL << page_order(rb)))
+ if (pgoff > (rb->nr_pages << page_order(rb)))
return NULL;

return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
@@ -336,10 +336,10 @@ static void rb_free_work(struct work_struct *work)
int i, nr;

rb = container_of(work, struct ring_buffer, work);
- nr = 1 << page_order(rb);
+ nr = rb->nr_pages << page_order(rb);

base = rb->user_page;
- for (i = 0; i < nr + 1; i++)
+ for (i = 0; i <= nr; i++)
perf_mmap_unmark_page(base + (i * PAGE_SIZE));

vfree(base);
@@ -373,7 +373,7 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
rb->user_page = all_buf;
rb->data_pages[0] = all_buf + PAGE_SIZE;
rb->page_order = ilog2(nr_pages);
- rb->nr_pages = 1;
+ rb->nr_pages = !!nr_pages;

ring_buffer_init(rb, watermark, flags);



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