On Tue, 2013-03-12 at 11:05 +0100, Jiri Olsa wrote:
> +/*
> + * Returns the total number of pages allocated
> + * by ring buffer including the user page.
> + */
> +static int page_nr(struct ring_buffer *rb)
> +{
> + return page_order(rb) == -1 ?
> + 1 : /* no data, just user page */
> + 1 + (1 << page_order(rb)); /* user page + data pages */
> +}
> @@ -371,9 +381,24 @@ struct ring_buffer *rb_alloc(int nr_pages, long
> watermark, int cpu, int flags)
> goto fail_all_buf;
>
> rb->user_page = all_buf;
> - rb->data_pages[0] = all_buf + PAGE_SIZE;
> - rb->page_order = ilog2(nr_pages);
> - rb->nr_pages = 1;
> +
> + rb->data_pages[0] = nr_pages ? all_buf + PAGE_SIZE : NULL;
> + rb->nr_pages = nr_pages ? 1 : 0;
> + rb->page_order = ilog2(nr_pages);
>
> ring_buffer_init(rb, watermark, flags);
Still somewhat confused by this.. wouldn't something 'simple' like the
below suffice?
Note how the !vmalloc branch also sets rb->nr_pages = nr_pages.
---
kernel/events/ring_buffer.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 23cb34f..4f48d02 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)
return NULL;
return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
@@ -336,7 +336,7 @@ 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;
base = rb->user_page;
for (i = 0; i < nr + 1; i++)
@@ -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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