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| author | Vincent Donnefort <vdonnefort@google.com> | 2026-09-11 20:39:37 +0100 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2026-10-15 18:31:09 -0400 |
| commit | 20d432b4454b54f32afaaa1b0ac336078c3b6be7 (patch) | |
| tree | 2db2badc2a3e96b849890254f5c76ecfa1e0add7 /include/linux | |
| parent | 8acb31975a55e5cf3efc36750dad5d0788ff8bb7 (diff) | |
| download | linux-20d432b4454b54f32afaaa1b0ac336078c3b6be7.tar.gz linux-20d432b4454b54f32afaaa1b0ac336078c3b6be7.zip | |
ring-buffer: Unify ring buffer minimum page calculations
The codebase scatters hardcoded minimum page limits across multiple
places. Introduce RING_BUFFER_MIN_NR_PAGES and rb_calculate_nr_pages()
to formalize the requirement of two pages in a ring buffer.
Link: https://patch.msgid.link/20260911193937.602202-4-vdonnefort@google.com
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/ring_buffer.h | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index eac3e9080c3c..e4370064273e 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -99,6 +99,13 @@ struct trace_buffer *__ring_buffer_alloc_range(unsigned long size, unsigned flag void *ring_buffer_meta_scratch(struct trace_buffer *buffer, unsigned int *size); /* + * A minimum of 2 pages ensures we can always swap a page out of the ring + * buffer. This does not account for the reader page or any other page + * containing meta data used by static ring buffers. + */ +#define RING_BUFFER_MIN_NR_PAGES 2UL + +/* * Because the ring buffer is generic, if other users of the ring buffer get * traced by ftrace, it can produce lockdep warnings. We need to keep each * ring buffer's lock class separate. @@ -287,7 +294,7 @@ static inline struct ring_buffer_desc *__first_ring_buffer_desc(struct trace_buf static inline unsigned long __calc_nr_pages_ring_buffer_desc(size_t size) { /* Takes into account the reader page */ - return max(DIV_ROUND_UP(size, PAGE_SIZE - BUF_PAGE_HDR_SIZE), 2UL) + 1; + return max(DIV_ROUND_UP(size, PAGE_SIZE - BUF_PAGE_HDR_SIZE), RING_BUFFER_MIN_NR_PAGES) + 1; } static inline size_t trace_buffer_desc_size(size_t buffer_size, unsigned int nr_cpus) |