From: David Carlier Date: Tue, 12 May 2026 13:54:20 +0000 (+0100) Subject: tracing: Fix nr_subbufs initialization in simple_ring_buffer_init_mm() X-Git-Tag: v7.1-rc5~42^2~2 X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=c2d2856cf6c9efccdf5e0d2564162ec616ce58cf;p=thirdparty%2Fkernel%2Flinux.git tracing: Fix nr_subbufs initialization in simple_ring_buffer_init_mm() nr_subbufs in the ring buffer metadata is always initialized to zero because it is assigned from cpu_buffer->nr_pages before the page initialization loop has run. While nr_subbufs is not currently read by the kernel, it should reflect the actual buffer geometry in the meta page for correctness. Move the assignment after the page loop so that cpu_buffer->nr_pages holds the final count. Link: https://patch.msgid.link/20260512135420.99194-1-devnexen@gmail.com Fixes: 34e5b958bdad ("tracing: Introduce simple_ring_buffer") Reviewed-by: Vincent Donnefort Assisted-by: Claude:claude-opus-4-7 Signed-off-by: David Carlier Signed-off-by: Steven Rostedt --- diff --git a/kernel/trace/simple_ring_buffer.c b/kernel/trace/simple_ring_buffer.c index 02af2297ae5a9..f731f14d0ff72 100644 --- a/kernel/trace/simple_ring_buffer.c +++ b/kernel/trace/simple_ring_buffer.c @@ -395,7 +395,6 @@ int simple_ring_buffer_init_mm(struct simple_rb_per_cpu *cpu_buffer, memset(cpu_buffer->meta, 0, sizeof(*cpu_buffer->meta)); cpu_buffer->meta->meta_page_size = PAGE_SIZE; - cpu_buffer->meta->nr_subbufs = cpu_buffer->nr_pages; /* The reader page is not part of the ring initially */ page = load_page(desc->page_va[0]); @@ -437,6 +436,7 @@ int simple_ring_buffer_init_mm(struct simple_rb_per_cpu *cpu_buffer, return ret; } + cpu_buffer->meta->nr_subbufs = cpu_buffer->nr_pages; /* Close the ring */ bpage->link.next = &cpu_buffer->tail_page->link; cpu_buffer->tail_page->link.prev = &bpage->link;