From c2d2856cf6c9efccdf5e0d2564162ec616ce58cf Mon Sep 17 00:00:00 2001 From: David Carlier Date: Tue, 12 May 2026 14:54:20 +0100 Subject: 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 --- kernel/trace/simple_ring_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/trace/simple_ring_buffer.c') diff --git a/kernel/trace/simple_ring_buffer.c b/kernel/trace/simple_ring_buffer.c index 02af2297ae5a..f731f14d0ff7 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; -- cgit v1.2.3 From a0a2f42a37f90b29d8c43374dd9c8bd2f3e7bdcc Mon Sep 17 00:00:00 2001 From: Vincent Donnefort Date: Tue, 12 May 2026 15:16:14 +0100 Subject: tracing: Fix unload_page for simple_ring_buffer init rollback The unload_page callback expects the return value of load_page() as its argument: ret = load_page(va); unload(ret). Fix the rollback code in simple_ring_buffer_init_mm() where the descriptor's VA is used instead of the loaded page address. Link: https://patch.msgid.link/20260512141614.1759430-1-vdonnefort@google.com Fixes: 635923081c79 ("tracing: load/unload page callbacks for simple_ring_buffer") Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt --- kernel/trace/simple_ring_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/trace/simple_ring_buffer.c') diff --git a/kernel/trace/simple_ring_buffer.c b/kernel/trace/simple_ring_buffer.c index f731f14d0ff7..f4642f5adda3 100644 --- a/kernel/trace/simple_ring_buffer.c +++ b/kernel/trace/simple_ring_buffer.c @@ -430,7 +430,7 @@ int simple_ring_buffer_init_mm(struct simple_rb_per_cpu *cpu_buffer, if (ret) { for (i--; i >= 0; i--) - unload_page((void *)desc->page_va[i]); + unload_page(bpages[i].page); unload_page(cpu_buffer->meta); return ret; -- cgit v1.2.3