From: Masami Hiramatsu (Google) Date: Fri, 24 Apr 2026 06:52:10 +0000 (+0900) Subject: ring-buffer: Do not double count the reader_page X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=92d5a606721f759ebebf448b3bd2b7a781d50bd0;p=thirdparty%2Flinux.git ring-buffer: Do not double count the reader_page Since the cpu_buffer->reader_page is updated if there are unwound pages. After that update, we should skip the page if it is the original reader_page, because the original reader_page is already checked. Cc: stable@vger.kernel.org Cc: Catalin Marinas Cc: Will Deacon Cc: Mathieu Desnoyers Cc: Ian Rogers Link: https://patch.msgid.link/177701353063.2223789.1471163147644103306.stgit@mhiramat.tok.corp.google.com Fixes: ca296d32ece3 ("tracing: ring_buffer: Rewind persistent ring buffer on reboot") Signed-off-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt --- diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index cef49f8871d2..5326924615a4 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1884,7 +1884,7 @@ static int rb_validate_buffer(struct buffer_data_page *dpage, int cpu) static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer) { struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta; - struct buffer_page *head_page, *orig_head; + struct buffer_page *head_page, *orig_head, *orig_reader; unsigned long entry_bytes = 0; unsigned long entries = 0; int ret; @@ -1895,16 +1895,17 @@ static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer) return; orig_head = head_page = cpu_buffer->head_page; + orig_reader = cpu_buffer->reader_page; /* Do the reader page first */ - ret = rb_validate_buffer(cpu_buffer->reader_page->page, cpu_buffer->cpu); + ret = rb_validate_buffer(orig_reader->page, cpu_buffer->cpu); if (ret < 0) { pr_info("Ring buffer reader page is invalid\n"); goto invalid; } entries += ret; - entry_bytes += local_read(&cpu_buffer->reader_page->page->commit); - local_set(&cpu_buffer->reader_page->entries, ret); + entry_bytes += local_read(&orig_reader->page->commit); + local_set(&orig_reader->entries, ret); ts = head_page->page->time_stamp; @@ -2007,8 +2008,8 @@ static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer) /* Iterate until finding the commit page */ for (i = 0; i < meta->nr_subbufs + 1; i++, rb_inc_page(&head_page)) { - /* Reader page has already been done */ - if (head_page == cpu_buffer->reader_page) + /* The original reader page has already been checked/counted. */ + if (head_page == orig_reader) continue; ret = rb_validate_buffer(head_page->page, cpu_buffer->cpu);