From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3753A4FC8D1 for ; Tue, 22 Sep 2026 07:29:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.71 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790062199; cv=none; b=i/jSwxzdDaQRYa6YbYdmofwTct/StPpeY574SW3N2jazmmaPk0ZaGEOB+OZo9XdrGlnxeTYyhHj3KQCg5/XZ1TXZpDIxkS3809uvqmDGRAGHUn6HQmu1+8IzrxrParUVfoShch1QDS0yCSgCAPNY2yA2ISXoimLN3SwnunZRVtU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790062199; c=relaxed/simple; bh=d4W1CAKZqJFP+rhzc/mGkXmSM4enJRB9Jj4NgZnjZbc=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=XXwq797pXGf/iVH+qYnm2mHigw/+2HV4e7OrGe4KH0RIyBnL2/gro9jdWqNaGZdBzpV1dkE+hIBjFkUhYqvy2JpRQOGOc4OLc0XMOjZrktnIBfkuQ/3BAyjRSWxxE5AWoe/0fg7YKyPy+JW6IPfCyMxAqLBmsPsqRRb+PdO4Lz8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=G/Ik0XL7; arc=none smtp.client-ip=209.85.128.71 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="G/Ik0XL7" Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-490a767c7dcso28239485e9.2 for ; Tue, 22 Sep 2026 00:29:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1790062196; x=1790666996; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=j1G2B+1jiMpXjFmSkI0X0frbWg2TCjpXRk9JIZopsjE=; b=G/Ik0XL73T6Ln+9drxC5PWRNnCyhPGJztUXGtf1kJBuwJS8jF5d9Kfh+gUK2rAsZLC 1y7lOSG3WLo+AGpdD/i0oA94wCwg4+R0ggMWVC/i19tiTQTYiH/rF/R6o7gG4sIptmY9 B5zw6Ofu0rLfrgAlxvB3HYYV5lasCS1Xog93klxnldeD8XPDXApUtPjxhxxyz2L15QSO UI5QAVi+EUcCGskSFJYpG78m4AdVeC8cfV4WuKitzZc+Zsn+CjRxVJXwj7bnViFKeCSU WwvDv6eMNediewj7KZTrmPczqeDEYqEC0qCXUZ1+E/2FOlsILgt9bnoDhJzdZ3iiwDd/ qYDA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790062196; x=1790666996; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=j1G2B+1jiMpXjFmSkI0X0frbWg2TCjpXRk9JIZopsjE=; b=gDTdz8cfm1K86sEbF+Q34lAnvzS7pTvj/z9t2ZHVf0AN5DtuFrmqW5zR7O0xFKAWgU ba5KIILLtNjifWRSBG2PvUFYP17/kmC0EI4RvuxXhwzKnSFuhykqZtKuEVL6BUITX92O JKZVPWB0fqd1U4WTa4UZrQECV2wcGAiJd+FzsyhL8EatkBD5bKChHQ6HeP5bhtxM2J2Y 4mv7ToBOZzQk1qa+vNZtcJv8T9/Rcz6AckhHonoKOco5DQIkG3n5ROeEMlxvi6xpJfRi yMOVZ0KZqEMM05BVkCy9IF/6zCp2WF7+UoBjnTmi5lWcklXtv8AybsEfAYjOOUg8xNeZ Zm7Q== X-Forwarded-Encrypted: i=1; AKwUvBw92qH4m2J45zQ83rpJuapTfdnU5bvzSkVOMcSgToerxlTn1gGjhSbXi1Ex4d5Mi6BLlKPJawW2nuVz/jw=@vger.kernel.org X-Gm-Message-State: AFuF++lalXHLsFey24uL33UER7yUYaRxLYmeKAqZO4de98vH+CevLZaP fyLYU5h54T1OUD67QnfRdlN6mfH1+s9K04uw5gVI+TDmrS8kG29Ufz/nWz1frkFHBrOkd+1OSAt d6XSB5XdYG9Bpis7KHas9dg== X-Received: from wmxe3-n1.prod.google.com ([2002:a05:600d:6503:10b0:49e:6ad9:14a2]) (user=vdonnefort job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:3e07:b0:49c:fc6c:be09 with SMTP id 5b1f17b1804b1-49fc58594d0mr181580785e9.32.1790062196167; Tue, 22 Sep 2026 00:29:56 -0700 (PDT) Date: Tue, 22 Sep 2026 08:29:43 +0100 In-Reply-To: <20260922072944.1281427-1-vdonnefort@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260922072944.1281427-1-vdonnefort@google.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Message-ID: <20260922072944.1281427-4-vdonnefort@google.com> Subject: [PATCH 3/4] ring-buffer: Drop redundant ring_buffer_iter::event_size From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, linux-kernel@vger.kernel.org, Vincent Donnefort Content-Type: text/plain; charset="UTF-8" event_size contains the maximum size the iterator can read for each event. It corresponds to the maximum capacity of a ring-buffer page. During non-consuming read, resizing is disabled. It is therefore safe to just use rb_subbuf_capacity(), making event_size redundant. Remove it. Signed-off-by: Vincent Donnefort --- kernel/trace/ring_buffer.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 1a158a24b3c8..3129589e2d0e 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -680,7 +680,6 @@ struct ring_buffer_iter { u64 read_stamp; u64 page_stamp; struct ring_buffer_event *event; - size_t event_size; int missed_events; }; @@ -3558,9 +3557,11 @@ rb_iter_head_event(struct ring_buffer_iter *iter) */ barrier(); - if ((iter->head + length) > commit || length > iter->event_size) + if ((iter->head + length) > commit || + length > rb_subbuf_capacity(iter->cpu_buffer->buffer)) { /* Writer corrupted the read? */ goto reset; + } memcpy(iter->event, event, length); /* @@ -6488,8 +6489,7 @@ ring_buffer_read_start(struct trace_buffer *buffer, int cpu, gfp_t flags) mutex_unlock(&buffer->mutex); /* Holds the entire event: data and meta data. */ - iter->event_size = rb_page_capacity(READ_ONCE(cpu_buffer->reader_page)); - iter->event = kmalloc(iter->event_size, flags); + iter->event = kmalloc(rb_subbuf_capacity(buffer), flags); if (!iter->event) { atomic_dec(&cpu_buffer->resize_disabled); return NULL; -- 2.55.0.1082.g2b9226bbc0-goog