From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 94F4623957D; Tue, 13 Jan 2026 00:31:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768264264; cv=none; b=fp5KN8JvoMAOO1uxx+dbxghFhfZr3NVfABy46CwcQoyuM1EaLsNHOlAil5FwHjFxeDeyVdO231jpoDVYTX2YFQ7/7TNS8Va0yGabbX2EAxOqmg2FNyXIAAVYAIwx1CeRnVWecIgBGALOISOuISt9EvEvTVALrp4Zl5lw1T3NSZs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768264264; c=relaxed/simple; bh=Xevtm1WOm9kyWXgohDFOUCvL20aHqTvicjIWscU/byo=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=qxqzkioaf78RQrld77XGVoCHuVLupIDDA/v8sogHDdfMZuNhi+Vgse/CuDmjwPpeQOQiaOpgNzA32Vq0kLZyFnvhbko9EJ/AlFwVyugaACJOWSm6yKT8nR8PpgxJhHLolxHGV0o3ffjaXYB126R9/0PGoV2vdZ8a4DVm/OIYWJQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=rl1uzUoZ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="rl1uzUoZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B10FAC116D0; Tue, 13 Jan 2026 00:31:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768264264; bh=Xevtm1WOm9kyWXgohDFOUCvL20aHqTvicjIWscU/byo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=rl1uzUoZpyM2H95cXB/Hg7BpKEE9QBFrws+zWKs4tOVXebju0HPeUme1Pv6D4LiXz YpSzAiBHGyHzlqoZ3DRAp2RkKgKSyjFPzmBwDMuSDGyLF1646gJS4n/JbEiwpKj9CQ YlH9PkqO82U7IyhrgEaaAkMTKnzn4vl+beMjOFhfhYFwP3xpQ5dOXRgX0T9j2AyHOY dP0dyEOgl33uEKVf4IpMApJNybEJsahTeoIqu7Y1+2XWO/Wj5lU+2gHgjxiH1tB5H+ kwyE1dZWo1JjTEgZwwZREVRCOdkzy8jjbof3JC/3g4/gKlDmOaiW+ouZKHsGNUyOmC nhiWjNHkqIUuw== Date: Tue, 13 Jan 2026 09:31:00 +0900 From: Masami Hiramatsu (Google) To: "Masami Hiramatsu (Google)" Cc: Steven Rostedt , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] tracing: Make the backup instance readonly Message-Id: <20260113093100.e91c5be8b8fa5f1e64899ba4@kernel.org> In-Reply-To: <176788218294.1398317.13118277798168167277.stgit@mhiramat.tok.corp.google.com> References: <176788217131.1398317.11144318616426272901.stgit@mhiramat.tok.corp.google.com> <176788218294.1398317.13118277798168167277.stgit@mhiramat.tok.corp.google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 8 Jan 2026 23:23:03 +0900 "Masami Hiramatsu (Google)" wrote: > diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c > index 9b07ad9eb284..741b16b54d90 100644 > --- a/kernel/trace/trace_events.c > +++ b/kernel/trace/trace_events.c > @@ -1379,6 +1379,9 @@ static int __ftrace_set_clr_event(struct trace_array *tr, const char *match, > { > int ret; > > + if (trace_array_is_readonly(tr)) > + return -EPERM; > + > mutex_lock(&event_mutex); > ret = __ftrace_set_clr_event_nolock(tr, match, sub, event, set, mod); > mutex_unlock(&event_mutex); > @@ -2817,8 +2820,8 @@ event_subsystem_dir(struct trace_array *tr, const char *name, > } else > __get_system(system); > > - /* ftrace only has directories no files */ > - if (strcmp(name, "ftrace") == 0) > + /* ftrace only has directories no files, readonly instance too. */ > + if (strcmp(name, "ftrace") == 0 || trace_array_is_readonly(tr)) > nr_entries = 0; > else > nr_entries = ARRAY_SIZE(system_entries); > @@ -2979,7 +2982,6 @@ event_create_dir(struct eventfs_inode *parent, struct trace_event_file *file) > struct eventfs_inode *e_events; > struct eventfs_inode *ei; > const char *name; > - int nr_entries; > int ret; > static struct eventfs_entry event_entries[] = { > { > @@ -3024,6 +3026,18 @@ event_create_dir(struct eventfs_inode *parent, struct trace_event_file *file) > }, > #endif > }; > + static struct eventfs_entry event_ro_entries[] = { > + { > + .name = "format", > + .callback = event_callback, > + }, > +#ifdef CONFIG_PERF_EVENTS > + { > + .name = "id", > + .callback = event_callback, > + }, > +#endif > + }; Thinking about this hack again, it would be easier to maintain if I add a readonly flag to each eventfs_entry and specify readonly when creating the eventfs top directory. Let me update it. Thank you, -- Masami Hiramatsu (Google)