Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753176Ab3G2JnO (ORCPT ); Mon, 29 Jul 2013 05:43:14 -0400 Received: from mail4.hitachi.co.jp ([133.145.228.5]:33508 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750926Ab3G2JnM (ORCPT ); Mon, 29 Jul 2013 05:43:12 -0400 Message-ID: <51F6392C.8000806@hitachi.com> Date: Mon, 29 Jul 2013 18:43:08 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 5.2; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Oleg Nesterov Cc: Steven Rostedt , Alexander Z Lam , Arnaldo Carvalho de Melo , David Sharp , Frederic Weisbecker , Greg Kroah-Hartman , Ingo Molnar , Peter Zijlstra , Srikar Dronamraju , Vaibhav Nagarnaik , "zhangwei(Jovi)" , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 6/6] tracing: Change remove_event_file_dir() to clear "d_subdirs"->i_private References: <20130726172551.GA3632@redhat.com> In-Reply-To: <20130726172551.GA3632@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3753 Lines: 119 (2013/07/27 2:25), Oleg Nesterov wrote: > Change remove_event_file_dir() to clear ->i_private for every > file we are going to remove. Oleg, I think this should be done first. AFAICS, your former patches depend strongly on this change. Without this, they don't work as you expected, and it may prevent git-bisect. I see, including this patch also breaks current ftrace. Thus, IMHO, it would better to make a separate patch which just nullifies i_private with adding some NULL checks where accessing i_private to avoid the breakages. This looks a bit long way round, but it ensures bisecting. Thank you, > tracing_open_generic_file() and tracing_release_generic_file() > can go away, ftrace_enable_fops and ftrace_event_filter_fops() > use tracing_open_generic() but only to check tracing_disabled. > > This fixes all races with event_remove() or instance_delete(). > f_op->read/write/whatever can never use the freed file/call, > all event/* files were changed to check and use ->i_private > under event_mutex. > > Note: this doesn't not fix other problems, event_remove() can > destroy the active ftrace_event_call, we need more changes but > those changes are completely orthogonal. > > Signed-off-by: Oleg Nesterov > --- > kernel/trace/trace_events.c | 41 +++++++++-------------------------------- > 1 files changed, 9 insertions(+), 32 deletions(-) > > diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c > index 2a4f68a..1112fa0 100644 > --- a/kernel/trace/trace_events.c > +++ b/kernel/trace/trace_events.c > @@ -428,42 +428,20 @@ static void *event_file_data(struct file *filp) > > static void remove_event_file_dir(struct ftrace_event_file *file) > { > + struct dentry *dir = file->dir; > + struct dentry *child; > + > + /* ->i_mutex is not needed, nobody can create/remove a file */ > + list_for_each_entry(child, &dir->d_subdirs, d_u.d_child) > + child->d_inode->i_private = NULL; > + > list_del(&file->list); > - debugfs_remove_recursive(file->dir); > + debugfs_remove_recursive(dir); > remove_subsystem(file->system); > kmem_cache_free(file_cachep, file); > } > > /* > - * Open and update trace_array ref count. > - * Must have the current trace_array passed to it. > - */ > -static int tracing_open_generic_file(struct inode *inode, struct file *filp) > -{ > - struct ftrace_event_file *file = inode->i_private; > - struct trace_array *tr = file->tr; > - int ret; > - > - if (trace_array_get(tr) < 0) > - return -ENODEV; > - > - ret = tracing_open_generic(inode, filp); > - if (ret < 0) > - trace_array_put(tr); > - return ret; > -} > - > -static int tracing_release_generic_file(struct inode *inode, struct file *filp) > -{ > - struct ftrace_event_file *file = inode->i_private; > - struct trace_array *tr = file->tr; > - > - trace_array_put(tr); > - > - return 0; > -} > - > -/* > * __ftrace_set_clr_event(NULL, NULL, NULL, set) will set/unset all events. > */ > static int > @@ -1277,10 +1255,9 @@ static const struct file_operations ftrace_set_event_fops = { > }; > > static const struct file_operations ftrace_enable_fops = { > - .open = tracing_open_generic_file, > + .open = tracing_open_generic, > .read = event_enable_read, > .write = event_enable_write, > - .release = tracing_release_generic_file, > .llseek = default_llseek, > }; > > -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/