linux-kernel - Re: [PATCH v2 1/5] exec: Only compute current once in flush_old

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Date:   Mon, 09 Mar 2020 12:34:24 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Bernd Edlinger <bernd.edlinger@...mail.de>
Cc:     Christian Brauner <christian.brauner@...ntu.com>,
        Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Oleg Nesterov <oleg@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Andrei Vagin <avagin@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        "Peter Zijlstra \(Intel\)" <peterz@...radead.org>,
        Yuyang Du <duyuyang@...il.com>,
        David Hildenbrand <david@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Anshuman Khandual <anshuman.khandual@....com>,
        David Howells <dhowells@...hat.com>,
        James Morris <jamorris@...ux.microsoft.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christian Kellner <christian@...lner.me>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Aleksa Sarai <cyphar@...har.com>,
        "Dmitry V. Levin" <ldv@...linux.org>,
        "linux-doc\@vger.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-fsdevel\@vger.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-mm\@kvack.org" <linux-mm@...ck.org>,
        "stable\@vger.kernel.org" <stable@...r.kernel.org>,
        "linux-api\@vger.kernel.org" <linux-api@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] exec: Only compute current once in flush_old_exec

Bernd Edlinger <bernd.edlinger@...mail.de> writes:

> On 3/8/20 10:35 PM, Eric W. Biederman wrote:
>> 
>> Make it clear that current only needs to be computed once in
>> flush_old_exec.  This may have some efficiency improvements and it
>> makes the code easier to change.
>> 
>> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
>> ---
>>  fs/exec.c | 9 +++++----
>>  1 file changed, 5 insertions(+), 4 deletions(-)
>> 
>> diff --git a/fs/exec.c b/fs/exec.c
>> index db17be51b112..c3f34791f2f0 100644
>> --- a/fs/exec.c
>> +++ b/fs/exec.c
>> @@ -1260,13 +1260,14 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
>>   */
>>  int flush_old_exec(struct linux_binprm * bprm)
>>  {
>> +	struct task_struct *me = current;
>>  	int retval;
>>  
>>  	/*
>>  	 * Make sure we have a private signal table and that
>>  	 * we are unassociated from the previous thread group.
>>  	 */
>> -	retval = de_thread(current);
>> +	retval = de_thread(me);
>>  	if (retval)
>>  		goto out;
>>  
>> @@ -1294,10 +1295,10 @@ int flush_old_exec(struct linux_binprm * bprm)
>>  	bprm->mm = NULL;
>>  
>>  	set_fs(USER_DS);
>> -	current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
>> +	me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
>>  					PF_NOFREEZE | PF_NO_SETAFFINITY);
>
> I wonder if this line should be aligned with the previous?

In this case I don't think so.  The style used for second line is indent
with tabs as much as possible to the right.  I haven't changed that.

Further mixing a change in indentation style with just a variable rename
will make the patch confusing to read because two things have to be
verified at the same time.

So while I see why you ask I think this bit needs to stay as is.

Eric