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Date:   Tue, 3 Mar 2020 07:01:28 +0800
From:   Philip Li <philip.li@intel.com>
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     kbuild test robot <lkp@intel.com>, kbuild-all@lists.01.org,
        linux-kernel@vger.kernel.org
Subject: Re: [kbuild-all] Re: [PATCH 3/3] proc: Remove the now unnecessary
 internal mount of proc
Message-ID: <20200302230128.GE5513@intel.com>
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 <8736auov5g.fsf@x220.int.ebiederm.org>
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On Fri, Feb 28, 2020 at 10:49:15PM -0600, Eric W. Biederman wrote:
> kbuild test robot <lkp@intel.com> writes:
> 
> > Hi "Eric,
> >
> > Thank you for the patch! Yet something to improve:
> 
> Dear kbuild robot,
> 
> Yep. You got it the wrong base.  I will see about using --base
thanks for the feedback, we will also take a look to see
how to better identify the base automatically.

> if I repost, or have another patchset that so clearly needs
> to be applied on top of a non-default base.
> 
> Thank you for writing me how to do that.
> 
> Eric
> 
> 
> > [auto build test ERROR on uml/linux-next]
> > [also build test ERROR on linux/master kees/for-next/pstore linus/master v5.6-rc3 next-20200228]
> > [if your patch is applied to the wrong git tree, please drop us a note to help
> > improve the system. BTW, we also suggest to use '--base' option to specify the
> > base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
> >
> > url:    https://github.com/0day-ci/linux/commits/Eric-W-Biederman/proc-Actually-honor-the-mount-options/20200229-100926
> > base:   https://git.kernel.org/pub/scm/linux/kernel/git/rw/uml.git linux-next
> > config: x86_64-defconfig (attached as .config)
> > compiler: gcc-7 (Debian 7.5.0-5) 7.5.0
> > reproduce:
> >         # save the attached .config to linux build tree
> >         make ARCH=x86_64 
> >
> > If you fix the issue, kindly add following tag
> > Reported-by: kbuild test robot <lkp@intel.com>
> >
> > All errors (new ones prefixed by >>):
> >
> >    fs/proc/base.c: In function 'proc_flush_task':
> >>> fs/proc/base.c:3217:33: error: 'struct pid_namespace' has no member named 'proc_mnt'; did you mean 'proc_self'?
> >       proc_flush_task_mnt(upid->ns->proc_mnt, upid->nr,
> >                                     ^~~~~~~~
> >                                     proc_self
> >
> > vim +3217 fs/proc/base.c
> >
> > ^1da177e4c3f41 Linus Torvalds    2005-04-16  3180  
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3181  /**
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3182   * proc_flush_task -  Remove dcache entries for @task from the /proc dcache.
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3183   * @task: task that should be flushed.
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3184   *
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3185   * When flushing dentries from proc, one needs to flush them from global
> > 60347f6716aa49 Pavel Emelyanov   2007-10-18  3186   * proc (proc_mnt) and from all the namespaces' procs this task was seen
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3187   * in. This call is supposed to do all of this job.
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3188   *
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3189   * Looks in the dcache for
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3190   * /proc/@pid
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3191   * /proc/@tgid/task/@pid
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3192   * if either directory is present flushes it and all of it'ts children
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3193   * from the dcache.
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3194   *
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3195   * It is safe and reasonable to cache /proc entries for a task until
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3196   * that task exits.  After that they just clog up the dcache with
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3197   * useless entries, possibly causing useful dcache entries to be
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3198   * flushed instead.  This routine is proved to flush those useless
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3199   * dcache entries at process exit time.
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3200   *
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3201   * NOTE: This routine is just an optimization so it does not guarantee
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3202   *       that no dcache entries will exist at process exit time it
> > 0895e91d60ef9b Randy Dunlap      2007-10-21  3203   *       just makes it very unlikely that any will persist.
> > 60347f6716aa49 Pavel Emelyanov   2007-10-18  3204   */
> > 60347f6716aa49 Pavel Emelyanov   2007-10-18  3205  
> > 60347f6716aa49 Pavel Emelyanov   2007-10-18  3206  void proc_flush_task(struct task_struct *task)
> > 60347f6716aa49 Pavel Emelyanov   2007-10-18  3207  {
> > 9fcc2d15b14894 Eric W. Biederman 2007-11-14  3208  	int i;
> > 9b4d1cbef8f41a Oleg Nesterov     2009-09-22  3209  	struct pid *pid, *tgid;
> > 130f77ecb2e7d5 Pavel Emelyanov   2007-10-18  3210  	struct upid *upid;
> > 130f77ecb2e7d5 Pavel Emelyanov   2007-10-18  3211  
> > 130f77ecb2e7d5 Pavel Emelyanov   2007-10-18  3212  	pid = task_pid(task);
> > 130f77ecb2e7d5 Pavel Emelyanov   2007-10-18  3213  	tgid = task_tgid(task);
> > 9fcc2d15b14894 Eric W. Biederman 2007-11-14  3214  
> > 9fcc2d15b14894 Eric W. Biederman 2007-11-14  3215  	for (i = 0; i <= pid->level; i++) {
> > 130f77ecb2e7d5 Pavel Emelyanov   2007-10-18  3216  		upid = &pid->numbers[i];
> > 130f77ecb2e7d5 Pavel Emelyanov   2007-10-18 @3217  		proc_flush_task_mnt(upid->ns->proc_mnt, upid->nr,
> > 9b4d1cbef8f41a Oleg Nesterov     2009-09-22  3218  					tgid->numbers[i].nr);
> > 130f77ecb2e7d5 Pavel Emelyanov   2007-10-18  3219  	}
> > 60347f6716aa49 Pavel Emelyanov   2007-10-18  3220  }
> > 60347f6716aa49 Pavel Emelyanov   2007-10-18  3221  
> >
> > :::::: The code at line 3217 was first introduced by commit
> > :::::: 130f77ecb2e7d5ac3e53e620f55e374f4a406b20 pid namespaces: make proc_flush_task() actually from entries from multiple namespaces
> >
> > :::::: TO: Pavel Emelyanov <xemul@openvz.org>
> > :::::: CC: Linus Torvalds <torvalds@woody.linux-foundation.org>
> >
> > ---
> > 0-DAY CI Kernel Test Service, Intel Corporation
> > https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
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