linux-kernel - Re: [PATCH 2/4] staging/lustre/obdclass: read jobid from proc

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Message-ID: <20131030142017.GB30896@kroah.com>
Date:	Wed, 30 Oct 2013 07:20:17 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Peng Tao <bergwolf@...il.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andreas Dilger <andreas.dilger@...el.com>
Subject: Re: [PATCH 2/4] staging/lustre/obdclass: read jobid from proc

On Wed, Oct 30, 2013 at 09:31:24PM +0800, Peng Tao wrote:
> On Wed, Oct 30, 2013 at 9:21 PM, Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
> > On Wed, Oct 30, 2013 at 07:30:34PM +0800, Peng Tao wrote:
> >> so that we can get rid of cfs_get_environ() that needs access_process_vm() that
> >> is a core mm function and is not available on some architectures.
> >>
> >> Reviewed-by: Niu Yawei <yawei.niu@...el.com>
> >> Signed-off-by: Peng Tao <bergwolf@...il.com>
> >> Signed-off-by: Andreas Dilger <andreas.dilger@...el.com>
> >> ---
> >>  drivers/staging/lustre/lustre/obdclass/class_obd.c |  119 +++++++++++++++++++-
> >>  1 file changed, 115 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/staging/lustre/lustre/obdclass/class_obd.c b/drivers/staging/lustre/lustre/obdclass/class_obd.c
> >> index b1024a6..99ce863 100644
> >> --- a/drivers/staging/lustre/lustre/obdclass/class_obd.c
> >> +++ b/drivers/staging/lustre/lustre/obdclass/class_obd.c
> >> @@ -96,8 +96,117 @@ EXPORT_SYMBOL(obd_dirty_transit_pages);
> >>  char obd_jobid_var[JOBSTATS_JOBID_VAR_MAX_LEN + 1] = JOBSTATS_DISABLE;
> >>  EXPORT_SYMBOL(obd_jobid_var);
> >>
> >> -/* Get jobid of current process by reading the environment variable
> >> - * stored in between the "env_start" & "env_end" of task struct.
> >> +static char *self_environ_file = "/proc/self/environ";
> >
> > Heh, no, that's not ok at all.
> >
> > This is a _huge_ sign that you are doing something wrong in your driver
> > if you need something that isn't exported, or that you have to dig out
> > of proc.
> >
> Lustre has a functionality that lets applications specify a global
> jobid by setting the same environment variable across the cluster and
> thus server can trace IO that is issued by different job. Currently it
> is implemented by having a private version of cfs_access_process_vm
> because access_process_vm is not exported. The patch intends to change
> it to reading from proc. If we cannot dig it out from proc either, how
> can we keep the functionality then? Please advise.

Kernel code should not care about environment variables.  Just because
you created a crazy requirement, does not mean it is a valid one, nor
that I have to be the one to tell you how to implement it.

I'm never going to take code that parses proc files, you all know better
than that.

greg k-h
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