[CC David as well]

The original patch has been posted here:
http://lkml.kernel.org/r/65a10261038346b1a778443fd15f0980%40SHMBX01.spreadtrum.com

On Tue 20-10-15 12:27:58, Eric W. Biederman wrote:
> "Hongjie Fang (方洪杰)" <[email protected]> writes:
> 
> > The oom_adj's value reading through /proc/<pid>/oom_adj is different 
> > with the value written into /proc/<pid>/oom_adj.
> > Fix this by adding a adjustment factor.
> 
> *Scratches my head*
> 
> Won't changing the interpretation of what is written break existing
> userspace applications that write this value?

No, because they will see the same value they wrote. The current state
is broken because you get a different value than you wrote.

I am just wondering, how have you found this problem? Code review or
have you encountered a real failure because of this?

> Added a few more likely memory management suspects that might understand
> what is going on here.
> 
> Eric
> 
> >
> > Signed-off-by: Hongjie Fang <[email protected]>
> > ---
> > diff --git a/fs/proc/base.c b/fs/proc/base.c
> > index b25eee4..1ea0589 100644
> > --- a/fs/proc/base.c
> > +++ b/fs/proc/base.c
> > @@ -1043,6 +1043,7 @@ static ssize_t oom_adj_write(struct file *file, const 
> > char __user *buf,
> >     int oom_adj;
> >     unsigned long flags;
> >     int err;
> > +   int adjust;

This doesn't need the function visibility.

> >  
> >     memset(buffer, 0, sizeof(buffer));
> >     if (count > sizeof(buffer) - 1)
> > @@ -1084,8 +1085,10 @@ static ssize_t oom_adj_write(struct file *file, 
> > const char __user *buf,
> >      */
> >     if (oom_adj == OOM_ADJUST_MAX)
> >             oom_adj = OOM_SCORE_ADJ_MAX;
> > -   else
> > -           oom_adj = (oom_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE;
> > +   else{

space after else and checkpatch will probably complain about missing { }
for if...

Other than that the patch looks good to me. The changelog coul be
slightly improved as well.

> > +           adjust = oom_adj > 0 ? (-OOM_DISABLE-1) : -(-OOM_DISABLE-1);
> > +           oom_adj = (oom_adj * OOM_SCORE_ADJ_MAX + adjust) / -OOM_DISABLE;
> > +   }
> >  
> >     if (oom_adj < task->signal->oom_score_adj &&
> >         !capable(CAP_SYS_RESOURCE)) {
> >
> > --
> 
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-- 
Michal Hocko
SUSE Labs
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