Messages in this thread |  | | | Date | Fri, 9 Sep 2011 08:17:11 -0700 | | From | Andrew Morton <> | | Subject | Re: [PATCH 08/12] cgroups: Pull up res counter charge failure interpretation to caller |
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On Fri, 9 Sep 2011 15:33:20 +0200 Frederic Weisbecker <fweisbec@gmail.com> wrote:
> On Tue, Sep 06, 2011 at 03:26:50PM -0700, Andrew Morton wrote: > > On Tue, 6 Sep 2011 02:13:02 +0200 > > Frederic Weisbecker <fweisbec@gmail.com> wrote: > > > > > res_counter_charge() always returns -ENOMEM when the limit is reached > > > and the charge thus can't happen. > > > > > > However it's up to the caller to interpret this failure and return > > > the appropriate error value. The task counter subsystem will need > > > to report the user that a fork() has been cancelled because of some > > > limit reached, not because we are too short on memory. > > > > > > Fix this by returning -1 when res_counter_charge() fails. > > > > > > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> > > > Cc: Paul Menage <paul@paulmenage.org> > > > Cc: Li Zefan <lizf@cn.fujitsu.com> > > > Cc: Johannes Weiner <hannes@cmpxchg.org> > > > Cc: Aditya Kali <adityakali@google.com> > > > Cc: Oleg Nesterov <oleg@redhat.com> > > > Cc: Andrew Morton <akpm@linux-foundation.org> > > > Cc: Kay Sievers <kay.sievers@vrfy.org> > > > Cc: Tim Hockin <thockin@hockin.org> > > > Cc: Tejun Heo <tj@kernel.org> > > > --- > > > kernel/res_counter.c | 2 +- > > > 1 files changed, 1 insertions(+), 1 deletions(-) > > > > > > diff --git a/kernel/res_counter.c b/kernel/res_counter.c > > > index 4aaa790..45fa6fb 100644 > > > --- a/kernel/res_counter.c > > > +++ b/kernel/res_counter.c > > > @@ -26,7 +26,7 @@ int res_counter_charge_locked(struct res_counter *counter, unsigned long val) > > > { > > > if (counter->usage + val > counter->limit) { > > > counter->failcnt++; > > > - return -ENOMEM; > > > + return -1; > > > } > > > > > > counter->usage += val; > > > > This also affects the return value of your new and undocumented > > res_counter_charge_until(). > > > > That's a bit of a hand-grenade which could lead to system calls > > returning -1 (ie: EPERM) to userspace. > > Right. What about making it a boolean?
mmm, not sure. 0/-1 is a reasonable return value for a function which either did or didn't succeed. Adding appropriate interface documentation is a way of reducing the opportunity for making this mistake.
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