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    SubjectRe: [PATCH 08/12] cgroups: Pull up res counter charge failure interpretation to caller
    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.



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