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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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