On Thu 22-02-18 20:34:48, Amir Goldstein wrote: > On Thu, Feb 22, 2018 at 6:22 PM, Jan Kara <jack@xxxxxxx> wrote: > > On Thu 22-02-18 18:04:36, Amir Goldstein wrote: > >> On Wed, Feb 21, 2018 at 5:44 PM, Jan Kara <jack@xxxxxxx> wrote: > >> > Fanotify queues of unlimited length do not expect events can be lost. > >> > Since these queues are used for system auditing and other security > >> > >> Change looks good to me, but the reasoning is going backwards. > >> IMO, you should mention that we are going to change -ENOMEM > >> behavior to result in Q_OVERFLOW and user does not expect > >> Q_OVERFLOW from an UNLIMITED queue. > > > > See below. > > > >> > related tasks, loosing events can even have security implications. So > >> > avoid loosing events due to failure to allocate memory by making event > >> > allocation use __GFP_NOFAIL. Since the allocation is small (32-bytes), > >> > currently there is no practical difference of this change but still it > >> > is good to have the expectation explicitely documented. > >> > > >> > >> But if currently allocations cannot fail, then why do we need patch > >> 2/2 (queue overflow event). It is because small allocations can fail when > >> accounted to non-root memcg? > > > > Yes. So how about changelog like: > > > > Fanotify queues of unlimited length do not expect events can be lost. > > Since these queues are used for system auditing and other security > > related tasks, loosing events can even have security implications. > > Currently, since the allocation is small (32-bytes), it cannot fail > > however when we start accounting events in memcgs, allocation can start > > failing. So avoid loosing events due to failure to allocate memory by > > making event allocation use __GFP_NOFAIL. > > > > Very good. Can I add your reviewed-by to the patch then? Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
