On Fri 23-07-21 01:11:51, Suren Baghdasaryan wrote: > On Thu, Jul 22, 2021, 11:20 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > On Thu 22-07-21 21:47:56, Suren Baghdasaryan wrote: > > > On Thu, Jul 22, 2021, 7:04 PM Shakeel Butt <shakeelb@xxxxxxxxxx> wrote: > > > > > > > On Thu, Jul 22, 2021 at 6:14 PM Suren Baghdasaryan <surenb@xxxxxxxxxx> > > > > wrote: > > > > > > > > > [...] > > > > > + > > > > > + mmap_read_lock(mm); > > > > > > > > How about mmap_read_trylock(mm) and return -EAGAIN on failure? > > > > > > > > > > That sounds like a good idea. Thanks! I'll add that in the next respin. > > > > Why is that a good idea? Can you do anything meaningful about the > > failure other than immediately retry the syscall and hope for the best? > > > > I was thinking if this syscall implements "best effort without blocking" > approach then for a more strict usage user can simply retry. I do not think we really want to promise non blocking behavior at this stage unless that is absolutely necessary. The current implementation goes an extra mile to not block but I wouldn't carve it into stone via userspace expectations. > However > retrying means issuing another syscall, so additional overhead... > I guess such "best effort" approach would be unusual for a syscall, so > maybe we can keep it as it is now and if such "do not block" mode is needed > we can use flags to implement it later? Yeah, an explicit opt-in via flags would be an option if that turns out to be really necessary. -- Michal Hocko SUSE Labs
