On Thu, Mar 2, 2023 at 5:13 PM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > > Current 500ms min window size for psi triggers limits polling interval > to 50ms to prevent polling threads from using too much cpu bandwidth by > polling too frequently. However the number of cgroups with triggers is > unlimited, so this protection can be defeated by creating multiple > cgroups with psi triggers (triggers in each cgroup are served by a single > "psimon" kernel thread). > Instead of limiting min polling period, which also limits the latency of > psi events, it's better to limit psi trigger creation to authorized users > only, like we do for system-wide psi triggers (/proc/pressure/* files can > be written only by processes with CAP_SYS_RESOURCE capability). This also > makes access rules for cgroup psi files consistent with system-wide ones. > Add a CAP_SYS_RESOURCE capability check for cgroup psi file writers and > remove the psi window min size limitation. > > Suggested-by: Sudarshan Rajagopalan <quic_sudaraja@xxxxxxxxxxx> > Link: https://lore.kernel.org/all/cover.1676067791.git.quic_sudaraja@xxxxxxxxxxx/ > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx> > Acked-by: Michal Hocko <mhocko@xxxxxxxx> > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Forgot to change the --to field from Tejun to PeterZ. Peter, just to clarify, this change is targeted for inclusion in your tree. Thanks! > --- > kernel/cgroup/cgroup.c | 10 ++++++++++ > kernel/sched/psi.c | 4 +--- > 2 files changed, 11 insertions(+), 3 deletions(-) > > diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c > index 935e8121b21e..b600a6baaeca 100644 > --- a/kernel/cgroup/cgroup.c > +++ b/kernel/cgroup/cgroup.c > @@ -3867,6 +3867,12 @@ static __poll_t cgroup_pressure_poll(struct kernfs_open_file *of, > return psi_trigger_poll(&ctx->psi.trigger, of->file, pt); > } > > +static int cgroup_pressure_open(struct kernfs_open_file *of) > +{ > + return (of->file->f_mode & FMODE_WRITE && !capable(CAP_SYS_RESOURCE)) ? > + -EPERM : 0; > +} > + > static void cgroup_pressure_release(struct kernfs_open_file *of) > { > struct cgroup_file_ctx *ctx = of->priv; > @@ -5266,6 +5272,7 @@ static struct cftype cgroup_psi_files[] = { > { > .name = "io.pressure", > .file_offset = offsetof(struct cgroup, psi_files[PSI_IO]), > + .open = cgroup_pressure_open, > .seq_show = cgroup_io_pressure_show, > .write = cgroup_io_pressure_write, > .poll = cgroup_pressure_poll, > @@ -5274,6 +5281,7 @@ static struct cftype cgroup_psi_files[] = { > { > .name = "memory.pressure", > .file_offset = offsetof(struct cgroup, psi_files[PSI_MEM]), > + .open = cgroup_pressure_open, > .seq_show = cgroup_memory_pressure_show, > .write = cgroup_memory_pressure_write, > .poll = cgroup_pressure_poll, > @@ -5282,6 +5290,7 @@ static struct cftype cgroup_psi_files[] = { > { > .name = "cpu.pressure", > .file_offset = offsetof(struct cgroup, psi_files[PSI_CPU]), > + .open = cgroup_pressure_open, > .seq_show = cgroup_cpu_pressure_show, > .write = cgroup_cpu_pressure_write, > .poll = cgroup_pressure_poll, > @@ -5291,6 +5300,7 @@ static struct cftype cgroup_psi_files[] = { > { > .name = "irq.pressure", > .file_offset = offsetof(struct cgroup, psi_files[PSI_IRQ]), > + .open = cgroup_pressure_open, > .seq_show = cgroup_irq_pressure_show, > .write = cgroup_irq_pressure_write, > .poll = cgroup_pressure_poll, > diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c > index 02e011cabe91..0945f956bf80 100644 > --- a/kernel/sched/psi.c > +++ b/kernel/sched/psi.c > @@ -160,7 +160,6 @@ __setup("psi=", setup_psi); > #define EXP_300s 2034 /* 1/exp(2s/300s) */ > > /* PSI trigger definitions */ > -#define WINDOW_MIN_US 500000 /* Min window size is 500ms */ > #define WINDOW_MAX_US 10000000 /* Max window size is 10s */ > #define UPDATES_PER_WINDOW 10 /* 10 updates per window */ > > @@ -1278,8 +1277,7 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, > if (state >= PSI_NONIDLE) > return ERR_PTR(-EINVAL); > > - if (window_us < WINDOW_MIN_US || > - window_us > WINDOW_MAX_US) > + if (window_us == 0 || window_us > WINDOW_MAX_US) > return ERR_PTR(-EINVAL); > > /* Check threshold */ > -- > 2.40.0.rc0.216.gc4246ad0f0-goog >
