On Fri, Feb 28, 2020 at 02:14:56PM -0800, Suren Baghdasaryan wrote:
< snip >
> > > diff --git a/mm/madvise.c b/mm/madvise.c
> > > index f75c86b6c463..f29155b8185d 100644
> > > --- a/mm/madvise.c
> > > +++ b/mm/madvise.c
> > > @@ -17,6 +17,7 @@
> > > #include <linux/falloc.h>
> > > #include <linux/fadvise.h>
> > > #include <linux/sched.h>
> > > +#include <linux/sched/mm.h>
> > > #include <linux/ksm.h>
> > > #include <linux/fs.h>
> > > #include <linux/file.h>
> > > @@ -986,6 +987,18 @@ madvise_behavior_valid(int behavior)
> > > }
> > > }
> > >
> > > +static bool
> > > +process_madvise_behavior_valid(int behavior)
> > > +{
> > > + switch (behavior) {
> > > + case MADV_COLD:
> > > + case MADV_PAGEOUT:
> > > + return true;
> > > + default:
> > > + return false;
> > > + }
> > > +}
> > > +
> > > /*/
> > > * The madvise(2) system call.
> > > *
> > > @@ -1033,6 +1046,11 @@ madvise_behavior_valid(int behavior)
> > > * MADV_DONTDUMP - the application wants to prevent pages in the given range
> > > * from being included in its core dump.
> > > * MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
> > > + * MADV_COLD - the application uses the memory less so the kernel can
>
> "kernel can" implies that kernel might not deactivate the pages, which
> IIUC is not the case. Maybe rephrase as "MADV_COLD - the application
> is not expected to use this memory soon, deactivate pages in this
> range so that they can be reclaimed easily if memory pressure
> happens.""
That is much better.
>
> > > + * deactivate the memory to evict them quickly when the memory
> > > + * pressure happen.
> > > + * MADV_PAGEOUT - the application uses the memroy very rarely so kernel can
>
> s/memroy/memory
Fixed.
>
> > > + * page out the memory instantly.
>
> same nit about the usage of "kernel can". Maybe rephrase as
> "MADV_PAGEOUT - the application is not expected to use this memory
> soon, page out the pages in this range immediately.""
Yub.
>
> > > *
> > > * return values:
> > > * zero - success
> > > @@ -1150,3 +1168,49 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
> > > {
> > > return do_madvise(current, current->mm, start, len_in, behavior);
> > > }
> > > +
> > > +SYSCALL_DEFINE5(process_madvise, int, pidfd, unsigned long, start,
> > > + size_t, len_in, int, behavior, unsigned long, flags)
> > > +{
> > > + int ret;
> > > + struct fd f;
> > > + struct pid *pid;
> > > + struct task_struct *task;
> > > + struct mm_struct *mm;
> > > +
> > > + if (flags != 0)
> > > + return -EINVAL;
> > > +
> > > + if (!process_madvise_behavior_valid(behavior))
> > > + return -EINVAL;
> > > +
> > > + f = fdget(pidfd);
> > > + if (!f.file)
> > > + return -EBADF;
> > > +
> > > + pid = pidfd_pid(f.file);
> > > + if (IS_ERR(pid)) {
> > > + ret = PTR_ERR(pid);
> > > + goto fdput;
> > > + }
> > > +
> > > + task = get_pid_task(pid, PIDTYPE_PID);
> > > + if (!task) {
> > > + ret = -ESRCH;
> > > + goto fdput;
> > > + }
> > > +
> > > + mm = mm_access(task, PTRACE_MODE_ATTACH_FSCREDS);
> > > + if (IS_ERR_OR_NULL(mm)) {
> > > + ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
> > > + goto release_task;
> > > + }
> > > +
> > > + ret = do_madvise(task, mm, start, len_in, behavior);
> > > + mmput(mm);
> > > +release_task:
> > > + put_task_struct(task);
> > > +fdput:
> > > + fdput(f);
> > > + return ret;
> > > +}
> > > --
> > > 2.25.0.265.gbab2e86ba0-goog
> > >
> >
>
> Reviewed-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Thanks, Suren!
