Hi Mel, Adding Alexei to the discussion. On Mon, Aug 21, 2023 at 3:32 AM Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: > > On Thu, Aug 17, 2023 at 11:05:22PM -0700, Chris Li wrote: > > In this patch series I want to safeguard > > the free_pcppage_bulk against change in the > > pcp->count outside of this function. e.g. > > by BPF program inject on the function tracepoint. > > > > I break up the patches into two seperate patches > > for the safeguard and clean up. > > > > Hopefully that is easier to review. > > > > Signed-off-by: Chris Li <chrisl@xxxxxxxxxx> > > This sounds like a maintenance nightmare if internal state can be arbitrary > modified by a BPF program and still expected to work properly in all cases. > Every review would have to take into account "what if a BPF script modifies > state behind our back?" Thanks for the feedback. I agree that it is hard to support if we allow BPF to change any internal stage as a rule. That is why it is a RFC. Would you consider it case by case basis? The kernel panic is bad, the first patch is actually very small. I can also change it to generate warnings if we detect the inconsistent state. How about the second (clean up) patch or Keming's clean up version? I can modify it to take out the pcp->count if the verdict is just not supporting BPF changing internal state at all. I do wish to get rid of the pindex_min and pindex_max. Thanks Chris
