On Fri, Apr 07, 2023 at 01:26:08PM -0700, Suren Baghdasaryan wrote:
> True. do_swap_page() has the same issue. Can we move these
> count_vm_event() calls to the end of handle_mm_fault():
I was going to suggest something similar, so count that as an
Acked-by. This will change the accounting for the current retry
situation, where we drop the mmap_lock in filemap_fault(), initiate I/O
and return RETRY. I think that's probably a good change though; I don't
see why applications should have their fault counters incremented twice
for that situation.
> mm_account_fault(regs, address, flags, ret);
> +out:
> + if (ret != VM_FAULT_RETRY) {
> + count_vm_event(PGFAULT);
> + count_memcg_event_mm(vma->vm_mm, PGFAULT);
> + }
Nit: this is a bitmask, so we should probably have:
if (!(ret & VM_FAULT_RETRY)) {
in case somebody's ORed it with VM_FAULT_MAJOR or something.
Hm, I wonder if we're handling that correctly; if we need to start I/O,
do we preserve VM_FAULT_MAJOR returned from the first attempt? Not
in a position where I can look at the code right now.
