On 6/14/22 13:56, Nadav Amit wrote: ...
So if you have a choice, I implore you to prefer flags and/or enums. :)Thanks for the feedback - I am aware it is very confusing to have booleans and especially multiple ones in a func call. Just not sure how it maps to what I proposed. I thought of passing as an argument reference (pointer) to something similar to the following struct, which I think is very self-descriptive: struct uffd_op { /* various fields */ struct vm_area_struct *dst_vma; unsigned long len; atomic_t *mmap_changing; ... /* ... and some flags */ int wp: 1; int zero: 1; int read_likely: 1;
I am more accustomed to seeing: unsigned int flags; ...and then some #defines or enums nearby that are used for .flags. The bitfields are not used as much, Linus wrote some words about why, (which I'm not hopeful I can find). Basically they are not a very robust C feature, and the kernel has good support for dealing with flags within a word.
... }; I think that fits what you were asking for. The only thing I am not sure of, is whether to include in uffd_op fields that are internal to mm/userfaultfd such as “page” and “newly_allocated”. I guess not.
Actually, I think passing around a struct might be overkill, when you can simply collapse the various boolean args into a single flags arg. It looked like a lot of the new args were bools... thanks, -- John Hubbard NVIDIA
