Hi David,
On 2024/8/22 17:29, David Hildenbrand wrote:
On 21.08.24 12:03, Qi Zheng wrote:
[...]
- vmf->pte = pte_offset_map_nolock(vmf->vma->vm_mm,
vmf->pmd,
- vmf->address, &vmf->ptl);
+ vmf->pte = pte_offset_map_maywrite_nolock(vmf->vma->vm_mm,
+ vmf->pmd, vmf->address,
+ NULL, &vmf->ptl);
I think we discussed that passing NULL should be forbidden for that
function.
Yes, but for some maywrite case, there is no need to get pmdval to
do pmd_same() check. So I passed NULL and added a comment to
explain this.
I wonder if it's better to pass a dummy variable instead. One has to
think harder why that is required compared to blindly passing "NULL" :)
You are afraid that subsequent caller will abuse this function, right?
Yes! "oh, I don't need a pmdval, why would I? let's just pass NULL,
easy" :)
My initial concern was that this would add a useless local vaiable, but
perhaps that is not a big deal.
How many of these "special" instances do we have?
We have 5 such special instances.
Both are fine for me. ;)
Also no strong opinion, but having to pass a variable makes you think
what you are supposed to do with it and why it is not optional.
Yeah, I added 'BUG_ON(!pmdvalp);' in pte_offset_map_ro_nolock(), and
have updated the v2 version [1].
[1].
https://lore.kernel.org/lkml/cover.1724310149.git.zhengqi.arch@xxxxxxxxxxxxx/
Thanks,
Qi
