Re: [PATCH v2 1/3] hugetlb: simplify prep_compound_gigantic_page ref count racing code

[Oscar Salvador]

On 2021-08-09 20:48, Mike Kravetz wrote:
> Code in prep_compound_gigantic_page waits for a rcu grace period if it
> notices a temporarily inflated ref count on a tail page.  This was due
> to the identified potential race with speculative page cache references
> which could only last for a rcu grace period.  This is overly 
> complicated
> as this situation is VERY unlikely to ever happen.  Instead, just 
> quickly
> return an error.
> Also, only print a warning in prep_compound_gigantic_page instead of
> multiple callers.

The above makes sense to me.
My only question would be: gather_bootmem_prealloc() is an __init 
function.
Can we have speculative refcounts due to e.g: pagecache at that early 
stage?
I think we cannot, but I am not really sure.

We might be able to remove that else() in case we cannot have such 
scenarios.


--
Oscar Salvador
SUSE L3