[PATCHv6 12/17] mm: Drop fake head checks

[Vlastimil Babka]

On 2/2/26 16:56, Kiryl Shutsemau wrote:
> With fake head pages eliminated in the previous commit, remove the
> supporting infrastructure:
> 
>   - page_fixed_fake_head(): no longer needed to detect fake heads;
>   - page_is_fake_head(): no longer needed;
>   - page_count_writable(): no longer needed for RCU protection;
>   - RCU read_lock in page_ref_add_unless(): no longer needed;
> 
> This substantially simplifies compound_head() and page_ref_add_unless(),
> removing both branches and RCU overhead from these hot paths.
> 
> Signed-off-by: Kiryl Shutsemau <kas at kernel.org>
> Reviewed-by: Muchun Song <muchun.song at linux.dev>

Reviewed-by: Vlastimil Babka <vbabka at suse.cz>