Re: [PATCH v2 7/7] mm/mremap: thread state through move page table operation

[Vlastimil Babka <vbabka@suse.cz>]

On 3/6/25 11:34, Lorenzo Stoakes wrote:
> Finish refactoring the page table logic by threading the PMC state
> throughout the operation, allowing us to control the operation as we go.
> 
> Additionally, update the old_addr, new_addr fields in move_page_tables()
> as we progress through the process making use of the fact we have this
> state object now to track this.
> 
> With these changes made, not only is the code far more readable, but we
> can finally transmit state throughout the entire operation, which lays the
> groundwork for sensibly making changes in future to how the mremap()
> operation is performed.
> 
> Additionally take the opportunity to refactor the means of determining the
> progress of the operation, abstracting this to pmc_progress() and
> simplifying the logic to make it clearer what's going on.
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

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

Small nit:

>  
> +/*
> + * Should move_pgt_entry() acquire the rmap locks? This is either expressed in
> + * the PMC, or overridden in the case of normal, larger page tables.
> + */
> +static bool should_take_rmap_locks(struct pagetable_move_control *pmc,
> +				   enum pgt_entry entry)
> +{
> +	if (pmc->need_rmap_locks)
> +		return true;
> +
> +	switch (entry) {
> +	case NORMAL_PMD:
> +	case NORMAL_PUD:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +

IMHO the "overriden" logic would be more obvious if we removed the initial
"if" and just had default: return pmc->need_rmap_locks