Re: [PATCH v4 07/12] dax: coordinate locking for offsets in PMD range

[Christoph Hellwig]

> +static pgoff_t dax_entry_start(pgoff_t index, void *entry)
> +{
> +	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
> +		index &= (PMD_MASK >> PAGE_SHIFT);
> +	return index;
> +}
> +
>  static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
> -					      pgoff_t index)
> +					      pgoff_t entry_start)
>  {
> -	unsigned long hash = hash_long((unsigned long)mapping ^ index,
> +	unsigned long hash = hash_long((unsigned long)mapping ^ entry_start,
>  				       DAX_WAIT_TABLE_BITS);
>  	return wait_table + hash;
>  }

All callers of dax_entry_waitqueue need to calculate entry_start
using this new dax_entry_start helper.  Either we should move the
call to dax_entry_start into this helper.  Or at least use local
variables for in the callers as both of them also fill out a
wait_exceptional_entry_queue structure with it.  Or do both by
letting dax_entry_waitqueue fill out that structure as well.