Re: [PATCH V7 02/19] dax: Factor out dax_folio_reset_order() helper

[Ira Weiny]

John Groves wrote:
> From: John Groves <John@xxxxxxxxxx>
> 
> Both fs/dax.c:dax_folio_put() and drivers/dax/fsdev.c:
> fsdev_clear_folio_state() (the latter coming in the next commit after this
> one) contain nearly identical code to reset a compound DAX folio back to
> order-0 pages. Factor this out into a shared helper function.
> 
> The new dax_folio_reset_order() function:
> - Clears the folio's mapping and share count
> - Resets compound folio state via folio_reset_order()
> - Clears PageHead and compound_head for each sub-page
> - Restores the pgmap pointer for each resulting order-0 folio
> - Returns the original folio order (for callers that need to advance by
>   that many pages)
> 
> This simplifies fsdev_clear_folio_state() from ~50 lines to ~15 lines while
> maintaining the same functionality in both call sites.
> 
> Suggested-by: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>
> Signed-off-by: John Groves <john@xxxxxxxxxx>

Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>

[snip]