Re: [PATCH 02/10] mm/truncate: Inline invalidate_complete_page() into its one caller

[John Hubbard <jhubbard@nvidia.com>]

On 2/14/22 3:32 PM, Matthew Wilcox wrote:
> On Mon, Feb 14, 2022 at 03:09:09PM -0800, John Hubbard wrote:
>>> @@ -309,7 +288,10 @@ int invalidate_inode_page(struct page *page)
>>
>> It would be nice to retain some of the original comments. May I suggest
>> this (it has an additional paragraph) for an updated version of comments
>> above invalidate_inode_page():
>>
>> /*
>>   * Safely invalidate one page from its pagecache mapping.
>>   * It only drops clean, unused pages. The page must be locked.
>>   *
>>   * This function can be called at any time, and is not supposed to throw away
>>   * dirty pages.  But pages can be marked dirty at any time too, so use
>>   * remove_mapping(), which safely discards clean, unused pages.
>>   *
>>   * Returns 1 if the page is successfully invalidated, otherwise 0.
>>   */
> 
> By the end of this series, it becomes:
> 
> /**
>   * invalidate_inode_page() - Remove an unused page from the pagecache.
>   * @page: The page to remove.
>   *
>   * Safely invalidate one page from its pagecache mapping.
>   * It only drops clean, unused pages.
>   *
>   * Context: Page must be locked.
>   * Return: The number of pages successfully removed.
>   */

OK.

> 
>> Also, as long as you're there, a newline after the mapping declaration
>> would bring this routine into compliance with that convention.
> 
> Again, by the end, we're at:
> 
>          struct folio *folio = page_folio(page);
>          struct address_space *mapping = folio_mapping(folio);
> 
>          /* The page may have been truncated before it was locked */
>          if (!mapping)
>                  return 0;
>          return mapping_shrink_folio(mapping, folio);
> 

Also good.

>> hmmm, now I wonder why this isn't a boolean function. And I think the
>> reason is that it's quite old.
> 
> We could make this return a bool and have the one user that cares
> call folio_nr_pages().  I don't have a strong preference.

Neither do I. No need to add churn for that.


thanks,

-- 
John Hubbard
NVIDIA