Re: [PATCH 22/71] btrfs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros

[David Sterba]

On Sun, Mar 20, 2016 at 09:40:29PM +0300, Kirill A. Shutemov wrote:
> PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time ago
> with promise that one day it will be possible to implement page cache with
> bigger chunks than PAGE_SIZE.
> 
> This promise never materialized. And unlikely will.
> 
> We have many places where PAGE_CACHE_SIZE assumed to be equal to
> PAGE_SIZE. And it's constant source of confusion on whether PAGE_CACHE_*
> or PAGE_* constant should be used in a particular case, especially on the
> border between fs and mm.
> 
> Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much
> breakage to be doable.
> 
> Let's stop pretending that pages in page cache are special. They are not.
> 
> The changes are pretty straight-forward:
> 
>  - <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;
> 
>  - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN};
> 
>  - page_cache_get() -> get_page();
> 
>  - page_cache_release() -> put_page();
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: Chris Mason <clm@xxxxxx>
> Cc: Josef Bacik <jbacik@xxxxxx>
> Cc: David Sterba <dsterba@xxxxxxxx>

Acked-by: David Sterba <dsterba@xxxxxxxx>