On Mon 21-03-16 15:06:36, 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>;
>
> - <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();
>
> This patch contains automated changes generated with coccinelle using
> script below. For some reason, coccinelle doesn't patch header files.
> I've called spatch for them manually.
>
> The only adjustment after coccinelle is revert of changes to
> PAGE_CAHCE_ALIGN definition: we are going to drop it later.
>
> There are few places in the code where coccinelle didn't reach.
> I'll fix them manually in a separate patch. Comments and documentation
> also will be addressed with the separate patch.
>
> virtual patch
>
> @@
> expression E;
> @@
> - E << (PAGE_CACHE_SHIFT - PAGE_SHIFT)
> + E
>
> @@
> expression E;
> @@
> - E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT)
> + E
>
> @@
> @@
> - PAGE_CACHE_SHIFT
> + PAGE_SHIFT
>
> @@
> @@
> - PAGE_CACHE_SIZE
> + PAGE_SIZE
>
> @@
> @@
> - PAGE_CACHE_MASK
> + PAGE_MASK
>
> @@
> expression E;
> @@
> - PAGE_CACHE_ALIGN(E)
> + PAGE_ALIGN(E)
>
> @@
> expression E;
> @@
> - page_cache_get(E)
> + get_page(E)
>
> @@
> expression E;
> @@
> - page_cache_release(E)
> + put_page(E)
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
It is great to see PAGE_CACHE_* going away finally.
It is even better that a large part of the removal could be automated.
The semantic patch makes sense to me.
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Thanks!
[...]
--
Michal Hocko
SUSE Labs
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