by Richard Knutsson

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Subject: Re: [PATCH] add page->mapping handling interface [1/35] interface definitions

KAMEZAWA Hiroyuki wrote:
> - changes page->mapping from address_space* to unsigned long
> - add page_mapping_anon() function.
> - add linux/page-cache.h
> - add page_inode() function
> - add page_is_pagecache() function
> - add pagecaceh_consisten() function for pagecache consistency test.
> - expoterd swapper_space. inline function page_mapping() refers this.
>
> Signed-off-by: KAMEZAWA Hiroyuki <[email protected]>
>
> ---
> include/linux/fs.h | 1 +
> include/linux/mm.h | 20 +++++++++++++++++---
> include/linux/mm_types.h | 2 +-
> include/linux/page-cache.h | 39 +++++++++++++++++++++++++++++++++++++++
> mm/swap_state.c | 2 ++
> 5 files changed, 60 insertions(+), 4 deletions(-)
>
> Index: test-2.6.23-rc4-mm1/include/linux/page-cache.h
> ===================================================================
> --- /dev/null
> +++ test-2.6.23-rc4-mm1/include/linux/page-cache.h
> @@ -0,0 +1,39 @@
> +/*
> + * For interface definitions between memory management and file systems.
> + * - This file defines small interface functions for handling page cache.
> + */
> +
> +#ifndef _LINUX_PAGECACHE_H
> +#define _LINUX_PAGECACHE_H
> +
> +#include <linux/mm.h>
> +/* page_mapping_xxx() function is defined in mm.h */
> +
> +static inline int page_is_pagecache(struct page *page)
>
Why return it as an 'int' instead of 'bool'?
> +{
> + if (!page->mapping || (page->mapping & PAGE_MAPPING_ANON))
> + return 0;
> + return 1;
> +}
>
Not easier with 'return page->mapping && (page->mapping &
PAGE_MAPPING_ANON) == 0;'?
> +
> +/*
> + * Return an inode this page belongs to
> + */
> +
> +static inline struct inode *page_inode(struct page *page)
> +{
> + if (!page_is_pagecache(page))
> + return NULL;
> + return page_mapping_cache(page)->host;
> +}
> +
> +/*
> + * Test a page is a page-cache of an address_space.
> + */
> +static inline int
> +pagecache_consistent(struct page *page, struct address_space *as)
> +{
> + return (page_mapping(page) == as);
> +}
> +
> +#endif
<snip>
> Index: test-2.6.23-rc4-mm1/include/linux/mm.h
> ===================================================================
> --- test-2.6.23-rc4-mm1.orig/include/linux/mm.h
> +++ test-2.6.23-rc4-mm1/include/linux/mm.h
> @@ -563,7 +563,7 @@ void page_address_init(void);
> extern struct address_space swapper_space;
> static inline struct address_space *page_mapping(struct page *page)
> {
> - struct address_space *mapping = page->mapping;
> + struct address_space *mapping = (struct address_space *)page->mapping;
>
> VM_BUG_ON(PageSlab(page));
> if (unlikely(PageSwapCache(page)))
> @@ -579,7 +579,21 @@ static inline struct address_space *page
>
> static inline int PageAnon(struct page *page)
>
Change to bool? Then "you" can also remove the '!!' from:
mm/memory.c:483: rss[!!PageAnon(page)]++;
> {
> - return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
> + return (page->mapping & PAGE_MAPPING_ANON) != 0;
> +}
> +
>
<snip>

If you don't mind bool(eans) (for some reason), I can/will check out the
rest.

Richard Knutsson

2007-09-14 01:04:54

by Kamezawa Hiroyuki

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Subject: Re: [PATCH] add page->mapping handling interface [1/35] interface definitions

On Thu, 13 Sep 2007 22:19:20 +0200
Richard Knutsson <[email protected]> wrote:
> > +static inline int page_is_pagecache(struct page *page)
> >
> Why return it as an 'int' instead of 'bool'?
> > +{
> > + if (!page->mapping || (page->mapping & PAGE_MAPPING_ANON))
> > + return 0;
> > + return 1;
> > +}

Ah, I missed bool type just because I have no experience to use 'bool' in
Linux kernel. ok, will try in the next version. thank you.

> >
> Not easier with 'return page->mapping && (page->mapping &
> PAGE_MAPPING_ANON) == 0;'?
> > +

yours seems better.

>
> > static inline int PageAnon(struct page *page)
> >
> Change to bool? Then "you" can also remove the '!!' from:
> mm/memory.c:483: rss[!!PageAnon(page)]++;

Hmm, will try unless it makes diff big.

> > {
> > - return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
> > + return (page->mapping & PAGE_MAPPING_ANON) != 0;
> > +}
> > +
> >
> <snip>
>
> If you don't mind bool(eans) (for some reason), I can/will check out the
> rest.
>

Thank you. I'll try 'bool' type.

Regards,
-Kame