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    SubjectRe: [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 <kamezawa.hiroyu@jp.fujitsu.com>
    >
    > ---
    > 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

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