On Fri, 21 Sep 2007 13:48:28 +0200
Peter Zijlstra <[email protected]> wrote:
> > Followings are moved
> > * page_mapping() ... returns swapper_space or address_space a page is on.
> > (from mm.h)
> > * page_index() ... returns position of a page in its inode
> > (from mm.h)
> > * remove_mapping() ... a safe routine to remove page->mapping from page.
> > (from swap.h)
>
> I have two other functions that might want integration with this scheme:
>
> page_file_mapping() ... returns backing address space
> page_file_index() ... returns the index therein
>
> They are identical to page_mapping_cache() and page_index() for
> page cache pages, but they also work on swap cache pages.
>
> That is, for swapcache pages they return:
>
> page_file_mapping:
> page_swap_info(page)->swap_file->f_mapping
>
> page_file_index:
> swp_offset((swp_offset_t)page_private(page))
>
> When a filesystem uses these functions instead of page->mapping and
> page->index, it allows passing swap cache pages into the regular
> filesystem read/write paths.
>
Oh,
> This is useful for things like swap over NFS, where swap is backed by a
> swapfile on a 'regular' filesystem.
>
Okay, I'll try to add them in the next set.
Thanks,
-Kame
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