On Fri, 2004-07-02 at 17:37, Perez-Gonzalez, Inaky wrote:

Hi Ken

quoted

From: Chen, Kenneth W [mailto:kenneth.w.chen@intel.com]

Perez-Gonzalez, Inaky wrote on Thursday, July 01, 2004 11:35 PM

quoted

Dummy question that has been evading me for the last hours. Can you
help? Please bear with me here, I am a little lost in how to deal
with inodes and the cache.

....

Thus, what I need is a way that given the pair (inode,pgoff)
returns to me the 'struct page *' if the thing is cached in memory or
pulls it up from swap/file into memory and gets me a 'struct page *'.

Is there a way to do this?

find_get_page() might be the one you are looking for.

Something like this? [I am trying blindly]

page = find_get_page (inode->i_mapping, pgoff)

I would like at the logic of do_generic_mapping_read(). The code below
is perhaps roughly what you want.

page = find_get_page(inode->i_mapping, pgoff);
if(unlikely(page==NULL)) {

	page = page_cache_alloc_cold(mapping);
	if (!page) {
                /* NO LUCK SORRY :-( */
        }

        if(add_to_page_cache_lru(page, mapping, pgoff, GFP_KERNEL)) {
                /* NO LUCK SORRY :-( */
        }
}
if (!PageUptodate(page)) { 
     lock_page(page);
     mapping->a_ops->readpage(filp /*i guess this can be null */,
			 page);
}
	
	


	

Under which circumstances will this fail? [I am guessing the only ones
are if the page offset is out of the limits of the map]. What about 
i_mapping? When is it not defined? [ie: NULL].

Thanks

IA+-aky PA(C)rez-GonzA!lez -- Not speaking for Intel -- all opinions are my own (and my fault)
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