Re: How to reclaim inode pages on demand

[Dave Hansen <haveblue@us.ibm.com>]

On Wed, 2005-08-10 at 18:27 +0100, Mel Gorman wrote:
> I later linearly scan the mem_map looking for pages that can be freed up
> (usually LRU pages). I was expecting any page with PG_inode set to have a
> page->mapping but not all of them do. It is the pages without a ->mapping
> that are confusing the hell out of me.

How about putting a check for PG_inode and a periodic dump_stack()
wherever page->mapping is cleared?  That should at least let you catch
the culprit who is clearing them. __remove_from_page_cache() is the only
real place I see this being done.

Are you remembering to clean PG_inode when a page is freed?  Perhaps
it's allocated for the page cache, reclaimed, returned to the allocator,
and reallocated as anonymous memory where you're seeing the null
->mapping.  Might want to check for PG_inode in free_pages_check().

-- Dave