On Wed, Nov 23, 2011 at 02:30:18AM +0900, Minchan Kim wrote:
> > <SNIP>
> > + /*
> > + * To minimise LRU disruption, the caller can indicate that it only
> > + * wants to isolate pages it will be able to operate on without
> > + * blocking - clean pages for the most part.
> > + *
> > + * ISOLATE_CLEAN means that only clean pages should be isolated. This
> > + * is used by reclaim when it is cannot write to backing storage
> > + *
> > + * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
> > + * that it is possible to migrate without blocking with a ->migratepage
> > + * handler
> > + */
> > + if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
> > + /* All the caller can do on PageWriteback is block */
> > + if (PageWriteback(page))
> > + return ret;
> > +
> > + if (PageDirty(page)) {
> > + struct address_space *mapping;
> > +
> > + /* ISOLATE_CLEAN means only clean pages */
> > + if (mode & ISOLATE_CLEAN)
> > + return ret;
> > +
> > + /*
> > + * Only the ->migratepage callback knows if a dirty
> > + * page can be migrated without blocking. Skip the
> > + * page unless there is a ->migratepage callback.
> > + */
> > + mapping = page_mapping(page);
> > + if (!mapping || !mapping->a_ops->migratepage)
>
> I didn't review 4/7 carefully yet.
Thanks for reviewing the others.
> In case of page_mapping is NULL, move_to_new_page calls migrate_page
> which is non-blocking function. So, I guess it could be migrated without blocking.
>
Well spotted
/*
* Only pages without mappings or that have a
* ->migratepage callback are possible to
* migrate without blocking
*/
mapping = page_mapping(page);
if (mapping && !mapping->a_ops->migratepage)
return ret;
--
Mel Gorman
SUSE Labs
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