Re: [PATCH 5/8] Direct Migration V2: upgrade MPOL_MF_MOVE and sys_migrate_pages()

[KAMEZAWA Hiroyuki]

Christoph Lameter wrote:
> On Wed, 9 Nov 2005, KAMEZAWA Hiroyuki wrote:
>
>
> > Christoph Lameter wrote:
> >
> > > +	err = migrate_pages(pagelist, &newlist, &moved, &failed);
> > > +
> > > +	putback_lru_pages(&moved);	/* Call release pages instead ?? */
> > > +
> > > +	if (err >= 0 && list_empty(&newlist) && !list_empty(pagelist))
> > > +		goto redo;
> >
> >
> > Here, list_empty(&newlist) is needed ?
> > For checking permanent failure case, list_empty(&failed) looks better.
>
>
> We only allocate 256 pages which are on the newlist. If the newlist is 
> empty but there are still pages that could be migrated 
> (!list_empty(pagelist)) then we need to allocate more pages and call 
> migrate_pages() again.
Ah, Okay.

confirmation:
1. Because mm->sem is held, there is no page-is-truncated/freed case.
2. Because pages in pagelist are removed from zone's lru, kswapd and others will not
   find and unmap them. There is no page-is-swapedout-by-others case.

So if all target pages are successfuly remvoed from pagelist, newlist must be empty.
Right ?


-- Kame


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