Messages in this thread | | | Date | Thu, 20 Jan 2011 12:49:15 -0600 (CST) | From | Christoph Lameter <> | Subject | Re: [PATCH 1/3] When migrate_pages returns 0, all pages must have been released |
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On Thu, 20 Jan 2011, Andrea Arcangeli wrote:
> Hello, > > On Thu, Jan 20, 2011 at 11:30:35AM -0600, Christoph Lameter wrote: > > On Fri, 21 Jan 2011, Minchan Kim wrote: > > > > > diff --git a/mm/migrate.c b/mm/migrate.c > > > index 46fe8cc..7d34237 100644 > > > --- a/mm/migrate.c > > > +++ b/mm/migrate.c > > > @@ -772,6 +772,7 @@ uncharge: > > > unlock: > > > unlock_page(page); > > > > > > +move_newpage: > > > if (rc != -EAGAIN) { > > > /* > > > * A page that has been migrated has all references > > > @@ -785,8 +786,6 @@ unlock: > > > putback_lru_page(page); > > > } > > > > > > -move_newpage: > > > - > > > /* > > > * Move the new page to the LRU. If migration was not successful > > > * then this will free the page. > > > > > > > What does this do? Not covered by the description. > > It makes a difference for the two goto move_newpage, when rc = > 0. Otherwise the function will return 0, despite > putback_lru_page(page) wasn't called (and the caller of migrate_pages > won't call putback_lru_pages if migrate_pages returned 0).
Think about the difference:
Moving the move_newpage will now cause another removal and freeing of the page if rc != -EAGAIN.
The first goto move_newpage (because page count is 1) will now mean that the page is freed twice. One because of the rc != EAGAIN branch and then another time by the following putback_lru_page().
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