Re: [PATCH 5/5] Direct Migration V9: Avoid writeback / page_migrate()method

[Christoph Lameter]

On Tue, 10 Jan 2006, Andrew Morton wrote:

> So let's see.  Suppose the kernel is about to dink with a page's buffer
> ring.  It does:
> 
> 	get_page(page);
> 	lock_page(page);
> 	dink_with(page_buffers(page));
> 
> how do these patches ensure that the page doesn't get migrated under my
> feet?

The page is locked when buffer_migrate_page is called. Thus 

lock_page

will block.

If the refcount was increased before the migration code does the lock 
on the tree_lock then the migration will be aborted.

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