[RFC][PATCH] release mmap_sem before starting migration (Was Re: Need to take mmap_sem lock in move_pages.

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Wed, 4 Feb 2009 18:40:28 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> On Wed, 4 Feb 2009 18:36:00 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>       Maybe up_read() can be moved before do_migrate_pages(), I think.
> 
How about this ?
==

mmap_sem can be released after page table walk ends.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 mm/migrate.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: mmotm-2.6.29-Feb03/mm/migrate.c
===================================================================
--- mmotm-2.6.29-Feb03.orig/mm/migrate.c
+++ mmotm-2.6.29-Feb03/mm/migrate.c
@@ -875,13 +875,13 @@ put_and_set:
 set_status:
 		pp->status = err;
 	}
+	up_read(&mm->mmap_sem);
 
 	err = 0;
 	if (!list_empty(&pagelist))
 		err = migrate_pages(&pagelist, new_page_node,
 				(unsigned long)pm);
 
-	up_read(&mm->mmap_sem);
 	return err;
 }
 

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