From: Hirokazu Takahashi Hi Dave, The following patch also checks whether mapping->a_ops exits before checking mapping->a_ops->migrate_page . Please apply it after P13.3-Add_comment_why_writeback_isnt_needed.patch . Thanks, Hirokazu Takahashi. Signed-off-by: Dave Hansen --- memhotplug-dave/mm/mmigrate.c | 2 +- 1 files changed, 1 insertion(+), 1 deletion(-) diff -puN mm/mmigrate.c~AA-PM-13.4-check-a_ops mm/mmigrate.c --- memhotplug/mm/mmigrate.c~AA-PM-13.4-check-a_ops 2005-03-28 16:38:22.000000000 -0800 +++ memhotplug-dave/mm/mmigrate.c 2005-03-28 16:38:22.000000000 -0800 @@ -420,7 +420,7 @@ static inline void page_start_writeback( * Writeback is not needed if it has migrate_page method, * because it can move all of them without writeback I/O. */ - if (mapping->a_ops->migrate_page) + if (mapping->a_ops && mapping->a_ops->migrate_page) goto out_unlock; if (!need_writeback(page)) goto out_unlock; _