When fully deactivated, it is meaningless to keep the value of a section's mem_map. And its mem_map will be reassigned during re-added. Beside this, it breaks the user space tool "makedumpfile", which makes assumption that a hot-removed section having mem_map as NULL. The bug can be reproduced on IBM POWERVM by "drmgr -c mem -r -q 5" , trigger a crash, and save vmcore by makedumpfile Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx> To: linux-mm@xxxxxxxxx Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Oscar Salvador <osalvador@xxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: kexec@xxxxxxxxxxxxxxxxxxx Cc: Kazuhito Hagio <k-hagio@xxxxxxxxxxxxx> --- mm/sparse.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/sparse.c b/mm/sparse.c index 3822ecb..fddac80 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -789,7 +789,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, ms->usage = NULL; } memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr); - ms->section_mem_map = sparse_encode_mem_map(NULL, section_nr); + ms->section_mem_map = NULL; } if (section_is_early && memmap) -- 2.7.5
