| From 1f503443e7df8dc8366608b4d810ce2d6669827c Mon Sep 17 00:00:00 2001 |
| From: Pingfan Liu <kernelfans@gmail.com> |
| Date: Thu, 30 Jan 2020 22:11:10 -0800 |
| Subject: mm/sparse.c: reset section's mem_map when fully deactivated |
| |
| From: Pingfan Liu <kernelfans@gmail.com> |
| |
| commit 1f503443e7df8dc8366608b4d810ce2d6669827c upstream. |
| |
| After commit ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug"), |
| when a mem section is fully deactivated, section_mem_map still records |
| the section's start pfn, which is not used any more and will be |
| reassigned during re-addition. |
| |
| In analogy with alloc/free pattern, it is better to clear all fields of |
| section_mem_map. |
| |
| Beside this, it breaks the user space tool "makedumpfile" [1], which |
| makes assumption that a hot-removed section has mem_map as NULL, instead |
| of checking directly against SECTION_MARKED_PRESENT bit. (makedumpfile |
| will be better to change the assumption, and need a patch) |
| |
| The bug can be reproduced on IBM POWERVM by "drmgr -c mem -r -q 5" , |
| trigger a crash, and save vmcore by makedumpfile |
| |
| [1]: makedumpfile, commit e73016540293 ("[v1.6.7] Update version") |
| |
| Link: http://lkml.kernel.org/r/1579487594-28889-1-git-send-email-kernelfans@gmail.com |
| Signed-off-by: Pingfan Liu <kernelfans@gmail.com> |
| Acked-by: Michal Hocko <mhocko@suse.com> |
| Acked-by: David Hildenbrand <david@redhat.com> |
| Cc: Dan Williams <dan.j.williams@intel.com> |
| Cc: Oscar Salvador <osalvador@suse.de> |
| Cc: Baoquan He <bhe@redhat.com> |
| Cc: Qian Cai <cai@lca.pw> |
| Cc: Kazuhito Hagio <k-hagio@ab.jp.nec.com> |
| Cc: <stable@vger.kernel.org> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| mm/sparse.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/mm/sparse.c |
| +++ b/mm/sparse.c |
| @@ -789,7 +789,7 @@ static void section_deactivate(unsigned |
| 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 = (unsigned long)NULL; |
| } |
| |
| if (section_is_early && memmap) |