linux-kernel - [PATCH 4.16 32/72] mm: sections are not offlined during memory hotremove

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Message-Id: <20180514064824.476481364@linuxfoundation.org>
Date:   Mon, 14 May 2018 08:48:49 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Pavel Tatashin <pasha.tatashin@...cle.com>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Steven Sistare <steven.sistare@...cle.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.16 32/72] mm: sections are not offlined during memory hotremove

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pavel Tatashin <pasha.tatashin@...cle.com>

commit 27227c733852f71008e9bf165950bb2edaed3a90 upstream.

Memory hotplug and hotremove operate with per-block granularity.  If the
machine has a large amount of memory (more than 64G), the size of a
memory block can span multiple sections.  By mistake, during hotremove
we set only the first section to offline state.

The bug was discovered because kernel selftest started to fail:
  https://lkml.kernel.org/r/20180423011247.GK5563@yexl-desktop

After commit, "mm/memory_hotplug: optimize probe routine".  But, the bug
is older than this commit.  In this optimization we also added a check
for sections to be in a proper state during hotplug operation.

Link: http://lkml.kernel.org/r/20180427145257.15222-1-pasha.tatashin@oracle.com
Fixes: 2d070eab2e82 ("mm: consider zone which is not fully populated to have holes")
Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Steven Sistare <steven.sistare@...cle.com>
Cc: Daniel Jordan <daniel.m.jordan@...cle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/sparse.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -666,7 +666,7 @@ void offline_mem_sections(unsigned long
 	unsigned long pfn;

 	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
-		unsigned long section_nr = pfn_to_section_nr(start_pfn);
+		unsigned long section_nr = pfn_to_section_nr(pfn);
 		struct mem_section *ms;

 		/*