linux-kernel - [PATCH v2 1/2] mm,sparse: Fix deactivate

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Message-Id: <20190717090725.23618-2-osalvador@suse.de>
Date:   Wed, 17 Jul 2019 11:07:24 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     akpm@...ux-foundation.org
Cc:     dan.j.williams@...el.com, david@...hat.com,
        pasha.tatashin@...een.com, mhocko@...e.com,
        aneesh.kumar@...ux.ibm.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Oscar Salvador <osalvador@...e.de>
Subject: [PATCH v2 1/2] mm,sparse: Fix deactivate_section for early sections

deactivate_section checks whether a section is early or not
in order to either call free_map_bootmem() or depopulate_section_memmap().
Being the former for sections added at boot time, and the latter for
sections hotplugged.

The problem is that we zero section_mem_map, so the last early_section()
will always report false and the section will not be removed.

Fix this checking whether a section is early or not at function
entry.

Fixes: mmotm ("mm/sparsemem: Support sub-section hotplug")
Signed-off-by: Oscar Salvador <osalvador@...e.de>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>
Reviewed-by: Dan Williams <dan.j.wiliams@...el.com>
---
 mm/sparse.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 3267c4001c6d..1e224149aab6 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -738,6 +738,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
 	DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
 	struct mem_section *ms = __pfn_to_section(pfn);
+	bool section_is_early = early_section(ms);
 	struct page *memmap = NULL;
 	unsigned long *subsection_map = ms->usage
 		? &ms->usage->subsection_map[0] : NULL;
@@ -772,7 +773,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
 
-		if (!early_section(ms)) {
+		if (!section_is_early) {
 			kfree(ms->usage);
 			ms->usage = NULL;
 		}
@@ -780,7 +781,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		ms->section_mem_map = sparse_encode_mem_map(NULL, section_nr);
 	}
 
-	if (early_section(ms) && memmap)
+	if (section_is_early && memmap)
 		free_map_bootmem(memmap);
 	else
 		depopulate_section_memmap(pfn, nr_pages, altmap);
-- 
2.12.3