Re: [PATCH v2 3/7] mm/sparse.c: introduce a new function clear_subsection_map()

[Wei Yang]

On Thu, Feb 20, 2020 at 12:33:12PM +0800, Baoquan He wrote:
>Wrap the codes which clear subsection map of one memory region from
>section_deactivate() into clear_subsection_map().
>
>Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>

Reviewed-by: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>

>---
> mm/sparse.c | 46 ++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 38 insertions(+), 8 deletions(-)
>
>diff --git a/mm/sparse.c b/mm/sparse.c
>index 977b47acd38d..df857ee9330c 100644
>--- a/mm/sparse.c
>+++ b/mm/sparse.c
>@@ -726,14 +726,25 @@ static void free_map_bootmem(struct page *memmap)
> }
> #endif /* CONFIG_SPARSEMEM_VMEMMAP */
> 
>-static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
>-		struct vmem_altmap *altmap)
>+/**
>+ * clear_subsection_map - Clear subsection map of one memory region
>+ *
>+ * @pfn - start pfn of the memory range
>+ * @nr_pages - number of pfns to add in the region
>+ *
>+ * This is only intended for hotplug, and clear the related subsection
>+ * map inside one section.
>+ *
>+ * Return:
>+ * * -EINVAL	- Section already deactived.
>+ * * 0		- Subsection map is emptied.
>+ * * 1		- Subsection map is not empty.
>+ */
>+static int clear_subsection_map(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;
> 
>@@ -744,8 +755,28 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> 	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
> 				"section already deactivated (%#lx + %ld)\n",
> 				pfn, nr_pages))
>-		return;
>+		return -EINVAL;
>+
>+	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
> 
>+	if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION))
>+		return 0;
>+
>+	return 1;
>+}
>+
>+static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
>+		struct vmem_altmap *altmap)
>+{
>+	struct mem_section *ms = __pfn_to_section(pfn);
>+	bool section_is_early = early_section(ms);
>+	struct page *memmap = NULL;
>+	int rc;
>+
>+
>+	rc = clear_subsection_map(pfn, nr_pages);
>+	if (IS_ERR_VALUE((unsigned long)rc))
>+		return;
> 	/*
> 	 * There are 3 cases to handle across two configurations
> 	 * (SPARSEMEM_VMEMMAP={y,n}):
>@@ -763,8 +794,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> 	 *
> 	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
> 	 */
>-	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
>-	if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) {
>+	if (!rc) {
> 		unsigned long section_nr = pfn_to_section_nr(pfn);
> 
> 		/*
>@@ -786,7 +816,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> 	else
> 		depopulate_section_memmap(pfn, nr_pages, altmap);
> 
>-	if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION))
>+	if (!rc)
> 		ms->section_mem_map = (unsigned long)NULL;
> }
> 
>-- 
>2.17.2

-- 
Wei Yang
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