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Date:   Mon, 10 Feb 2020 07:23:19 +0800
From:   Wei Yang <richardw.yang@linux.intel.com>
To:     Baoquan He <bhe@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        akpm@linux-foundation.org, dan.j.williams@intel.com,
        richardw.yang@linux.intel.com, david@redhat.com
Subject: Re: [PATCH 3/7] mm/sparse.c: only use subsection map in VMEMMAP case
Message-ID: <20200209232319.GA8705@richard>
Reply-To: Wei Yang <richardw.yang@linux.intel.com>
References: <20200209104826.3385-1-bhe@redhat.com>
 <20200209104826.3385-4-bhe@redhat.com>
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On Sun, Feb 09, 2020 at 06:48:22PM +0800, Baoquan He wrote:
>Currently, subsection map is used when SPARSEMEM is enabled, including
>VMEMMAP case and !VMEMMAP case. However, subsection hotplug is not
>supported at all in SPARSEMEM|!VMEMMAP case, subsection map is unnecessary
>and misleading. Let's adjust code to only allow subsection map being
>used in SPARSEMEM|VMEMMAP case.
>
>Signed-off-by: Baoquan He <bhe@redhat.com>

The change looks good to me.

Reviewed-by: Wei Yang <richardw.yang@linux.intel.com>

>---
> include/linux/mmzone.h |   2 +
> mm/sparse.c            | 231 ++++++++++++++++++++++-------------------
> 2 files changed, 124 insertions(+), 109 deletions(-)
>
>diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>index 462f6873905a..fc0de3a9a51e 100644
>--- a/include/linux/mmzone.h
>+++ b/include/linux/mmzone.h
>@@ -1185,7 +1185,9 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec)
> #define SUBSECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SUBSECTION_MASK)
> 
> struct mem_section_usage {
>+#ifdef CONFIG_SPARSEMEM_VMEMMAP
> 	DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION);
>+#endif
> 	/* See declaration of similar field in struct zone */
> 	unsigned long pageblock_flags[0];
> };
>diff --git a/mm/sparse.c b/mm/sparse.c
>index 696f6b9f706e..cf55d272d0a9 100644
>--- a/mm/sparse.c
>+++ b/mm/sparse.c
>@@ -209,41 +209,6 @@ static inline unsigned long first_present_section_nr(void)
> 	return next_present_section_nr(-1);
> }
> 
>-static void subsection_mask_set(unsigned long *map, unsigned long pfn,
>-		unsigned long nr_pages)
>-{
>-	int idx = subsection_map_index(pfn);
>-	int end = subsection_map_index(pfn + nr_pages - 1);
>-
>-	bitmap_set(map, idx, end - idx + 1);
>-}
>-
>-void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
>-{
>-	int end_sec = pfn_to_section_nr(pfn + nr_pages - 1);
>-	unsigned long nr, start_sec = pfn_to_section_nr(pfn);
>-
>-	if (!nr_pages)
>-		return;
>-
>-	for (nr = start_sec; nr <= end_sec; nr++) {
>-		struct mem_section *ms;
>-		unsigned long pfns;
>-
>-		pfns = min(nr_pages, PAGES_PER_SECTION
>-				- (pfn & ~PAGE_SECTION_MASK));
>-		ms = __nr_to_section(nr);
>-		subsection_mask_set(ms->usage->subsection_map, pfn, pfns);
>-
>-		pr_debug("%s: sec: %lu pfns: %lu set(%d, %d)\n", __func__, nr,
>-				pfns, subsection_map_index(pfn),
>-				subsection_map_index(pfn + pfns - 1));
>-
>-		pfn += pfns;
>-		nr_pages -= pfns;
>-	}
>-}
>-
> /* Record a memory area against a node. */
> void __init memory_present(int nid, unsigned long start, unsigned long end)
> {
>@@ -432,12 +397,134 @@ static unsigned long __init section_map_size(void)
> 	return ALIGN(sizeof(struct page) * PAGES_PER_SECTION, PMD_SIZE);
> }
> 
>+static void subsection_mask_set(unsigned long *map, unsigned long pfn,
>+		unsigned long nr_pages)
>+{
>+	int idx = subsection_map_index(pfn);
>+	int end = subsection_map_index(pfn + nr_pages - 1);
>+
>+	bitmap_set(map, idx, end - idx + 1);
>+}
>+
>+void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
>+{
>+	int end_sec = pfn_to_section_nr(pfn + nr_pages - 1);
>+	unsigned long nr, start_sec = pfn_to_section_nr(pfn);
>+
>+	if (!nr_pages)
>+		return;
>+
>+	for (nr = start_sec; nr <= end_sec; nr++) {
>+		struct mem_section *ms;
>+		unsigned long pfns;
>+
>+		pfns = min(nr_pages, PAGES_PER_SECTION
>+				- (pfn & ~PAGE_SECTION_MASK));
>+		ms = __nr_to_section(nr);
>+		subsection_mask_set(ms->usage->subsection_map, pfn, pfns);
>+
>+		pr_debug("%s: sec: %lu pfns: %lu set(%d, %d)\n", __func__, nr,
>+				pfns, subsection_map_index(pfn),
>+				subsection_map_index(pfn + pfns - 1));
>+
>+		pfn += pfns;
>+		nr_pages -= pfns;
>+	}
>+}
>+
>+/**
>+ * 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);
>+	unsigned long *subsection_map = ms->usage
>+		? &ms->usage->subsection_map[0] : NULL;
>+
>+	subsection_mask_set(map, pfn, nr_pages);
>+	if (subsection_map)
>+		bitmap_and(tmp, map, subsection_map, SUBSECTIONS_PER_SECTION);
>+
>+	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
>+				"section already deactivated (%#lx + %ld)\n",
>+				pfn, nr_pages))
>+		return -EINVAL;
>+
>+	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
>+
>+	if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION))
>+		return 0;
>+
>+	return 1;
>+}
>+
>+/**
>+ * fill_subsection_map - fill subsection map of a memory region
>+ * @pfn - start pfn of the memory range
>+ * @nr_pages - number of pfns to add in the region
>+ *
>+ * This clears the related subsection map inside one section, and only
>+ * intended for hotplug.
>+ *
>+ * Return:
>+ * * 0		- On success.
>+ * * -EINVAL	- Invalid memory region.
>+ * * -EEXIST	- Subsection map has been set.
>+ */
>+static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
>+{
>+	struct mem_section *ms = __pfn_to_section(pfn);
>+	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
>+	unsigned long *subsection_map;
>+	int rc = 0;
>+
>+	subsection_mask_set(map, pfn, nr_pages);
>+
>+	subsection_map = &ms->usage->subsection_map[0];
>+
>+	if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))
>+		rc = -EINVAL;
>+	else if (bitmap_intersects(map, subsection_map, SUBSECTIONS_PER_SECTION))
>+		rc = -EEXIST;
>+	else
>+		bitmap_or(subsection_map, map, subsection_map,
>+				SUBSECTIONS_PER_SECTION);
>+
>+	return rc;
>+}
>+
> #else
> static unsigned long __init section_map_size(void)
> {
> 	return PAGE_ALIGN(sizeof(struct page) * PAGES_PER_SECTION);
> }
> 
>+void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
>+{
>+}
>+
>+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
>+{
>+	return 0;
>+}
>+static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
>+{
>+	return 0;
>+}
>+
> struct page __init *__populate_section_memmap(unsigned long pfn,
> 		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
> {
>@@ -726,45 +813,6 @@ static void free_map_bootmem(struct page *memmap)
> }
> #endif /* CONFIG_SPARSEMEM_VMEMMAP */
> 
>-/**
>- * 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);
>-	unsigned long *subsection_map = ms->usage
>-		? &ms->usage->subsection_map[0] : NULL;
>-
>-	subsection_mask_set(map, pfn, nr_pages);
>-	if (subsection_map)
>-		bitmap_and(tmp, map, subsection_map, SUBSECTIONS_PER_SECTION);
>-
>-	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
>-				"section already deactivated (%#lx + %ld)\n",
>-				pfn, nr_pages))
>-		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)
> {
>@@ -818,41 +866,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> 		depopulate_section_memmap(pfn, nr_pages, altmap);
> }
> 
>-/**
>- * fill_subsection_map - fill subsection map of a memory region
>- * @pfn - start pfn of the memory range
>- * @nr_pages - number of pfns to add in the region
>- *
>- * This clears the related subsection map inside one section, and only
>- * intended for hotplug.
>- *
>- * Return:
>- * * 0		- On success.
>- * * -EINVAL	- Invalid memory region.
>- * * -EEXIST	- Subsection map has been set.
>- */
>-static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
>-{
>-	struct mem_section *ms = __pfn_to_section(pfn);
>-	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
>-	unsigned long *subsection_map;
>-	int rc = 0;
>-
>-	subsection_mask_set(map, pfn, nr_pages);
>-
>-	subsection_map = &ms->usage->subsection_map[0];
>-
>-	if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))
>-		rc = -EINVAL;
>-	else if (bitmap_intersects(map, subsection_map, SUBSECTIONS_PER_SECTION))
>-		rc = -EEXIST;
>-	else
>-		bitmap_or(subsection_map, map, subsection_map,
>-				SUBSECTIONS_PER_SECTION);
>-
>-	return rc;
>-}
>-
> static struct page * __meminit section_activate(int nid, unsigned long pfn,
> 		unsigned long nr_pages, struct vmem_altmap *altmap)
> {
>-- 
>2.17.2

-- 
Wei Yang
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