linux-kernel - Re: [PATCH 2/7] mm/sparse.c: Introduce a new function clear_subsection

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Date:   Mon, 10 Feb 2020 14:02:53 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     Wei Yang <richardw.yang@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, dan.j.williams@...el.com,
        david@...hat.com
Subject: Re: [PATCH 2/7] mm/sparse.c: Introduce a new function
 clear_subsection_map()

On Mon, Feb 10, 2020 at 11:36:27AM +0800, Baoquan He wrote:
>On 02/10/20 at 07:07am, Wei Yang wrote:
>> On Sun, Feb 09, 2020 at 06:48:21PM +0800, Baoquan He wrote:
>> >Wrap the codes clearing subsection map of one memory region in
>> >section_deactivate() into clear_subsection_map().
>> >
>> 
>> Patch 1 and 2 server the same purpose -- to #ifdef the VMEMMAP.
>
>Hmm, I didn't say patch 1 and 2 are preparation works because they had
>better be done even if we don't take off subsection map from
>SPARSEMEM|!VMEMMAP case. Wrapping the subsection map filling and clearing
>codes into separate new functions, can make section_activate() and
>section_deactivate() much clearer on code logic.
>
>If you don't mind, I will keep them for now, and see what other people
>will say.

No objection.

>
>Thanks
>Baoquan
>
>> 
>> >---
>> > mm/sparse.c | 44 +++++++++++++++++++++++++++++++++++++-------
>> > 1 file changed, 37 insertions(+), 7 deletions(-)
>> >
>> >diff --git a/mm/sparse.c b/mm/sparse.c
>> >index 9ad741ccbeb6..696f6b9f706e 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);
>> > 
>> > 		/*
>> >-- 
>> >2.17.2
>> 
>> -- 
>> Wei Yang
>> Help you, Help me
>> 

-- 
Wei Yang
Help you, Help me