From: Baoquan He <bhe@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@suse.com,
david@redhat.com, richard.weiyang@gmail.com,
dan.j.williams@intel.com, bhe@redhat.com
Subject: [PATCH v4 4/5] mm/sparse.c: add note about only VMEMMAP supporting sub-section hotplug
Date: Thu, 12 Mar 2020 20:44:13 +0800 [thread overview]
Message-ID: <20200312124414.439-5-bhe@redhat.com> (raw)
In-Reply-To: <20200312124414.439-1-bhe@redhat.com>
And tell check_pfn_span() gating the porper alignment and size of
hot added memory region.
And also move the code comments from inside section_deactivate()
to being above it. The code comments are reasonable for the whole
function, and the moving makes code cleaner.
Signed-off-by: Baoquan He <bhe@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
---
mm/sparse.c | 38 +++++++++++++++++++++-----------------
1 file changed, 21 insertions(+), 17 deletions(-)
diff --git a/mm/sparse.c b/mm/sparse.c
index 117fe4554c38..f02a524e17d1 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -771,6 +771,22 @@ static bool is_subsection_map_empty(struct mem_section *ms)
}
#endif
+/*
+ * To deactivate a memory region, there are 3 cases to handle across
+ * two configurations (SPARSEMEM_VMEMMAP={y,n}):
+ *
+ * 1. deactivation of a partial hot-added section (only possible in
+ * the SPARSEMEM_VMEMMAP=y case).
+ * a) section was present at memory init.
+ * b) section was hot-added post memory init.
+ * 2. deactivation of a complete hot-added section.
+ * 3. deactivation of a complete section from memory init.
+ *
+ * For 1, when subsection_map does not empty we will not be freeing the
+ * usage map, but still need to free the vmemmap range.
+ *
+ * For 2 and 3, the SPARSEMEM_VMEMMAP={y,n} cases are unified
+ */
static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
struct vmem_altmap *altmap)
{
@@ -781,23 +797,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
if (clear_subsection_map(pfn, nr_pages))
return;
- /*
- * There are 3 cases to handle across two configurations
- * (SPARSEMEM_VMEMMAP={y,n}):
- *
- * 1/ deactivation of a partial hot-added section (only possible
- * in the SPARSEMEM_VMEMMAP=y case).
- * a/ section was present at memory init
- * b/ section was hot-added post memory init
- * 2/ deactivation of a complete hot-added section
- * 3/ deactivation of a complete section from memory init
- *
- * For 1/, when subsection_map does not empty we will not be
- * freeing the usage map, but still need to free the vmemmap
- * range.
- *
- * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
- */
+
empty = is_subsection_map_empty(ms);
if (empty) {
unsigned long section_nr = pfn_to_section_nr(pfn);
@@ -905,6 +905,10 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,
*
* This is only intended for hotplug.
*
+ * Note that only VMEMMAP supports sub-section aligned hotplug,
+ * the proper alignment and size are gated by check_pfn_span().
+ *
+ *
* Return:
* * 0 - On success.
* * -EEXIST - Section has been present.
--
2.17.2
next prev parent reply other threads:[~2020-03-12 12:44 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-12 12:44 [PATCH v4 0/5] mm/hotplug: Only use subsection map for VMEMMAP Baoquan He
2020-03-12 12:44 ` [PATCH v4 1/5] mm/sparse.c: introduce new function fill_subsection_map() Baoquan He
2020-03-12 13:30 ` Pankaj Gupta
2020-03-12 12:44 ` [PATCH v4 2/5] mm/sparse.c: introduce a new function clear_subsection_map() Baoquan He
2020-03-12 13:26 ` Pankaj Gupta
2020-03-12 12:44 ` [PATCH v4 3/5] mm/sparse.c: only use subsection map in VMEMMAP case Baoquan He
2020-03-12 12:44 ` Baoquan He [this message]
2020-03-12 13:45 ` [PATCH v4 4/5] mm/sparse.c: add note about only VMEMMAP supporting sub-section hotplug David Hildenbrand
2020-03-12 12:44 ` [PATCH v4 5/5] mm/sparse.c: move subsection_map related functions together Baoquan He
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