lkml.org 
[lkml]   [2020]   [Feb]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 5/7] mm/sparse.c: update code comment about section activate/deactivate
Date
It's helpful to note that sub-section is only supported in
SPARSEMEM_VMEMMAP case, but not in SPARSEMEM|!VMEMMAP case. Add
sentences into the code comment above sparse_add_section.

And move the code comments inside section_deactivate() to be above
it, this makes code cleaner.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
mm/sparse.c | 40 +++++++++++++++++++++++-----------------
1 file changed, 23 insertions(+), 17 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 36e6565ec67e..a7e78bfe0dce 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -809,6 +809,23 @@ static void free_map_bootmem(struct page *memmap)
}
#endif /* CONFIG_SPARSEMEM_VMEMMAP */

+/*
+ * To deactivate a memory region, there are 3 cases across two
+ * 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)
{
@@ -821,23 +838,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
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}):
- *
- * 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
- */
+
if (!rc) {
unsigned long section_nr = pfn_to_section_nr(pfn);

@@ -913,6 +914,11 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,
*
* This is only intended for hotplug.
*
+ * Note that the added memory region is either section aligned, or
+ * sub-section aligned. The sub-section aligned region can only be
+ * hot added in SPARSEMEM_VMEMMAP case, please refer to ZONE_DEVICE
+ * part of memory-model.rst for more details.
+ *
* Return:
* * 0 - On success.
* * -EEXIST - Section has been present.
--
2.17.2
\
 
 \ /
  Last update: 2020-02-09 11:49    [W:0.248 / U:2.456 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site