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Message-Id: <20220621135313.ae6fbc28338f1220328694f7@linux-foundation.org>
Date: Tue, 21 Jun 2022 13:53:13 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Muchun Song <songmuchun@...edance.com>
Cc: corbet@....net, david@...hat.com, mike.kravetz@...cle.com,
osalvador@...e.de, paulmck@...nel.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
duanxiongchun@...edance.com, smuchun@...il.com
Subject: Re: [PATCH v5 0/2] make hugetlb_optimize_vmemmap compatible with
memmap_on_memory
On Mon, 20 Jun 2022 19:06:14 +0800 Muchun Song <songmuchun@...edance.com> wrote:
> This series makes hugetlb_optimize_vmemmap compatible with memmap_on_memory
> and is based on mm-stable. The reason refers to the patch 2's commit log.
>
> v5:
> - Replace enum to defines per David.
> - Walk vmemmap page tables to avoid false-positive.
I can't see this second change in the v3->v5 deltas?
From: Muchun Song <songmuchun@...edance.com>
Subject: mm-memory_hotplug-enumerate-all-supported-section-flags-v5
Date: Mon, 20 Jun 2022 19:06:15 +0800
replace enum with defines per David
Link: https://lkml.kernel.org/r/20220620110616.12056-2-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@...edance.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---
include/linux/mmzone.h | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)
--- a/include/linux/mmzone.h~mm-memory_hotplug-enumerate-all-supported-section-flags-v5
+++ a/include/linux/mmzone.h
@@ -1439,16 +1439,13 @@ enum {
SECTION_MAP_LAST_BIT,
};
-enum {
- SECTION_MARKED_PRESENT = BIT(SECTION_MARKED_PRESENT_BIT),
- SECTION_HAS_MEM_MAP = BIT(SECTION_HAS_MEM_MAP_BIT),
- SECTION_IS_ONLINE = BIT(SECTION_IS_ONLINE_BIT),
- SECTION_IS_EARLY = BIT(SECTION_IS_EARLY_BIT),
+#define SECTION_MARKED_PRESENT BIT(SECTION_MARKED_PRESENT_BIT)
+#define SECTION_HAS_MEM_MAP BIT(SECTION_HAS_MEM_MAP_BIT)
+#define SECTION_IS_ONLINE BIT(SECTION_IS_ONLINE_BIT)
+#define SECTION_IS_EARLY BIT(SECTION_IS_EARLY_BIT)
#ifdef CONFIG_ZONE_DEVICE
- SECTION_TAINT_ZONE_DEVICE = BIT(SECTION_TAINT_ZONE_DEVICE_BIT),
+#define SECTION_TAINT_ZONE_DEVICE BIT(SECTION_TAINT_ZONE_DEVICE_BIT)
#endif
-};
-
#define SECTION_MAP_MASK (~(BIT(SECTION_MAP_LAST_BIT) - 1))
#define SECTION_NID_SHIFT SECTION_MAP_LAST_BIT
_
From: Muchun Song <songmuchun@...edance.com>
Subject: mm-memory_hotplug-make-hugetlb_optimize_vmemmap-compatible-with-memmap_on_memory-v5
Date: Mon, 20 Jun 2022 19:06:16 +0800
walk vmemmap page tables to avoid false-positive
Link: https://lkml.kernel.org/r/20220620110616.12056-3-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@...edance.com>
Co-developed-by: Oscar Salvador <osalvador@...e.de>
Signed-off-by: Oscar Salvador <osalvador@...e.de>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---
mm/hugetlb_vmemmap.c | 69 ++++++++++++++++++++++++++---------------
1 file changed, 44 insertions(+), 25 deletions(-)
--- a/mm/hugetlb_vmemmap.c~mm-memory_hotplug-make-hugetlb_optimize_vmemmap-compatible-with-memmap_on_memory-v5
+++ a/mm/hugetlb_vmemmap.c
@@ -10,6 +10,7 @@
*/
#define pr_fmt(fmt) "HugeTLB: " fmt
+#include <linux/memory.h>
#include "hugetlb_vmemmap.h"
/*
@@ -99,34 +100,52 @@ int hugetlb_vmemmap_alloc(struct hstate
static unsigned int vmemmap_optimizable_pages(struct hstate *h,
struct page *head)
{
- struct mem_section *ms;
- struct page *vmemmap_page;
- unsigned long pfn = page_to_pfn(head);
-
if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF)
return 0;
- ms = __pfn_to_section(pfn);
- vmemmap_page = sparse_decode_mem_map(ms->section_mem_map,
- pfn_to_section_nr(pfn));
- /*
- * Only the vmemmap pages' vmemmap may be marked as VmemmapSelfHosted.
- *
- * Due to HugeTLB alignment requirements, and the vmemmap pages being
- * at the start of the hotplugged memory region. Checking any vmemmap
- * page's vmemmap is fine.
- *
- * [ hotplugged memory ]
- * [ vmemmap ][ usable memory ]
- * ^ | | |
- * +---+ | |
- * ^ | |
- * +--------+ |
- * ^ |
- * +-----------------+
- */
- if (PageVmemmapSelfHosted(vmemmap_page))
- return 0;
+ if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) {
+ pmd_t *pmdp, pmd;
+ struct page *vmemmap_page;
+ unsigned long vaddr = (unsigned long)head;
+
+ /*
+ * Only the vmemmap page's vmemmap page can be self-hosted.
+ * Walking the page tables to find the backing page of the
+ * vmemmap page.
+ */
+ pmdp = pmd_off_k(vaddr);
+ /*
+ * The READ_ONCE() is used to stabilize *pmdp in a register or
+ * on the stack so that it will stop changing under the code.
+ * The only concurrent operation where it can be changed is
+ * split_vmemmap_huge_pmd() (*pmdp will be stable after this
+ * operation).
+ */
+ pmd = READ_ONCE(*pmdp);
+ if (pmd_leaf(pmd))
+ vmemmap_page = pmd_page(pmd) + pte_index(vaddr);
+ else
+ vmemmap_page = pte_page(*pte_offset_kernel(pmdp, vaddr));
+ /*
+ * Due to HugeTLB alignment requirements and the vmemmap pages
+ * being at the start of the hotplugged memory region in
+ * memory_hotplug.memmap_on_memory case. Checking any vmemmap
+ * page's vmemmap page if it is marked as VmemmapSelfHosted is
+ * sufficient.
+ *
+ * [ hotplugged memory ]
+ * [ section ][...][ section ]
+ * [ vmemmap ][ usable memory ]
+ * ^ | | |
+ * +---+ | |
+ * ^ | |
+ * +-------+ |
+ * ^ |
+ * +-------------------------------------------+
+ */
+ if (PageVmemmapSelfHosted(vmemmap_page))
+ return 0;
+ }
return hugetlb_optimize_vmemmap_pages(h);
}
_
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