The patch titled
Subject: mm-memory_hotplug-make-hugetlb_optimize_vmemmap-compatible-with-memmap_on_memory-v5
has been added to the -mm mm-unstable branch. Its filename is
mm-memory_hotplug-make-hugetlb_optimize_vmemmap-compatible-with-memmap_on_memory-v5.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memory_hotplug-make-hugetlb_optimize_vmemmap-compatible-with-memmap_on_memory-v5.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Co-developed-by: Oscar Salvador <osalvador@xxxxxxx>
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Xiongchun Duan <duanxiongchun@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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);
}
_
Patches currently in -mm which might be from songmuchun@xxxxxxxxxxxxx are
mm-memory_hotplug-enumerate-all-supported-section-flags.patch
mm-memory_hotplug-enumerate-all-supported-section-flags-v5.patch
mm-memory_hotplug-make-hugetlb_optimize_vmemmap-compatible-with-memmap_on_memory.patch
mm-memory_hotplug-make-hugetlb_optimize_vmemmap-compatible-with-memmap_on_memory-v5.patch
mm-hugetlb-remove-minimum_order-variable.patch
mm-memcontrol-remove-dead-code-and-comments.patch
mm-rename-unlock_page_lruvec_irq-_irqrestore-to-lruvec_unlock_irq-_irqrestore.patch
mm-memcontrol-prepare-objcg-api-for-non-kmem-usage.patch
mm-memcontrol-make-lruvec-lock-safe-when-lru-pages-are-reparented.patch
mm-vmscan-rework-move_pages_to_lru.patch
mm-thp-make-split-queue-lock-safe-when-lru-pages-are-reparented.patch
mm-memcontrol-make-all-the-callers-of-foliopage_memcg-safe.patch
mm-memcontrol-introduce-memcg_reparent_ops.patch
mm-memcontrol-use-obj_cgroup-apis-to-charge-the-lru-pages.patch
mm-lru-add-vm_warn_on_once_folio-to-lru-maintenance-function.patch
mm-lru-use-lruvec-lock-to-serialize-memcg-changes.patch
