Hi Tang,

Thanks for your review and comments, Please see below for my reply.

On 2012/12/4 17:13, Tang Chen wrote:

Hi Wu,

Sorry to make noise here. Please see below. :)

On 12/03/2012 10:23 AM, Jianguo Wu wrote:

quoted

Signed-off-by: Jianguo Wu<redacted>
Signed-off-by: Jiang Liu<redacted>
---
  include/linux/mm.h  |    1 +
  mm/sparse-vmemmap.c |  231 +++++++++++++++++++++++++++++++++++++++++++++++++++
  mm/sparse.c         |    3 +-
  3 files changed, 234 insertions(+), 1 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5657670..1f26af5 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h

@@ -1642,6 +1642,7 @@ int vmemmap_populate(struct page *start_page, unsigned long pages, int node);
  void vmemmap_populate_print_last(void);
  void register_page_bootmem_memmap(unsigned long section_nr, struct page *map,
                    unsigned long size);
+void vmemmap_free(struct page *memmap, unsigned long nr_pages);

  enum mf_flags {
      MF_COUNT_INCREASED = 1<<  0,

diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index 1b7e22a..748732d 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c

@@ -29,6 +29,10 @@
  #include<asm/pgalloc.h>
  #include<asm/pgtable.h>

+#ifdef CONFIG_MEMORY_HOTREMOVE
+#include<asm/tlbflush.h>
+#endif
+
  /*
   * Allocate a block of memory to be used to back the virtual memory map
   * or to back the page tables that are used to create the mapping.

@@ -224,3 +228,230 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
          vmemmap_buf_end = NULL;
      }
  }
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+
+#define PAGE_INUSE 0xFD
+
+static void vmemmap_free_pages(struct page *page, int order)
+{
+    struct zone *zone;
+    unsigned long magic;
+
+    magic = (unsigned long) page->lru.next;
+    if (magic == SECTION_INFO || magic == MIX_SECTION_INFO) {
+        put_page_bootmem(page);
+
+        zone = page_zone(page);
+        zone_span_writelock(zone);
+        zone->present_pages++;
+        zone_span_writeunlock(zone);
+        totalram_pages++;

Seems that we have different ways to handle pages allocated by bootmem
or by regular allocator. Is the checking way in [PATCH 09/12] available
here ?

+    /* bootmem page has reserved flag */
+    if (PageReserved(page)) {
......
+    }

If so, I think we can just merge these two functions.

Hmm, direct mapping table isn't allocated by bootmem allocator such as memblock, can't be free by put_page_bootmem().
But I will try to merge these two functions.

quoted

+    } else
+        free_pages((unsigned long)page_address(page), order);
+}
+
+static void free_pte_table(pmd_t *pmd)
+{
+    pte_t *pte, *pte_start;
+    int i;
+
+    pte_start = (pte_t *)pmd_page_vaddr(*pmd);
+    for (i = 0; i<  PTRS_PER_PTE; i++) {
+        pte = pte_start + i;
+        if (pte_val(*pte))
+            return;
+    }
+
+    /* free a pte talbe */
+    vmemmap_free_pages(pmd_page(*pmd), 0);
+    spin_lock(&init_mm.page_table_lock);
+    pmd_clear(pmd);
+    spin_unlock(&init_mm.page_table_lock);
+}
+
+static void free_pmd_table(pud_t *pud)
+{
+    pmd_t *pmd, *pmd_start;
+    int i;
+
+    pmd_start = (pmd_t *)pud_page_vaddr(*pud);
+    for (i = 0; i<  PTRS_PER_PMD; i++) {
+        pmd = pmd_start + i;
+        if (pmd_val(*pmd))
+            return;
+    }
+
+    /* free a pmd talbe */
+    vmemmap_free_pages(pud_page(*pud), 0);
+    spin_lock(&init_mm.page_table_lock);
+    pud_clear(pud);
+    spin_unlock(&init_mm.page_table_lock);
+}
+
+static void free_pud_table(pgd_t *pgd)
+{
+    pud_t *pud, *pud_start;
+    int i;
+
+    pud_start = (pud_t *)pgd_page_vaddr(*pgd);
+    for (i = 0; i<  PTRS_PER_PUD; i++) {
+        pud = pud_start + i;
+        if (pud_val(*pud))
+            return;
+    }
+
+    /* free a pud table */
+    vmemmap_free_pages(pgd_page(*pgd), 0);
+    spin_lock(&init_mm.page_table_lock);
+    pgd_clear(pgd);
+    spin_unlock(&init_mm.page_table_lock);
+}

All the free_xxx_table() are very similar to the functions in
[PATCH 09/12]. Could we reuse them anyway ?

yes, we can reuse them.

quoted

+
+static int split_large_page(pte_t *kpte, unsigned long address, pte_t *pbase)
+{
+    struct page *page = pmd_page(*(pmd_t *)kpte);
+    int i = 0;
+    unsigned long magic;
+    unsigned long section_nr;
+
+    __split_large_page(kpte, address, pbase);

Is this patch going to replace [PATCH 08/12] ?

I wish to replace [PATCH 08/12], but need Congyang and Yasuaki to confirm first:)

If so, __split_large_page() was added and exported in [PATCH 09/12],
then we should move it here, right ?

yes.

and what do you think about moving vmemmap_pud[pmd/pte]_remove() to arch/x86/mm/init_64.c,
to be consistent with vmemmap_populate() ?

I will rework [PATCH 08/12] and [PATCH 09/12] soon.

Thanks,
Jianguo Wu.

If not, free_map_bootmem() and __kfree_section_memmap() were changed in
[PATCH 08/12], and we need to handle this.

quoted

+    __flush_tlb_all();
+
+    magic = (unsigned long) page->lru.next;
+    if (magic == SECTION_INFO) {
+        section_nr = pfn_to_section_nr(page_to_pfn(page));
+        while (i<  PTRS_PER_PMD) {
+            page++;
+            i++;
+            get_page_bootmem(section_nr, page, SECTION_INFO);
+        }
+    }
+
+    return 0;
+}
+
+static void vmemmap_pte_remove(pmd_t *pmd, unsigned long addr, unsigned long end)
+{
+    pte_t *pte;
+    unsigned long next;
+    void *page_addr;
+
+    pte = pte_offset_kernel(pmd, addr);
+    for (; addr<  end; pte++, addr += PAGE_SIZE) {
+        next = (addr + PAGE_SIZE)&  PAGE_MASK;
+        if (next>  end)
+            next = end;
+
+        if (pte_none(*pte))
+            continue;
+        if (IS_ALIGNED(addr, PAGE_SIZE)&&
+            IS_ALIGNED(next, PAGE_SIZE)) {
+            vmemmap_free_pages(pte_page(*pte), 0);
+            spin_lock(&init_mm.page_table_lock);
+            pte_clear(&init_mm, addr, pte);
+            spin_unlock(&init_mm.page_table_lock);
+        } else {
+            /*
+             * Removed page structs are filled with 0xFD.
+             */
+            memset((void *)addr, PAGE_INUSE, next - addr);
+            page_addr = page_address(pte_page(*pte));
+
+            if (!memchr_inv(page_addr, PAGE_INUSE, PAGE_SIZE)) {
+                spin_lock(&init_mm.page_table_lock);
+                pte_clear(&init_mm, addr, pte);
+                spin_unlock(&init_mm.page_table_lock);
+            }
+        }
+    }
+
+    free_pte_table(pmd);
+    __flush_tlb_all();
+}
+
+static void vmemmap_pmd_remove(pud_t *pud, unsigned long addr, unsigned long end)
+{
+    unsigned long next;
+    pmd_t *pmd;
+
+    pmd = pmd_offset(pud, addr);
+    for (; addr<  end; addr = next, pmd++) {
+        next = pmd_addr_end(addr, end);
+        if (pmd_none(*pmd))
+            continue;
+
+        if (cpu_has_pse) {
+            unsigned long pte_base;
+
+            if (IS_ALIGNED(addr, PMD_SIZE)&&
+                IS_ALIGNED(next, PMD_SIZE)) {
+                vmemmap_free_pages(pmd_page(*pmd),
+                           get_order(PMD_SIZE));
+                spin_lock(&init_mm.page_table_lock);
+                pmd_clear(pmd);
+                spin_unlock(&init_mm.page_table_lock);
+                continue;
+            }
+
+            /*
+             * We use 2M page, but we need to remove part of them,
+             * so split 2M page to 4K page.
+             */
+            pte_base = get_zeroed_page(GFP_ATOMIC | __GFP_NOTRACK);
+            if (!pte_base) {
+                WARN_ON(1);
+                continue;
+            }
+
+            split_large_page((pte_t *)pmd, addr, (pte_t *)pte_base);
+            __flush_tlb_all();
+
+            spin_lock(&init_mm.page_table_lock);
+            pmd_populate_kernel(&init_mm, pmd, (pte_t *)pte_base);
+            spin_unlock(&init_mm.page_table_lock);
+        }
+
+        vmemmap_pte_remove(pmd, addr, next);
+    }
+
+    free_pmd_table(pud);
+    __flush_tlb_all();
+}
+
+static void vmemmap_pud_remove(pgd_t *pgd, unsigned long addr, unsigned long end)
+{
+    unsigned long next;
+    pud_t *pud;
+
+    pud = pud_offset(pgd, addr);
+    for (; addr<  end; addr = next, pud++) {
+        next = pud_addr_end(addr, end);
+        if (pud_none(*pud))
+            continue;
+
+        vmemmap_pmd_remove(pud, addr, next);
+    }
+
+    free_pud_table(pgd);
+    __flush_tlb_all();
+}
+
+void vmemmap_free(struct page *memmap, unsigned long nr_pages)
+{
+    unsigned long addr = (unsigned long)memmap;
+    unsigned long end = (unsigned long)(memmap + nr_pages);
+    unsigned long next;
+
+    for (; addr<  end; addr = next) {
+        pgd_t *pgd = pgd_offset_k(addr);
+
+        next = pgd_addr_end(addr, end);
+        if (!pgd_present(*pgd))
+            continue;
+
+        vmemmap_pud_remove(pgd, addr, next);
+        sync_global_pgds(addr, next - 1);
+    }
+}
+#endif

diff --git a/mm/sparse.c b/mm/sparse.c
index fac95f2..4060229 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c

@@ -615,10 +615,11 @@ static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
  }
  static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
  {
-    return; /* XXX: Not implemented yet */
+    vmemmap_free(memmap, nr_pages);
  }
  static void free_map_bootmem(struct page *page, unsigned long nr_pages)

In the latest kernel, this line was:
static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)

quoted

  {
+    vmemmap_free(page, nr_pages);
  }
  #else
  static struct page *__kmalloc_section_memmap(unsigned long nr_pages)

.