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Subject[PATCH -V5 04/14] hugetlb: Use mmu_gather instead of a temporary linked list for accumulating pages
Date
From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>

Use mmu_gather instead of temporary linked list for accumulating pages when
we unmap a hugepage range. This also allows us to get rid of i_mmap_mutex
unmap_hugepage_range in the following patch.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
fs/hugetlbfs/inode.c | 4 ++--
include/linux/hugetlb.h | 6 ++---
mm/hugetlb.c | 59 ++++++++++++++++++++++++++++-------------------
mm/memory.c | 7 ++++--
4 files changed, 45 insertions(+), 31 deletions(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index ea25174..92f75aa 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -416,8 +416,8 @@ hugetlb_vmtruncate_list(struct prio_tree_root *root, pgoff_t pgoff)
else
v_offset = 0;

- __unmap_hugepage_range(vma,
- vma->vm_start + v_offset, vma->vm_end, NULL);
+ unmap_hugepage_range(vma, vma->vm_start + v_offset,
+ vma->vm_end, NULL);
}
}

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 876457e..46c6cbd 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -40,9 +40,9 @@ int follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *,
struct page **, struct vm_area_struct **,
unsigned long *, int *, int, unsigned int flags);
void unmap_hugepage_range(struct vm_area_struct *,
- unsigned long, unsigned long, struct page *);
-void __unmap_hugepage_range(struct vm_area_struct *,
- unsigned long, unsigned long, struct page *);
+ unsigned long, unsigned long, struct page *);
+void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *,
+ unsigned long, unsigned long, struct page *);
int hugetlb_prefault(struct address_space *, struct vm_area_struct *);
void hugetlb_report_meminfo(struct seq_file *);
int hugetlb_report_node_meminfo(int, char *);
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d94c987..a3ac624 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -24,8 +24,9 @@

#include <asm/page.h>
#include <asm/pgtable.h>
-#include <linux/io.h>
+#include <asm/tlb.h>

+#include <linux/io.h>
#include <linux/hugetlb.h>
#include <linux/node.h>
#include "internal.h"
@@ -2300,30 +2301,26 @@ static int is_hugetlb_entry_hwpoisoned(pte_t pte)
return 0;
}

-void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
- unsigned long end, struct page *ref_page)
+void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
+ unsigned long start, unsigned long end,
+ struct page *ref_page)
{
+ int force_flush = 0;
struct mm_struct *mm = vma->vm_mm;
unsigned long address;
pte_t *ptep;
pte_t pte;
struct page *page;
- struct page *tmp;
struct hstate *h = hstate_vma(vma);
unsigned long sz = huge_page_size(h);

- /*
- * A page gathering list, protected by per file i_mmap_mutex. The
- * lock is used to avoid list corruption from multiple unmapping
- * of the same page since we are using page->lru.
- */
- LIST_HEAD(page_list);
-
WARN_ON(!is_vm_hugetlb_page(vma));
BUG_ON(start & ~huge_page_mask(h));
BUG_ON(end & ~huge_page_mask(h));

+ tlb_start_vma(tlb, vma);
mmu_notifier_invalidate_range_start(mm, start, end);
+again:
spin_lock(&mm->page_table_lock);
for (address = start; address < end; address += sz) {
ptep = huge_pte_offset(mm, address);
@@ -2362,30 +2359,45 @@ void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
}

pte = huge_ptep_get_and_clear(mm, address, ptep);
+ tlb_remove_tlb_entry(tlb, ptep, address);
if (pte_dirty(pte))
set_page_dirty(page);
- list_add(&page->lru, &page_list);

+ page_remove_rmap(page);
+ force_flush = !__tlb_remove_page(tlb, page);
+ if (force_flush)
+ break;
/* Bail out after unmapping reference page if supplied */
if (ref_page)
break;
}
- flush_tlb_range(vma, start, end);
spin_unlock(&mm->page_table_lock);
- mmu_notifier_invalidate_range_end(mm, start, end);
- list_for_each_entry_safe(page, tmp, &page_list, lru) {
- page_remove_rmap(page);
- list_del(&page->lru);
- put_page(page);
+ /*
+ * mmu_gather ran out of room to batch pages, we break out of
+ * the PTE lock to avoid doing the potential expensive TLB invalidate
+ * and page-free while holding it.
+ */
+ if (force_flush) {
+ force_flush = 0;
+ tlb_flush_mmu(tlb);
+ if (address < end && !ref_page)
+ goto again;
}
+ mmu_notifier_invalidate_range_end(mm, start, end);
+ tlb_end_vma(tlb, vma);
}

void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
unsigned long end, struct page *ref_page)
{
- mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
- __unmap_hugepage_range(vma, start, end, ref_page);
- mutex_unlock(&vma->vm_file->f_mapping->i_mmap_mutex);
+ struct mm_struct *mm;
+ struct mmu_gather tlb;
+
+ mm = vma->vm_mm;
+
+ tlb_gather_mmu(&tlb, mm, 0);
+ __unmap_hugepage_range(&tlb, vma, start, end, ref_page);
+ tlb_finish_mmu(&tlb, start, end);
}

/*
@@ -2430,9 +2442,8 @@ static int unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
* from the time of fork. This would look like data corruption
*/
if (!is_vma_resv_set(iter_vma, HPAGE_RESV_OWNER))
- __unmap_hugepage_range(iter_vma,
- address, address + huge_page_size(h),
- page);
+ unmap_hugepage_range(iter_vma, address,
+ address + huge_page_size(h), page);
}
mutex_unlock(&mapping->i_mmap_mutex);

diff --git a/mm/memory.c b/mm/memory.c
index 6105f47..4b11961 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1326,8 +1326,11 @@ static void unmap_single_vma(struct mmu_gather *tlb,
* Since no pte has actually been setup, it is
* safe to do nothing in this case.
*/
- if (vma->vm_file)
- unmap_hugepage_range(vma, start, end, NULL);
+ if (vma->vm_file) {
+ mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
+ __unmap_hugepage_range(tlb, vma, start, end, NULL);
+ mutex_unlock(&vma->vm_file->f_mapping->i_mmap_mutex);
+ }
} else
unmap_page_range(tlb, vma, start, end, details);
}
--
1.7.10.rc3.3.g19a6c


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