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Subject[patch] hugetlb: add hugepage reservation upon mremap expansion.
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hugetlb: add hugepage reservation upon mremap expansion

hugetlb page has a semantics that it reserves pages up front at the time
of mmap. We need to extend the same reservation scheme for the mremap
expansion case.

Signed-off-by: Ken Chen <kenchen@google.com>

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index c36d851..5d22933 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -28,6 +28,8 @@ int hugetlb_mempolicy_sysctl_handler(

int move_hugetlb_page_tables(struct vm_area_struct *vma, unsigned long old_addr,
unsigned long new_addr, unsigned long len);
+int hugetlb_expand_resv(struct vm_area_struct *vma, unsigned long old_len,
+ unsigned long new_len);
int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, struct vm_area_struct *);
int follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *,
struct page **, struct vm_area_struct **,
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 6f5b56f..1f8e333 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2250,6 +2250,34 @@ int move_hugetlb_page_tables(
return len + old_addr - old_end;
}

+int hugetlb_expand_resv(struct vm_area_struct *vma, unsigned long old_len,
+ unsigned long new_len)
+{
+ struct hstate *h = hstate_vma(vma);
+ int ret = 0;
+
+ if (old_len >= new_len)
+ goto out;
+
+ if (vma->vm_flags & VM_MAYSHARE) {
+ struct inode *inode = vma->vm_file->f_mapping->host;
+ unsigned long from, to, vm_flags;
+
+ from = (vma->vm_pgoff >> huge_page_order(h)) +
+ (old_len >> huge_page_shift(h));
+ to = (vma->vm_pgoff >> huge_page_order(h)) +
+ (new_len >> huge_page_shift(h));
+ vm_flags = vma->vm_flags;
+
+ ret = hugetlb_reserve_pages(inode, from, to, vma, vm_flags);
+ } else if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
+ long expand = (new_len - old_len) >> huge_page_shift(h);
+ ret = hugetlb_acct_memory(h, expand);
+ }
+out:
+ return ret;
+}
+
void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
unsigned long end, struct page *ref_page)
{
diff --git a/mm/mremap.c b/mm/mremap.c
index 9f6c903..010f93a 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -410,7 +410,7 @@ unsigned long do_mremap(unsigned long addr,
unsigned long flags, unsigned long new_addr)
{
struct mm_struct *mm = current->mm;
- struct vm_area_struct *vma;
+ struct vm_area_struct *vma = NULL;
unsigned long ret = -EINVAL;
unsigned long charged = 0;

@@ -525,6 +525,15 @@ unsigned long do_mremap(unsigned long addr,
out:
if (ret & ~PAGE_MASK)
vm_unacct_memory(charged);
+ else if (vma && is_vm_hugetlb_page(vma)) {
+ unsigned long ret2;
+
+ ret2 = hugetlb_expand_resv(vma, old_len, new_len);
+ if (ret2) {
+ ret = ret2;
+ vm_unacct_memory(charged);
+ }
+ }
return ret;
}


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