hugetlb fault processing code would COW all write faults where the
pte was not writable. Soft dirty will write protect ptes as part
of it's tracking mechanism. The existing hugetlb_cow code will do
the right thing for PRIVATE mappings as it checks map_count. However,
for SHARED mappings it would actually allocate and install a COW page.
Modify the code to not call hugetlb_cow for SHARED mappings and just
update the pte.
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
mm/hugetlb.c | 23 ++++++++++++++++-------
1 file changed, 16 insertions(+), 7 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 47f3123afd1a..b561b6867ec1 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4584,8 +4584,10 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
* spinlock. For private mappings, we also lookup the pagecache
* page now as it is used to determine if a reservation has been
* consumed.
+ * Only non-shared mappings are sent to hugetlb_cow.
*/
- if ((flags & FAULT_FLAG_WRITE) && !huge_pte_write(entry)) {
+ if ((flags & FAULT_FLAG_WRITE) && !huge_pte_write(entry) &&
+ !(vma->vm_flags & VM_SHARED)) {
if (vma_needs_reservation(h, vma, haddr) < 0) {
ret = VM_FAULT_OOM;
goto out_mutex;
@@ -4593,9 +4595,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
/* Just decrements count, does not deallocate */
vma_end_reservation(h, vma, haddr);
- if (!(vma->vm_flags & VM_MAYSHARE))
- pagecache_page = hugetlbfs_pagecache_page(h,
- vma, haddr);
+ pagecache_page = hugetlbfs_pagecache_page(h, vma, haddr);
}
ptl = huge_pte_lock(h, mm, ptep);
@@ -4620,9 +4620,18 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (flags & FAULT_FLAG_WRITE) {
if (!huge_pte_write(entry)) {
- ret = hugetlb_cow(mm, vma, address, ptep,
- pagecache_page, ptl);
- goto out_put_page;
+ if (!(vma->vm_flags & VM_SHARED)) {
+ ret = hugetlb_cow(mm, vma, address, ptep,
+ pagecache_page, ptl);
+ goto out_put_page;
+ }
+
+ /* write protected for soft dirty processing */
+ if ((vma->vm_flags & VM_WRITE) &&
+ (vma->vm_flags & VM_SHARED))
+ entry = huge_pte_mkwrite(entry);
+
+ entry = huge_pte_mkdirty(entry);
}
entry = huge_pte_mkdirty(entry);
}
--
2.29.2
