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 <[email protected]> --- 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
