[PATCH v5 14/17] fs/proc: Support COW PTE with clear_refs_write

[Chih-En Lin <shiyn.lin@xxxxxxxxx>]

Before clearing the entry in COW-ed PTE, break COW PTE first.

Signed-off-by: Chih-En Lin <shiyn.lin@xxxxxxxxx>
---
 fs/proc/task_mmu.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 6a96e1713fd5..c76b74029dfd 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1195,6 +1195,11 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
 	if (pmd_trans_unstable(pmd))
 		return 0;
 
+	/* Only break COW when we modify the soft-dirty bit. */
+	if (cp->type == CLEAR_REFS_SOFT_DIRTY &&
+	    break_cow_pte(vma, pmd, addr))
+		return 0;
+
 	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 	for (; addr != end; pte++, addr += PAGE_SIZE) {
 		ptent = *pte;
-- 
2.34.1