From: Andres Lagar-Cavilla <andreslc@xxxxxxxxxx>
Reviewed-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Signed-off-by: Andres Lagar-Cavilla <andreslc@xxxxxxxxxx>
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
include/linux/mm.h | 1 +
mm/gup.c | 4 ++++
2 files changed, 5 insertions(+)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8981cc8..0f4196a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1985,6 +1985,7 @@ static inline struct page *follow_page(struct vm_area_struct *vma,
#define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */
#define FOLL_NUMA 0x200 /* force NUMA hinting page fault */
#define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */
+#define FOLL_TRIED 0x800 /* a retry, previous pass started an IO */
typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
void *data);
diff --git a/mm/gup.c b/mm/gup.c
index 91d044b..af7ea3e 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -281,6 +281,10 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
fault_flags |= FAULT_FLAG_ALLOW_RETRY;
if (*flags & FOLL_NOWAIT)
fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
+ if (*flags & FOLL_TRIED) {
+ VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
+ fault_flags |= FAULT_FLAG_TRIED;
+ }
ret = handle_mm_fault(mm, vma, address, fault_flags);
if (ret & VM_FAULT_ERROR) {
--
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