[PATCH] Remove redundant flush_dcache_page in GUP

[Minchan Kim]

If we get the page with handle_mm_fault, it already handled
page flush. So GUP's flush_dcache_page call is redundant.

Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Nick Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx>

---
 mm/memory.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index ebfeedf..9166f4b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1430,6 +1430,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 		do {
 			struct page *page;
 			unsigned int foll_flags = gup_flags;
+			bool dcache_flushed = false;
 
 			/*
 			 * If we have a pending SIGKILL, don't keep faulting
@@ -1464,6 +1465,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 					tsk->maj_flt++;
 				else
 					tsk->min_flt++;
+				dcache_flushed = true;
 
 				/*
 				 * The VM_FAULT_WRITE bit tells us that
@@ -1489,7 +1491,8 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 				pages[i] = page;
 
 				flush_anon_page(vma, page, start);
-				flush_dcache_page(page);
+				if (!dcache_flushed)
+					flush_dcache_page(page);
 			}
 			if (vmas)
 				vmas[i] = vma;
-- 
1.7.0.4

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-- 
Kind regards,
Minchan Kim
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