[PATCH 19/35] mm: gup_huge_pmd() for dmem huge pmd

[yulei . kernel]

From: Yulei Zhang <yuleixzh...@tencent.com>

Add pmd_special() check in gup_huge_pmd() to support dmem huge pmd.
GUP will return zero if enconter dmem page, and we could handle it
outside GUP routine.

Signed-off-by: Chen Zhuo <sagazc...@tencent.com>
Signed-off-by: Yulei Zhang <yuleixzh...@tencent.com>
---
 mm/gup.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/mm/gup.c b/mm/gup.c
index 726ffc5b0ea9..a8edbb6a2b2f 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2440,6 +2440,10 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, 
unsigned long addr,
        if (!pmd_access_permitted(orig, flags & FOLL_WRITE))
                return 0;
 
+       /* Bypass dmem huge pmd. It will be handled in outside routine. */
+       if (pmd_special(orig))
+               return 0;
+
        if (pmd_devmap(orig)) {
                if (unlikely(flags & FOLL_LONGTERM))
                        return 0;
@@ -2542,7 +2546,7 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, 
unsigned long end,
                        return 0;
 
                if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
-                            pmd_devmap(pmd))) {
+                            pmd_devmap(pmd) || pmd_special(pmd))) {
                        /*
                         * NUMA hinting faults need to be handled in the GUP
                         * slowpath for accounting purposes and so that they
-- 
2.28.0