From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Date: Tue, 26 Jul 2016 22:24:03 +0000 (-0700)
Subject: mm: thp: check pmd_trans_unstable() after split_huge_pmd()
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=337d9abf1cd1a59645d91b6d0b1685a476b81978;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

mm: thp: check pmd_trans_unstable() after split_huge_pmd()

split_huge_pmd() doesn't guarantee that the pmd is normal pmd pointing
to pte entries, which can be checked with pmd_trans_unstable().  Some
callers make this assertion and some do it differently and some not, so
let's do it in a unified manner.

Link: http://lkml.kernel.org/r/1464741400-12143-1-git-send-email-n-horiguchi@ah.jp.nec.com
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/gup.c b/mm/gup.c
index c057784c8444..dee142e100f4 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -279,6 +279,8 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
 			spin_unlock(ptl);
 			ret = 0;
 			split_huge_pmd(vma, pmd, address);
+			if (pmd_trans_unstable(pmd))
+				ret = -EBUSY;
 		} else {
 			get_page(page);
 			spin_unlock(ptl);
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 297d6854f849..fe90e5051012 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -512,6 +512,8 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
 		}
 	}
 
+	if (pmd_trans_unstable(pmd))
+		return 0;
 retry:
 	pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
 	for (; addr != end; pte++, addr += PAGE_SIZE) {
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 5019a1ef2848..a4830f0325fe 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -163,7 +163,7 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
 		if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
 			if (next - addr != HPAGE_PMD_SIZE) {
 				split_huge_pmd(vma, pmd, addr);
-				if (pmd_none(*pmd))
+				if (pmd_trans_unstable(pmd))
 					continue;
 			} else {
 				int nr_ptes = change_huge_pmd(vma, pmd, addr,
diff --git a/mm/mremap.c b/mm/mremap.c
index 1f157adfdaf9..da22ad2a5678 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -210,9 +210,8 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
 				}
 			}
 			split_huge_pmd(vma, old_pmd, old_addr);
-			if (pmd_none(*old_pmd))
+			if (pmd_trans_unstable(old_pmd))
 				continue;
-			VM_BUG_ON(pmd_trans_huge(*old_pmd));
 		}
 		if (pte_alloc(new_vma->vm_mm, new_pmd, new_addr))
 			break;