linux-kernel - [PATCH] mm: do not call do_fault

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Date:	Tue, 15 Jul 2014 15:58:32 +0400
From:	Konstantin Khlebnikov <k.khlebnikov@...sung.com>
To:	linux-mm@...ck.org, Hugh Dickins <hughd@...gle.com>,
	linux-kernel@...r.kernel.org, Sasha Levin <sasha.levin@...cle.com>
Cc:	Ingo Korb <ingo.korb@...dortmund.de>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Dave Jones <davej@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ning Qu <quning@...gle.com>,
	Konstantin Khlebnikov <koct9i@...il.com>
Subject: [PATCH] mm: do not call do_fault_around for non-linear fault

From: Konstantin Khlebnikov <koct9i@...il.com>

Faulting around non-linear page-fault has no sense and
breaks logic in do_fault_around because pgoff is shifted.

Signed-off-by: Konstantin Khlebnikov <koct9i@...il.com>
Reported-by: "Ingo Korb" <ingo.korb@...dortmund.de>
---
 mm/memory.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index d67fd9f..7e8d820 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2882,7 +2882,8 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	 * if page by the offset is not ready to be mapped (cold cache or
 	 * something).
 	 */
-	if (vma->vm_ops->map_pages && fault_around_pages() > 1) {
+	if (vma->vm_ops->map_pages && !(flags & FAULT_FLAG_NONLINEAR) &&
+	    fault_around_pages() > 1) {
 		pte = pte_offset_map_lock(mm, pmd, address, &ptl);
 		do_fault_around(vma, address, pte, pgoff, flags);
 		if (!pte_same(*pte, orig_pte))

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