Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752119AbbKPMJt (ORCPT ); Mon, 16 Nov 2015 07:09:49 -0500 Received: from mail-wm0-f51.google.com ([74.125.82.51]:37532 "EHLO mail-wm0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751822AbbKPMJq (ORCPT ); Mon, 16 Nov 2015 07:09:46 -0500 From: Yigal Korman To: linux-kernel@vger.kernel.org Cc: linux-nvdimm@ml01.01.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, david@fromorbit.com, akpm@linux-foundation.org, Yigal Korman , Stable Tree , Boaz Harrosh , Ross Zwisler , Alexander Viro , Dan Williams , Dave Chinner , Jan Kara , "Kirill A. Shutemov" , Matthew Wilcox Subject: [PATCH] mm, dax: fix DAX deadlocks (COW fault) Date: Mon, 16 Nov 2015 14:09:15 +0200 Message-Id: <1447675755-5692-1-git-send-email-yigal@plexistor.com> X-Mailer: git-send-email 1.9.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2277 Lines: 67 DAX handling of COW faults has wrong locking sequence: dax_fault does i_mmap_lock_read do_cow_fault does i_mmap_unlock_write Ross's commit[1] missed a fix[2] that Kirill added to Matthew's commit[3]. Original COW locking logic was introduced by Matthew here[4]. This should be applied to v4.3 as well. [1] 0f90cc6609c7 mm, dax: fix DAX deadlocks [2] 52a2b53ffde6 mm, dax: use i_mmap_unlock_write() in do_cow_fault() [3] 843172978bb9 dax: fix race between simultaneous faults [4] 2e4cdab0584f mm: allow page fault handlers to perform the COW Signed-off-by: Yigal Korman Cc: Stable Tree Cc: Boaz Harrosh Cc: Ross Zwisler Cc: Alexander Viro Cc: Dan Williams Cc: Dave Chinner Cc: Jan Kara Cc: "Kirill A. Shutemov" Cc: Matthew Wilcox --- mm/memory.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index c716913..e5071af 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3015,9 +3015,9 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, } else { /* * The fault handler has no page to lock, so it holds - * i_mmap_lock for write to protect against truncate. + * i_mmap_lock for read to protect against truncate. */ - i_mmap_unlock_write(vma->vm_file->f_mapping); + i_mmap_unlock_read(vma->vm_file->f_mapping); } goto uncharge_out; } @@ -3031,9 +3031,9 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, } else { /* * The fault handler has no page to lock, so it holds - * i_mmap_lock for write to protect against truncate. + * i_mmap_lock for read to protect against truncate. */ - i_mmap_unlock_write(vma->vm_file->f_mapping); + i_mmap_unlock_read(vma->vm_file->f_mapping); } return ret; uncharge_out: -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/