From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f50.google.com (mail-wm0-f50.google.com [74.125.82.50]) by kanga.kvack.org (Postfix) with ESMTP id 77D376B0253 for ; Mon, 16 Nov 2015 07:09:47 -0500 (EST) Received: by wmvv187 with SMTP id v187so172863789wmv.1 for ; Mon, 16 Nov 2015 04:09:46 -0800 (PST) Received: from mail-wm0-x22e.google.com (mail-wm0-x22e.google.com. [2a00:1450:400c:c09::22e]) by mx.google.com with ESMTPS id i26si25254262wmc.111.2015.11.16.04.09.45 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 16 Nov 2015 04:09:46 -0800 (PST) Received: by wmdw130 with SMTP id w130so108015792wmd.0 for ; Mon, 16 Nov 2015 04:09:45 -0800 (PST) From: Yigal Korman 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> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: linux-nvdimm@lists.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 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org