From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f42.google.com (mail-wm0-f42.google.com [74.125.82.42]) by kanga.kvack.org (Postfix) with ESMTP id 9792A6B0038 for ; Mon, 16 Nov 2015 13:15:57 -0500 (EST) Received: by wmww144 with SMTP id w144so131380313wmw.0 for ; Mon, 16 Nov 2015 10:15:57 -0800 (PST) Received: from mail-wm0-x22a.google.com (mail-wm0-x22a.google.com. [2a00:1450:400c:c09::22a]) by mx.google.com with ESMTPS id n123si7011768wmd.100.2015.11.16.10.15.56 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 16 Nov 2015 10:15:56 -0800 (PST) Received: by wmdw130 with SMTP id w130so123027949wmd.0 for ; Mon, 16 Nov 2015 10:15:56 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1447675755-5692-1-git-send-email-yigal@plexistor.com> References: <1447675755-5692-1-git-send-email-yigal@plexistor.com> Date: Mon, 16 Nov 2015 10:15:56 -0800 Message-ID: Subject: Re: [PATCH] mm, dax: fix DAX deadlocks (COW fault) From: Dan Williams Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Yigal Korman Cc: "linux-kernel@vger.kernel.org" , "linux-nvdimm@lists.01.org" , Linux MM , linux-fsdevel , david , Andrew Morton , Stable Tree , Boaz Harrosh , Ross Zwisler , Alexander Viro , Dave Chinner , Jan Kara , "Kirill A. Shutemov" , Matthew Wilcox On Mon, Nov 16, 2015 at 4:09 AM, Yigal Korman wrote: > 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: Looks good to me. I'll include this with some other DAX fixes I have pending. -- 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