From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f48.google.com (mail-pa0-f48.google.com [209.85.220.48]) by kanga.kvack.org (Postfix) with ESMTP id CB26B6B0038 for ; Mon, 16 Nov 2015 13:34:11 -0500 (EST) Received: by pacej9 with SMTP id ej9so76045556pac.2 for ; Mon, 16 Nov 2015 10:34:11 -0800 (PST) Received: from mga14.intel.com (mga14.intel.com. [192.55.52.115]) by mx.google.com with ESMTP id rs4si52114383pbb.50.2015.11.16.10.34.10 for ; Mon, 16 Nov 2015 10:34:10 -0800 (PST) Date: Mon, 16 Nov 2015 11:34:04 -0700 From: Ross Zwisler Subject: Re: [PATCH] mm, dax: fix DAX deadlocks (COW fault) Message-ID: <20151116183404.GA22996@linux.intel.com> References: <1447675755-5692-1-git-send-email-yigal@plexistor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: Yigal Korman , "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 10:15:56AM -0800, Dan Williams wrote: > 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. Looks good to me as well. Thanks for catching this. -- 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