From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Boaz Harrosh <boaz@plexistor.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Matthew Wilcox <matthew.r.wilcox@intel.com>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org,
Yigal Korman <yigal@plexistor.com>, Jan Kara <jack@suse.cz>,
Dave Chinner <david@fromorbit.com>
Subject: Re: [PATCH] mm, dax: VMA with vm_ops->pfn_mkwrite wants to be write-notified
Date: Tue, 1 Sep 2015 14:10:20 +0300 [thread overview]
Message-ID: <20150901111020.GA7820@node.dhcp.inet.fi> (raw)
In-Reply-To: <55E583E2.9000200@plexistor.com>
On Tue, Sep 01, 2015 at 01:54:26PM +0300, Boaz Harrosh wrote:
> On 09/01/2015 01:22 PM, Kirill A. Shutemov wrote:
> > For VM_PFNMAP and VM_MIXEDMAP we use vm_ops->pfn_mkwrite instead of
> > vm_ops->page_mkwrite to notify abort write access. This means we want
> > vma->vm_page_prot to be write-protected if the VMA provides this vm_ops.
> >
>
> Hi Kirill
>
> I will test with this right away and ACK on this.
>
> Hmm so are you saying we might be missing some buffer modifications right now.
>
> What would be a theoretical scenario that will cause these missed events?
On writable mapping with vm_ops->pfn_mkwrite, but without
vm_ops->page_mkwrite: read fault followed by write access to the pfn.
Writable pte will be set up on read fault and write fault will not be
generated.
I found it examining Dave's complain on generic/080:
http://lkml.kernel.org/g/20150831233803.GO3902@dastard
Although I don't think it's the reason.
> I would like to put a test in our test rigs that should fail today and this
> patch fixes.
>
> [In our system every modified pmem block is also RDMAed to a remote
> pmem for HA, a missed modification will make the two copies unsynced]
It shouldn't be a problem for ext2/ext4 as they provide both pfn_mkwrite
and page_mkwrite.
--
Kirill A. Shutemov
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next prev parent reply other threads:[~2015-09-01 11:10 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-01 10:22 [PATCH] mm, dax: VMA with vm_ops->pfn_mkwrite wants to be write-notified Kirill A. Shutemov
2015-09-01 10:54 ` Boaz Harrosh
2015-09-01 11:10 ` Kirill A. Shutemov [this message]
2015-09-01 11:21 ` Boaz Harrosh
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