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Date:   Wed, 23 Sep 2020 16:04:27 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Mikulas Patocka <mpatocka@redhat.com>
Cc:     Jan Kara <jack@suse.cz>, Dave Chinner <david@fromorbit.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Eric Sandeen <esandeen@redhat.com>,
        Dave Chinner <dchinner@redhat.com>,
        "Kani, Toshi" <toshi.kani@hpe.com>,
        "Norton, Scott J" <scott.norton@hpe.com>,
        "Tadakamadla, Rajesh (DCIG/CDI/HPS Perf)" 
        <rajesh.tadakamadla@hpe.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-nvdimm <linux-nvdimm@lists.01.org>
Subject: Re: NVFS XFS metadata (was: [PATCH] pmem: export the symbols
 __copy_user_flushcache and __copy_from_user_flushcache)
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On Wed, Sep 23, 2020 at 09:11:43AM -0400, Mikulas Patocka wrote:
> I also don't know how to implement journling on persistent memory :) On 
> EXT4 or XFS you can pin dirty buffers in memory until the journal is 
> flushed. This is obviously impossible on persistent memory. So, I'm 
> considering implementing only some lightweight journaling that will 
> guarantee atomicity between just a few writes.

That's a bit disappointing considering people have been publishing
papers on how to do umpteen different variations on persistent memory
journalling for the last five years.

https://www.google.com/search?q=intel+persistent+memory+atomic+updates

for example