linux-kernel - Re: [PATCH v2] libnvdimm: re-enable deep flush for pmem devices

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Message-ID: <x49inb1n7kb.fsf@segfault.boston.devel.redhat.com>
Date:   Mon, 12 Feb 2018 17:53:40 -0500
From:   Jeff Moyer <jmoyer@...hat.com>
To:     Dave Jiang <dave.jiang@...el.com>
Cc:     dan.j.williams@...el.com, ross.zwisler@...el.com,
        linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org
Subject: Re: [PATCH v2] libnvdimm: re-enable deep flush for pmem devices

Dave Jiang <dave.jiang@...el.com> writes:

> Re-enable deep flush so that users always have a way to be sure that a write
> does make it all the way out to the NVDIMM. The PMEM driver writes always
> make it "all the way to the NVDIMM", and it relies on the ADR mechanism to
> flush the write buffers on power failure. Deep flush is there to explicitly
> flush those write buffers to protect against (rare) ADR failure.
> This change prevents a regression in deep flush behavior so that applications
> can continue to depend on fsync() as a mechanism to trigger deep flush in the
> filesystem-dax case.

That's still very confusing text.  Specifically, the part where you say
that pmem driver writes always make it to the DIMM.  I think the
changelog could start with "Deep flush is there to explicitly flush
write buffers...."  Anyway, the fix looks right to me.

Reviewed-by: Jeff Moyer <jmoyer@...hat.com>