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Message-ID: <563BC1FB.60004@kernel.dk>
Date: Thu, 5 Nov 2015 13:54:19 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Dave Chinner <david@...morbit.com>, Jeff Moyer <jmoyer@...hat.com>
Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>,
linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
"J. Bruce Fields" <bfields@...ldses.org>,
Theodore Ts'o <tytso@....edu>,
Alexander Viro <viro@...iv.linux.org.uk>,
Andreas Dilger <adilger.kernel@...ger.ca>,
Dan Williams <dan.j.williams@...el.com>,
Ingo Molnar <mingo@...hat.com>, Jan Kara <jack@...e.com>,
Jeff Layton <jlayton@...chiereds.net>,
Matthew Wilcox <willy@...ux.intel.com>,
Thomas Gleixner <tglx@...utronix.de>,
linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-mm@...ck.org, linux-nvdimm@...1.01.org, x86@...nel.org,
xfs@....sgi.com, Andrew Morton <akpm@...ux-foundation.org>,
Matthew Wilcox <matthew.r.wilcox@...el.com>
Subject: Re: [RFC 00/11] DAX fsynx/msync support
On 11/05/2015 01:33 AM, Dave Chinner wrote:
>> Des xfs rely on this model for correctness? If so, I'd say we've got a
>> problem
>
> No, it doesn't. The XFS integrity model doesn't trust the IO layers
> to tell the truth about IO ordering and completion or for it's
> developers to fully understand how IO layer ordering works. :P
That's good, because the storage developers simplified the model so that
fs developers would be able to get and use it.
> i.e. we wait for full completions of all dependent IO before issuing
> flushes or log writes that use REQ_FLUSH|REQ_FUA semantics to ensure
> the dependent IOs are fully caught by the cache flushes...
... which is what you are supposed to do, that's how it works.
--
Jens Axboe
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