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Date:   Tue, 5 Jul 2022 18:11:32 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Josef Bacik <josef@toxicpanda.com>
Cc:     Jens Axboe <axboe@kernel.dk>,
        "Darrick J. Wong" <djwong@kernel.org>,
        Al Viro <viro@zeniv.linux.org.uk>, Stefan Roesch <shr@fb.com>,
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        david@fromorbit.com, jack@suse.cz, hch@infradead.org,
        Christoph Hellwig <hch@lst.de>, rgoldwyn@suse.com
Subject: Re: [PATCH v7 15/15] xfs: Add async buffered write support
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On Tue, Jul 05, 2022 at 09:47:25AM -0400, Josef Bacik wrote:
> This appears to be just a confusion about what we think NOWAIT should mean.
> Looking at the btrfs code it seems like Goldwyn took it as literally as possible
> so we wouldn't do any NOWAIT IO's unless it was into a NOCOW area, meaning we
> literally wouldn't do anything other than wrap the bio up and fire it off.

It means don't do anything that would block.  And I suspect in btrfs
the above is about as much as you can do without blocking.