From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Martin K. Petersen" <martin.petersen@oracle.com>
Subject: Re: [PATCH v7 0/6] block: Introduce REQ_ALLOCATE flag for REQ_OP_WRITE_ZEROES
Date: Thu, 26 Mar 2020 10:34:42 -0400
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In-Reply-To: <20200326092935.GA6478@infradead.org> (Christoph Hellwig's
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To: Christoph Hellwig <hch@infradead.org>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>, "Darrick J. Wong" <darrick.wong@oracle.com>, Kirill Tkhai <ktkhai@virtuozzo.com>, axboe@kernel.dk, bob.liu@oracle.com, agk@redhat.com, snitzer@redhat.com, dm-devel@redhat.com, song@kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, Chaitanya.Kulkarni@wdc.com, ming.lei@redhat.com, osandov@fb.com, jthumshirn@suse.de, minwoo.im.dev@gmail.com, damien.lemoal@wdc.com, andrea.parri@amarulasolutions.com, hare@suse.com, tj@kernel.org, ajay.joshi@wdc.com, sagi@grimberg.me, dsterba@suse.com, bvanassche@acm.org, dhowells@redhat.com, asml.silence@gmail.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
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Christoph,

> That's why I don't like the whole flags game very much.  I'd rather
> have REQ_OP_WRITE_ZEROES as the integrity operation that gurantees
> zeroing, and a REQ_ALLOCATE that doesn't guarantee zeroing, just some
> deterministic state of the blocks.

I just worry about the proliferation of identical merging and splitting
code throughout the block stack as we add additional single-range, no
payload operations (Verify, etc.). I prefer to enforce the semantics in
the LLD and not in the plumbing. But I won't object to a separate
REQ_OP_ALLOCATE if you find the resulting code duplication acceptable.

-- 
Martin K. Petersen	Oracle Linux Engineering