linux-kernel - Re: [PATCH v7 0/6] block: Introduce REQ_ALLOCATE flag for REQ_OP_WRITE

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Date:   Thu, 26 Mar 2020 10:34:42 -0400
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     "Martin K. Petersen" <martin.petersen@...cle.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>, axboe@...nel.dk,
        bob.liu@...cle.com, agk@...hat.com, snitzer@...hat.com,
        dm-devel@...hat.com, song@...nel.org, tytso@....edu,
        adilger.kernel@...ger.ca, Chaitanya.Kulkarni@....com,
        ming.lei@...hat.com, osandov@...com, jthumshirn@...e.de,
        minwoo.im.dev@...il.com, damien.lemoal@....com,
        andrea.parri@...rulasolutions.com, hare@...e.com, tj@...nel.org,
        ajay.joshi@....com, sagi@...mberg.me, dsterba@...e.com,
        bvanassche@....org, dhowells@...hat.com, asml.silence@...il.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 0/6] block: Introduce REQ_ALLOCATE flag for REQ_OP_WRITE_ZEROES


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