linux-ext4 - Re: [PATCH RFC 1/3] block: Add support for REQ_OP_ASSIGN

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Message-ID: <yq1woatc8zd.fsf@oracle.com>
Date:   Wed, 18 Dec 2019 22:03:34 -0500
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-ext4@...r.kernel.org, axboe@...nel.dk, tytso@....edu,
        adilger.kernel@...ger.ca, 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,
        chaitanya.kulkarni@....com, bvanassche@....org,
        dhowells@...hat.com, asml.silence@...il.com
Subject: Re: [PATCH RFC 1/3] block: Add support for REQ_OP_ASSIGN_RANGE operation


Hi Kirill!

> The patch adds a new blkdev_issue_assign_range() primitive, which is
> rather similar to existing blkdev_issue_{*} api.  Also, a new queue
> limit.max_assign_range_sectors is added.

I am not so keen on the assign_range name. What's wrong with "allocate"?

But why introduce a completely new operation? Isn't this essentially a
write zeroes with BLKDEV_ZERO_NOUNMAP flag set?

If the zeroing aspect is perceived to be a problem we could add a
BLKDEV_ZERO_ALLOCATE flag (or BLKDEV_ZERO_ANCHOR since that's the
terminology used in SCSI).

-- 
Martin K. Petersen	Oracle Linux Engineering