From: Kirill Tkhai <ktkhai@virtuozzo.com>
To: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
axboe@kernel.dk, tytso@mit.edu, adilger.kernel@dilger.ca,
Chaitanya.Kulkarni@wdc.com, darrick.wong@oracle.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
Subject: Re: [PATCH block v2 2/3] block: Add support for REQ_NOZERO flag
Date: Tue, 21 Jan 2020 12:47:09 +0300 [thread overview]
Message-ID: <3791a7fa-ea0c-d8ea-4b41-c968454b3787@virtuozzo.com> (raw)
In-Reply-To: <yq14kwpibf6.fsf@oracle.com>
On 21.01.2020 09:14, Martin K. Petersen wrote:
>
> Kirill,
>
>> + if (flags & BLKDEV_ZERO_NOUNMAP)
>> + req_flags |= REQ_NOUNMAP;
>> + if (flags & BLKDEV_ZERO_ALLOCATE)
>> + req_flags |= REQ_NOZERO|REQ_NOUNMAP;
>
> I find there is some dissonance between using BLKDEV_ZERO_ALLOCATE to
> describe this operation in one case and REQ_NOZERO in the other.
>
> I understand why not zeroing is important in your case. However, I think
> the allocation aspect is semantically more important. Also, in the case
> of SCSI, the allocated blocks will typically appear zeroed. So from that
> perspective REQ_NOZERO doesn't really make sense. I would really prefer
> to use REQ_ALLOCATE to describe this operation. I agree that "do not
> write every block" is important too. I just don't have a good suggestion
> for how to express that as an additional qualifier to REQ_ALLOCATE_?.
No problem, I'll rename the modifier.
> Also, adding to the confusion: In the context of SCSI, ANCHOR requires
> UNMAP. So my head hurts a bit when I read REQ_NOZERO|REQ_NOUNMAP and
> have to translate that into ANCHOR|UNMAP.
>
> Longer term, I think we should consider introducing REQ_OP_SINGLE_RANGE
> or something like that as an umbrella operation that can be used to
> describe zeroing, allocating, and other things that operate on a single
> LBA range with no payload. Thus removing both the writiness and the
> zeroness from the existing REQ_OP_WRITE_ZEROES conduit.
>
> Naming issues aside, your patch looks fine. I'll try to rebase my SCSI
> patches on top of your series to see how things fit.
Ok, thanks.
next prev parent reply other threads:[~2020-01-21 9:47 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 12:35 [PATCH block v2 0/3] block: Introduce REQ_NOZERO flag for REQ_OP_WRITE_ZEROES operation Kirill Tkhai
2020-01-16 12:35 ` [PATCH block v2 1/3] block: Add @flags argument to bdev_write_zeroes_sectors() Kirill Tkhai
2020-01-19 1:46 ` Bob Liu
2020-01-20 11:11 ` Kirill Tkhai
2020-01-21 5:45 ` Martin K. Petersen
2020-01-16 12:36 ` [PATCH block v2 2/3] block: Add support for REQ_NOZERO flag Kirill Tkhai
2020-01-19 1:50 ` Bob Liu
2020-01-20 10:02 ` Kirill Tkhai
2020-01-21 6:13 ` Bob Liu
2020-01-21 9:45 ` Kirill Tkhai
2020-01-21 6:14 ` Martin K. Petersen
2020-01-21 9:47 ` Kirill Tkhai [this message]
2020-01-31 6:23 ` Christoph Hellwig
2020-01-31 9:15 ` Kirill Tkhai
2020-01-16 12:36 ` [PATCH block v2 3/3] loop: Add support for REQ_NOZERO Kirill Tkhai
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