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From: Christoph Hellwig <hch@lst.de>
To: Coly Li <colyli@suse.de>
Cc: Christoph Hellwig <hch@lst.de>,
	linux-block@vger.kernel.org, damien.lemoal@wdc.com,
	hare@suse.com, axboe@kernel.dk, linux-bcache@vger.kernel.org,
	kbusch@kernel.org, Hannes Reinecke <hare@suse.de>,
	Jens Axboe <axboe@fb.com>,
	Johannes Thumshirn <johannes.thumshirn@wdc.com>,
	Shaun Tancheff <shaun.tancheff@seagate.com>
Subject: Re: [RFC PATCH v2 1/4] block: change REQ_OP_ZONE_RESET from 6 to 13
Date: Sat, 16 May 2020 17:36:49 +0200	[thread overview]
Message-ID: <20200516153649.GB16693@lst.de> (raw)
In-Reply-To: <f57da1e7-1563-db1e-8730-8daca219cbe7@suse.de>

On Sat, May 16, 2020 at 09:05:39PM +0800, Coly Li wrote:
> On 2020/5/16 20:50, Christoph Hellwig wrote:
> > On Sat, May 16, 2020 at 08:44:45PM +0800, Coly Li wrote:
> >> Yes you are right, just like REQ_OP_DISCARD which does not transfer any
> >> data but changes the data on device. If the request changes the stored
> >> data, it does transfer data.
> > 
> > REQ_OP_DISCARD is a special case, because most implementation end up
> > transferring data, it just gets attached in the low-level driver.
> > 
> 
> Yes, REQ_OP_ZONE_RESET and REQ_OP_ZONE_RESET_ALL are quite similar to
> REQ_OP_DISCARD. Data read from the LBA range of reset zone is not
> suggested and the content is undefined.
> 
> For bcache, similar to REQ_OP_DISCARD, REQ_OP_ZONE_RESET and
> REQ_OP_ZONE_RESET_ALL are handled in same way: If the backing device
> supports discard/zone_reset, and the operation successes, then cached
> data on SSD covered by the LBA range should be invalid, otherwise users
> will read outdated and garbage data.
> 
> We should treat REQ_OP_ZONE_RESET and REQ_OP_ZONE_RESET_ALL being in
> WRITE direction.

No, the difference is that the underlying SCSI/ATA/NVMe command tend to
usually actually transfer data.  Take a look at the special_vec field
in struct request and the RQF_SPECIAL_PAYLOAD flag.

  reply	other threads:[~2020-05-16 15:36 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-16  3:54 [RFC PATCH v2 0/4] block layer change necessary for bcache zoned device support Coly Li
2020-05-16  3:54 ` [RFC PATCH v2 1/4] block: change REQ_OP_ZONE_RESET from 6 to 13 Coly Li
2020-05-16  4:06   ` Chaitanya Kulkarni
2020-05-16  9:33     ` Coly Li
2020-05-16 12:38   ` Christoph Hellwig
2020-05-16 12:44     ` Coly Li
2020-05-16 12:50       ` Christoph Hellwig
2020-05-16 13:05         ` Coly Li
2020-05-16 15:36           ` Christoph Hellwig [this message]
2020-05-17  5:30             ` Coly Li
2020-05-18  6:53               ` Hannes Reinecke
2020-05-18  6:56                 ` Damien Le Moal
2020-05-18  0:33   ` Damien Le Moal
2020-05-18  5:09     ` Chaitanya Kulkarni
2020-05-16  3:54 ` [RFC PATCH v2 2/4] block: block: change REQ_OP_ZONE_RESET_ALL from 8 to 15 Coly Li
2020-05-18  0:36   ` Damien Le Moal
2020-05-16  3:54 ` [RFC PATCH v2 3/4] block: remove queue_is_mq restriction from blk_revalidate_disk_zones() Coly Li
2020-05-16 12:40   ` Christoph Hellwig
2020-05-16 13:13     ` Coly Li
2020-05-16 15:35       ` Christoph Hellwig
2020-05-18  1:07       ` Damien Le Moal
2020-05-18  0:39   ` Damien Le Moal
2020-05-16  3:54 ` [RFC PATCH v2 4/4] block: set bi_size to REQ_OP_ZONE_RESET bio Coly Li
2020-05-16 12:53   ` Christoph Hellwig
2020-05-18  0:59   ` Damien Le Moal
2020-05-18  2:32     ` Coly Li

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