From:   Niklas Cassel <Niklas.Cassel@wdc.com>
To:     Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@fb.com>,
        Christoph Hellwig <hch@lst.de>,
        Sagi Grimberg <sagi@grimberg.me>
CC:     "damien.lemoal@opensource.wdc.com" <damien.lemoal@opensource.wdc.com>,
        Niklas Cassel <Niklas.Cassel@wdc.com>,
        "linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: [PATCH v2] nvme: report write pointer for a full zone as zone start +
 zone len
Thread-Topic: [PATCH v2] nvme: report write pointer for a full zone as zone
 start + zone len
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Date:   Fri, 26 Nov 2021 10:42:44 +0000
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From: Niklas Cassel <niklas.cassel@wdc.com>

The write pointer in NVMe ZNS is invalid for a zone in zone state full.
The same also holds true for ZAC/ZBC.

The current behavior for NVMe is to simply propagate the wp reported by
the drive, even for full zones. Since the wp is invalid for a full zone,
the wp reported by the drive may be any value.

The way that the sd_zbc driver handles a full zone is to always report
the wp as zone start + zone len, regardless of what the drive reported.
null_blk also follows this convention.

Do the same for NVMe, so that a BLKREPORTZONE ioctl reports the write
pointer for a full zone in a consistent way, regardless of the interface
of the underlying zoned block device.

blkzone report before patch:
start: 0x000040000, len 0x040000, cap 0x03e000, wptr 0xfffffffffffbfff8
reset:0 non-seq:0, zcond:14(fu) [type: 2(SEQ_WRITE_REQUIRED)]

blkzone report after patch:
start: 0x000040000, len 0x040000, cap 0x03e000, wptr 0x040000 reset:0
non-seq:0, zcond:14(fu) [type: 2(SEQ_WRITE_REQUIRED)]

Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
---
Changes since v1:
- Minor commit message rewording.
- Use if/else instead of setting wp unconditionally and then
  conditionally updating it.

 drivers/nvme/host/zns.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/zns.c b/drivers/nvme/host/zns.c
index bfc259e0d7b8..9f81beb4df4e 100644
--- a/drivers/nvme/host/zns.c
+++ b/drivers/nvme/host/zns.c
@@ -166,7 +166,10 @@ static int nvme_zone_parse_entry(struct nvme_ns *ns,
 	zone.len =3D ns->zsze;
 	zone.capacity =3D nvme_lba_to_sect(ns, le64_to_cpu(entry->zcap));
 	zone.start =3D nvme_lba_to_sect(ns, le64_to_cpu(entry->zslba));
-	zone.wp =3D nvme_lba_to_sect(ns, le64_to_cpu(entry->wp));
+	if (zone.cond =3D=3D BLK_ZONE_COND_FULL)
+		zone.wp =3D zone.start + zone.len;
+	else
+		zone.wp =3D nvme_lba_to_sect(ns, le64_to_cpu(entry->wp));
=20
 	return cb(&zone, idx, data);
 }
--=20
2.33.1