RE: [PATCH 2/2] block: add BLKSETDESCZONE ioctl for Zoned Block Devices

From: Matias Bjorling
Date: Tue Jul 07 2020 - 12:03:32 EST

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In reply to: Javier GonzÃlez: "Re: [PATCH 2/2] block: add BLKSETDESCZONE ioctl for Zoned Block Devices"
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> -----Original Message-----
> From: Javier GonzÃlez <javier@xxxxxxxxxxx>
> Sent: Tuesday, 7 July 2020 10.43
> To: Matias Bjorling <Matias.Bjorling@xxxxxxx>
> Cc: Damien Le Moal <Damien.LeMoal@xxxxxxx>; axboe@xxxxxxxxx;
> kbusch@xxxxxxxxxx; hch@xxxxxx; sagi@xxxxxxxxxxx;
> martin.petersen@xxxxxxxxxx; Niklas Cassel <Niklas.Cassel@xxxxxxx>; Hans
> Holmberg <Hans.Holmberg@xxxxxxx>; linux-scsi@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; linux-block@xxxxxxxxxxxxxxx; linux-
> nvme@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH 2/2] block: add BLKSETDESCZONE ioctl for Zoned Block
> Devices
>
> On 03.07.2020 09:44, Matias Bjorling wrote:
> >> -----Original Message-----
> >> From: Javier GonzÃlez <javier@xxxxxxxxxxx>
> >> Sent: Monday, 29 June 2020 21.39
> >> To: Damien Le Moal <Damien.LeMoal@xxxxxxx>
> >> Cc: Matias Bjorling <Matias.Bjorling@xxxxxxx>; axboe@xxxxxxxxx;
> >> kbusch@xxxxxxxxxx; hch@xxxxxx; sagi@xxxxxxxxxxx;
> >> martin.petersen@xxxxxxxxxx; Niklas Cassel <Niklas.Cassel@xxxxxxx>;
> >> Hans Holmberg <Hans.Holmberg@xxxxxxx>; linux-scsi@xxxxxxxxxxxxxxx;
> >> linux- kernel@xxxxxxxxxxxxxxx; linux-block@xxxxxxxxxxxxxxx; linux-
> >> nvme@xxxxxxxxxxxxxxxxxxx
> >> Subject: Re: [PATCH 2/2] block: add BLKSETDESCZONE ioctl for Zoned
> >> Block Devices
> >>
> >> On 29.06.2020 01:00, Damien Le Moal wrote:
> >> >On 2020/06/29 8:01, Matias Bjorling wrote:
> >> >> The NVMe Zoned Namespace Command Set adds support for associating
> >> >> data to a zone through the Zone Descriptor Extension feature.
> >> >>
> >> >> To allow user-space to associate data to a zone, add support
> >> >> through the BLKSETDESCZONE ioctl. The ioctl requires that it is
> >> >> issued to a zoned block device, and that it supports the Zone
> >> >> Descriptor Extension feature. Support is detected through the the
> >> >> zone_desc_ext_bytes sysfs queue entry for the specific block device.
> >> >> A value larger than zero communicates that the device supports the
> >> >> feature.
> >>
> >> Have you considered the possibility of adding this an action to a
> >> IOCTL that looks like the zone management one we discussed last week?
> >> We would start saving IOCTLs already if we count the offline transition and
> this one.
> >
> >Yes, I considered it. Damien and Christoph have asked for it to separate ioctls.
>
> Ok.
>
> >
> >>
> >> >>
> >> >> The ioctl associates data to a zone by issuing a Zone Management
> >> >> Send command with the Zone Send Action set as the Set Zone
> >> >> Descriptor Extension.
> >> >>
> >> >> For the command to complete successfully, the specified zone must
> >> >> be in the Empty state, and active resources must be available. On
> >> >> success, the specified zone is transioned to Closed state by the
> >> >> device. If less data is supplied by user-space then reported by
> >> >> the the Zone Descriptor Extension size, the rest is zero-filled.
> >> >> If more data or no data is supplied by user-space, the ioctl fails.
> >> >>
> >> >> To issue the ioctl, a new blk_zone_set_desc data structure is defined.
> >> >> It has following parameters:
> >> >>
> >> >> * the sector of the specific zone.
> >> >> * the length of the data to be associated to the zone.
> >> >> * any flags be used by the ioctl. None is defined.
> >> >> * data associated to the zone.
> >> >>
> >> >> The data is laid out after the flags parameter, and it is the
> >> >> caller's responsibility to allocate memory for the data that is
> >> >> specified in the length parameter.
> >> >>
> >> >> Signed-off-by: Matias BjÃrling <matias.bjorling@xxxxxxx>
> >> >> ---
> >> >> block/blk-zoned.c | 108 ++++++++++++++++++++++++++++++++++
> >> >> block/ioctl.c | 2 +
> >> >> drivers/nvme/host/core.c | 3 +
> >> >> drivers/nvme/host/nvme.h | 9 +++
> >> >> drivers/nvme/host/zns.c | 11 ++++
> >> >> include/linux/blk_types.h | 2 +
> >> >> include/linux/blkdev.h | 9 ++-
> >> >> include/uapi/linux/blkzoned.h | 20 ++++++-
> >> >> 8 files changed, 162 insertions(+), 2 deletions(-)
> >> >>
> >> >> diff --git a/block/blk-zoned.c b/block/blk-zoned.c index
> >> >> 81152a260354..4dc40ec006a2 100644
> >> >> --- a/block/blk-zoned.c
> >> >> +++ b/block/blk-zoned.c
> >> >> @@ -259,6 +259,50 @@ int blkdev_zone_mgmt(struct block_device
> >> >> *bdev, enum req_opf op, } EXPORT_SYMBOL_GPL(blkdev_zone_mgmt);
> >> >>
> >> >> +/**
> >> >> + * blkdev_zone_set_desc - Execute a zone management set zone
> >> descriptor
> >> >> + * extension operation on a zone
> >> >> + * @bdev: Target block device
> >> >> + * @sector: Start sector of the zone to operate on
> >> >> + * @data: Pointer to the data that is to be associated to the zone
> >> >> + * @gfp_mask: Memory allocation flags (for bio_alloc)
> >> >> + *
> >> >> + * Description:
> >> >> + * Associate zone descriptor extension data to a specified zone.
> >> >> + * The block device must support zone descriptor extensions.
> >> >> + * i.e., by exposing a positive zone descriptor extension size.
> >> >> + */
> >> >> +int blkdev_zone_set_desc(struct block_device *bdev, sector_t sector,
> >> >> + struct page *data, gfp_t gfp_mask)
> >> >
> >> >struct page for the data ? Why not just a "void *" to allow for
> >> >kmalloc/vmalloc data ? And no length for the data ? This is a bit odd.
> >> >
> >> >> +{
> >> >> + struct request_queue *q = bdev_get_queue(bdev);
> >> >> + sector_t zone_sectors = blk_queue_zone_sectors(q);
> >> >> + struct bio_vec bio_vec;
> >> >> + struct bio bio;
> >> >> +
> >> >> + if (!blk_queue_is_zoned(q))
> >> >> + return -EOPNOTSUPP;
> >> >> +
> >> >> + if (bdev_read_only(bdev))
> >> >> + return -EPERM;
> >> >
> >> >You are not checking the zone_desc_ext_bytes limit here. You should.
> >> >> +
> >> >> + /* Check alignment (handle eventual smaller last zone) */
> >> >> + if (sector & (zone_sectors - 1))
> >> >> + return -EINVAL;
> >> >
> >> >The comment is incorrect. There is nothing special for handling the
> >> >last zone in this test.
> >> >
> >> >> +
> >> >> + bio_init(&bio, &bio_vec, 1);
> >> >> + bio.bi_opf = REQ_OP_ZONE_SET_DESC | REQ_SYNC;
> >> >> + bio.bi_iter.bi_sector = sector;
> >> >> + bio_set_dev(&bio, bdev);
> >> >> + bio_add_page(&bio, data, queue_zone_desc_ext_bytes(q), 0);
> >> >> +
> >> >> + /* This may take a while, so be nice to others */
> >> >> + cond_resched();
> >> >
> >> >This is not a loop, so you do not need this.
> >> >
> >> >> +
> >> >> + return submit_bio_wait(&bio);
> >> >> +}
> >> >> +EXPORT_SYMBOL_GPL(blkdev_zone_set_desc);
> >> >> +
> >> >> struct zone_report_args {
> >> >> struct blk_zone __user *zones;
> >> >> };
> >> >> @@ -370,6 +414,70 @@ int blkdev_zone_mgmt_ioctl(struct
> >> >> block_device
> >> *bdev, fmode_t mode,
> >> >> GFP_KERNEL);
> >> >> }
> >> >>
> >> >> +/*
> >> >> + * BLKSETDESCZONE ioctl processing.
> >> >> + * Called from blkdev_ioctl.
> >> >> + */
> >> >> +int blkdev_zone_set_desc_ioctl(struct block_device *bdev, fmode_t
> >> mode,
> >> >> + unsigned int cmd, unsigned long arg) {
> >> >> + void __user *argp = (void __user *)arg;
> >> >> + struct request_queue *q;
> >> >> + struct blk_zone_set_desc zsd;
> >> >> + void *zsd_data;
> >> >> + int ret;
> >> >> +
> >> >> + if (!argp)
> >> >> + return -EINVAL;
> >> >> +
> >> >> + q = bdev_get_queue(bdev);
> >> >> + if (!q)
> >> >> + return -ENXIO;
> >> >> +
> >> >> + if (!blk_queue_is_zoned(q))
> >> >> + return -ENOTTY;
> >> >> +
> >> >> + if (!capable(CAP_SYS_ADMIN))
> >> >> + return -EACCES;
> >> >> +
> >> >> + if (!(mode & FMODE_WRITE))
> >> >> + return -EBADF;
> >> >> +
> >> >> + if (!queue_zone_desc_ext_bytes(q))
> >> >> + return -EOPNOTSUPP;
> >> >> +
> >> >> + if (copy_from_user(&zsd, argp, sizeof(struct blk_zone_set_desc)))
> >> >> + return -EFAULT;
> >> >> +
> >> >> + /* no flags is currently supported */
> >> >> + if (zsd.flags)
> >> >> + return -ENOTTY;
> >> >> +
> >> >> + if (!zsd.len || zsd.len > queue_zone_desc_ext_bytes(q))
> >> >> + return -ENOTTY;
> >> >
> >> >This should go into blkdev_zone_set_desc() as well so that in-kernel
> >> >users are checked. So there may be no need to check this here.
> >> >
> >> >> +
> >> >> + /* allocate the size of the zone descriptor extension and fill
> >> >> + * with the data in the user data buffer. If the data size is less
> >> >> + * than the zone descriptor extension size, then the rest of the
> >> >> + * zone description extension data buffer is zero-filled.
> >> >> + */
> >> >> + zsd_data = (void *) get_zeroed_page(GFP_KERNEL);
> >> >> + if (!zsd_data)
> >> >> + return -ENOMEM;
> >> >> +
> >> >> + if (copy_from_user(zsd_data, argp + sizeof(struct blk_zone_set_desc),
> >> >> + zsd.len)) {
> >> >> + ret = -EFAULT;
> >> >> + goto free;
> >> >> + }
> >> >> +
> >> >> + ret = blkdev_zone_set_desc(bdev, zsd.sector, virt_to_page(zsd_data),
> >> >> + GFP_KERNEL);
> >> >> +free:
> >> >> + free_page((unsigned long) zsd_data);
> >> >> + return ret;
> >> >> +}
> >> >> +
> >> >> static inline unsigned long *blk_alloc_zone_bitmap(int node,
> >> >> unsigned int nr_zones)
> >> >> {
> >> >> diff --git a/block/ioctl.c b/block/ioctl.c index
> >> >> bdb3bbb253d9..b9744705835b 100644
> >> >> --- a/block/ioctl.c
> >> >> +++ b/block/ioctl.c
> >> >> @@ -515,6 +515,8 @@ static int blkdev_common_ioctl(struct
> >> >> block_device
> >> *bdev, fmode_t mode,
> >> >> case BLKCLOSEZONE:
> >> >> case BLKFINISHZONE:
> >> >> return blkdev_zone_mgmt_ioctl(bdev, mode, cmd, arg);
> >> >> + case BLKSETDESCZONE:
> >> >> + return blkdev_zone_set_desc_ioctl(bdev, mode, cmd, arg);
> >> >> case BLKGETZONESZ:
> >> >> return put_uint(argp, bdev_zone_sectors(bdev));
> >> >> case BLKGETNRZONES:
> >> >> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> >> >> index e961910da4ac..b8f25b0d00ad 100644
> >> >> --- a/drivers/nvme/host/core.c
> >> >> +++ b/drivers/nvme/host/core.c
> >> >> @@ -776,6 +776,9 @@ blk_status_t nvme_setup_cmd(struct nvme_ns
> >> >> *ns,
> >> struct request *req,
> >> >> case REQ_OP_ZONE_FINISH:
> >> >> ret = nvme_setup_zone_mgmt_send(ns, req, cmd,
> >> NVME_ZONE_FINISH);
> >> >> break;
> >> >> + case REQ_OP_ZONE_SET_DESC:
> >> >> + ret = nvme_setup_zone_set_desc(ns, req, cmd);
> >> >> + break;
> >> >> case REQ_OP_WRITE_ZEROES:
> >> >> ret = nvme_setup_write_zeroes(ns, req, cmd);
> >> >> break;
> >> >> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> >> >> index 662f95fbd909..5bd5a437b038 100644
> >> >> --- a/drivers/nvme/host/nvme.h
> >> >> +++ b/drivers/nvme/host/nvme.h
> >> >> @@ -708,6 +708,9 @@ int nvme_report_zones(struct gendisk *disk,
> >> >> sector_t sector, blk_status_t nvme_setup_zone_mgmt_send(struct
> >> nvme_ns *ns, struct request *req,
> >> >> struct nvme_command *cmnd,
> >> >> enum nvme_zone_mgmt_action action);
> >> >> +
> >> >> +blk_status_t nvme_setup_zone_set_desc(struct nvme_ns *ns, struct
> >> request *req,
> >> >> + struct nvme_command *cmnd);
> >> >> #else
> >> >> #define nvme_report_zones NULL
> >> >>
> >> >> @@ -718,6 +721,12 @@ static inline blk_status_t
> >> nvme_setup_zone_mgmt_send(struct nvme_ns *ns,
> >> >> return BLK_STS_NOTSUPP;
> >> >> }
> >> >>
> >> >> +static inline blk_status_t nvme_setup_zone_set_desc(struct nvme_ns
> *ns,
> >> >> + struct request *req, struct nvme_command *cmnd) {
> >> >> + return BLK_STS_NOTSUPP;
> >> >> +}
> >> >> +
> >> >> static inline int nvme_update_zone_info(struct gendisk *disk,
> >> >> struct nvme_ns *ns,
> >> >> unsigned lbaf)
> >> >> diff --git a/drivers/nvme/host/zns.c b/drivers/nvme/host/zns.c
> >> >> index
> >> >> 5792d953a8f3..bfa64cc685d3 100644
> >> >> --- a/drivers/nvme/host/zns.c
> >> >> +++ b/drivers/nvme/host/zns.c
> >> >> @@ -239,3 +239,14 @@ blk_status_t
> >> nvme_setup_zone_mgmt_send(struct
> >> >> nvme_ns *ns, struct request *req,
> >> >>
> >> >> return BLK_STS_OK;
> >> >> }
> >> >> +
> >> >> +blk_status_t nvme_setup_zone_set_desc(struct nvme_ns *ns, struct
> >> request *req,
> >> >> + struct nvme_command *c)
> >> >> +{
> >> >> + c->zms.opcode = nvme_cmd_zone_mgmt_send;
> >> >> + c->zms.nsid = cpu_to_le32(ns->head->ns_id);
> >> >> + c->zms.slba = cpu_to_le64(nvme_sect_to_lba(ns, blk_rq_pos(req)));
> >> >> + c->zms.action = NVME_ZONE_SET_DESC_EXT;
> >> >> +
> >> >> + return BLK_STS_OK;
> >> >> +}
> >> >> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> >> >> index ccb895f911b1..53b7b05b0004 100644
> >> >> --- a/include/linux/blk_types.h
> >> >> +++ b/include/linux/blk_types.h
> >> >> @@ -316,6 +316,8 @@ enum req_opf {
> >> >> REQ_OP_ZONE_FINISH = 12,
> >> >> /* write data at the current zone write pointer */
> >> >> REQ_OP_ZONE_APPEND = 13,
> >> >> + /* associate zone desc extension data to a zone */
> >> >> + REQ_OP_ZONE_SET_DESC = 14,
> >> >>
> >> >> /* SCSI passthrough using struct scsi_request */
> >> >> REQ_OP_SCSI_IN = 32,
> >> >> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index
> >> >> 2ed55055f68d..c5f092dd5aa3 100644
> >> >> --- a/include/linux/blkdev.h
> >> >> +++ b/include/linux/blkdev.h
> >> >> @@ -370,7 +370,8 @@ extern int blkdev_report_zones_ioctl(struct
> >> block_device *bdev, fmode_t mode,
> >> >> unsigned int cmd, unsigned long arg);
> >> extern int
> >> >> blkdev_zone_mgmt_ioctl(struct block_device *bdev, fmode_t mode,
> >> >> unsigned int cmd, unsigned long arg);
> >> >> -
> >> >> +extern int blkdev_zone_set_desc_ioctl(struct block_device *bdev,
> >> fmode_t mode,
> >> >> + unsigned int cmd, unsigned long arg);
> >> >> #else /* CONFIG_BLK_DEV_ZONED */
> >> >>
> >> >> static inline unsigned int blkdev_nr_zones(struct gendisk *disk)
> >> >> @@
> >> >> -392,6 +393,12 @@ static inline int blkdev_zone_mgmt_ioctl(struct
> >> block_device *bdev,
> >> >> return -ENOTTY;
> >> >> }
> >> >>
> >> >> +static inline int blkdev_zone_set_desc_ioctl(struct block_device *bdev,
> >> >> + fmode_t mode, unsigned int cmd,
> >> >> + unsigned long arg)
> >> >> +{
> >> >> + return -ENOTTY;
> >> >> +}
> >> >> #endif /* CONFIG_BLK_DEV_ZONED */
> >> >>
> >> >> struct request_queue {
> >> >> diff --git a/include/uapi/linux/blkzoned.h
> >> >> b/include/uapi/linux/blkzoned.h index 42c3366cc25f..68abda9abf33
> >> >> 100644
> >> >> --- a/include/uapi/linux/blkzoned.h
> >> >> +++ b/include/uapi/linux/blkzoned.h
> >> >> @@ -142,6 +142,20 @@ struct blk_zone_range {
> >> >> __u64 nr_sectors;
> >> >> };
> >> >>
> >> >> +/**
> >> >> + * struct blk_zone_set_desc - BLKSETDESCZONE ioctl requests
> >> >> + * @sector: Starting sector of the zone to operate on.
> >> >> + * @flags: Feature flags.
> >> >> + * @len: size, in bytes, of the data to be associated to the zone.
> >> >> + * @data: data to be associated.
> >> >> + */
> >> >> +struct blk_zone_set_desc {
> >> >> + __u64 sector;
> >> >> + __u32 flags;
> >> >> + __u32 len;
> >> >> + __u8 data[0];
> >> >> +};
> >>
> >> Would it make sense to add nr_sectors if the host wants to associate
> >> the same metadata to several zones. The use case would be the
> >> grouping of larger zones in software.
> >
> >I believe we get into atomicity concerns if we do ranges, and action
> >only supports a single zone. I like to align with the ZNS API as much
> >as possible, and let the user-space application track errors per set
> >desc ext action.
>
> The atomicity concerns should be the same as current zone management
> using nr_sectors, and these are already being supported for open, close, etc.
>
> TBH, the comment is most about making sure that the IOCTL is extendable
> from conception.
>
> >
> >>
> >> >> +
> >> >> /**
> >> >> * Zoned block device ioctl's:
> >> >> *
> >> >> @@ -158,6 +172,10 @@ struct blk_zone_range {
> >> >> * The 512 B sector range must be zone aligned.
> >> >> * @BLKFINISHZONE: Mark the zones as full in the specified sector
> range.
> >> >> * The 512 B sector range must be zone aligned.
> >> >> + * @BLKSETDESCZONE: Set zone description extension data for the
> zone
> >> >> + * in the specified sector. On success, the zone
> >> >> + * will transition to the closed zone state.
> >> >> + * The 512B sector must be zone aligned.
> >> >> */
> >> >> #define BLKREPORTZONE _IOWR(0x12, 130, struct blk_zone_report)
> >> >> #define BLKRESETZONE _IOW(0x12, 131, struct blk_zone_range)
> >> >> @@ -166,5 +184,5 @@ struct blk_zone_range {
> >> >> #define BLKOPENZONE _IOW(0x12, 134, struct blk_zone_range)
> >> >> #define BLKCLOSEZONE _IOW(0x12, 135, struct blk_zone_range)
> >> >> #define BLKFINISHZONE _IOW(0x12, 136, struct blk_zone_range)
> >> >> -
> >> >> +#define BLKSETDESCZONE _IOW(0x12, 137, struct
> blk_zone_set_desc)
> >> >> #endif /* _UAPI_BLKZONED_H */
> >> >>
> >> >
> >> >How to you retreive an extended descriptor that was set ? I do not
> >> >see any code doing that. Report zones is not changed, but I would
> >> >leave that one as is and implement a BLKGETDESCZONE ioctl & in-kernel
> API.
> >> >
> >>
> >> In any case, this is needed. I also could not find a way to read the
> >> extended descriptor back.
> >
> >Thanks for the feedback.
> >
> >Besides the users I have in mind, do you have users for which you need
> >the ability for user-space to access zone descriptor extensions data?
> >Is this a need to have or nice to have feature from your point of view?
>
> At this moment most of the users we have in mind are user-space applications
> that are zone-aware, so I would way this is necessary.

Thanks - I appreciate the feedback.

>
> This said, I understand if you prioritize pushing the code that enables in-kernel
> users and then re-iterate on this.
>
> Thanks,
> Javier

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In reply to: Javier GonzÃlez: "Re: [PATCH 2/2] block: add BLKSETDESCZONE ioctl for Zoned Block Devices"
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