Re: [PATCH v4 3/4] ublk: enable zoned storage support

From: Damien Le Moal
Date: Wed Jun 28 2023 - 19:17:02 EST

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In reply to: Andreas Hindborg: "[PATCH v4 3/4] ublk: enable zoned storage support"
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On 6/29/23 04:06, Andreas Hindborg wrote:
> From: Andreas Hindborg <a.hindborg@xxxxxxxxxxx>
>
> Add zoned storage support to ublk: report_zones and operations:
> - REQ_OP_ZONE_OPEN
> - REQ_OP_ZONE_CLOSE
> - REQ_OP_ZONE_FINISH
> - REQ_OP_ZONE_RESET
>
> Note: This commit changes the ublk kernel module name from `ublk_drv.ko` to
> `ublk.ko` in order to link multiple translation units into the module.

You probably could rename ublk_drv.c to ublk.c to avoid that and keep the module
name as it was, ublk_drv.ko.

>
> Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxxx>
> ---
> MAINTAINERS | 1 +
> drivers/block/Kconfig | 4 +
> drivers/block/Makefile | 4 +-
> drivers/block/ublk_drv-zoned.c | 144 +++++++++++++++++++++++++++++++++
> drivers/block/ublk_drv.c | 64 +++++++++++++--
> drivers/block/ublk_drv.h | 15 ++++
> include/uapi/linux/ublk_cmd.h | 14 ++++
> 7 files changed, 239 insertions(+), 7 deletions(-)
> create mode 100644 drivers/block/ublk_drv-zoned.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index ace71c90751c..db8a8deb5926 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -21555,6 +21555,7 @@ S: Maintained
> F: Documentation/block/ublk.rst
> F: drivers/block/ublk_drv.c
> F: drivers/block/ublk_drv.h
> +F: drivers/block/ublk_drv-zoned.c
> F: include/uapi/linux/ublk_cmd.h
>
> UCLINUX (M68KNOMMU AND COLDFIRE)
> diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
> index 5b9d4aaebb81..c58dfd035557 100644
> --- a/drivers/block/Kconfig
> +++ b/drivers/block/Kconfig
> @@ -402,6 +402,10 @@ config BLKDEV_UBLK_LEGACY_OPCODES
> suggested to enable N if your application(ublk server) switches to
> ioctl command encoding.
>
> +config BLK_DEV_UBLK_ZONED
> + def_bool y

This can be "bool" only.

> + depends on BLK_DEV_UBLK && BLK_DEV_ZONED
> +
> source "drivers/block/rnbd/Kconfig"
>
> endif # BLK_DEV
> diff --git a/drivers/block/Makefile b/drivers/block/Makefile
> index 101612cba303..bc1649e20ec2 100644
> --- a/drivers/block/Makefile
> +++ b/drivers/block/Makefile
> @@ -37,6 +37,8 @@ obj-$(CONFIG_BLK_DEV_RNBD) += rnbd/
>
> obj-$(CONFIG_BLK_DEV_NULL_BLK) += null_blk/
>
> -obj-$(CONFIG_BLK_DEV_UBLK) += ublk_drv.o
> +obj-$(CONFIG_BLK_DEV_UBLK) += ublk.o
> +ublk-$(CONFIG_BLK_DEV_UBLK) += ublk_drv.o
> +ublk-$(CONFIG_BLK_DEV_UBLK_ZONED) += ublk_drv-zoned.o
>
> swim_mod-y := swim.o swim_asm.o
> diff --git a/drivers/block/ublk_drv-zoned.c b/drivers/block/ublk_drv-zoned.c
> new file mode 100644
> index 000000000000..ea86bf4b3681
> --- /dev/null
> +++ b/drivers/block/ublk_drv-zoned.c
> @@ -0,0 +1,144 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2023 Andreas Hindborg <a.hindborg@xxxxxxxxxxx>
> + */
> +#include <linux/blkzoned.h>
> +#include <linux/ublk_cmd.h>
> +#include <linux/vmalloc.h>
> +
> +#include "ublk_drv.h"
> +
> +void ublk_set_nr_zones(struct ublk_device *ub)
> +{
> + const struct ublk_param_basic *p = &ub->params.basic;
> +
> + if (ub->dev_info.flags & UBLK_F_ZONED && p->chunk_sectors)

If UBLK_F_ZONED is set but chunk_sectors is not, that is a bug on the user
driver side, no ? So an error message about that would be nice instead of
silently ignoring the zoned flag.

> + ub->ub_disk->nr_zones = p->dev_sectors / p->chunk_sectors;
> +}
> +
> +void ublk_dev_param_zoned_apply(struct ublk_device *ub)
> +{
> + const struct ublk_param_zoned *p = &ub->params.zoned;
> +
> + if (ub->dev_info.flags & UBLK_F_ZONED) {
> + disk_set_max_active_zones(ub->ub_disk, p->max_active_zones);
> + disk_set_max_open_zones(ub->ub_disk, p->max_open_zones);

You do not need to check if the max_active_zones and max_open_zones values are
sensible ? E.g. what if they are larger than the number of zones ?

> + }
> +}
> +
> +int ublk_revalidate_disk_zones(struct gendisk *disk)
> +{
> + return blk_revalidate_disk_zones(disk, NULL);
> +}

I do not think this helper is needed at all (see below comment on the call site).

> +
> +/* Based on virtblk_alloc_report_buffer */
> +static void *ublk_alloc_report_buffer(struct ublk_device *ublk,
> + unsigned int nr_zones,
> + unsigned int zone_sectors, size_t *buflen)
> +{
> + struct request_queue *q = ublk->ub_disk->queue;
> + size_t bufsize;
> + void *buf;
> +
> + nr_zones = min_t(unsigned int, nr_zones,
> + get_capacity(ublk->ub_disk) >> ilog2(zone_sectors));
> +
> + bufsize = nr_zones * sizeof(struct blk_zone);
> + bufsize =
> + min_t(size_t, bufsize, queue_max_hw_sectors(q) << SECTOR_SHIFT);
> + bufsize = min_t(size_t, bufsize, queue_max_segments(q) << PAGE_SHIFT);
> +
> + while (bufsize >= sizeof(struct blk_zone)) {
> + buf = __vmalloc(bufsize, GFP_KERNEL | __GFP_NORETRY);
> + if (buf) {
> + *buflen = bufsize;
> + return buf;
> + }
> + bufsize >>= 1;
> + }
> +
> + bufsize = 0;

This is not needed. This should rather be "*buflen = 0;".

> + return NULL;
> +}
> +
> +int ublk_report_zones(struct gendisk *disk, sector_t sector,
> + unsigned int nr_zones, report_zones_cb cb, void *data)
> +{
> + struct ublk_device *ub = disk->private_data;
> + unsigned int zone_size_sectors = disk->queue->limits.chunk_sectors;
> + unsigned int first_zone = sector >> ilog2(zone_size_sectors);
> + unsigned int done_zones = 0;
> + unsigned int max_zones_per_request;
> + struct blk_zone *buffer;
> + size_t buffer_length;
> +
> + if (!(ub->dev_info.flags & UBLK_F_ZONED))

This is repeated a lot. So a small inline helper ublk_dev_is_zoned() would be nice.

> + return -EOPNOTSUPP;
> +
> + nr_zones = min_t(unsigned int, ub->ub_disk->nr_zones - first_zone,
> + nr_zones);
> +
> + buffer = ublk_alloc_report_buffer(ub, nr_zones, zone_size_sectors,
> + &buffer_length);
> + if (!buffer)
> + return -ENOMEM;
> +
> + max_zones_per_request = buffer_length / sizeof(struct blk_zone);
> +
> + while (done_zones < nr_zones) {
> + unsigned int remaining_zones = nr_zones - done_zones;
> + unsigned int zones_in_request = min_t(
> + unsigned int, remaining_zones, max_zones_per_request);
> + int err = 0;
> + struct request *req;
> + struct ublk_rq_data *pdu;
> + blk_status_t status;
> +
> + memset(buffer, 0, buffer_length);
> +
> + req = blk_mq_alloc_request(disk->queue, REQ_OP_DRV_IN, 0);
> + if (IS_ERR(req))
> + return PTR_ERR(req);

You are leaking buffer.

> +
> + pdu = blk_mq_rq_to_pdu(req);
> + pdu->operation = UBLK_IO_OP_REPORT_ZONES;
> + pdu->sector = sector;
> + pdu->nr_sectors = remaining_zones * zone_size_sectors;
> +
> + err = blk_rq_map_kern(disk->queue, req, buffer, buffer_length,
> + GFP_KERNEL);
> + if (err) {
> + blk_mq_free_request(req);
> + kvfree(buffer);
> + return err;
> + }
> +
> + status = blk_execute_rq(req, 0);
> + err = blk_status_to_errno(status);
> + blk_mq_free_request(req);
> + if (err) {
> + kvfree(buffer);
> + return err;

You are repeating this a lot. Use a goto to cleanup on error.

> + }
> +
> + for (unsigned int i = 0; i < zones_in_request; i++) {
> + struct blk_zone *zone = buffer + i;
> +
> + err = cb(zone, i, data);
> + if (err)
> + return err;
> +
> + done_zones++;
> + sector += zone_size_sectors;
> +
> + /* A zero length zone means don't ask for more zones */
> + if (!zone->len) {
> + kvfree(buffer);
> + return done_zones;
> + }
> + }
> + }
> +
> + kvfree(buffer);
> + return done_zones;
> +}
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index e519dc0d9fe7..88fa39853c61 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -57,12 +57,13 @@
> | UBLK_F_USER_RECOVERY_REISSUE \
> | UBLK_F_UNPRIVILEGED_DEV \
> | UBLK_F_CMD_IOCTL_ENCODE \
> - | UBLK_F_USER_COPY)
> + | UBLK_F_USER_COPY \
> + | UBLK_F_ZONED)
>
> /* All UBLK_PARAM_TYPE_* should be included here */
> -#define UBLK_PARAM_TYPE_ALL (UBLK_PARAM_TYPE_BASIC | \
> - UBLK_PARAM_TYPE_DISCARD | UBLK_PARAM_TYPE_DEVT)
> -
> +#define UBLK_PARAM_TYPE_ALL \
> + (UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD | \
> + UBLK_PARAM_TYPE_DEVT | UBLK_PARAM_TYPE_ZONED)
>
> struct ublk_uring_cmd_pdu {
> struct ublk_queue *ubq;
> @@ -209,6 +210,9 @@ static void ublk_dev_param_basic_apply(struct ublk_device *ub)
> set_disk_ro(ub->ub_disk, true);
>
> set_capacity(ub->ub_disk, p->dev_sectors);
> +
> + if (IS_ENABLED(CONFIG_BLK_DEV_ZONED))
> + ublk_set_nr_zones(ub);

So if the user is attempting to setup a zoned drive but the kernel does not have
CONFIG_BLK_DEV_ZONED=y, the user setup will be silently ignored. Not exactly
nice I think, unless I am missing something.

Also, repeating that "if (IS_ENABLED(CONFIG_BLK_DEV_ZONED))" for all zone
related functions is very verbose. Stub the functions in ublk_drv.h. That will
make the main C code lighter.

> }
>
> static void ublk_dev_param_discard_apply(struct ublk_device *ub)
> @@ -269,6 +273,9 @@ static int ublk_apply_params(struct ublk_device *ub)
> if (ub->params.types & UBLK_PARAM_TYPE_DISCARD)
> ublk_dev_param_discard_apply(ub);
>
> + if (IS_ENABLED(CONFIG_BLK_DEV_ZONED) && (ub->params.types & UBLK_PARAM_TYPE_ZONED))
> + ublk_dev_param_zoned_apply(ub);

Similar comment as above. If the user tries to apply zoned parameters to a non
zoned drive, no error reported...

> +
> return 0;
> }
>
> @@ -439,6 +446,7 @@ static const struct block_device_operations ub_fops = {
> .owner = THIS_MODULE,
> .open = ublk_open,
> .free_disk = ublk_free_disk,
> + .report_zones = ublk_report_zones,
> };
>
> #define UBLK_MAX_PIN_PAGES 32
> @@ -553,7 +561,8 @@ static inline bool ublk_need_map_req(const struct request *req)
>
> static inline bool ublk_need_unmap_req(const struct request *req)
> {
> - return ublk_rq_has_data(req) && req_op(req) == REQ_OP_READ;
> + return ublk_rq_has_data(req) &&
> + (req_op(req) == REQ_OP_READ || req_op(req) == REQ_OP_DRV_IN);
> }
>
> static int ublk_map_io(const struct ublk_queue *ubq, const struct request *req,
> @@ -637,6 +646,7 @@ static blk_status_t ublk_setup_iod(struct ublk_queue *ubq, struct request *req)
> {
> struct ublksrv_io_desc *iod = ublk_get_iod(ubq, req->tag);
> struct ublk_io *io = &ubq->ios[req->tag];
> + struct ublk_rq_data *pdu = blk_mq_rq_to_pdu(req);
> u32 ublk_op;
>
> switch (req_op(req)) {
> @@ -655,6 +665,35 @@ static blk_status_t ublk_setup_iod(struct ublk_queue *ubq, struct request *req)
> case REQ_OP_WRITE_ZEROES:
> ublk_op = UBLK_IO_OP_WRITE_ZEROES;
> break;
> + case REQ_OP_ZONE_OPEN:
> + ublk_op = UBLK_IO_OP_ZONE_OPEN;
> + break;
> + case REQ_OP_ZONE_CLOSE:
> + ublk_op = UBLK_IO_OP_ZONE_CLOSE;
> + break;
> + case REQ_OP_ZONE_FINISH:
> + ublk_op = UBLK_IO_OP_ZONE_FINISH;
> + break;
> + case REQ_OP_ZONE_RESET:
> + ublk_op = UBLK_IO_OP_ZONE_RESET;
> + break;
> + case REQ_OP_DRV_IN:
> + ublk_op = pdu->operation;
> + switch (ublk_op) {
> + case UBLK_IO_OP_REPORT_ZONES:
> + iod->op_flags = ublk_op | ublk_req_build_flags(req);
> + iod->nr_sectors = pdu->nr_sectors;
> + iod->start_sector = pdu->sector;
> + iod->addr = io->addr;
> + return BLK_STS_OK;
> + default:
> + return BLK_STS_IOERR;
> + }
> + case REQ_OP_ZONE_APPEND:
> + case REQ_OP_ZONE_RESET_ALL:
> + case REQ_OP_DRV_OUT:
> + /* We do not support zone append or reset_all yet */
> + fallthrough;

Not OK ! zone append is mandatory for zoned block devices. So zone append
support needs to come with this patch. reset all can be a different patch as
that is optional.

> default:
> return BLK_STS_IOERR;
> }
> @@ -708,7 +747,8 @@ static inline void __ublk_complete_rq(struct request *req)
> *
> * Both the two needn't unmap.
> */
> - if (req_op(req) != REQ_OP_READ && req_op(req) != REQ_OP_WRITE)
> + if (req_op(req) != REQ_OP_READ && req_op(req) != REQ_OP_WRITE &&
> + req_op(req) != REQ_OP_DRV_IN)
> goto exit;
>
> /* for READ request, writing data in iod->addr to rq buffers */
> @@ -1835,6 +1875,15 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub, struct io_uring_cmd *cmd)
> if (ub->nr_privileged_daemon != ub->nr_queues_ready)
> set_bit(GD_SUPPRESS_PART_SCAN, &disk->state);
>
> + if (IS_ENABLED(CONFIG_BLK_DEV_ZONED) &&
> + ub->dev_info.flags & UBLK_F_ZONED) {

Same comment as above about error return instead of silently ignoring the zoned
flag for the CONFIG_BLK_DEV_ZONED=n case.

> + disk_set_zoned(disk, BLK_ZONED_HM);
> + blk_queue_required_elevator_features(disk->queue, ELEVATOR_F_ZBD_SEQ_WRITE);
> + ret = ublk_revalidate_disk_zones(disk);
> + if (ret)
> + goto out_put_disk;

This should be all a helper ublk_set_zoned() or something.

> + }
> +
> get_device(&ub->cdev_dev);
> ub->dev_info.state = UBLK_S_DEV_LIVE;
> ret = add_disk(disk);
> @@ -1997,6 +2046,9 @@ static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd)
> if (ub->dev_info.flags & UBLK_F_USER_COPY)
> ub->dev_info.flags &= ~UBLK_F_NEED_GET_DATA;
>
> + if (!IS_ENABLED(CONFIG_BLK_DEV_ZONED))
> + ub->dev_info.flags &= ~UBLK_F_ZONED;

Arg, no. The user should be notified with an error that he/she is attempting to
create a zoned device that cannot be supported.

> +
> /* We are not ready to support zero copy */
> ub->dev_info.flags &= ~UBLK_F_SUPPORT_ZERO_COPY;
>
> diff --git a/drivers/block/ublk_drv.h b/drivers/block/ublk_drv.h
> index f81e62256456..7242430fd6b9 100644
> --- a/drivers/block/ublk_drv.h
> +++ b/drivers/block/ublk_drv.h
> @@ -50,6 +50,21 @@ struct ublk_rq_data {
> struct llist_node node;
>
> struct kref ref;
> + enum ublk_op operation;
> + __u64 sector;
> + __u32 nr_sectors;
> };
>
> +void ublk_set_nr_zones(struct ublk_device *ub);
> +void ublk_dev_param_zoned_apply(struct ublk_device *ub);
> +int ublk_revalidate_disk_zones(struct gendisk *disk);
> +
> +#ifdef CONFIG_BLK_DEV_UBLK_ZONED
> +int ublk_report_zones(struct gendisk *disk, sector_t sector,
> + unsigned int nr_zones, report_zones_cb cb,
> + void *data);
> +#else
> +#define ublk_report_zones NULL
> +#endif
> +
> #endif
> diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
> index 471b3b983045..436525afffe8 100644
> --- a/include/uapi/linux/ublk_cmd.h
> +++ b/include/uapi/linux/ublk_cmd.h
> @@ -176,6 +176,11 @@
> /* Copy between request and user buffer by pread()/pwrite() */
> #define UBLK_F_USER_COPY (1UL << 7)
>
> +/*
> + * Enable zoned device support

Isn't this for "Indicate that the device is zoned" ?

> + */
> +#define UBLK_F_ZONED (1ULL << 8)
> +
> /* device state */
> #define UBLK_S_DEV_DEAD 0
> #define UBLK_S_DEV_LIVE 1
> @@ -242,6 +247,7 @@ enum ublk_op {
> UBLK_IO_OP_ZONE_APPEND = 13,
> UBLK_IO_OP_ZONE_RESET = 15,
> __UBLK_IO_OP_DRV_IN_START = 32,
> + UBLK_IO_OP_REPORT_ZONES = __UBLK_IO_OP_DRV_IN_START,
> __UBLK_IO_OP_DRV_IN_END = 96,
> __UBLK_IO_OP_DRV_OUT_START = __UBLK_IO_OP_DRV_IN_END,
> __UBLK_IO_OP_DRV_OUT_END = 160,
> @@ -342,6 +348,12 @@ struct ublk_param_devt {
> __u32 disk_minor;
> };
>
> +struct ublk_param_zoned {
> + __u32 max_open_zones;
> + __u32 max_active_zones;
> + __u8 reserved[24];
> +};
> +
> struct ublk_params {
> /*
> * Total length of parameters, userspace has to set 'len' for both
> @@ -353,11 +365,13 @@ struct ublk_params {
> #define UBLK_PARAM_TYPE_BASIC (1 << 0)
> #define UBLK_PARAM_TYPE_DISCARD (1 << 1)
> #define UBLK_PARAM_TYPE_DEVT (1 << 2)
> +#define UBLK_PARAM_TYPE_ZONED (1 << 3)
> __u32 types; /* types of parameter included */
>
> struct ublk_param_basic basic;
> struct ublk_param_discard discard;
> struct ublk_param_devt devt;
> + struct ublk_param_zoned zoned;
> };
>
> #endif

--
Damien Le Moal
Western Digital Research

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