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Message-ID: <87ttz79u8p.fsf@metaspace.dk>
Date: Mon, 27 Feb 2023 12:59:45 +0100
From: Andreas Hindborg <nmi@...aspace.dk>
To: Niklas Cassel <Niklas.Cassel@....com>
Cc: "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
Hans Holmberg <Hans.Holmberg@....com>,
Matias Bjørling <Matias.Bjorling@....com>,
kernel test robot <lkp@...el.com>,
Ming Lei <ming.lei@...hat.com>, Jens Axboe <axboe@...nel.dk>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] block: ublk: enable zoned storage support
Niklas Cassel <Niklas.Cassel@....com> writes:
> On Fri, Feb 24, 2023 at 09:05:01PM +0100, Andreas Hindborg wrote:
>> 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
>>
>> This allows implementation of zoned storage devices in user space. An
>> example user space implementation based on ubdsrv is available [1].
>>
>> [1] https://github.com/metaspace/ubdsrv/commit/14a2b708f74f70cfecb076d92e680dc718cc1f6d
>>
>> Signed-off-by: Andreas Hindborg <a.hindborg@...sung.com>
>> ---
>> Changes since v1:
>> - Fixed conditional compilation bug
>> - Refactored to collect conditional code additions together
>> - Fixed style errors
>> - Zero stack allocated value used for zone report
>>
>> Reported-by: Niklas Cassel <Niklas.Cassel@....com>
>> Reported-by: kernel test robot <lkp@...el.com>
>> Link: https://lore.kernel.org/oe-kbuild-all/202302250222.XOrw9j6z-lkp@intel.com/
>> v1: https://lore.kernel.org/linux-block/20230224125950.214779-1-nmi@metaspace.dk/
>>
>> drivers/block/ublk_drv.c | 150 ++++++++++++++++++++++++++++++++--
>> include/uapi/linux/ublk_cmd.h | 18 ++++
>> 2 files changed, 162 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
>> index 6368b56eacf1..37e516903867 100644
>> --- a/drivers/block/ublk_drv.c
>> +++ b/drivers/block/ublk_drv.c
>> @@ -20,6 +20,7 @@
>> #include <linux/major.h>
>> #include <linux/wait.h>
>> #include <linux/blkdev.h>
>> +#include <linux/blkzoned.h>
>> #include <linux/init.h>
>> #include <linux/swap.h>
>> #include <linux/slab.h>
>> @@ -51,10 +52,12 @@
>> | UBLK_F_URING_CMD_COMP_IN_TASK \
>> | UBLK_F_NEED_GET_DATA \
>> | UBLK_F_USER_RECOVERY \
>> - | UBLK_F_USER_RECOVERY_REISSUE)
>> + | UBLK_F_USER_RECOVERY_REISSUE \
>> + | UBLK_F_ZONED)
>>
>> /* All UBLK_PARAM_TYPE_* should be included here */
>> -#define UBLK_PARAM_TYPE_ALL (UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD)
>> +#define UBLK_PARAM_TYPE_ALL (UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD \
>> + | UBLK_PARAM_TYPE_ZONED)
>>
>> struct ublk_rq_data {
>> struct llist_node node;
>> @@ -187,6 +190,98 @@ static DEFINE_MUTEX(ublk_ctl_mutex);
>>
>> static struct miscdevice ublk_misc;
>>
>> +#ifdef CONFIG_BLK_DEV_ZONED
>> +static 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)
>> + ub->ub_disk->nr_zones = p->dev_sectors / p->chunk_sectors;
>> +}
>> +
>> +static 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);
>> + }
>> +}
>> +
>> +static int ublk_revalidate_disk_zones(struct gendisk *disk)
>> +{
>> + return blk_revalidate_disk_zones(disk, NULL);
>> +}
>> +
>> +static int ublk_report_zones(struct gendisk *disk, sector_t sector,
>> + unsigned int nr_zones, report_zones_cb cb,
>> + void *data)
>> +{
>> + struct ublk_device *ub;
>> + unsigned int zone_size;
>> + unsigned int first_zone;
>> + int ret = 0;
>> +
>> + ub = disk->private_data;
>> +
>> + if (!(ub->dev_info.flags & UBLK_F_ZONED))
>> + return -EINVAL;
>> +
>> + zone_size = disk->queue->limits.chunk_sectors;
>> + first_zone = sector >> ilog2(zone_size);
>> + nr_zones = min(ub->ub_disk->nr_zones - first_zone, nr_zones);
>> +
>> + for (unsigned int i = 0; i < nr_zones; i++) {
>> + struct request *req;
>> + blk_status_t status;
>> + struct blk_zone info = {0};
>> +
>> + req = blk_mq_alloc_request(disk->queue, REQ_OP_DRV_IN, 0);
>> +
>> + if (IS_ERR(req)) {
>> + ret = PTR_ERR(req);
>> + goto out;
>> + }
>> +
>> + req->__sector = sector;
>> +
>> + ret = blk_rq_map_kern(disk->queue, req, &info, sizeof(info),
>> + GFP_KERNEL);
>> +
>> + if (ret)
>> + goto out;
>> +
>> + status = blk_execute_rq(req, 0);
>> + ret = blk_status_to_errno(status);
>> + if (ret)
>> + goto out;
>> +
>> + blk_mq_free_request(req);
>> +
>> + ret = cb(&info, i, data);
>> + if (ret)
>> + goto out;
>> +
>> + /* A zero length zone means don't ask for more zones */
>> + if (!info.len) {
>> + nr_zones = i;
>> + break;
>> + }
>> +
>> + sector += zone_size;
>> + }
>> + ret = nr_zones;
>> +
>> + out:
>> + return ret;
>> +}
>> +#else
>> +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);
>
> These are declarations, shouldn't they be dummy definitions instead?
I looked at how nvme host defines nvme_revalidate_zones() when I did
this. The functions become undefined symbols but because the call sites
are optimized out they go away.
>
> e.g.
> static int ublk_revalidate_disk_zones(struct gendisk *disk) { return -EOPNOTSUPP; };
Not sure how this is better?
>
>
> It would be nice if they could be avoided altogether.
>
> Looking how e.g. null-blk and btrfs has solved this:
> https://github.com/torvalds/linux/blob/v6.2/fs/btrfs/Makefile#L39
> https://github.com/torvalds/linux/blob/v6.2/drivers/block/null_blk/Makefile#L11
>
> They have put the zoned stuff in a separate C file that is only compiled
> when CONFIG_BLK_DEV_ZONED is set.
>
> I'm not sure if a similar design is desired for ublk or not.
>
> However, if a similar design pattern was used, it could probably avoid
> some of these unpleasant dummy definitions altogether.
This is the same as I do here, except I put the declarations in the c
file instead of a header. I did this for two reasons 1) there is no ublk
header besides the uapi header (I would add a header just for this), 2)
the declarations need only exist inside ublk_drv.c. For btrfs, null_blk,
nvme, the declarations go in a header file and the functions in question
do not have static linkage.
I could move the function declarations out of the #else block, but then
they would need to be declared static and that gives a compiler warning
when the implementation is not present.
BR Andreas
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