Re: [PATCH] nvmet: fix mar and mor off-by-one errors

Niklas Cassel
2022-09-05T12:40:38Z

On Mon, Sep 05, 2022 at 02:21:16PM +0200, Dennis Maisenbacher wrote:
> From: Dennis Maisenbacher <dennis.maisenbacher@wdc.com>
>
> Maximum Active Resources (MAR) and Maximum Open Resources (MOR) are 0's
> based vales where a value of 0xffffffff indicates that there is no limit.
>
> Cast the unsigned int values that are returned by bdev_max_open_zones and
> bdev_max_active_zones into u32 vales which need to be decremented as the
> returned values of the block layer helpers are not 0's based.
> The cast to u32 is necessary because the size of unsigned int is
> architecture dependent and a 0 reported by the block layer helpers
> indicates no limit, thus it needs to be converted to 0xffffffff which
> happens by underflowing the u32.
>
> Suggested-by: Niklas Cassel <niklas.cassel@wdc.com>
> Signed-off-by: Dennis Maisenbacher <dennis.maisenbacher@wdc.com>
> ---
> drivers/nvme/target/zns.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/nvme/target/zns.c b/drivers/nvme/target/zns.c
> index c7ef69f29fe4..606f21ee21bf 100644
> --- a/drivers/nvme/target/zns.c
> +++ b/drivers/nvme/target/zns.c
> @@ -100,6 +100,7 @@ void nvmet_execute_identify_cns_cs_ns(struct nvmet_req *req)
> struct nvme_id_ns_zns *id_zns;
> u64 zsze;
> u16 status;
> + u32 mar, mor;
>
> if (le32_to_cpu(req->cmd->identify.nsid) == NVME_NSID_ALL) {
> req->error_loc = offsetof(struct nvme_identify, nsid);
> @@ -130,8 +131,10 @@ void nvmet_execute_identify_cns_cs_ns(struct nvmet_req *req)
> zsze = (bdev_zone_sectors(req->ns->bdev) << 9) >>
> req->ns->blksize_shift;
> id_zns->lbafe[0].zsze = cpu_to_le64(zsze);
> - id_zns->mor = cpu_to_le32(bdev_max_open_zones(req->ns->bdev));
> - id_zns->mar = cpu_to_le32(bdev_max_active_zones(req->ns->bdev));
> + mor = bdev_max_open_zones(req->ns->bdev);
> + id_zns->mor = cpu_to_le32(--mor);
> + mar = bdev_max_active_zones(req->ns->bdev);
> + id_zns->mar = cpu_to_le32(--mar);
>
> done:
> status = nvmet_copy_to_sgl(req, 0, id_zns, sizeof(*id_zns));
> --
> 2.25.1
>

Reviewed-by: Niklas Cassel <niklas.cassel@wdc.com>