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SubjectRe: [PATCH v2] nvmet: fix mar and mor off-by-one errors
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On 9/7/22 06:53, Chaitanya Kulkarni wrote:
> On 9/6/22 00:39, 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.
>>
>> Decrement the values that are returned by bdev_max_open_zones and
>> bdev_max_active_zones as the block layer helpers are not 0's based.
>> A 0 returned by the block layer helpers indicates no limit, thus convert
>> it to 0xffffffff (U32_MAX).
>>
>> Fixes: aaf2e048af27 ("nvmet: add ZBD over ZNS backend support")
>> Suggested-by: Niklas Cassel <niklas.cassel@wdc.com>
>> Signed-off-by: Dennis Maisenbacher <dennis.maisenbacher@wdc.com>
>> ---
>> Changes in v2:
>> - Add explicit check if block layer helpers return a 0 and if so
>> convert it to U32_MAX.
>> - Add Fixes tag.
>>
>> drivers/nvme/target/zns.c | 17 +++++++++++++++--
>> 1 file changed, 15 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/nvme/target/zns.c b/drivers/nvme/target/zns.c
>> index c7ef69f29fe4..eae81f939067 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;
>
> consider :-
> + u32 mar, mor;
> u64 zsze;
> u16 status;
>
>>
>> if (le32_to_cpu(req->cmd->identify.nsid) == NVME_NSID_ALL) {
>> req->error_loc = offsetof(struct nvme_identify, nsid);
>> @@ -130,8 +131,20 @@ 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);
>> + if (!mor)
>> + mor = U32_MAX;
>> + else
>> + --mor;
>> + id_zns->mor = cpu_to_le32(mor);
>> +
>> + mar = bdev_max_active_zones(req->ns->bdev);
>> + if (!mar)
>> + mar = U32_MAX;
>> + else
>> + --mar;
>> + id_zns->mar = cpu_to_le32(mar);
>>
>
> above 14 lines of code can be simplified as in 4-5 lines :-

Simplified ? It is much harder to read in my opinion...

>
> mor = bdev_max_open_zones(req->ns->bdev);
> id->zns->mor = cpu_tp_le32(mor ? mor - 1 : U32_MAX);
>
> mar = bdev_max_active_zones(req->ns->bdev);
> id->zns->mar = cpu_tp_le32(mar ? mar - 1 : U32_MAX);
>
>> done:
>> status = nvmet_copy_to_sgl(req, 0, id_zns, sizeof(*id_zns));
>
>
> either way,
>
> Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
>

--
Damien Le Moal
Western Digital Research

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