[PATCH v2 1/2] nvmet-passthru: Limit mdts by BIO_MAX_PAGES

[Logan Gunthorpe]

On 2020-10-19 5:20 a.m., Max Gurtovoy wrote:
> 
> On 10/17/2020 1:19 AM, Logan Gunthorpe wrote:
>> nvmet_passthru_map_sg() only supports mapping a single BIO, not a chain
>> so the effective maximum transfer should also be limitted by BIO_MAX_PAGES
>> (presently this works out to 1MB).
>>
>> For PCI passthru devices the max_sectors would typically be more limitting
>> than BIO_MAX_PAGES, but this may not be true for all passthru devices.
>>
>> Fixes: c1fef73f793b ("nvmet: add passthru code to process commands")
>> Suggested-by: Christoph Hellwig <hch at lst.de>
>> Signed-off-by: Logan Gunthorpe <logang at deltatee.com>
>> Cc: Christoph Hellwig <hch at lst.de>
>> Cc: Sagi Grimberg <sagi at grimberg.me>
>> Cc: Chaitanya Kulkarni <chaitanya.kulkarni at wdc.com>
>> ---
>>   drivers/nvme/target/passthru.c | 9 ++++++++-
>>   1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/nvme/target/passthru.c b/drivers/nvme/target/passthru.c
>> index dacfa7435d0b..1ab88df3310f 100644
>> --- a/drivers/nvme/target/passthru.c
>> +++ b/drivers/nvme/target/passthru.c
>> @@ -26,7 +26,7 @@ static u16 nvmet_passthru_override_id_ctrl(struct nvmet_req *req)
>>   	struct nvme_ctrl *pctrl = ctrl->subsys->passthru_ctrl;
>>   	u16 status = NVME_SC_SUCCESS;
>>   	struct nvme_id_ctrl *id;
>> -	u32 max_hw_sectors;
>> +	int max_hw_sectors;
>>   	int page_shift;
>>   
>>   	id = kzalloc(sizeof(*id), GFP_KERNEL);
>> @@ -48,6 +48,13 @@ static u16 nvmet_passthru_override_id_ctrl(struct nvmet_req *req)
>>   	max_hw_sectors = min_not_zero(pctrl->max_segments << (PAGE_SHIFT - 9),
>>   				      pctrl->max_hw_sectors);
>>   
>> +	/*
>> +	 * nvmet_passthru_map_sg is limitted to using a single bio so limit
>> +	 * the mdts based on BIO_MAX_PAGES as well
>> +	 */
>> +	max_hw_sectors = min_not_zero(BIO_MAX_PAGES << (PAGE_SHIFT - 9),
>> +				      max_hw_sectors);
> 
> can 9 be replaced with SECTOR_SHIFT ?

Oh, yes, that does sound better. Thanks.

Logan