linux-kernel - Re: [PATCH 3/3] ibmvfc: use correlation token to tag commands

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Date:   Mon, 21 Dec 2020 23:24:03 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Tyrel Datwyler <tyreld@...ux.ibm.com>
Cc:     james.bottomley@...senpartnership.com, martin.petersen@...cle.com,
        linux-scsi@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, brking@...ux.ibm.com,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH 3/3] ibmvfc: use correlation token to tag commands

On Tue, Nov 17, 2020 at 12:50:31PM -0600, Tyrel Datwyler wrote:
> The vfcFrame correlation field is 64bit handle that is intended to trace
> I/O operations through both the client stack and VIOS stack when the
> underlying physical FC adapter supports tagging.
> 
> Tag vfcFrames with the associated ibmvfc_event pointer handle.
> 
> Signed-off-by: Tyrel Datwyler <tyreld@...ux.ibm.com>
> ---
>  drivers/scsi/ibmvscsi/ibmvfc.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c
> index 0cab4b852b48..3922441a117d 100644
> --- a/drivers/scsi/ibmvscsi/ibmvfc.c
> +++ b/drivers/scsi/ibmvscsi/ibmvfc.c
> @@ -1693,6 +1693,8 @@ static int ibmvfc_queuecommand_lck(struct scsi_cmnd *cmnd,
>  		vfc_cmd->iu.pri_task_attr = IBMVFC_SIMPLE_TASK;
>  	}
>  
> +	vfc_cmd->correlation = cpu_to_be64(evt);
> +
>  	if (likely(!(rc = ibmvfc_map_sg_data(cmnd, evt, vfc_cmd, vhost->dev))))
>  		return ibmvfc_send_event(evt, vhost, 0);
>  
> @@ -2370,6 +2372,8 @@ static int ibmvfc_abort_task_set(struct scsi_device *sdev)
>  		tmf->iu.tmf_flags = IBMVFC_ABORT_TASK_SET;
>  		evt->sync_iu = &rsp_iu;
>  
> +		tmf->correlation = cpu_to_be64(evt);
> +
>  		init_completion(&evt->comp);
>  		rsp_rc = ibmvfc_send_event(evt, vhost, default_timeout);
>  	}
> -- 
> 2.27.0
> 

This patch introduces a clang warning, is this intentional behavior?

$ make -skj"$(nproc)" ARCH=powerpc CROSS_COMPILE=powerpc64le-linux-gnu- LLVM=1 O=out distclean ppc64le_defconfig drivers/scsi/ibmvscsi/ibmvfc.o
Using ../arch/powerpc/configs/ppc64_defconfig as base
Merging ../arch/powerpc/configs/le.config
#
# merged configuration written to .config (needs make)
#
../drivers/scsi/ibmvscsi/ibmvfc.c:1747:25: warning: incompatible pointer to integer conversion passing 'struct ibmvfc_event *' to parameter of type '__u64' (aka 'unsigned long long') [-Wint-conversion]
        vfc_cmd->correlation = cpu_to_be64(evt);
                               ^~~~~~~~~~~~~~~~
../include/linux/byteorder/generic.h:92:21: note: expanded from macro 'cpu_to_be64'
#define cpu_to_be64 __cpu_to_be64
                    ^
../include/uapi/linux/byteorder/little_endian.h:37:52: note: expanded from macro '__cpu_to_be64'
#define __cpu_to_be64(x) ((__force __be64)__swab64((x)))
                                          ~~~~~~~~~^~~~
../include/uapi/linux/swab.h:133:12: note: expanded from macro '__swab64'
        __fswab64(x))
                  ^
../include/uapi/linux/swab.h:66:57: note: passing argument to parameter 'val' here
static inline __attribute_const__ __u64 __fswab64(__u64 val)
                                                        ^
../drivers/scsi/ibmvscsi/ibmvfc.c:2421:22: warning: incompatible pointer to integer conversion passing 'struct ibmvfc_event *' to parameter of type '__u64' (aka 'unsigned long long') [-Wint-conversion]
                tmf->correlation = cpu_to_be64(evt);
                                   ^~~~~~~~~~~~~~~~
../include/linux/byteorder/generic.h:92:21: note: expanded from macro 'cpu_to_be64'
#define cpu_to_be64 __cpu_to_be64
                    ^
../include/uapi/linux/byteorder/little_endian.h:37:52: note: expanded from macro '__cpu_to_be64'
#define __cpu_to_be64(x) ((__force __be64)__swab64((x)))
                                          ~~~~~~~~~^~~~
../include/uapi/linux/swab.h:133:12: note: expanded from macro '__swab64'
        __fswab64(x))
                  ^
../include/uapi/linux/swab.h:66:57: note: passing argument to parameter 'val' here
static inline __attribute_const__ __u64 __fswab64(__u64 val)
                                                        ^
2 warnings generated.

Cheers,
Nathan