linux-kernel - Re: [PATCH RFC v2] fcoe: make use of fip

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Message-ID: <0a37de95-a440-12a7-d99d-72d815f0b56f@suse.de>
Date:   Fri, 15 Feb 2019 08:35:41 +0100
From:   Hannes Reinecke <hare@...e.de>
To:     Nathan Chancellor <natechancellor@...il.com>,
        Sedat Dilek <sedat.dilek@...il.com>
Cc:     Sedat Dilek <sedat.dilek@...dativ.de>,
        QLogic-Storage-Upstream@...gic.com,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Johannes Thumshirn <jth@...nel.org>,
        QLogic-Storage-Upstream@...ium.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Hannes Reinecke <hare@...e.com>,
        Johannes Thumshirn <jthumshirn@...e.de>
Subject: Re: [PATCH RFC v2] fcoe: make use of fip_mode enum complete

On 2/12/19 11:42 PM, Nathan Chancellor wrote:
> On Tue, Feb 12, 2019 at 08:50:04AM +0100, Sedat Dilek wrote:
>> On Mon, Feb 11, 2019 at 6:53 PM Nathan Chancellor
>> <natechancellor@...il.com> wrote:
>>>
>>> On Mon, Feb 11, 2019 at 06:07:51PM +0100, Sedat Dilek wrote:
>>>> From: Sedat Dilek <sedat.dilek@...il.com>
>>>>
>>>> commit 1917d42d14b7 ("fcoe: use enum for fip_mode") introduces a separate
>>>> enum for the fip_mode that shall be used during initialisation handling
>>>> until it is passed to fcoe_ctrl_link_up to set the initial fip_state.
>>>> That change was incomplete and gcc quietly converted in various places
>>>> between the fip_mode and the fip_state enum values with implicit enum
>>>> conversions, which fortunately cannot cause any issues in the actual
>>>> code's execution.
>>>>
>>>> clang however warns about these implicit enum conversions in the scsi
>>>> drivers. This commit consolidates the use of the two enums, guided by
>>>> clang's enum-conversion warnings.
>>>>
>>>> This commit now completes the use of the fip_mode:
>>>> It expects and uses fip_mode in {bnx2fc,fcoe}_interface_create and
>>>> fcoe_ctlr_init, and it explicitly converts from fip_mode to fip_state
>>>> only at the single point in fcoe_ctlr_link_up.
>>>>
>>>> To eliminate that adding or removing values from fip_mode or fip_state enum
>>>> break the right mapping of values, all fip_mode values are assigned to
>>>> their fip_state counterparts.
>>>>
>>>> Link: https://github.com/ClangBuiltLinux/linux/issues/151
>>>> Fixes: 1917d42d14b7 ("fcoe: use enum for fip_mode")
>>>> Reported-by: Dmitry Golovin "Twisted Pair in my Hair" <dima@...ovin.in>
>>>> CC: Lukas Bulwahn <lukas.bulwahn@...il.com>
>>>> CC: Nick Desaulniers <ndesaulniers@...gle.com>
>>>> CC: Nathan Chancellor <natechancellor@...il.com>
>>>> CC: Hannes Reinecke <hare@...e.com>
>>>> Suggested-by: Johannes Thumshirn <jthumshirn@...e.de>
>>>> ---
>>>>
>>>> [ v2:
>>>>     - Based on the original patch by Lukas Bulwahn
>>>>     - Suggestion by Johannes T. [1] required some changes:
>>>>       + s/case FIP_ST_VMMP_START/case FIP_ST_V*N*MP_START
>>>>       + s/return FIP_ST_AUTO/return FIP_MODE_AUTO
>>>>     - Add Link to ClangBuiltLinux issue #151
>>>>     - S-o-b line later when there is an OK from the FCoE maintainers
>>>>
>>>> NOTE: Compile-tested against Linux-v5.0-rc6 with LLVM/Clang from Git with
>>>>        experimental asm-goto support via executing:
>>>>        $ make V=1 CC=clang-9 HOSTCC=clang-9 drivers/scsi/fcoe/
>>>>
>>>> [1] https://marc.info/?l=linux-scsi&m=154745527612152&w=2
>>>>
>>>>    -dileks ]
>>>>
>>>>   drivers/scsi/bnx2fc/bnx2fc_fcoe.c  |  2 +-
>>>>   drivers/scsi/fcoe/fcoe.c           |  2 +-
>>>>   drivers/scsi/fcoe/fcoe_ctlr.c      |  4 ++--
>>>>   drivers/scsi/fcoe/fcoe_transport.c |  2 +-
>>>>   drivers/scsi/qedf/qedf_main.c      |  2 +-
>>>>   include/scsi/libfcoe.h             | 22 ++++++++++++++++++++--
>>>>   6 files changed, 26 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
>>>> index 2e4e7159ebf9..a75e74ad1698 100644
>>>> --- a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
>>>> +++ b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
>>>> @@ -1438,7 +1438,7 @@ static struct bnx2fc_hba *bnx2fc_hba_create(struct cnic_dev *cnic)
>>>>   static struct bnx2fc_interface *
>>>>   bnx2fc_interface_create(struct bnx2fc_hba *hba,
>>>>                        struct net_device *netdev,
>>>> -                     enum fip_state fip_mode)
>>>> +                     enum fip_mode fip_mode)
>>>>   {
>>>>        struct fcoe_ctlr_device *ctlr_dev;
>>>>        struct bnx2fc_interface *interface;
>>>> diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c
>>>> index cd19be3f3405..8ba8862d3292 100644
>>>> --- a/drivers/scsi/fcoe/fcoe.c
>>>> +++ b/drivers/scsi/fcoe/fcoe.c
>>>> @@ -389,7 +389,7 @@ static int fcoe_interface_setup(struct fcoe_interface *fcoe,
>>>>    * Returns: pointer to a struct fcoe_interface or NULL on error
>>>>    */
>>>>   static struct fcoe_interface *fcoe_interface_create(struct net_device *netdev,
>>>> -                                                 enum fip_state fip_mode)
>>>> +                                                 enum fip_mode fip_mode)
>>>>   {
>>>>        struct fcoe_ctlr_device *ctlr_dev;
>>>>        struct fcoe_ctlr *ctlr;
>>>> diff --git a/drivers/scsi/fcoe/fcoe_ctlr.c b/drivers/scsi/fcoe/fcoe_ctlr.c
>>>> index 54da3166da8d..a52d3ad94876 100644
>>>> --- a/drivers/scsi/fcoe/fcoe_ctlr.c
>>>> +++ b/drivers/scsi/fcoe/fcoe_ctlr.c
>>>> @@ -147,7 +147,7 @@ static void fcoe_ctlr_map_dest(struct fcoe_ctlr *fip)
>>>>    * fcoe_ctlr_init() - Initialize the FCoE Controller instance
>>>>    * @fip: The FCoE controller to initialize
>>>>    */
>>>> -void fcoe_ctlr_init(struct fcoe_ctlr *fip, enum fip_state mode)
>>>> +void fcoe_ctlr_init(struct fcoe_ctlr *fip, enum fip_mode mode)
>>>>   {
>>>>        fcoe_ctlr_set_state(fip, FIP_ST_LINK_WAIT);
>>>>        fip->mode = mode;
>>>> @@ -454,7 +454,7 @@ void fcoe_ctlr_link_up(struct fcoe_ctlr *fip)
>>>>                mutex_unlock(&fip->ctlr_mutex);
>>>>                fc_linkup(fip->lp);
>>>>        } else if (fip->state == FIP_ST_LINK_WAIT) {
>>>> -             fcoe_ctlr_set_state(fip, fip->mode);
>>>> +             fcoe_ctlr_set_state(fip, (enum fip_state) fip->mode);
>>>>                switch (fip->mode) {
>>>>                default:
>>>>                        LIBFCOE_FIP_DBG(fip, "invalid mode %d\n", fip->mode);

Watch out for this one.
fip_mode != fip_state.

This arguably is an error even now; it might _just_ work if we have 
fip->mode == FIP_MODE_FABRIC, but we probably will be getting 
interesting results when fip->mode == FIP_MODE_VN2VN ...

We should rather call

fcoe_ctrl_set_state(fip, FIP_ST_AUTO)

here and update it to NON_FIP in the switch statement itself.
But I'll have to think about it some more to figure out what would 
happen for VN2VN mode.

Will be sending an updated patch.

Cheers,

Hannes