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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Fri, 5 Mar 2021 14:31:52 +0100
Message-ID: <CAK8P3a0EhxvQ3pP6iMwHdR3RwF3CcAaWvfodPnzPip2iW2wBgQ@mail.gmail.com>
Subject: Re: [bisected] 5.12-rc1 hpsa regression: "scsi: hpsa: Correct dev
 cmds outstanding for retried cmds" breaks hpsa P600
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Don.Brace@microchip.com, slyich@gmail.com,
        John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
        storagedev@microchip.com, scsi <linux-scsi@vger.kernel.org>,
        "linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        jszczype@redhat.com, Scott.Benesh@microchip.com,
        Scott.Teel@microchip.com, thenzl@redhat.com,
        "Martin K. Petersen" <martin.petersen@oracle.com>
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On Fri, Mar 5, 2021 at 10:24 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> On Fri, Mar 5, 2021 at 12:26 AM <Don.Brace@microchip.com> wrote:
> > > > On 3/2/21 11:26 PM, Sergei Trofimovich wrote:
> > struct CommandList {
> >         struct CommandListHeader Header;                 /*     0    20 */
> >         struct RequestBlock Request;                     /*    20    20 */
> >         struct ErrDescriptor ErrDesc;                    /*    40    12 */
> >         struct SGDescriptor SG[32];                      /*    52   512 */
> >         /* --- cacheline 8 boundary (512 bytes) was 52 bytes ago --- */
> >         u32                        busaddr;              /*   564     4 */
> >         struct ErrorInfo *         err_info;             /*   568     8 */
> >         /* --- cacheline 9 boundary (576 bytes) --- */
> >         struct ctlr_info *         h;                    /*   576     8 */
> >         int                        cmd_type;             /*   584     4 */
> >         long int                   cmdindex;             /*   588     8 */
> >         struct completion *        waiting;              /*   596     8 */
> >         struct scsi_cmnd *         scsi_cmd;             /*   604     8 */
> >         struct work_struct work;                         /*   612    32 */
> >         /* --- cacheline 10 boundary (640 bytes) was 4 bytes ago --- */
> >         struct hpsa_scsi_dev_t *   phys_disk;            /*   644     8 */
> >         struct hpsa_scsi_dev_t *   device;               /*   652     8 */
> >         bool                       retry_pending;        /*   660     1 */
> >         atomic_t                   refcount;             /*   661     4 */
>
> How come this atomic_t is no longer aligned to its natural alignment?

There is a

#pragma pack(1)

in linux 203 of this file!

It looks like some of the members in struct raid_map_data
and struct CommandListHeader need to be annotated as packed,
but the file accidentally packs everything until the '#pragma pack()'
in line 875, including the kernel-side CommandList data structure
that clearly must not be packed.

        Arnd