linux-kernel - Re: [PATCH v5] scsi/ata: Use unsigned int for cmd's type in ioctls in scsi_host

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Message-ID: <20190208160044.GB26005@archlinux-ryzen>
Date:   Fri, 8 Feb 2019 09:00:44 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Jens Axboe <axboe@...nel.dk>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "Manoj N. Kumar" <manoj@...ux.ibm.com>,
        "Matthew R. Ochs" <mrochs@...ux.ibm.com>,
        Uma Krishnan <ukrishn@...ux.ibm.com>,
        Brian King <brking@...ibm.com>,
        Adaptec OEM Raid Solutions <aacraid@...rosemi.com>,
        Marc Gonzalez <marc.w.gonzalez@...e.fr>,
        linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-scsi@...r.kernel.org, esc.storagedev@...rosemi.com,
        Bradley Grove <bgrove@...otech.com>,
        Don Brace <don.brace@...rosemi.com>,
        Bart Van Assche <bvanassche@....org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH v5] scsi/ata: Use unsigned int for cmd's type in ioctls
 in scsi_host_template

On Fri, Feb 08, 2019 at 12:05:01AM -0800, Christoph Hellwig wrote:
> On Thu, Feb 07, 2019 at 09:07:20AM -0700, Nathan Chancellor wrote:
> > Clang warns several times in the scsi subsystem (trimmed for brevity):
> > 
> > drivers/scsi/hpsa.c:6209:7: warning: overflow converting case value to
> > switch condition type (2147762695 to 18446744071562347015) [-Wswitch]
> >         case CCISS_GETBUSTYPES:
> >              ^
> > drivers/scsi/hpsa.c:6208:7: warning: overflow converting case value to
> > switch condition type (2147762694 to 18446744071562347014) [-Wswitch]
> >         case CCISS_GETHEARTBEAT:
> >              ^
> > 
> > The root cause is that the _IOC macro can generate really large numbers,
> > which don't fit into type 'int', which is used for the cmd parameter in
> > the ioctls in scsi_host_template. My research into how GCC and Clang are
> > handling this at a low level didn't prove fruitful. However, looking at
> > the rest of the kernel tree, all ioctls use an 'unsigned int' for the
> > cmd parameter, which will fit all of the _IOC values in the scsi/ata
> > subsystems.
> > 
> > Make that change because none of the ioctls expect a negative value for
> > any command, it brings the ioctls inline with the reset of the kernel,
> > and it removes ambiguity, which is never good when dealing with compilers.
> > 
> > Link: https://github.com/ClangBuiltLinux/linux/issues/85
> > Link: https://github.com/ClangBuiltLinux/linux/issues/154
> > Link: https://github.com/ClangBuiltLinux/linux/issues/157
> > Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> > Acked-by: Bradley Grove <bgrove@...otech.com>
> > Acked-by: Don Brace <don.brace@...rosemi.com>
> > Reviewed-by: Bart Van Assche <bvanassche@....org>
> > Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>
> 
> Looks good:
> 
> Reviewed-by: Christoph Hellwig <hch@....de>

Thank you for the review, it is much appreciated!

Nathan