linux-kernel - Re: [PATCH] staging: lustre/lustre/libcfs: Fix type mismatch reported by sparse

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Date:	Tue, 22 Dec 2015 07:26:14 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Niranjan Dighe <niranjan.dighe@...il.com>
Cc:	devel@...verdev.osuosl.org,
	Dmitry Eremin <dmitry.eremin@...el.com>,
	Andreas Dilger <andreas.dilger@...el.com>,
	Patrick Boettcher <patrick.boettcher@...teo.de>,
	linux-kernel@...r.kernel.org, Oleg Drokin <oleg.drokin@...el.com>,
	James Simmons <jsimmons@...radead.org>,
	Matthew Tyler <matt.tyler@...shics.com>,
	lustre-devel@...ts.lustre.org
Subject: Re: [PATCH] staging: lustre/lustre/libcfs: Fix type mismatch
 reported by sparse

On Tue, Dec 22, 2015 at 06:35:21PM +0530, Niranjan Dighe wrote:
> On Tue, Dec 22, 2015 at 5:14 AM, Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
> > On Wed, Dec 09, 2015 at 10:38:13PM +0530, Niranjan Dighe wrote:
> >> The third argument to function kportal_memhog_alloc is expected to
> >> be gfp_t whereas the actual argument was unsigned int. Fix this by
> >> explicitly typecasting to gfp_t
> >>
> >> Signed-off-by: Niranjan Dighe <niranjan.dighe@...il.com>
> >> ---
> >>  drivers/staging/lustre/lustre/libcfs/module.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/staging/lustre/lustre/libcfs/module.c b/drivers/staging/lustre/lustre/libcfs/module.c
> >> index 96d9d46..9c79f6e 100644
> >> --- a/drivers/staging/lustre/lustre/libcfs/module.c
> >> +++ b/drivers/staging/lustre/lustre/libcfs/module.c
> >> @@ -268,7 +268,7 @@ static int libcfs_ioctl_int(struct cfs_psdev_file *pfile, unsigned long cmd,
> >>                       /* XXX The ioc_flags is not GFP flags now, need to be fixed */
> >>                       err = kportal_memhog_alloc(pfile->private_data,
> >>                                                  data->ioc_count,
> >> -                                                data->ioc_flags);
> >> +                                     (__force gfp_t)data->ioc_flags);
> >
> > No, please fix the type to be correct properly, like the comment says
> > needs to be done.
> >
> > thanks,
> >
> > greg k-h
> 
> Hello Greg,
> 
> I could see that the ioc_flags member of the struct libcfs_ioctl_data
> is used as gfp_t only in the
> case of the ioctl IOC_LIBCFS_MEMHOG. I can think of following ways to
> correct it -
> 
> 1. Create a union that has 2 different types encapsulated, something like this -
>         union {
>                 __u32 ioc_flags;
>                 gfp_t alloc_flags;
>         }flags;
> Because, the ioc_flags seems to be used in different contexts at
> different places throughout the
> drivers/staging/lustre directory.

This crosses the user/kernel boundry?  Hah, no, just drop it, don't
touch this at all, lustre ioctls are a complete mess and need to be
fixed up by the authors who can test them, just leave this alone for
now, sorry.

greg k-h
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