linux-kernel - Re: [PATCH v1 1/1] ceph: Amend checking to fix `make W=1` build breakage

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Message-ID: <aSR1FU6uCqpOUFeb@smile.fi.intel.com>
Date: Mon, 24 Nov 2025 17:09:09 +0200
From: "andriy.shevchenko@...ux.intel.com" <andriy.shevchenko@...ux.intel.com>
To: Viacheslav Dubeyko <Slava.Dubeyko@....com>
Cc: Xiubo Li <xiubli@...hat.com>,
	"justinstitt@...gle.com" <justinstitt@...gle.com>,
	"llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
	"ceph-devel@...r.kernel.org" <ceph-devel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"nathan@...nel.org" <nathan@...nel.org>,
	"morbo@...gle.com" <morbo@...gle.com>,
	"idryomov@...il.com" <idryomov@...il.com>,
	"nick.desaulniers+lkml@...il.com" <nick.desaulniers+lkml@...il.com>
Subject: Re: [PATCH v1 1/1] ceph: Amend checking to fix `make W=1` build
 breakage

On Mon, Nov 10, 2025 at 08:42:13PM +0000, Viacheslav Dubeyko wrote:
> On Mon, 2025-11-10 at 21:43 +0200, andriy.shevchenko@...ux.intel.com wrote:
> > On Mon, Nov 10, 2025 at 07:37:13PM +0000, Viacheslav Dubeyko wrote:
> > > On Mon, 2025-11-10 at 15:44 +0100, Andy Shevchenko wrote:
> > > > In a few cases the code compares 32-bit value to a SIZE_MAX derived
> > > > constant which is much higher than that value on 64-bit platforms,
> > > > Clang, in particular, is not happy about this
> > > > 
> > > > fs/ceph/snap.c:377:10: error: result of comparison of constant 2305843009213693948 with expression of type 'u32' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
> > > >   377 |         if (num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
> > > >       |             ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > > 
> > > > Fix this by casting to size_t. Note, that possible replacement of SIZE_MAX
> > > > by U32_MAX may lead to the behaviour changes on the corner cases.
> > 
> > ...
> > 
> > > > -	if (num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
> > > > +	if ((size_t)num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
> > > 
> > > The same question is here. Does it makes sense to declare num as size_t? Could
> > > it be more clean solution? Or could it introduce another warnings/errors?
> > 
> > Maybe. Or even maybe the U32_MAX is the way to go: Does anybody check those
> > corner cases? Are those never tested? Potential (security) bug?
> > 
> > ...
> > 
> > Whatever you find, in case if it will be not the proposed solution as is,
> > consider these patches as Reported-by.
> > 
> > And thanks for the reviews!
> 
> I think we can take the patch as it. It looks good. Probably, it makes sense to
> take a deeper look in the code on our side.
> 
> Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@....com>

Thanks, can this be applied? My builds are still broken.

-- 
With Best Regards,
Andy Shevchenko