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Date: Thu, 12 Dec 2024 07:23:53 +0100
From: Christoph Hellwig <hch@lst.de>
To: Coly Li <colyli@suse.de>
Cc: kernel test robot <lkp@intel.com>, Christoph Hellwig <hch@lst.de>,
	oe-kbuild-all@lists.linux.dev, linux-kernel@vger.kernel.org,
	Jens Axboe <axboe@kernel.dk>
Subject: Re: drivers/md/bcache/super.c:108:14: sparse: sparse: restricted
 __le64 degrades to integer
Message-ID: <20241212062353.GB5586@lst.de>
References: <202412071044.tthTVBw4-lkp@intel.com> <33E9C2B1-BF96-46DD-BE45-00811C986ABD@suse.de>
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On Wed, Dec 11, 2024 at 12:34:20AM +0800, Coly Li wrote:
> >   drivers/md/bcache/super.c:108:24: sparse:     expected unsigned int nr_keys
> >   drivers/md/bcache/super.c:108:24: sparse:     got restricted __le16 [usertype] keys
> >>> drivers/md/bcache/super.c:108:14: sparse: sparse: restricted __le64 degrades to integer
> 
> It complains about line 108 which is,
> > cafe563591446cf Kent Overstreet   2013-03-23  107   err = "Bad checksum";
> > cafe563591446cf Kent Overstreet   2013-03-23 @108   if (s->csum != csum_set(s))
> > cafe563591446cf Kent Overstreet   2013-03-23  109   goto err;
> 
> Here s->sum is __le64, csum_set() is uint64_t, these two types have same length. I don’t see the direct connection between code and warning.

The are the same size, but not the same endianess.  In other words this
is a hint that this code is most likely broken on big endian systems
due to the lack of a bytespace (which is a no-op on little endian
systems).