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From: Christoph Hellwig <hch@infradead.org>
Subject: Re: Kernel 3.1.0-rc4 oops when connecting iPod
Date: Sun, 11 Sep 2011 10:14:26 -0400
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Cc: Pavel Ivanov <paivanof@gmail.com>, linux-fsdevel@vger.kernel.org,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@tuxera.com>
To: Hin-Tak Leung <hintak_leung@yahoo.co.uk>
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On Sun, Sep 11, 2011 at 02:46:08PM +0100, Hin-Tak Leung wrote:
> > +?????* and difference between it
> > and alloc_blksz_shift will be always in
> > +?????* fs_shift.
> > +?????*/
> > +??? err =
> > generic_check_addressable(sb->s_blocksize_bits,
> > +??? ??? ???
> > (u64)sbi->total_blocks << sbi->fs_shift);
> >  ??? if (err) {
> >  ??? ??? printk(KERN_ERR
> > "hfs: filesystem size too large.\n");
> >  ??? ??? goto out_free_vhdr;
> 
> Why is the u64 needed? If it is needed, it probably means sbi->total_blocks should have been u64 in the first place.

No.  When you shift values to the left they obviously become larger.
The total_blocks count on disk 32-bit so there is no need to store
it in a larger variable in the in-core superblock.