Re: [patch] arca-vm-2.2.5

[David Miller <davem@twiddle.net>]

   On Tue, 6 Apr 1999, Stephen C. Tweedie wrote:

   -#define i (((unsigned long) inode)/(sizeof(struct inode) \
		    & ~ (sizeof(struct inode) - 1)))
   +#define i (((unsigned long) inode-PAGE_OFFSET)/(sizeof(struct inode) \
		    & ~ (sizeof(struct inode) - 1)))

 ...

   btw. shouldnt it rather be something like: 

   #define log2(x) \

Look at the code just the 'i' in question will output :-)

     mov    inode, %o0
     srlx   %o0, 3, %o4

So on sparc64 atleast, it amounts to "inode >> 3".  So:

(sizeof(struct inode) & ~ (sizeof(struct inode) - 1))

is 8 on sparc64.  The 'i' construct is just meant to get rid of the
"non significant" lower bits of the inode pointer and it does so very
nicely. :-)

Later,
David S. Miller
davem@redhat.com

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