Re: [patch] arca-vm-2.2.5

David Miller
1999-04-06T22:40:28Z

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