Hi Nishanth,
On Thu, Feb 14, 2008 at 7:38 PM, Nishanth Aravamudan <nacc@xxxxxxxxxx> wrote:
> Is it just me, or does
>
> ((user_addr + iov[seg].iov_len + PAGE_SIZE - 1)/PAGE_SIZE - user_addr/PAGE_SIZE)
>
> not simplify to
>
> = ((iov[seg].iov_len + PAGE_SIZE - 1)/PAGE_SIZE + user_addr/PAGE_SIZE - user_addr/PAGE_SIZE)
>
> = ((iov[seg].iov_len + PAGE_SIZE - 1)/PAGE_SIZE)
>
> = DIV_ROUND_UP(iov[seg].iov_len, PAGE_SIZE)
>
> CMIIW.
I double-checked this and I believe you're correct. It's simpler to
see when you do:
x = user_addr
y = iov[seg].iov_len
z = PAGE_SIZE
So
(x + y + z - 1)/z - x/z
= [x + (y + z - 1)]/z - x/z
= [xz + z(y + z - 1)]/z^2 - x/z
= x/z + (y + z - 1)/z - x/z
And the rest follows from your simplifications.
Pekka
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