2006-12-30 02:59:16

by Chen, Kenneth W

Subject: [patch] aio: remove spurious ring head index modulo info->nr

In aio_read_evt(), the ring->head will never wrap info->nr because
we already does the wrap when updating the ring head index:

if (head != ring->tail) {
...
head = (head + 1) % info->nr;
ring->head = head;
}

This makes the modulo of ring->head into local variable head unnecessary.
This patch removes that bogus code.


Signed-off-by: Ken Chen <[email protected]>


--- ./fs/aio.c.orig 2006-12-24 22:01:36.000000000 -0800
+++ ./fs/aio.c 2006-12-24 22:34:48.000000000 -0800
@@ -1019,7 +1019,7 @@ static int aio_read_evt(struct kioctx *i
{
struct aio_ring_info *info = &ioctx->ring_info;
struct aio_ring *ring;
- unsigned long head;
+ unsigned int head;
int ret = 0;

ring = kmap_atomic(info->ring_pages[0], KM_USER0);
@@ -1032,7 +1032,7 @@ static int aio_read_evt(struct kioctx *i

spin_lock(&info->ring_lock);

- head = ring->head % info->nr;
+ head = ring->head;
if (head != ring->tail) {
struct io_event *evp = aio_ring_event(info, head, KM_USER1);
*ent = *evp;

2007-01-03 01:12:09

by Zach Brown

Subject: Re: [patch] aio: remove spurious ring head index modulo info->nr

> This makes the modulo of ring->head into local variable head
> unnecessary.
> This patch removes that bogus code.

Looks fine to me:

Acked-by: Zach Brown <[email protected]>

- z