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

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Date:	Fri, 29 Dec 2006 18:59:14 -0800
From:	"Chen, Kenneth W" <kenneth.w.chen@...el.com>
To:	"'Andrew Morton'" <akpm@...l.org>, <zach.brown@...cle.com>
Cc:	<linux-aio@...ck.org>, <linux-kernel@...r.kernel.org>,
	"'Benjamin LaHaise'" <bcrl@...ck.org>, <suparna@...ibm.com>
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 <kenneth.w.chen@...el.com>


--- ./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;
-
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