From: Ken Chen <kenneth.w.chen@intel.com>
Date: Sun, 1 May 2005 15:59:15 +0000 (-0700)
Subject: [PATCH] aio: ring wrapping simplification
X-Git-Tag: v2.6.12-rc4~136^2~58
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4bf69b2a06090c01c27f25ea5cd1440f7bf9256f;p=linux-2.6

[PATCH] aio: ring wrapping simplification

Since the tail pointer in aio_ring structure never wrap ring size more than
once, so a simple compare is sufficient to wrap the index around.  This avoid
a more expensive mod operation.

Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Suparna Bhattacharya <suparna@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/fs/aio.c b/fs/aio.c
index 9f807a541f..40517f35da 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -978,7 +978,8 @@ int fastcall aio_complete(struct kiocb *iocb, long res, long res2)
 
 	tail = info->tail;
 	event = aio_ring_event(info, tail, KM_IRQ0);
-	tail = (tail + 1) % info->nr;
+	if (++tail >= info->nr)
+		tail = 0;
 
 	event->obj = (u64)(unsigned long)iocb->ki_obj.user;
 	event->data = iocb->ki_user_data;