From c30e624d5d04efdb581c841f9bf8b06302b96575 Mon Sep 17 00:00:00 2001
From: Frediano Ziglio <freddy77@gmail.com>
Date: Tue, 30 Aug 2011 09:46:11 +0200
Subject: linux aio: some comments

Add some notes about Linux AIO explaining why we don't use AIO in
some situations.

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/raw-posix.c | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'block')

diff --git a/block/raw-posix.c b/block/raw-posix.c
index c5c99446c0..bcf50b2cf7 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -236,6 +236,10 @@ static int raw_open_common(BlockDriverState *bs, const char *filename,
     }
 
 #ifdef CONFIG_LINUX_AIO
+    /*
+     * Currently Linux do AIO only for files opened with O_DIRECT
+     * specified so check NOCACHE flag too
+     */
     if ((bdrv_flags & (BDRV_O_NOCACHE|BDRV_O_NATIVE_AIO)) ==
                       (BDRV_O_NOCACHE|BDRV_O_NATIVE_AIO)) {
 
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