Hi,
Can anyone please justify me the logic of fs/bufferc.c:buffer_busy()
How can we perform bit-wise operation for ->b_count and ->b_state?
static inline int buffer_busy(struct buffer_head *bh)
{
return atomic_read(&bh->b_count) |
(bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
}
I try to digg inside git/cvs history and it is appeared that 2.4 was
also implemented like this. At least it was so in 2000'th
http://lkml.indiana.edu/hypermail/linux/kernel/0006.0/0412.html
Also I've found similar complain
http://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg24377.html
But seems nobody care about it. What's the point?
The only guess I have is that this is a miss typo because buffer
is busy if some one hold an reference (bh->b_count !=0 ) ||
it is (dirty | locked). So following patch should fix
>From dc45e525b647ed11f26781b80eed3894cc3ba325 Mon Sep 17 00:00:00 2001
From: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
Date: Tue, 23 Apr 2013 15:24:24 +0400
Subject: [PATCH] buffer: fix miss typo
Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
---
fs/buffer.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index b4dcb34..4ffa6c9 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3119,7 +3119,7 @@ EXPORT_SYMBOL(sync_dirty_buffer);
*/
static inline int buffer_busy(struct buffer_head *bh)
{
- return atomic_read(&bh->b_count) |
+ return atomic_read(&bh->b_count) ||
(bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
}
--
1.7.1
