[PATCH] lock_buffer_wq do lock

[PATCH] lock_buffer_wq do lock

[Hugh Dickins]

I've twice got fs/buffer.c:2668 submit_bh BUG_ON(!buffer_locked(bh)):
when called from sync_dirty_buffer which clearly does the lock_buffer.
My suspicion falls on lock_buffer_wq (whereas __lock_page_wq looks OK).

I'm leaving a test running,
can't judge until tomorrow whether this is indeed the fix to that.

Hugh

--- 2.5.71-mm1/include/linux/buffer_head.h	Sun Jun 15 12:36:11 2003
+++ linux/include/linux/buffer_head.h	Mon Jun 16 14:13:25 2003
@@ -291,9 +291,11 @@
 
 static inline int lock_buffer_wq(struct buffer_head *bh, wait_queue_t *wait)
 {
-	if (test_set_buffer_locked(bh))
-		return __wait_on_buffer_wq(bh, wait);
-
+	while (test_set_buffer_locked(bh)) {
+		int ret = __wait_on_buffer_wq(bh, wait);
+		if (ret)
+			return ret;
+	}
 	return 0;
 }
 

Re: [PATCH] lock_buffer_wq do lock

[Suparna Bhattacharya]

On Mon, Jun 16, 2003 at 02:47:32PM +0100, Hugh Dickins wrote:
> I've twice got fs/buffer.c:2668 submit_bh BUG_ON(!buffer_locked(bh)):
> when called from sync_dirty_buffer which clearly does the lock_buffer.
> My suspicion falls on lock_buffer_wq (whereas __lock_page_wq looks OK).
> 
> I'm leaving a test running,
> can't judge until tomorrow whether this is indeed the fix to that.
> 
> Hugh
> 
> --- 2.5.71-mm1/include/linux/buffer_head.h	Sun Jun 15 12:36:11 2003
> +++ linux/include/linux/buffer_head.h	Mon Jun 16 14:13:25 2003
> @@ -291,9 +291,11 @@
>  
>  static inline int lock_buffer_wq(struct buffer_head *bh, wait_queue_t *wait)
>  {
> -	if (test_set_buffer_locked(bh))
> -		return __wait_on_buffer_wq(bh, wait);
> -
> +	while (test_set_buffer_locked(bh)) {
> +		int ret = __wait_on_buffer_wq(bh, wait);
> +		if (ret)
> +			return ret;
> +	}
>  	return 0;
>  }

You are right - this should be a while loop mirroring what
lock_buffer does.

Actually, I probably ought to just avoid the dual paths,
and make lock_buffer a wrapper for lock_buffer_wq -- less
chances of divergence between the two. 

Regards
Suparna

-- 
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Labs, India