linux-kernel - Re: [PATCH -v3 2/3] xen-blkback: repleace check kthread_should_stop() to remove_requested in xen_blkif

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Date:	Thu, 4 Aug 2011 15:48:38 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Joe Jin <joe.jin@...cle.com>
Cc:	Daniel Stodden <daniel.stodden@...rix.com>,
	Jens Axboe <jaxboe@...ionio.com>,
	Annie Li <annie.li@...cle.com>,
	Ian Campbell <Ian.Campbell@...citrix.com>,
	Kurt C Hackel <KURT.HACKEL@...cle.com>,
	Greg Marsden <greg.marsden@...cle.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -v3 2/3] xen-blkback: repleace check
 kthread_should_stop() to remove_requested in xen_blkif_schedule() loop.

On Thu, Aug 04, 2011 at 03:24:44PM +0800, Joe Jin wrote:
> 
> When backend state change to XenbusStateClosed, remove_requested will be set,
> so repleace check kthread_should_stop() to remove_requested in 
> xen_blkif_schedule() loop.
> 
> Signed-off-by: Joe Jin <joe.jin@...cle.com>
> Cc: Daniel Stodden <daniel.stodden@...rix.com>
> Cc: Jens Axboe <jaxboe@...ionio.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Cc: Annie Li <annie.li@...cle.com>
> Cc: Ian Campbell <Ian.Campbell@...citrix.com>
> --
>  drivers/block/xen-blkback/blkback.c |   10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
> index 2330a9a..3d64b52 100644
> --- a/drivers/block/xen-blkback/blkback.c
> +++ b/drivers/block/xen-blkback/blkback.c
> @@ -274,7 +274,7 @@ int xen_blkif_schedule(void *arg)
>  
>  	xen_blkif_get(blkif);
>  
> -	while (!kthread_should_stop()) {
> +	while (!blkif->remove_requested) {
>  		if (try_to_freeze())
>  			continue;
>  		if (unlikely(vbd->size != vbd_sz(vbd)))
> @@ -282,11 +282,11 @@ int xen_blkif_schedule(void *arg)
>  
>  		wait_event_interruptible(
>  			blkif->wq,
> -			blkif->waiting_reqs || kthread_should_stop());
> +			blkif->waiting_reqs || blkif->remove_requested);
>  		wait_event_interruptible(
>  			blkbk->pending_free_wq,
>  			!list_empty(&blkbk->pending_free) ||
> -			kthread_should_stop());
> +			blkif->remove_requested);
>  
>  		blkif->waiting_reqs = 0;
>  		smp_mb(); /* clear flag *before* checking for work */
> @@ -301,8 +301,8 @@ int xen_blkif_schedule(void *arg)
>  	if (log_stats)
>  		print_stats(blkif);
>  
> -	blkif->xenblkd = NULL;
>  	xen_blkif_put(blkif);
> +	xen_blkback_close(blkif);

<sigh> I can't believe I didn't catch this earlier, but this a
big NO NO. Each patch _MUST_ be compile on its own. If I commit
patch 1 and this patch, the compile (actually linker) process
stops b/c xen_blkback_close is not defined:

drivers/built-in.o: In function `xen_blkif_schedule':
/home/konrad/ssd/linux/drivers/block/xen-blkback/blkback.c:305: undefined reference to `xen_blkback_close'
make[2]: *** [.tmp_vmlinux1] Error 1

You can move the xen_blkback_close() to the third patch
instead of having it here.

I will be nice and do it for you.

>  
>  	return 0;
>  }
> @@ -476,7 +476,7 @@ __do_block_io_op(struct xen_blkif *blkif)
>  		if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
>  			break;
>  
> -		if (kthread_should_stop()) {
> +		if (blkif->remove_requested) {
>  			more_to_do = 1;
>  			break;
>  		}
--
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