linux-kernel - Re: [PATCH 04/10] xen/blkfront: separate ring information to an new struct

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Date:	Wed, 18 Feb 2015 18:28:49 +0100
From:	Roger Pau Monné <roger.pau@...rix.com>
To:	Bob Liu <bob.liu@...cle.com>, <xen-devel@...ts.xen.org>
CC:	<david.vrabel@...rix.com>, <linux-kernel@...r.kernel.org>,
	<konrad.wilk@...cle.com>, <felipe.franciosi@...rix.com>,
	<axboe@...com>, <hch@...radead.org>, <avanzini.arianna@...il.com>
Subject: Re: [PATCH 04/10] xen/blkfront: separate ring information to an new
 struct

El 15/02/15 a les 9.18, Bob Liu ha escrit:
> A ring is the representation of a hardware queue, this patch separate ring
> information from blkfront_info to an new struct blkfront_ring_info to make
> preparation for real multi hardware queues supporting.
> 
> Signed-off-by: Arianna Avanzini <avanzini.arianna@...il.com>
> Signed-off-by: Bob Liu <bob.liu@...cle.com>
> ---
>  drivers/block/xen-blkfront.c | 403 +++++++++++++++++++++++--------------------
>  1 file changed, 218 insertions(+), 185 deletions(-)
> 
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 5a90a51..aaa4a0e 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -102,23 +102,15 @@ MODULE_PARM_DESC(max, "Maximum amount of segments in indirect requests (default
>  #define BLK_RING_SIZE __CONST_RING_SIZE(blkif, PAGE_SIZE)
>  
>  /*
> - * We have one of these per vbd, whether ide, scsi or 'other'.  They
> - * hang in private_data off the gendisk structure. We may end up
> - * putting all kinds of interesting stuff here :-)
> + *  Per-ring info.
> + *  A blkfront_info structure can associate with one or more blkfront_ring_info,
> + *  depending on how many hardware queues supported.
>   */
> -struct blkfront_info
> -{
> +struct blkfront_ring_info {
>  	spinlock_t io_lock;
> -	struct mutex mutex;
> -	struct xenbus_device *xbdev;
> -	struct gendisk *gd;
> -	int vdevice;
> -	blkif_vdev_t handle;
> -	enum blkif_state connected;
>  	int ring_ref;
>  	struct blkif_front_ring ring;
>  	unsigned int evtchn, irq;
> -	struct request_queue *rq;
>  	struct work_struct work;
>  	struct gnttab_free_callback callback;
>  	struct blk_shadow shadow[BLK_RING_SIZE];
> @@ -126,6 +118,22 @@ struct blkfront_info
>  	struct list_head indirect_pages;
>  	unsigned int persistent_gnts_c;
>  	unsigned long shadow_free;
> +	struct blkfront_info *info;

AFAICT you seem to have a list of persistent grants, indirect pages and
a grant table callback for each ring, isn't this supposed to be shared
between all rings?

I don't think we should be going down that route, or else we can hoard a
large amount of memory and grants.

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