linux-kernel - RE: [PATCH v4 1/2] xen/blkback: add stack variable 'blkif' in connect

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Date:   Mon, 7 Jan 2019 09:11:44 +0000
From:   Paul Durrant <Paul.Durrant@...rix.com>
To:     'Dongli Zhang' <dongli.zhang@...cle.com>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
        Roger Pau Monne <roger.pau@...rix.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>
Subject: RE: [PATCH v4 1/2] xen/blkback: add stack variable 'blkif' in
 connect_ring()

> -----Original Message-----
> From: Dongli Zhang [mailto:dongli.zhang@...cle.com]
> Sent: 07 January 2019 05:36
> To: xen-devel@...ts.xenproject.org; linux-block@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Cc: konrad.wilk@...cle.com; Roger Pau Monne <roger.pau@...rix.com>;
> axboe@...nel.dk; Paul Durrant <Paul.Durrant@...rix.com>
> Subject: [PATCH v4 1/2] xen/blkback: add stack variable 'blkif' in
> connect_ring()
> 
> As 'be->blkif' is used for many times in connect_ring(), the stack
> variable
> 'blkif' is added to substitute 'be-blkif'.
> 
> Suggested-by: Paul Durrant <paul.durrant@...rix.com>
> Signed-off-by: Dongli Zhang <dongli.zhang@...cle.com>

That looks better :-)

Reviewed-by: Paul Durrant <paul.durrant@...rix.com>

> ---
>  drivers/block/xen-blkback/xenbus.c | 27 ++++++++++++++-------------
>  1 file changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-
> blkback/xenbus.c
> index a4bc74e..a4aadac 100644
> --- a/drivers/block/xen-blkback/xenbus.c
> +++ b/drivers/block/xen-blkback/xenbus.c
> @@ -1023,6 +1023,7 @@ static int read_per_ring_refs(struct xen_blkif_ring
> *ring, const char *dir)
>  static int connect_ring(struct backend_info *be)
>  {
>  	struct xenbus_device *dev = be->dev;
> +	struct xen_blkif *blkif = be->blkif;
>  	unsigned int pers_grants;
>  	char protocol[64] = "";
>  	int err, i;
> @@ -1033,25 +1034,25 @@ static int connect_ring(struct backend_info *be)
> 
>  	pr_debug("%s %s\n", __func__, dev->otherend);
> 
> -	be->blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
> +	blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
>  	err = xenbus_scanf(XBT_NIL, dev->otherend, "protocol",
>  			   "%63s", protocol);
>  	if (err <= 0)
>  		strcpy(protocol, "unspecified, assuming default");
>  	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
> -		be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
> +		blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
>  	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
> -		be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
> +		blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
>  	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
> -		be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
> +		blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
>  	else {
>  		xenbus_dev_fatal(dev, err, "unknown fe protocol %s",
> protocol);
>  		return -ENOSYS;
>  	}
>  	pers_grants = xenbus_read_unsigned(dev->otherend, "feature-
> persistent",
>  					   0);
> -	be->blkif->vbd.feature_gnt_persistent = pers_grants;
> -	be->blkif->vbd.overflow_max_grants = 0;
> +	blkif->vbd.feature_gnt_persistent = pers_grants;
> +	blkif->vbd.overflow_max_grants = 0;
> 
>  	/*
>  	 * Read the number of hardware queues from frontend.
> @@ -1067,16 +1068,16 @@ static int connect_ring(struct backend_info *be)
>  				requested_num_queues, xenblk_max_queues);
>  		return -ENOSYS;
>  	}
> -	be->blkif->nr_rings = requested_num_queues;
> -	if (xen_blkif_alloc_rings(be->blkif))
> +	blkif->nr_rings = requested_num_queues;
> +	if (xen_blkif_alloc_rings(blkif))
>  		return -ENOMEM;
> 
>  	pr_info("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename,
> -		 be->blkif->nr_rings, be->blkif->blk_protocol, protocol,
> +		 blkif->nr_rings, blkif->blk_protocol, protocol,
>  		 pers_grants ? "persistent grants" : "");
> 
> -	if (be->blkif->nr_rings == 1)
> -		return read_per_ring_refs(&be->blkif->rings[0], dev-
> >otherend);
> +	if (blkif->nr_rings == 1)
> +		return read_per_ring_refs(&blkif->rings[0], dev->otherend);
>  	else {
>  		xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
>  		xspath = kmalloc(xspathsize, GFP_KERNEL);
> @@ -1085,10 +1086,10 @@ static int connect_ring(struct backend_info *be)
>  			return -ENOMEM;
>  		}
> 
> -		for (i = 0; i < be->blkif->nr_rings; i++) {
> +		for (i = 0; i < blkif->nr_rings; i++) {
>  			memset(xspath, 0, xspathsize);
>  			snprintf(xspath, xspathsize, "%s/queue-%u", dev-
> >otherend, i);
> -			err = read_per_ring_refs(&be->blkif->rings[i], xspath);
> +			err = read_per_ring_refs(&blkif->rings[i], xspath);
>  			if (err) {
>  				kfree(xspath);
>  				return err;
> --
> 2.7.4