linux-kernel - Re: [PATCH 1/3] xen-blkfront: introduce blkfront_gather_backend

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Date:	Tue, 21 Jul 2015 11:32:33 +0200
From:	Roger Pau Monné <roger.pau@...rix.com>
To:	Bob Liu <bob.liu@...cle.com>, <xen-devel@...ts.xenproject.org>
CC:	<david.vrabel@...rix.com>, <linux-kernel@...r.kernel.org>,
	<konrad.wilk@...cle.com>
Subject: Re: [PATCH 1/3] xen-blkfront: introduce blkfront_gather_backend_features()

El 21/07/15 a les 5.30, Bob Liu ha escrit:
> There is a bug when migrate from !feature-persistent host to feature-persistent
> host, because domU still think new host/backend don't support persistent.
> Dmesg like:
> backed has not unmapped grant: 839
> backed has not unmapped grant: 773
> backed has not unmapped grant: 773
> backed has not unmapped grant: 773
> backed has not unmapped grant: 839
> 
> The fix is to recheck feature-persistent of new backend in blkif_recover().
> See: https://lkml.org/lkml/2015/5/25/469
> 
> As Roger suggested, we can split the part of blkfront_connect that checks for
> optional features, like persistent grants, indirect descriptors and
> flush/barrier features to a separate function and call it from both
> blkfront_connect and blkif_recover
> 
> Signed-off-by: Bob Liu <bob.liu@...cle.com>

Thanks for taking care of this. The patch looks fine, just one minor nit.

> ---
>  drivers/block/xen-blkfront.c |  118 +++++++++++++++++++++++-------------------
>  1 file changed, 66 insertions(+), 52 deletions(-)
> 
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 5b45ee5..e266d17 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -181,6 +181,7 @@ static DEFINE_SPINLOCK(minor_lock);
>  	((_segs + SEGS_PER_INDIRECT_FRAME - 1)/SEGS_PER_INDIRECT_FRAME)
>  
>  static int blkfront_setup_indirect(struct blkfront_info *info);
> +static void blkfront_gather_backend_features(struct blkfront_info *info);
>  
>  static int get_id_from_freelist(struct blkfront_info *info)
>  {
> @@ -1514,6 +1515,7 @@ static int blkif_recover(struct blkfront_info *info)
>  	info->shadow_free = info->ring.req_prod_pvt;
>  	info->shadow[BLK_RING_SIZE(info)-1].req.u.rw.id = 0x0fffffff;
>  
> +	blkfront_gather_backend_features(info);
>  	rc = blkfront_setup_indirect(info);

AFAICT you can put the call to blkfront_setup_indirect inside of
blkfront_gather_backend_features, like it's done for blkfront_setup_discard.

Roger.
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