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Date: Tue, 14 Oct 2025 13:59:13 -0700
From: "Darrick J. Wong" <djwong@kernel.org>
To: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Zorro Lang <zlang@redhat.com>, Christoph Hellwig <hch@lst.de>,
	Naohiro Aota <naohiro.aota@wdc.com>, linux-btrfs@vger.kernel.org,
	Hans Holmberg <hans.holmberg@wdc.com>, fstests@vger.kernel.org,
	linux-xfs@vger.kernel.org, Carlos Maiolino <cem@kernel.org>
Subject: Re: [PATCH v4 2/3] common/zoned: add _create_zloop
Message-ID: <20251014205913.GB6188@frogsfrogsfrogs>
References: <20251014084625.422974-1-johannes.thumshirn@wdc.com>
 <20251014084625.422974-3-johannes.thumshirn@wdc.com>
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In-Reply-To: <20251014084625.422974-3-johannes.thumshirn@wdc.com>

On Tue, Oct 14, 2025 at 10:46:24AM +0200, Johannes Thumshirn wrote:
> Add _create_zloop a helper function for creating a zloop device.
> 
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> ---
>  common/zoned | 35 +++++++++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
> 
> diff --git a/common/zoned b/common/zoned
> index 41697b08..55acf120 100644
> --- a/common/zoned
> +++ b/common/zoned
> @@ -45,3 +45,38 @@ _require_zloop()
>  	    _notrun "This test requires zoned loopback device support"
>      fi
>  }
> +
> +_find_next_zloop()
> +{
> +    local last_id=$(ls /dev/zloop* 2> /dev/null | grep -E "zloop[0-9]+" | wc -l)
> +    echo $last_id

Er... what happens if there are discontiguities in the active zloop
devices?

Let's say you have

# ls /dev/zloop*
/dev/zloop1000
/dev/zloop1000000
/dev/zloop3

That will produce last_id=3, which I don't think is what we want.

> +}
> +
> +# Create a zloop device
> +# useage: _create_zloop <base_dir> <zone_size> <nr_conv_zones>
> +_create_zloop()
> +{
> +    local id="$(_find_next_zloop)"
> +
> +    if [ -n "$1" ]; then
> +        local zloop_base="$1"
> +    else
> +	local zloop_base="/var/local/zloop"

Maybe the default zloop_base should be under $tmp somewhere?

> +    fi
> +
> +    if [ -n "$2" ]; then
> +        local zone_size=",zone_size_mb=$2"
> +    fi
> +
> +    if [ -n "$3" ]; then
> +        local conv_zones=",conv_zones=$3"
> +    fi
> +
> +    mkdir -p "$zloop_base/$id"
> +
> +    local zloop_args="add id=$id,base_dir=$zloop_base$zone_size$conv_zones"
> +
> +    echo "$zloop_args" > /dev/zloop-control

I wonder, if /dev/zloop3 already exists, shouldn't we respect the failed
write?  e.g.

	echo "$zloop_args" > /dev/zloop-control && echo "/dev/zloop$id"

--D

> +
> +    echo "/dev/zloop$id"
> +}
> -- 
> 2.51.0
> 
>