On Thu, May 28, 2026 at 12:05:32PM +0800, Anand Jain wrote:
> Introduce _loop_image_create_clone() and _loop_image_destroy() to mkfs an
> image file and clone it to another image file, and attach a loop device to
> them. And its destroy part.
>
> Signed-off-by: Anand Jain <[email protected]>
> ---
> common/rc | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 63 insertions(+)
>
> diff --git a/common/rc b/common/rc
> index 79189e7e6e94..d7e3e0bdfb1e 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -1520,6 +1520,69 @@ _scratch_resvblks()
> esac
> }
>
> +# Create a small loop image, run an optional tuning function ($2) on it,
> +# clone it, and attach both to loop devices, returned in ($1).
> +# Args:
> +# $1: Nameref to return the array of allocated loop devices [base, clone].
> +# $2: Optional callback function to tune the base filesystem before
> cloning.
> +_loop_image_create_clone()
> +{
> + local -n _ret=$1
That switch ^^ is very clever. I always wondered how one did indirect
variables in bash.
> + local pre_clone_tune_func="$2"
> + local img_file=$TEST_DIR/${seq}.img
> + local img_file_clone=$TEST_DIR/${seq}_clone.img
> + local size=$(_small_fs_size_mb 128) # Smallest possible
> + local loop_devs
> +
> + # Since we copy the block device image, we keep its size small.
> + _require_fs_space $TEST_DIR $((size * 1024))
> +
> + _create_file_sized $((size * 1024 * 1024)) $img_file ||
> + _fail "Failed: Create $img_file $size"
> +
> + loop_devs=$(_create_loop_device $img_file)
> + _ret=($loop_devs)
Should this check that a loopdev actually got created?
> + case $FSTYP in
> + xfs)
> + _mkfs_dev "-s size=4096" ${loop_devs[0]}
> + ;;
> + btrfs)
> + _mkfs_dev ${loop_devs[0]}
> + ;;
> + *)
> + _mkfs_dev ${loop_devs[0]}
> + ;;
> + esac
> +
> + # Only execute if the function argument is not empty
> + if [ -n "$pre_clone_tune_func" ]; then
> + $pre_clone_tune_func ${loop_devs[0]}
> + fi
> +
> + sync ${loop_devs[0]}
> + cp $img_file $img_file_clone
> +
> + loop_devs="$loop_devs $(_create_loop_device $img_file_clone)"
local lodev="$(_create_loop_device ...)"
test -z "$lodev" && _fail "second loopdev not created"
_ret+=("$lodev")
?
> +
> + _ret=($loop_devs)
> +}
> +
> +# Teardown loop devices and delete their underlying backing image files.
> +# Accepts a list of loop device paths (e.g., /dev/loop0 /dev/loop1).
> +_loop_image_destroy()
> +{
> + for d in "$@"; do
> + # Retrieve the path of the backing file
> + local f=$(losetup --noheadings --output BACK-FILE $d)
> +
> + # Detach the loop device from the backing file
> + _destroy_loop_device "$d"
> +
> + # Clean up the backing disk image file
> + [ -n "$f" ] && rm -f "$f"
> + done
> +}
>
> # Repair scratch filesystem. Returns 0 if the FS is good to go (either no
> # errors found or errors were fixed) and nonzero otherwise; also spits out
> --
> 2.43.0
>
>
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