On Mon, Jun 08, 2026 at 10:39:04PM +0800, Anand Suveer Jain wrote:
> On 29/5/26 12:27, Darrick J. Wong wrote:
> > 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?
> >
>
> Hmm, in the function _create_loop_device(), we are
> calling _fail if create fails, so no need to duplicate, right?
Oh right. Question withdrawn.
> > > + 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")
> >
> > ?
>
> If the second `_create_loop_device()` happens to fail, it will
> already have called `_fail`, so "second loopdev..." won't be
> used at all.
<nod> Both comments withdrawn :)
--D
>
> Thanks, Anand
>
>
>
> > > +
> > > + _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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