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?
+ 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.
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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