[PATCH 3/5] populate: reformat external ext[34] journal devices when restoring a cached image

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

The fs population code has the ability to save cached metadumps of
filesystems to save time when running fstests.  The cached images should
be unmounted cleanly, so we never save the contents of external journal
devices.

Unfortunately, the cache restore code fails to reset the external
journal when restoring a clean image, so we ignore cached images because
the journal doesn't match the filesystem.  This makes test runtimes
longer than they need to be.

Solve this by reformatting the external journal to match the filesystem.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 common/populate |   20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)


diff --git a/common/populate b/common/populate
index 0bd78e0a0a..66c55b682f 100644
--- a/common/populate
+++ b/common/populate
@@ -16,6 +16,9 @@ _require_populate_commands() {
 		_require_command "$XFS_DB_PROG" "xfs_db"
 		_require_command "$WIPEFS_PROG" "wipefs"
 		;;
+	ext*)
+		_require_command "$DUMPE2FS_PROG" "dumpe2fs"
+		;;
 	esac
 }
 
@@ -871,9 +874,20 @@ _scratch_populate_restore_cached() {
 		return $res
 		;;
 	"ext2"|"ext3"|"ext4")
-		# ext4 cannot e2image external logs, so we cannot restore
-		test -n "${SCRATCH_LOGDEV}" && return 1
-		e2image -r "${metadump}" "${SCRATCH_DEV}" && return 0
+		e2image -r "${metadump}" "${SCRATCH_DEV}"
+		ret=$?
+		test $ret -ne 0 && return $ret
+
+		# ext4 cannot e2image external logs, so we have to reformat
+		# the scratch device to match the restored fs
+		if [ -n "${SCRATCH_LOGDEV}" ]; then
+			local fsuuid="$($DUMPE2FS_PROG -h "${SCRATCH_DEV}" 2>/dev/null | \
+					grep 'Journal UUID:' | \
+					sed -e 's/Journal UUID:[[:space:]]*//g')"
+			$MKFS_EXT4_PROG -O journal_dev "${SCRATCH_LOGDEV}" \
+					-F -U "${fsuuid}"
+		fi
+		return 0
 		;;
 	esac
 	return 1