[PATCH] generic/622: increase sleep time for lazytime expiration on compressed f2fs

[Jan Prusakowski <jprusakowski@google.com>]

In generic/622, expire_timestamps() tests whether lazytime timestamp
updates are persisted after dirtytime expiration. It configures
dirtytime_expire_seconds to 1 second and enables continuous writeback
of dirty inodes, followed by sleeping for 2 seconds to allow the
asynchronous VFS flusher thread to expire the I_DIRTY_TIME inode,
invoke the filesystem's write_inode callback, and flush the dirty
metadata before the test executes _scratch_shutdown -f.

However, on F2FS with transparent compression enabled, compressed files
cannot use inline data and writes use out-of-place updates (OPU) with
higher latency in the compression and writeback pipeline. Because the
inode is only eligible for expiration after 1 second, only about 1 second
remains in the 2-second sleep window for the flusher thread to schedule,
expire the inode, and mark the inode page dirty before
restore_expiration_settings resets dirtytime_expire_seconds to 24 hours
and shutdown occurs. If the flusher thread is delayed, the subsequent
shutdown checkpoint ignores the unexpired I_DIRTY_TIME inode, causing
the test to intermittently fail with:

    FAIL: lazytime mtime wasn't persisted by expiration
    ondisk_time (...) != expected_time (...)

Increase the sleep duration in expire_timestamps() from 2 to 4 seconds
when running on F2FS in compress mode to give sufficient margin for the
flusher thread to reliably expire the lazytime inode and dirty the inode
page before shutdown.

Change-Id: I208bf14c189b54cc209059b0fd2de9e403a073f2
Signed-off-by: Jan Prusakowski <jprusakowski@google.com>
---
 tests/generic/622 | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/tests/generic/622 b/tests/generic/622
index e8ead300..5879e85e 100755
--- a/tests/generic/622
+++ b/tests/generic/622
@@ -60,8 +60,14 @@ expire_timestamps()
 	__expire_inodes
 
 	# Userspace doesn't have direct visibility into when inodes are dirty,
-	# so the best we can do is sleep for a couple seconds.
-	sleep 2
+	# so the best we can do is sleep for a couple seconds.  On F2FS with
+	# compression enabled, out-of-place updates and compression writeback
+	# add extra latency, so sleep a bit longer.
+	if [[ "$FSTYP" == "f2fs" && "$MOUNT_OPTIONS" == *compress* ]]; then
+		sleep 4
+	else
+		sleep 2
+	fi
 	restore_expiration_settings
 }
 
-- 
2.55.0.1082.g2b9226bbc0-goog