Re: [PATCH v2] generic/622: increase sleep time for lazytime expiration

[Chao Yu <chao@kernel.org>]

On 10/9/26 16:55, Jan Prusakowski wrote:
> 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 filesystems or configurations with higher writeback
> overhead -- such as F2FS with transparent compression enabled, where
> compressed files cannot use inline data and writes use out-of-place
> updates (OPU) with higher latency in the compression and writeback

FYI, I encounter similar issue on non-compressed inode, so v2 w/o checking
compression makes sense to me.

> pipeline -- the 2-second sleep window can occasionally be insufficient.
> 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
> to give sufficient margin for the flusher thread to reliably expire the
> lazytime inode and dirty the inode page before shutdown.
> 
> Signed-off-by: Jan Prusakowski <jprusakowski@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,