On Sat, Jul 8, 2023 at 5:19 PM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote: > > From: Yu Kuai <yukuai3@xxxxxxxxxx> > > Commit b13015af94cf ("md/raid5-cache: Clear conf->log after finishing > work") introduce a new problem: > > // caller hold reconfig_mutex > r5l_exit_log > flush_work(&log->disable_writeback_work) > r5c_disable_writeback_async > wait_event > /* > * conf->log is not NULL, and mddev_trylock() > * will fail, wait_event() can never pass. > */ > conf->log = NULL > > Fix this problem by setting 'config->log' to NULL before wake_up() as it > used to be, so that wait_event() from r5c_disable_writeback_async() can > exist. In the meantime, move forward md_unregister_thread() so that > null-ptr-deref this commit fixed can still be fixed. > > Fixes: b13015af94cf ("md/raid5-cache: Clear conf->log after finishing work") > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx> Applied to md-next. Thanks! Song > --- > > Changes in v3: > - Use a different solution. > > drivers/md/raid5-cache.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c > index 47ba7d9e81e1..2eac4a50d99b 100644 > --- a/drivers/md/raid5-cache.c > +++ b/drivers/md/raid5-cache.c > @@ -3168,12 +3168,15 @@ void r5l_exit_log(struct r5conf *conf) > { > struct r5l_log *log = conf->log; > > - /* Ensure disable_writeback_work wakes up and exits */ > - wake_up(&conf->mddev->sb_wait); > - flush_work(&log->disable_writeback_work); > md_unregister_thread(&log->reclaim_thread); > > + /* > + * 'reconfig_mutex' is held by caller, set 'confg->log' to NULL to > + * ensure disable_writeback_work wakes up and exits. > + */ > conf->log = NULL; > + wake_up(&conf->mddev->sb_wait); > + flush_work(&log->disable_writeback_work); > > mempool_exit(&log->meta_pool); > bioset_exit(&log->bs); > -- > 2.39.2 >