From 4d5324f760aacaefeb721b172aa14bf66045c332 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 19 Oct 2017 12:17:16 +1100 Subject: md: always hold reconfig_mutex when calling mddev_suspend() Most often mddev_suspend() is called with reconfig_mutex held. Make this a requirement in preparation a subsequent patch. Also require reconfig_mutex to be held for mddev_resume(), partly for symmetry and partly to guarantee no races with incr/decr of mddev->suspend. Taking the mutex in r5c_disable_writeback_async() is a little tricky as this is called from a work queue via log->disable_writeback_work, and flush_work() is called on that while holding ->reconfig_mutex. If the work item hasn't run before flush_work() is called, the work function will not be able to get the mutex. So we use mddev_trylock() inside the wait_event() call, and have that abort when conf->log is set to NULL, which happens before flush_work() is called. We wait in mddev->sb_wait and ensure this is woken when any of the conditions change. This requires waking mddev->sb_wait in mddev_unlock(). This is only like to trigger extra wake_ups of threads that needn't be woken when metadata is being written, and that doesn't happen often enough that the cost would be noticeable. Signed-off-by: NeilBrown Signed-off-by: Shaohua Li --- drivers/md/raid5-cache.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) (limited to 'drivers/md/raid5-cache.c') diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c index 2b450eee21fa..59af7cf35092 100644 --- a/drivers/md/raid5-cache.c +++ b/drivers/md/raid5-cache.c @@ -693,6 +693,8 @@ static void r5c_disable_writeback_async(struct work_struct *work) struct r5l_log *log = container_of(work, struct r5l_log, disable_writeback_work); struct mddev *mddev = log->rdev->mddev; + struct r5conf *conf = mddev->private; + int locked = 0; if (log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH) return; @@ -701,11 +703,15 @@ static void r5c_disable_writeback_async(struct work_struct *work) /* wait superblock change before suspend */ wait_event(mddev->sb_wait, - !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)); - - mddev_suspend(mddev); - log->r5c_journal_mode = R5C_JOURNAL_MODE_WRITE_THROUGH; - mddev_resume(mddev); + conf->log == NULL || + (!test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags) && + (locked = mddev_trylock(mddev)))); + if (locked) { + mddev_suspend(mddev); + log->r5c_journal_mode = R5C_JOURNAL_MODE_WRITE_THROUGH; + mddev_resume(mddev); + mddev_unlock(mddev); + } } static void r5l_submit_current_io(struct r5l_log *log) @@ -3165,6 +3171,8 @@ void r5l_exit_log(struct r5conf *conf) conf->log = NULL; synchronize_rcu(); + /* 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); mempool_destroy(log->meta_pool); -- cgit