diff options
author | NeilBrown <neilb@suse.com> | 2017-10-19 12:17:16 +1100 |
---|---|---|
committer | Shaohua Li <shli@fb.com> | 2017-11-01 21:32:18 -0700 |
commit | 4d5324f760aacaefeb721b172aa14bf66045c332 (patch) | |
tree | 4115e3a5b37b7890c402d07ce551648b93f63844 /drivers/md/raid5-cache.c | |
parent | 230b55fa8d64007339319539f8f8e68114d08529 (diff) | |
download | linux-4d5324f760aacaefeb721b172aa14bf66045c332.tar.bz2 |
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 <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Diffstat (limited to 'drivers/md/raid5-cache.c')
-rw-r--r-- | drivers/md/raid5-cache.c | 18 |
1 files changed, 13 insertions, 5 deletions
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); |