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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>
This commit is contained in:
NeilBrown 2017-10-19 12:17:16 +11:00 committed by Shaohua Li
parent 230b55fa8d
commit 4d5324f760
3 changed files with 24 additions and 7 deletions
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10
drivers/md/dm-raid.c
View File

@ -3628,8 +3628,11 @@ static void raid_postsuspend(struct dm_target *ti)
{
struct raid_set *rs = ti->private;
if (!test_and_set_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags))
if (!test_and_set_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags)) {
mddev_lock_nointr(&rs->md);
mddev_suspend(&rs->md);
mddev_unlock(&rs->md);
}
rs->md.ro = 1;
}
@ -3886,8 +3889,11 @@ static void raid_resume(struct dm_target *ti)
if (!(rs->ctr_flags & RESUME_STAY_FROZEN_FLAGS))
clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
if (test_and_clear_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags))
if (test_and_clear_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags)) {
mddev_lock_nointr(mddev);
mddev_resume(mddev);
mddev_unlock(mddev);
}
}
static struct target_type raid_target = {

3
drivers/md/md.c
View File

@ -344,6 +344,7 @@ static blk_qc_t md_make_request(struct request_queue *q, struct bio *bio)
void mddev_suspend(struct mddev *mddev)
{
WARN_ON_ONCE(mddev->thread && current == mddev->thread->tsk);
lockdep_assert_held(&mddev->reconfig_mutex);
if (mddev->suspended++)
return;
synchronize_rcu();
@ -357,6 +358,7 @@ EXPORT_SYMBOL_GPL(mddev_suspend);
void mddev_resume(struct mddev *mddev)
{
lockdep_assert_held(&mddev->reconfig_mutex);
if (--mddev->suspended)
return;
wake_up(&mddev->sb_wait);
@ -663,6 +665,7 @@ void mddev_unlock(struct mddev *mddev)
*/
spin_lock(&pers_lock);
md_wakeup_thread(mddev->thread);
wake_up(&mddev->sb_wait);
spin_unlock(&pers_lock);
}
EXPORT_SYMBOL_GPL(mddev_unlock);

12
drivers/md/raid5-cache.c
View File

@ -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));
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);