Btrfs: Allow worker threads to exit when idle
The Btrfs worker threads don't currently die off after they have
been idle for a while, leading to a lot of threads sitting around
doing nothing for each mount.
Also, they are unable to start atomically (from end_io hanlders).
This commit reworks the worker threads so they can be started
from end_io handlers (just setting a flag that asks for a thread
to be added at a later date) and so they can exit if they
have been idle for a long time.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/async-thread.h b/fs/btrfs/async-thread.h
index 1b511c1..a562ad8 100644
--- a/fs/btrfs/async-thread.h
+++ b/fs/btrfs/async-thread.h
@@ -73,6 +73,15 @@
/* force completions in the order they were queued */
int ordered;
+ /* more workers required, but in an interrupt handler */
+ int atomic_start_pending;
+
+ /*
+ * are we allowed to sleep while starting workers or are we required
+ * to start them at a later time?
+ */
+ int atomic_worker_start;
+
/* list with all the work threads. The workers on the idle thread
* may be actively servicing jobs, but they haven't yet hit the
* idle thresh limit above.