fscache: convert object to use workqueue instead of slow-work

Make fscache object state transition callbacks use workqueue instead
of slow-work.  New dedicated unbound CPU workqueue fscache_object_wq
is created.  get/put callbacks are renamed and modified to take
@object and called directly from the enqueue wrapper and the work
function.  While at it, make all open coded instances of get/put to
use fscache_get/put_object().

* Unbound workqueue is used.

* work_busy() output is printed instead of slow-work flags in object
  debugging outputs.  They mean basically the same thing bit-for-bit.

* sysctl fscache.object_max_active added to control concurrency.  The
  default value is nr_cpus clamped between 4 and
  WQ_UNBOUND_MAX_ACTIVE.

* slow_work_sleep_till_thread_needed() is replaced with fscache
  private implementation fscache_object_sleep_till_congested() which
  waits on fscache_object_wq congestion.

* debugfs support is dropped for now.  Tracing API based debug
  facility is planned to be added.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David Howells <dhowells@redhat.com>

1 files changed, 6 insertions, 7 deletions

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index f4a7840bf42c..42c7fafc8bfe 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -37,9 +37,9 @@ void __cachefiles_printk_object(struct cachefiles_object *object,
 
         printk(KERN_ERR "%sobject: OBJ%x\n",
                prefix, object->fscache.debug_id);
-        printk(KERN_ERR "%sobjstate=%s fl=%lx swfl=%lx ev=%lx[%lx]\n",
+        printk(KERN_ERR "%sobjstate=%s fl=%lx wbusy=%x ev=%lx[%lx]\n",
                prefix, fscache_object_states[object->fscache.state],
-               object->fscache.flags, object->fscache.work.flags,
+               object->fscache.flags, work_busy(&object->fscache.work),
                object->fscache.events,
                object->fscache.event_mask & FSCACHE_OBJECT_EVENTS_MASK);
         printk(KERN_ERR "%sops=%u inp=%u exc=%u\n",
@@ -212,7 +212,7 @@ wait_for_old_object:
 
                 /* if the object we're waiting for is queued for processing,
                  * then just put ourselves on the queue behind it */
-                if (slow_work_is_queued(&xobject->fscache.work)) {
+                if (work_pending(&xobject->fscache.work)) {
                         _debug("queue OBJ%x behind OBJ%x immediately",
                                object->fscache.debug_id,
                                xobject->fscache.debug_id);
@@ -220,8 +220,7 @@ wait_for_old_object:
                 }
 
                 /* otherwise we sleep until either the object we're waiting for
-                 * is done, or the slow-work facility wants the thread back to
-                 * do other work */
+                 * is done, or the fscache_object is congested */
                 wq = bit_waitqueue(&xobject->flags, CACHEFILES_OBJECT_ACTIVE);
                 init_wait(&wait);
                 requeue = false;
@@ -229,8 +228,8 @@ wait_for_old_object:
                         prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
                         if (!test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags))
                                 break;
-                        requeue = slow_work_sleep_till_thread_needed(
-                                &object->fscache.work, &timeout);
+
+                        requeue = fscache_object_sleep_till_congested(&timeout);
                 } while (timeout > 0 && !requeue);
                 finish_wait(wq, &wait);