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, 3 deletions

diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index c57db27ac861..27c8df503152 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -21,6 +21,7 @@
 #include <linux/fscache.h>
 #include <linux/sched.h>
 #include <linux/slow-work.h>
+#include <linux/workqueue.h>
 
 #define NR_MAXCACHES BITS_PER_LONG
 
@@ -389,7 +390,7 @@ struct fscache_object {
         struct fscache_cache    *cache;         /* cache that supplied this object */
         struct fscache_cookie   *cookie;        /* netfs's file/index object */
         struct fscache_object   *parent;        /* parent object */
-        struct slow_work        work;           /* attention scheduling record */
+        struct work_struct      work;           /* attention scheduling record */
         struct list_head        dependents;     /* FIFO of dependent objects */
         struct list_head        dep_link;       /* link in parent's dependents list */
         struct list_head        pending_ops;    /* unstarted operations on this object */
@@ -411,7 +412,7 @@ extern const char *fscache_object_states[];
         (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&     \
          (obj)->state >= FSCACHE_OBJECT_DYING)
 
-extern const struct slow_work_ops fscache_object_slow_work_ops;
+extern void fscache_object_work_func(struct work_struct *work);
 
 /**
  * fscache_object_init - Initialise a cache object description
@@ -433,7 +434,7 @@ void fscache_object_init(struct fscache_object *object,
         spin_lock_init(&object->lock);
         INIT_LIST_HEAD(&object->cache_link);
         INIT_HLIST_NODE(&object->cookie_link);
-        vslow_work_init(&object->work, &fscache_object_slow_work_ops);
+        INIT_WORK(&object->work, fscache_object_work_func);
         INIT_LIST_HEAD(&object->dependents);
         INIT_LIST_HEAD(&object->dep_link);
         INIT_LIST_HEAD(&object->pending_ops);
@@ -534,6 +535,8 @@ extern void fscache_io_error(struct fscache_cache *cache);
 extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
                                       struct pagevec *pagevec);
 
+extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
+
 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
                                                const void *data,
                                                uint16_t datalen);