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

Make fscache operation to use only workqueue instead of combination of
workqueue and slow-work.  FSCACHE_OP_SLOW is dropped and
FSCACHE_OP_FAST is renamed to FSCACHE_OP_ASYNC and uses newly added
fscache_op_wq workqueue to execute op->processor().
fscache_operation_init_slow() is dropped and fscache_operation_init()
now takes @processor argument directly.

* Unbound workqueue is used.

* fscache_retrieval_work() is no longer necessary as OP_ASYNC now does
  the equivalent thing.

* sysctl fscache.operation_max_active added to control concurrency.
  The default value is nr_cpus clamped between 2 and
  WQ_UNBOUND_MAX_ACTIVE.

* 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, 11 insertions, 26 deletions

diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index 27c8df503152..17ed9c1dbfbe 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -77,18 +77,14 @@ typedef void (*fscache_operation_release_t)(struct fscache_operation *op);
 typedef void (*fscache_operation_processor_t)(struct fscache_operation *op);
 
 struct fscache_operation {
-        union {
-                struct work_struct fast_work;   /* record for fast ops */
-                struct slow_work slow_work;     /* record for (very) slow ops */
-        };
+        struct work_struct      work;           /* record for async ops */
         struct list_head        pend_link;      /* link in object->pending_ops */
         struct fscache_object   *object;        /* object to be operated upon */
 
         unsigned long           flags;
 #define FSCACHE_OP_TYPE         0x000f  /* operation type */
-#define FSCACHE_OP_FAST         0x0001  /* - fast op, processor may not sleep for disk */
-#define FSCACHE_OP_SLOW         0x0002  /* - (very) slow op, processor may sleep for disk */
-#define FSCACHE_OP_MYTHREAD     0x0003  /* - processing is done be issuing thread, not pool */
+#define FSCACHE_OP_ASYNC        0x0001  /* - async op, processor may sleep for disk */
+#define FSCACHE_OP_MYTHREAD     0x0002  /* - processing is done be issuing thread, not pool */
 #define FSCACHE_OP_WAITING      4       /* cleared when op is woken */
 #define FSCACHE_OP_EXCLUSIVE    5       /* exclusive op, other ops must wait */
 #define FSCACHE_OP_DEAD         6       /* op is now dead */
@@ -106,7 +102,8 @@ struct fscache_operation {
         /* operation releaser */
         fscache_operation_release_t release;
 
-#ifdef CONFIG_SLOW_WORK_DEBUG
+#ifdef CONFIG_WORKQUEUE_DEBUGFS
+        struct work_struct put_work;    /* work to delay operation put */
         const char *name;               /* operation name */
         const char *state;              /* operation state */
 #define fscache_set_op_name(OP, N)      do { (OP)->name  = (N); } while(0)
@@ -118,7 +115,7 @@ struct fscache_operation {
 };
 
 extern atomic_t fscache_op_debug_id;
-extern const struct slow_work_ops fscache_op_slow_work_ops;
+extern void fscache_op_work_func(struct work_struct *work);
 
 extern void fscache_enqueue_operation(struct fscache_operation *);
 extern void fscache_put_operation(struct fscache_operation *);
@@ -129,33 +126,21 @@ extern void fscache_put_operation(struct fscache_operation *);
  * @release: The release function to assign
  *
  * Do basic initialisation of an operation.  The caller must still set flags,
- * object, either fast_work or slow_work if necessary, and processor if needed.
+ * object and processor if needed.
  */
 static inline void fscache_operation_init(struct fscache_operation *op,
-                                          fscache_operation_release_t release)
+                                        fscache_operation_processor_t processor,
+                                        fscache_operation_release_t release)
 {
+        INIT_WORK(&op->work, fscache_op_work_func);
         atomic_set(&op->usage, 1);
         op->debug_id = atomic_inc_return(&fscache_op_debug_id);
+        op->processor = processor;
         op->release = release;
         INIT_LIST_HEAD(&op->pend_link);
         fscache_set_op_state(op, "Init");
 }
 
-/**
- * fscache_operation_init_slow - Do additional initialisation of a slow op
- * @op: The operation to initialise
- * @processor: The processor function to assign
- *
- * Do additional initialisation of an operation as required for slow work.
- */
-static inline
-void fscache_operation_init_slow(struct fscache_operation *op,
-                                 fscache_operation_processor_t processor)
-{
-        op->processor = processor;
-        slow_work_init(&op->slow_work, &fscache_op_slow_work_ops);
-}
-
 /*
  * data read operation
  */