4 files changed, 469 insertions, 3 deletions

diff --git a/fs/fscache/Makefile b/fs/fscache/Makefile
index 4420ac6ea10d..6f82da2aa9d1 100644
--- a/fs/fscache/Makefile
+++ b/fs/fscache/Makefile
@@ -8,7 +8,8 @@ fscache-y := \
         fsdef.o \
         main.o \
         netfs.o \
-        object.o
+        object.o \
+        operation.o
 
 fscache-$(CONFIG_PROC_FS) += proc.o
 fscache-$(CONFIG_FSCACHE_STATS) += stats.o
diff --git a/fs/fscache/cache.c b/fs/fscache/cache.c
index 355172f785fb..e21985bbb1fb 100644
--- a/fs/fscache/cache.c
+++ b/fs/fscache/cache.c
@@ -194,7 +194,7 @@ void fscache_init_cache(struct fscache_cache *cache,
         vsnprintf(cache->identifier, sizeof(cache->identifier), idfmt, va);
         va_end(va);
 
-        INIT_WORK(&cache->op_gc, NULL);
+        INIT_WORK(&cache->op_gc, fscache_operation_gc);
         INIT_LIST_HEAD(&cache->link);
         INIT_LIST_HEAD(&cache->object_list);
         INIT_LIST_HEAD(&cache->op_gc_list);
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index 529f4de328c2..014a830c8b37 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -95,7 +95,13 @@ extern void fscache_enqueue_object(struct fscache_object *);
 /*
  * fsc-operation.c
  */
-#define fscache_start_operations(obj) BUG()
+extern int fscache_submit_exclusive_op(struct fscache_object *,
+                                       struct fscache_operation *);
+extern int fscache_submit_op(struct fscache_object *,
+                             struct fscache_operation *);
+extern void fscache_abort_object(struct fscache_object *);
+extern void fscache_start_operations(struct fscache_object *);
+extern void fscache_operation_gc(struct work_struct *);
 
 /*
  * fsc-proc.c
diff --git a/fs/fscache/operation.c b/fs/fscache/operation.c
new file mode 100644
index 000000000000..e7f8d53b8b6b
--- /dev/null
+++ b/fs/fscache/operation.c
@@ -0,0 +1,459 @@
+/* FS-Cache worker operation management routines
+ *
+ * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * See Documentation/filesystems/caching/operations.txt
+ */
+
+#define FSCACHE_DEBUG_LEVEL OPERATION
+#include <linux/module.h>
+#include "internal.h"
+
+atomic_t fscache_op_debug_id;
+EXPORT_SYMBOL(fscache_op_debug_id);
+
+/**
+ * fscache_enqueue_operation - Enqueue an operation for processing
+ * @op: The operation to enqueue
+ *
+ * Enqueue an operation for processing by the FS-Cache thread pool.
+ *
+ * This will get its own ref on the object.
+ */
+void fscache_enqueue_operation(struct fscache_operation *op)
+{
+        _enter("{OBJ%x OP%x,%u}",
+               op->object->debug_id, op->debug_id, atomic_read(&op->usage));
+
+        ASSERT(op->processor != NULL);
+        ASSERTCMP(op->object->state, >=, FSCACHE_OBJECT_AVAILABLE);
+        ASSERTCMP(atomic_read(&op->usage), >, 0);
+
+        if (list_empty(&op->pend_link)) {
+                switch (op->flags & FSCACHE_OP_TYPE) {
+                case FSCACHE_OP_FAST:
+                        _debug("queue fast");
+                        atomic_inc(&op->usage);
+                        if (!schedule_work(&op->fast_work))
+                                fscache_put_operation(op);
+                        break;
+                case FSCACHE_OP_SLOW:
+                        _debug("queue slow");
+                        slow_work_enqueue(&op->slow_work);
+                        break;
+                case FSCACHE_OP_MYTHREAD:
+                        _debug("queue for caller's attention");
+                        break;
+                default:
+                        printk(KERN_ERR "FS-Cache: Unexpected op type %lx",
+                               op->flags);
+                        BUG();
+                        break;
+                }
+                fscache_stat(&fscache_n_op_enqueue);
+        }
+}
+EXPORT_SYMBOL(fscache_enqueue_operation);
+
+/*
+ * start an op running
+ */
+static void fscache_run_op(struct fscache_object *object,
+                           struct fscache_operation *op)
+{
+        object->n_in_progress++;
+        if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
+                wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
+        if (op->processor)
+                fscache_enqueue_operation(op);
+        fscache_stat(&fscache_n_op_run);
+}
+
+/*
+ * submit an exclusive operation for an object
+ * - other ops are excluded from running simultaneously with this one
+ * - this gets any extra refs it needs on an op
+ */
+int fscache_submit_exclusive_op(struct fscache_object *object,
+                                struct fscache_operation *op)
+{
+        int ret;
+
+        _enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
+
+        spin_lock(&object->lock);
+        ASSERTCMP(object->n_ops, >=, object->n_in_progress);
+        ASSERTCMP(object->n_ops, >=, object->n_exclusive);
+
+        ret = -ENOBUFS;
+        if (fscache_object_is_active(object)) {
+                op->object = object;
+                object->n_ops++;
+                object->n_exclusive++;  /* reads and writes must wait */
+
+                if (object->n_ops > 0) {
+                        atomic_inc(&op->usage);
+                        list_add_tail(&op->pend_link, &object->pending_ops);
+                        fscache_stat(&fscache_n_op_pend);
+                } else if (!list_empty(&object->pending_ops)) {
+                        atomic_inc(&op->usage);
+                        list_add_tail(&op->pend_link, &object->pending_ops);
+                        fscache_stat(&fscache_n_op_pend);
+                        fscache_start_operations(object);
+                } else {
+                        ASSERTCMP(object->n_in_progress, ==, 0);
+                        fscache_run_op(object, op);
+                }
+
+                /* need to issue a new write op after this */
+                clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
+                ret = 0;
+        } else if (object->state == FSCACHE_OBJECT_CREATING) {
+                op->object = object;
+                object->n_ops++;
+                object->n_exclusive++;  /* reads and writes must wait */
+                atomic_inc(&op->usage);
+                list_add_tail(&op->pend_link, &object->pending_ops);
+                fscache_stat(&fscache_n_op_pend);
+                ret = 0;
+        } else {
+                /* not allowed to submit ops in any other state */
+                BUG();
+        }
+
+        spin_unlock(&object->lock);
+        return ret;
+}
+
+/*
+ * report an unexpected submission
+ */
+static void fscache_report_unexpected_submission(struct fscache_object *object,
+                                                 struct fscache_operation *op,
+                                                 unsigned long ostate)
+{
+        static bool once_only;
+        struct fscache_operation *p;
+        unsigned n;
+
+        if (once_only)
+                return;
+        once_only = true;
+
+        kdebug("unexpected submission OP%x [OBJ%x %s]",
+               op->debug_id, object->debug_id,
+               fscache_object_states[object->state]);
+        kdebug("objstate=%s [%s]",
+               fscache_object_states[object->state],
+               fscache_object_states[ostate]);
+        kdebug("objflags=%lx", object->flags);
+        kdebug("objevent=%lx [%lx]", object->events, object->event_mask);
+        kdebug("ops=%u inp=%u exc=%u",
+               object->n_ops, object->n_in_progress, object->n_exclusive);
+
+        if (!list_empty(&object->pending_ops)) {
+                n = 0;
+                list_for_each_entry(p, &object->pending_ops, pend_link) {
+                        ASSERTCMP(p->object, ==, object);
+                        kdebug("%p %p", op->processor, op->release);
+                        n++;
+                }
+
+                kdebug("n=%u", n);
+        }
+
+        dump_stack();
+}
+
+/*
+ * submit an operation for an object
+ * - objects may be submitted only in the following states:
+ *   - during object creation (write ops may be submitted)
+ *   - whilst the object is active
+ *   - after an I/O error incurred in one of the two above states (op rejected)
+ * - this gets any extra refs it needs on an op
+ */
+int fscache_submit_op(struct fscache_object *object,
+                      struct fscache_operation *op)
+{
+        unsigned long ostate;
+        int ret;
+
+        _enter("{OBJ%x OP%x},{%u}",
+               object->debug_id, op->debug_id, atomic_read(&op->usage));
+
+        ASSERTCMP(atomic_read(&op->usage), >, 0);
+
+        spin_lock(&object->lock);
+        ASSERTCMP(object->n_ops, >=, object->n_in_progress);
+        ASSERTCMP(object->n_ops, >=, object->n_exclusive);
+
+        ostate = object->state;
+        smp_rmb();
+
+        if (fscache_object_is_active(object)) {
+                op->object = object;
+                object->n_ops++;
+
+                if (object->n_exclusive > 0) {
+                        atomic_inc(&op->usage);
+                        list_add_tail(&op->pend_link, &object->pending_ops);
+                        fscache_stat(&fscache_n_op_pend);
+                } else if (!list_empty(&object->pending_ops)) {
+                        atomic_inc(&op->usage);
+                        list_add_tail(&op->pend_link, &object->pending_ops);
+                        fscache_stat(&fscache_n_op_pend);
+                        fscache_start_operations(object);
+                } else {
+                        ASSERTCMP(object->n_exclusive, ==, 0);
+                        fscache_run_op(object, op);
+                }
+                ret = 0;
+        } else if (object->state == FSCACHE_OBJECT_CREATING) {
+                op->object = object;
+                object->n_ops++;
+                atomic_inc(&op->usage);
+                list_add_tail(&op->pend_link, &object->pending_ops);
+                fscache_stat(&fscache_n_op_pend);
+                ret = 0;
+        } else if (!test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
+                fscache_report_unexpected_submission(object, op, ostate);
+                ASSERT(!fscache_object_is_active(object));
+                ret = -ENOBUFS;
+        } else {
+                ret = -ENOBUFS;
+        }
+
+        spin_unlock(&object->lock);
+        return ret;
+}
+
+/*
+ * queue an object for withdrawal on error, aborting all following asynchronous
+ * operations
+ */
+void fscache_abort_object(struct fscache_object *object)
+{
+        _enter("{OBJ%x}", object->debug_id);
+
+        fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
+}
+
+/*
+ * jump start the operation processing on an object
+ * - caller must hold object->lock
+ */
+void fscache_start_operations(struct fscache_object *object)
+{
+        struct fscache_operation *op;
+        bool stop = false;
+
+        while (!list_empty(&object->pending_ops) && !stop) {
+                op = list_entry(object->pending_ops.next,
+                                struct fscache_operation, pend_link);
+
+                if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
+                        if (object->n_in_progress > 0)
+                                break;
+                        stop = true;
+                }
+                list_del_init(&op->pend_link);
+                object->n_in_progress++;
+
+                if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
+                        wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
+                if (op->processor)
+                        fscache_enqueue_operation(op);
+
+                /* the pending queue was holding a ref on the object */
+                fscache_put_operation(op);
+        }
+
+        ASSERTCMP(object->n_in_progress, <=, object->n_ops);
+
+        _debug("woke %d ops on OBJ%x",
+               object->n_in_progress, object->debug_id);
+}
+
+/*
+ * release an operation
+ * - queues pending ops if this is the last in-progress op
+ */
+void fscache_put_operation(struct fscache_operation *op)
+{
+        struct fscache_object *object;
+        struct fscache_cache *cache;
+
+        _enter("{OBJ%x OP%x,%d}",
+               op->object->debug_id, op->debug_id, atomic_read(&op->usage));
+
+        ASSERTCMP(atomic_read(&op->usage), >, 0);
+
+        if (!atomic_dec_and_test(&op->usage))
+                return;
+
+        _debug("PUT OP");
+        if (test_and_set_bit(FSCACHE_OP_DEAD, &op->flags))
+                BUG();
+
+        fscache_stat(&fscache_n_op_release);
+
+        if (op->release) {
+                op->release(op);
+                op->release = NULL;
+        }
+
+        object = op->object;
+
+        /* now... we may get called with the object spinlock held, so we
+         * complete the cleanup here only if we can immediately acquire the
+         * lock, and defer it otherwise */
+        if (!spin_trylock(&object->lock)) {
+                _debug("defer put");
+                fscache_stat(&fscache_n_op_deferred_release);
+
+                cache = object->cache;
+                spin_lock(&cache->op_gc_list_lock);
+                list_add_tail(&op->pend_link, &cache->op_gc_list);
+                spin_unlock(&cache->op_gc_list_lock);
+                schedule_work(&cache->op_gc);
+                _leave(" [defer]");
+                return;
+        }
+
+        if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
+                ASSERTCMP(object->n_exclusive, >, 0);
+                object->n_exclusive--;
+        }
+
+        ASSERTCMP(object->n_in_progress, >, 0);
+        object->n_in_progress--;
+        if (object->n_in_progress == 0)
+                fscache_start_operations(object);
+
+        ASSERTCMP(object->n_ops, >, 0);
+        object->n_ops--;
+        if (object->n_ops == 0)
+                fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
+
+        spin_unlock(&object->lock);
+
+        kfree(op);
+        _leave(" [done]");
+}
+EXPORT_SYMBOL(fscache_put_operation);
+
+/*
+ * garbage collect operations that have had their release deferred
+ */
+void fscache_operation_gc(struct work_struct *work)
+{
+        struct fscache_operation *op;
+        struct fscache_object *object;
+        struct fscache_cache *cache =
+                container_of(work, struct fscache_cache, op_gc);
+        int count = 0;
+
+        _enter("");
+
+        do {
+                spin_lock(&cache->op_gc_list_lock);
+                if (list_empty(&cache->op_gc_list)) {
+                        spin_unlock(&cache->op_gc_list_lock);
+                        break;
+                }
+
+                op = list_entry(cache->op_gc_list.next,
+                                struct fscache_operation, pend_link);
+                list_del(&op->pend_link);
+                spin_unlock(&cache->op_gc_list_lock);
+
+                object = op->object;
+
+                _debug("GC DEFERRED REL OBJ%x OP%x",
+                       object->debug_id, op->debug_id);
+                fscache_stat(&fscache_n_op_gc);
+
+                ASSERTCMP(atomic_read(&op->usage), ==, 0);
+
+                spin_lock(&object->lock);
+                if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
+                        ASSERTCMP(object->n_exclusive, >, 0);
+                        object->n_exclusive--;
+                }
+
+                ASSERTCMP(object->n_in_progress, >, 0);
+                object->n_in_progress--;
+                if (object->n_in_progress == 0)
+                        fscache_start_operations(object);
+
+                ASSERTCMP(object->n_ops, >, 0);
+                object->n_ops--;
+                if (object->n_ops == 0)
+                        fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
+
+                spin_unlock(&object->lock);
+
+        } while (count++ < 20);
+
+        if (!list_empty(&cache->op_gc_list))
+                schedule_work(&cache->op_gc);
+
+        _leave("");
+}
+
+/*
+ * allow the slow work item processor to get a ref on an operation
+ */
+static int fscache_op_get_ref(struct slow_work *work)
+{
+        struct fscache_operation *op =
+                container_of(work, struct fscache_operation, slow_work);
+
+        atomic_inc(&op->usage);
+        return 0;
+}
+
+/*
+ * allow the slow work item processor to discard a ref on an operation
+ */
+static void fscache_op_put_ref(struct slow_work *work)
+{
+        struct fscache_operation *op =
+                container_of(work, struct fscache_operation, slow_work);
+
+        fscache_put_operation(op);
+}
+
+/*
+ * execute an operation using the slow thread pool to provide processing context
+ * - the caller holds a ref to this object, so we don't need to hold one
+ */
+static void fscache_op_execute(struct slow_work *work)
+{
+        struct fscache_operation *op =
+                container_of(work, struct fscache_operation, slow_work);
+        unsigned long start;
+
+        _enter("{OBJ%x OP%x,%d}",
+               op->object->debug_id, op->debug_id, atomic_read(&op->usage));
+
+        ASSERT(op->processor != NULL);
+        start = jiffies;
+        op->processor(op);
+        fscache_hist(fscache_ops_histogram, start);
+
+        _leave("");
+}
+
+const struct slow_work_ops fscache_op_slow_work_ops = {
+        .get_ref        = fscache_op_get_ref,
+        .put_ref        = fscache_op_put_ref,
+        .execute        = fscache_op_execute,
+};