1 files changed, 529 insertions, 0 deletions

diff --git a/fs/fscache/operation.c b/fs/fscache/operation.c
new file mode 100644
index 000000000..e7b87a0e5
--- /dev/null
+++ b/fs/fscache/operation.c
@@ -0,0 +1,529 @@
+/* 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 <linux/seq_file.h>
+#include <linux/slab.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(list_empty(&op->pend_link));
+	ASSERT(op->processor != NULL);
+	ASSERT(fscache_object_is_available(op->object));
+	ASSERTCMP(atomic_read(&op->usage), >, 0);
+	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
+
+	fscache_stat(&fscache_n_op_enqueue);
+	switch (op->flags & FSCACHE_OP_TYPE) {
+	case FSCACHE_OP_ASYNC:
+		_debug("queue async");
+		atomic_inc(&op->usage);
+		if (!queue_work(fscache_op_wq, &op->work))
+			fscache_put_operation(op);
+		break;
+	case FSCACHE_OP_MYTHREAD:
+		_debug("queue for caller's attention");
+		break;
+	default:
+		pr_err("Unexpected op type %lx", op->flags);
+		BUG();
+		break;
+	}
+}
+EXPORT_SYMBOL(fscache_enqueue_operation);
+
+/*
+ * start an op running
+ */
+static void fscache_run_op(struct fscache_object *object,
+			   struct fscache_operation *op)
+{
+	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
+
+	op->state = FSCACHE_OP_ST_IN_PROGRESS;
+	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);
+
+	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
+	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);
+	ASSERT(list_empty(&op->pend_link));
+
+	op->state = FSCACHE_OP_ST_PENDING;
+	if (fscache_object_is_active(object)) {
+		op->object = object;
+		object->n_ops++;
+		object->n_exclusive++;	/* reads and writes must wait */
+
+		if (object->n_in_progress > 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 (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
+		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 {
+		/* If we're in any other state, there must have been an I/O
+		 * error of some nature.
+		 */
+		ASSERT(test_bit(FSCACHE_IOERROR, &object->cache->flags));
+		ret = -EIO;
+	}
+
+	spin_unlock(&object->lock);
+	return ret;
+}
+
+/*
+ * report an unexpected submission
+ */
+static void fscache_report_unexpected_submission(struct fscache_object *object,
+						 struct fscache_operation *op,
+						 const struct fscache_state *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, object->state->name);
+	kdebug("objstate=%s [%s]", object->state->name, ostate->name);
+	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)
+{
+	const struct fscache_state *ostate;
+	int ret;
+
+	_enter("{OBJ%x OP%x},{%u}",
+	       object->debug_id, op->debug_id, atomic_read(&op->usage));
+
+	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
+	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);
+	ASSERT(list_empty(&op->pend_link));
+
+	ostate = object->state;
+	smp_rmb();
+
+	op->state = FSCACHE_OP_ST_PENDING;
+	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 (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
+		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 (fscache_object_is_dying(object)) {
+		fscache_stat(&fscache_n_op_rejected);
+		op->state = FSCACHE_OP_ST_CANCELLED;
+		ret = -ENOBUFS;
+	} else if (!test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
+		fscache_report_unexpected_submission(object, op, ostate);
+		ASSERT(!fscache_object_is_active(object));
+		op->state = FSCACHE_OP_ST_CANCELLED;
+		ret = -ENOBUFS;
+	} else {
+		op->state = FSCACHE_OP_ST_CANCELLED;
+		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.  The 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);
+		fscache_run_op(object, 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);
+}
+
+/*
+ * cancel an operation that's pending on an object
+ */
+int fscache_cancel_op(struct fscache_operation *op,
+		      void (*do_cancel)(struct fscache_operation *))
+{
+	struct fscache_object *object = op->object;
+	int ret;
+
+	_enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
+
+	ASSERTCMP(op->state, >=, FSCACHE_OP_ST_PENDING);
+	ASSERTCMP(op->state, !=, FSCACHE_OP_ST_CANCELLED);
+	ASSERTCMP(atomic_read(&op->usage), >, 0);
+
+	spin_lock(&object->lock);
+
+	ret = -EBUSY;
+	if (op->state == FSCACHE_OP_ST_PENDING) {
+		ASSERT(!list_empty(&op->pend_link));
+		fscache_stat(&fscache_n_op_cancelled);
+		list_del_init(&op->pend_link);
+		if (do_cancel)
+			do_cancel(op);
+		op->state = FSCACHE_OP_ST_CANCELLED;
+		if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
+			object->n_exclusive--;
+		if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
+			wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
+		fscache_put_operation(op);
+		ret = 0;
+	}
+
+	spin_unlock(&object->lock);
+	_leave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * Cancel all pending operations on an object
+ */
+void fscache_cancel_all_ops(struct fscache_object *object)
+{
+	struct fscache_operation *op;
+
+	_enter("OBJ%x", object->debug_id);
+
+	spin_lock(&object->lock);
+
+	while (!list_empty(&object->pending_ops)) {
+		op = list_entry(object->pending_ops.next,
+				struct fscache_operation, pend_link);
+		fscache_stat(&fscache_n_op_cancelled);
+		list_del_init(&op->pend_link);
+
+		ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
+		op->state = FSCACHE_OP_ST_CANCELLED;
+
+		if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
+			object->n_exclusive--;
+		if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
+			wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
+		fscache_put_operation(op);
+		cond_resched_lock(&object->lock);
+	}
+
+	spin_unlock(&object->lock);
+	_leave("");
+}
+
+/*
+ * Record the completion or cancellation of an in-progress operation.
+ */
+void fscache_op_complete(struct fscache_operation *op, bool cancelled)
+{
+	struct fscache_object *object = op->object;
+
+	_enter("OBJ%x", object->debug_id);
+
+	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
+	ASSERTCMP(object->n_in_progress, >, 0);
+	ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
+		    object->n_exclusive, >, 0);
+	ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
+		    object->n_in_progress, ==, 1);
+
+	spin_lock(&object->lock);
+
+	op->state = cancelled ?
+		FSCACHE_OP_ST_CANCELLED : FSCACHE_OP_ST_COMPLETE;
+
+	if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
+		object->n_exclusive--;
+	object->n_in_progress--;
+	if (object->n_in_progress == 0)
+		fscache_start_operations(object);
+
+	spin_unlock(&object->lock);
+	_leave("");
+}
+EXPORT_SYMBOL(fscache_op_complete);
+
+/*
+ * 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");
+	ASSERTIFCMP(op->state != FSCACHE_OP_ST_COMPLETE,
+		    op->state, ==, FSCACHE_OP_ST_CANCELLED);
+	op->state = FSCACHE_OP_ST_DEAD;
+
+	fscache_stat(&fscache_n_op_release);
+
+	if (op->release) {
+		op->release(op);
+		op->release = NULL;
+	}
+
+	object = op->object;
+
+	if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
+		atomic_dec(&object->n_reads);
+	if (test_bit(FSCACHE_OP_UNUSE_COOKIE, &op->flags))
+		fscache_unuse_cookie(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;
+	}
+
+	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;
+		spin_lock(&object->lock);
+
+		_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);
+		ASSERTCMP(op->state, ==, FSCACHE_OP_ST_DEAD);
+
+		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);
+
+	} while (count++ < 20);
+
+	if (!list_empty(&cache->op_gc_list))
+		schedule_work(&cache->op_gc);
+
+	_leave("");
+}
+
+/*
+ * execute an operation using fs_op_wq to provide processing context -
+ * the caller holds a ref to this object, so we don't need to hold one
+ */
+void fscache_op_work_func(struct work_struct *work)
+{
+	struct fscache_operation *op =
+		container_of(work, struct fscache_operation, 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);
+	fscache_put_operation(op);
+
+	_leave("");
+}