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Commit 8af7c124 authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarDavid Howells <dhowells@redhat.com>
parent 8b8edefa

fs/cachefiles/rdwr.c

+2 −2
Original line number Diff line number Diff line
@@ -422,7 +422,7 @@ int cachefiles_read_or_alloc_page(struct fscache_retrieval *op, 
	shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;



	op->op.flags &= FSCACHE_OP_KEEP_FLAGS;

	op->op.flags |= FSCACHE_OP_FAST;

	op->op.flags |= FSCACHE_OP_ASYNC;

	op->op.processor = cachefiles_read_copier;



	pagevec_init(&pagevec, 0);
@@ -729,7 +729,7 @@ int cachefiles_read_or_alloc_pages(struct fscache_retrieval *op, 
	pagevec_init(&pagevec, 0);



	op->op.flags &= FSCACHE_OP_KEEP_FLAGS;

	op->op.flags |= FSCACHE_OP_FAST;

	op->op.flags |= FSCACHE_OP_ASYNC;

	op->op.processor = cachefiles_read_copier;



	INIT_LIST_HEAD(&backpages);

fs/fscache/internal.h

+1 −0
Original line number Diff line number Diff line
@@ -83,6 +83,7 @@ extern unsigned fscache_defer_create; 
extern unsigned fscache_debug;

extern struct kobject *fscache_root;

extern struct workqueue_struct *fscache_object_wq;

extern struct workqueue_struct *fscache_op_wq;

DECLARE_PER_CPU(wait_queue_head_t, fscache_object_cong_wait);



static inline bool fscache_object_congested(void)

fs/fscache/main.c

+23 −0
Original line number Diff line number Diff line
@@ -42,11 +42,13 @@ MODULE_PARM_DESC(fscache_debug, 


struct kobject *fscache_root;

struct workqueue_struct *fscache_object_wq;

struct workqueue_struct *fscache_op_wq;



DEFINE_PER_CPU(wait_queue_head_t, fscache_object_cong_wait);



/* these values serve as lower bounds, will be adjusted in fscache_init() */

static unsigned fscache_object_max_active = 4;

static unsigned fscache_op_max_active = 2;



#ifdef CONFIG_SYSCTL

static struct ctl_table_header *fscache_sysctl_header;
@@ -74,6 +76,14 @@ ctl_table fscache_sysctls[] = { 
		.proc_handler	= fscache_max_active_sysctl,

		.extra1		= &fscache_object_wq,

	},

	{

		.procname	= "operation_max_active",

		.data		= &fscache_op_max_active,

		.maxlen		= sizeof(unsigned),

		.mode		= 0644,

		.proc_handler	= fscache_max_active_sysctl,

		.extra1		= &fscache_op_wq,

	},

	{}

};
@@ -110,6 +120,16 @@ static int __init fscache_init(void) 
	if (!fscache_object_wq)

		goto error_object_wq;



	fscache_op_max_active =

		clamp_val(fscache_object_max_active / 2,

			  fscache_op_max_active, WQ_UNBOUND_MAX_ACTIVE);



	ret = -ENOMEM;

	fscache_op_wq = alloc_workqueue("fscache_operation", WQ_UNBOUND,

					fscache_op_max_active);

	if (!fscache_op_wq)

		goto error_op_wq;



	for_each_possible_cpu(cpu)

		init_waitqueue_head(&per_cpu(fscache_object_cong_wait, cpu));
@@ -152,6 +172,8 @@ error_sysctl: 
#endif

	fscache_proc_cleanup();

error_proc:

	destroy_workqueue(fscache_op_wq);

error_op_wq:

	destroy_workqueue(fscache_object_wq);

error_object_wq:

	slow_work_unregister_user(THIS_MODULE);
@@ -172,6 +194,7 @@ static void __exit fscache_exit(void) 
	kmem_cache_destroy(fscache_cookie_jar);

	unregister_sysctl_table(fscache_sysctl_header);

	fscache_proc_cleanup();

	destroy_workqueue(fscache_op_wq);

	destroy_workqueue(fscache_object_wq);

	slow_work_unregister_user(THIS_MODULE);

	printk(KERN_NOTICE "FS-Cache: Unloaded\n");

fs/fscache/operation.c

+8 −59
Original line number Diff line number Diff line
@@ -42,16 +42,12 @@ void fscache_enqueue_operation(struct fscache_operation *op) 


	fscache_stat(&fscache_n_op_enqueue);

	switch (op->flags & FSCACHE_OP_TYPE) {

	case FSCACHE_OP_FAST:

		_debug("queue fast");

	case FSCACHE_OP_ASYNC:

		_debug("queue async");

		atomic_inc(&op->usage);

		if (!schedule_work(&op->fast_work))

		if (!queue_work(fscache_op_wq, &op->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;
@@ -455,36 +451,13 @@ void fscache_operation_gc(struct work_struct *work) 
}



/*

 * allow the slow work item processor to get a ref on an operation

 * 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

 */

static int fscache_op_get_ref(struct slow_work *work)

void fscache_op_work_func(struct work_struct *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);

		container_of(work, struct fscache_operation, work);

	unsigned long start;



	_enter("{OBJ%x OP%x,%d}",
@@ -494,31 +467,7 @@ static void fscache_op_execute(struct slow_work *work) 
	start = jiffies;

	op->processor(op);

	fscache_hist(fscache_ops_histogram, start);

	fscache_put_operation(op);



	_leave("");

}
 


/*

 * describe an operation for slow-work debugging

 */

#ifdef CONFIG_SLOW_WORK_DEBUG

static void fscache_op_desc(struct slow_work *work, struct seq_file *m)

{

	struct fscache_operation *op =

		container_of(work, struct fscache_operation, slow_work);



	seq_printf(m, "FSC: OBJ%x OP%x: %s/%s fl=%lx",

		   op->object->debug_id, op->debug_id,

		   op->name, op->state, op->flags);

}

#endif



const struct slow_work_ops fscache_op_slow_work_ops = {

	.owner		= THIS_MODULE,

	.get_ref	= fscache_op_get_ref,

	.put_ref	= fscache_op_put_ref,

	.execute	= fscache_op_execute,

#ifdef CONFIG_SLOW_WORK_DEBUG

	.desc		= fscache_op_desc,

#endif

};

fs/fscache/page.c

+8 −28
Original line number Diff line number Diff line
@@ -105,7 +105,7 @@ bool __fscache_maybe_release_page(struct fscache_cookie *cookie, 


page_busy:

	/* we might want to wait here, but that could deadlock the allocator as

	 * the slow-work threads writing to the cache may all end up sleeping

	 * the work threads writing to the cache may all end up sleeping

	 * on memory allocation */

	fscache_stat(&fscache_n_store_vmscan_busy);

	return false;
@@ -188,9 +188,8 @@ int __fscache_attr_changed(struct fscache_cookie *cookie) 
		return -ENOMEM;

	}



	fscache_operation_init(op, NULL);

	fscache_operation_init_slow(op, fscache_attr_changed_op);

	op->flags = FSCACHE_OP_SLOW | (1 << FSCACHE_OP_EXCLUSIVE);

	fscache_operation_init(op, fscache_attr_changed_op, NULL);

	op->flags = FSCACHE_OP_ASYNC | (1 << FSCACHE_OP_EXCLUSIVE);

	fscache_set_op_name(op, "Attr");



	spin_lock(&cookie->lock);
@@ -217,24 +216,6 @@ nobufs: 
}

EXPORT_SYMBOL(__fscache_attr_changed);



/*

 * handle secondary execution given to a retrieval op on behalf of the

 * cache

 */

static void fscache_retrieval_work(struct work_struct *work)

{

	struct fscache_retrieval *op =

		container_of(work, struct fscache_retrieval, op.fast_work);

	unsigned long start;



	_enter("{OP%x}", op->op.debug_id);



	start = jiffies;

	op->op.processor(&op->op);

	fscache_hist(fscache_ops_histogram, start);

	fscache_put_operation(&op->op);

}



/*

 * release a retrieval op reference

 */
@@ -269,13 +250,12 @@ static struct fscache_retrieval *fscache_alloc_retrieval( 
		return NULL;

	}



	fscache_operation_init(&op->op, fscache_release_retrieval_op);

	fscache_operation_init(&op->op, NULL, fscache_release_retrieval_op);

	op->op.flags	= FSCACHE_OP_MYTHREAD | (1 << FSCACHE_OP_WAITING);

	op->mapping	= mapping;

	op->end_io_func	= end_io_func;

	op->context	= context;

	op->start_time	= jiffies;

	INIT_WORK(&op->op.fast_work, fscache_retrieval_work);

	INIT_LIST_HEAD(&op->to_do);

	fscache_set_op_name(&op->op, "Retr");

	return op;
@@ -795,9 +775,9 @@ int __fscache_write_page(struct fscache_cookie *cookie, 
	if (!op)

		goto nomem;



	fscache_operation_init(&op->op, fscache_release_write_op);

	fscache_operation_init_slow(&op->op, fscache_write_op);

	op->op.flags = FSCACHE_OP_SLOW | (1 << FSCACHE_OP_WAITING);

	fscache_operation_init(&op->op, fscache_write_op,

			       fscache_release_write_op);

	op->op.flags = FSCACHE_OP_ASYNC | (1 << FSCACHE_OP_WAITING);

	fscache_set_op_name(&op->op, "Write1");



	ret = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
@@ -852,7 +832,7 @@ int __fscache_write_page(struct fscache_cookie *cookie, 
	fscache_stat(&fscache_n_store_ops);

	fscache_stat(&fscache_n_stores_ok);



	/* the slow work queue now carries its own ref on the object */

	/* the work queue now carries its own ref on the object */

	fscache_put_operation(&op->op);

	_leave(" = 0");

	return 0;