Commit 5753c441 authored by David Howells's avatar David Howells
Browse files

FS-Cache: Permit cache retrieval ops to be interrupted in the initial wait phase 



Permit the operations to retrieve data from the cache or to allocate space in
the cache for future writes to be interrupted whilst they're waiting for
permission for the operation to proceed.  Typically this wait occurs whilst the
cache object is being looked up on disk in the background.

If an interruption occurs, and the operation has not yet been given the
go-ahead to run, the operation is dequeued and cancelled, and control returns
to the read operation of the netfs routine with none of the requested pages
having been read or in any way marked as known by the cache.

This means that the initial wait is done interruptibly rather than
uninterruptibly.

In addition, extra stats values are made available to show the number of ops
cancelled and the number of cache space allocations interrupted.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
parent b34df792

Documentation/filesystems/caching/fscache.txt

+2 −0
Original line number Diff line number Diff line
@@ -250,6 +250,7 @@ proc files. 
		ok=N	Number of successful alloc reqs

		wt=N	Number of alloc reqs that waited on lookup completion

		nbf=N	Number of alloc reqs rejected -ENOBUFS

		int=N	Number of alloc reqs aborted -ERESTARTSYS

		ops=N	Number of alloc reqs submitted

		owt=N	Number of alloc reqs waited for CPU time

	Retrvls	n=N	Number of retrieval (read) requests seen
@@ -271,6 +272,7 @@ proc files. 
	Ops	pend=N	Number of times async ops added to pending queues

		run=N	Number of times async ops given CPU time

		enq=N	Number of times async ops queued for processing

		can=N	Number of async ops cancelled

		dfr=N	Number of async ops queued for deferred release

		rel=N	Number of async ops released

		gc=N	Number of deferred-release async ops garbage collected

fs/fscache/internal.h

+3 −0
Original line number Diff line number Diff line
@@ -112,6 +112,7 @@ extern int fscache_submit_exclusive_op(struct fscache_object *, 
				       struct fscache_operation *);

extern int fscache_submit_op(struct fscache_object *,

			     struct fscache_operation *);

extern int fscache_cancel_op(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 *);
@@ -140,6 +141,7 @@ extern atomic_t fscache_n_op_enqueue; 
extern atomic_t fscache_n_op_deferred_release;

extern atomic_t fscache_n_op_release;

extern atomic_t fscache_n_op_gc;

extern atomic_t fscache_n_op_cancelled;



extern atomic_t fscache_n_attr_changed;

extern atomic_t fscache_n_attr_changed_ok;
@@ -151,6 +153,7 @@ extern atomic_t fscache_n_allocs; 
extern atomic_t fscache_n_allocs_ok;

extern atomic_t fscache_n_allocs_wait;

extern atomic_t fscache_n_allocs_nobufs;

extern atomic_t fscache_n_allocs_intr;

extern atomic_t fscache_n_alloc_ops;

extern atomic_t fscache_n_alloc_op_waits;

fs/fscache/operation.c

+54 −28
Original line number Diff line number Diff line
@@ -34,11 +34,12 @@ void fscache_enqueue_operation(struct fscache_operation *op) 


	fscache_set_op_state(op, "EnQ");



	ASSERT(list_empty(&op->pend_link));

	ASSERT(op->processor != NULL);

	ASSERTCMP(op->object->state, >=, FSCACHE_OBJECT_AVAILABLE);

	ASSERTCMP(atomic_read(&op->usage), >, 0);



	if (list_empty(&op->pend_link)) {

	fscache_stat(&fscache_n_op_enqueue);

	switch (op->flags & FSCACHE_OP_TYPE) {

	case FSCACHE_OP_FAST:

		_debug("queue fast");
@@ -59,8 +60,6 @@ void fscache_enqueue_operation(struct fscache_operation *op) 
		BUG();

		break;

	}

		fscache_stat(&fscache_n_op_enqueue);

	}

}

EXPORT_SYMBOL(fscache_enqueue_operation);
@@ -97,6 +96,7 @@ int fscache_submit_exclusive_op(struct fscache_object *object, 
	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));



	ret = -ENOBUFS;

	if (fscache_object_is_active(object)) {
@@ -202,6 +202,7 @@ int fscache_submit_op(struct fscache_object *object, 
	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();
@@ -273,12 +274,7 @@ void fscache_start_operations(struct fscache_object *object) 
			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);

		fscache_run_op(object, op);



		/* the pending queue was holding a ref on the object */

		fscache_put_operation(op);
@@ -290,6 +286,36 @@ void fscache_start_operations(struct fscache_object *object) 
	       object->n_in_progress, object->debug_id);

}



/*

 * cancel an operation that's pending on an object

 */

int fscache_cancel_op(struct fscache_operation *op)

{

	struct fscache_object *object = op->object;

	int ret;



	_enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);



	spin_lock(&object->lock);



	ret = -EBUSY;

	if (!list_empty(&op->pend_link)) {

		fscache_stat(&fscache_n_op_cancelled);

		list_del_init(&op->pend_link);

		object->n_ops--;

		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;

}



/*

 * release an operation

 * - queues pending ops if this is the last in-progress op

fs/fscache/page.c

+48 −7
Original line number Diff line number Diff line
@@ -295,8 +295,20 @@ int __fscache_read_or_alloc_page(struct fscache_cookie *cookie, 
	if (test_bit(FSCACHE_OP_WAITING, &op->op.flags)) {

		_debug(">>> WT");

		fscache_stat(&fscache_n_retrieval_op_waits);

		if (wait_on_bit(&op->op.flags, FSCACHE_OP_WAITING,

				fscache_wait_bit_interruptible,

				TASK_INTERRUPTIBLE) < 0) {

			ret = fscache_cancel_op(&op->op);

			if (ret == 0) {

				ret = -ERESTARTSYS;

				goto error;

			}



			/* it's been removed from the pending queue by another

			 * party, so we should get to run shortly */

			wait_on_bit(&op->op.flags, FSCACHE_OP_WAITING,

				    fscache_wait_bit, TASK_UNINTERRUPTIBLE);

		}

		_debug("<<< GO");

	}
@@ -313,6 +325,7 @@ int __fscache_read_or_alloc_page(struct fscache_cookie *cookie, 
		fscache_stat_d(&fscache_n_cop_read_or_alloc_page);

	}



error:

	if (ret == -ENOMEM)

		fscache_stat(&fscache_n_retrievals_nomem);

	else if (ret == -ERESTARTSYS)
@@ -412,8 +425,20 @@ int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie, 
	if (test_bit(FSCACHE_OP_WAITING, &op->op.flags)) {

		_debug(">>> WT");

		fscache_stat(&fscache_n_retrieval_op_waits);

		if (wait_on_bit(&op->op.flags, FSCACHE_OP_WAITING,

				fscache_wait_bit_interruptible,

				TASK_INTERRUPTIBLE) < 0) {

			ret = fscache_cancel_op(&op->op);

			if (ret == 0) {

				ret = -ERESTARTSYS;

				goto error;

			}



			/* it's been removed from the pending queue by another

			 * party, so we should get to run shortly */

			wait_on_bit(&op->op.flags, FSCACHE_OP_WAITING,

				    fscache_wait_bit, TASK_UNINTERRUPTIBLE);

		}

		_debug("<<< GO");

	}
@@ -430,6 +455,7 @@ int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie, 
		fscache_stat_d(&fscache_n_cop_read_or_alloc_pages);

	}



error:

	if (ret == -ENOMEM)

		fscache_stat(&fscache_n_retrievals_nomem);

	else if (ret == -ERESTARTSYS)
@@ -505,8 +531,20 @@ int __fscache_alloc_page(struct fscache_cookie *cookie, 
	if (test_bit(FSCACHE_OP_WAITING, &op->op.flags)) {

		_debug(">>> WT");

		fscache_stat(&fscache_n_alloc_op_waits);

		if (wait_on_bit(&op->op.flags, FSCACHE_OP_WAITING,

				fscache_wait_bit_interruptible,

				TASK_INTERRUPTIBLE) < 0) {

			ret = fscache_cancel_op(&op->op);

			if (ret == 0) {

				ret = -ERESTARTSYS;

				goto error;

			}



			/* it's been removed from the pending queue by another

			 * party, so we should get to run shortly */

			wait_on_bit(&op->op.flags, FSCACHE_OP_WAITING,

				    fscache_wait_bit, TASK_UNINTERRUPTIBLE);

		}

		_debug("<<< GO");

	}
@@ -515,7 +553,10 @@ int __fscache_alloc_page(struct fscache_cookie *cookie, 
	ret = object->cache->ops->allocate_page(op, page, gfp);

	fscache_stat_d(&fscache_n_cop_allocate_page);



	if (ret < 0)

error:

	if (ret == -ERESTARTSYS)

		fscache_stat(&fscache_n_allocs_intr);

	else if (ret < 0)

		fscache_stat(&fscache_n_allocs_nobufs);

	else

		fscache_stat(&fscache_n_allocs_ok);

fs/fscache/stats.c

+8 −4
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ atomic_t fscache_n_op_requeue; 
atomic_t fscache_n_op_deferred_release;

atomic_t fscache_n_op_release;

atomic_t fscache_n_op_gc;

atomic_t fscache_n_op_cancelled;



atomic_t fscache_n_attr_changed;

atomic_t fscache_n_attr_changed_ok;
@@ -36,6 +37,7 @@ atomic_t fscache_n_allocs; 
atomic_t fscache_n_allocs_ok;

atomic_t fscache_n_allocs_wait;

atomic_t fscache_n_allocs_nobufs;

atomic_t fscache_n_allocs_intr;

atomic_t fscache_n_alloc_ops;

atomic_t fscache_n_alloc_op_waits;
@@ -169,11 +171,12 @@ static int fscache_stats_show(struct seq_file *m, void *v) 
		   atomic_read(&fscache_n_attr_changed_nomem),

		   atomic_read(&fscache_n_attr_changed_calls));



	seq_printf(m, "Allocs : n=%u ok=%u wt=%u nbf=%u\n",

	seq_printf(m, "Allocs : n=%u ok=%u wt=%u nbf=%u int=%u\n",

		   atomic_read(&fscache_n_allocs),

		   atomic_read(&fscache_n_allocs_ok),

		   atomic_read(&fscache_n_allocs_wait),

		   atomic_read(&fscache_n_allocs_nobufs));

		   atomic_read(&fscache_n_allocs_nobufs),

		   atomic_read(&fscache_n_allocs_intr));

	seq_printf(m, "Allocs : ops=%u owt=%u\n",

		   atomic_read(&fscache_n_alloc_ops),

		   atomic_read(&fscache_n_alloc_op_waits));
@@ -201,10 +204,11 @@ static int fscache_stats_show(struct seq_file *m, void *v) 
		   atomic_read(&fscache_n_store_ops),

		   atomic_read(&fscache_n_store_calls));



	seq_printf(m, "Ops    : pend=%u run=%u enq=%u\n",

	seq_printf(m, "Ops    : pend=%u run=%u enq=%u can=%u\n",

		   atomic_read(&fscache_n_op_pend),

		   atomic_read(&fscache_n_op_run),

		   atomic_read(&fscache_n_op_enqueue));

		   atomic_read(&fscache_n_op_enqueue),

		   atomic_read(&fscache_n_op_cancelled));

	seq_printf(m, "Ops    : dfr=%u rel=%u gc=%u\n",

		   atomic_read(&fscache_n_op_deferred_release),

		   atomic_read(&fscache_n_op_release),

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