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authorDavid Howells <dhowells@redhat.com>2009-11-19 18:11:19 +0000
committerDavid Howells <dhowells@redhat.com>2009-11-19 18:11:19 +0000
commit5753c441889253e4323eee85f791a1d64cf08196 (patch)
tree55a0de053d0593d96e99710f978277df668412d1 /fs/fscache/operation.c
parentb34df792b4e9e311db47fad27949095d0629c197 (diff)
downloadop-kernel-dev-5753c441889253e4323eee85f791a1d64cf08196.zip
op-kernel-dev-5753c441889253e4323eee85f791a1d64cf08196.tar.gz
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: David Howells <dhowells@redhat.com>
Diffstat (limited to 'fs/fscache/operation.c')
-rw-r--r--fs/fscache/operation.c82
1 files changed, 54 insertions, 28 deletions
diff --git a/fs/fscache/operation.c b/fs/fscache/operation.c
index 09e43b6..296492e 100644
--- a/fs/fscache/operation.c
+++ b/fs/fscache/operation.c
@@ -34,32 +34,31 @@ 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)) {
- 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);
+ fscache_stat(&fscache_n_op_enqueue);
+ 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;
}
}
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);
@@ -291,6 +287,36 @@ void fscache_start_operations(struct fscache_object *object)
}
/*
+ * 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
*/
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