FS-Cache: The operation cancellation method needs calling in more places

Any time an incomplete operation is cancelled, the operation cancellation
function needs to be called to clean up.  This is currently being passed
directly to some of the functions that might want to call it, but not all.

Instead, pass the cancellation method pointer to the fscache_operation_init()
and have that cache it in the operation struct.  Further, plug in a dummy
cancellation handler if the caller declines to set one as this allows us to
call the function unconditionally (the extra overhead isn't worth bothering
about as we don't expect to be calling this typically).

The cancellation method must thence be called everywhere the CANCELLED state
is set.  Note that we call it *before* setting the CANCELLED state such that
the method can use the old state value to guide its operation.

fscache_do_cancel_retrieval() needs moving higher up in the sources so that
the init function can use it now.

Without this, the following oops may be seen:

	FS-Cache: Assertion failed
	FS-Cache: 3 == 0 is false
	------------[ cut here ]------------
	kernel BUG at ../fs/fscache/page.c:261!
	...
	RIP: 0010:[<ffffffffa0089c1b>]  fscache_release_retrieval_op+0x77/0x100
	 [<ffffffffa008853d>] fscache_put_operation+0x114/0x2da
	 [<ffffffffa008b8c2>] __fscache_read_or_alloc_pages+0x358/0x3b3
	 [<ffffffffa00b761f>] __nfs_readpages_from_fscache+0x59/0xbf [nfs]
	 [<ffffffffa00b06c5>] nfs_readpages+0x10c/0x185 [nfs]
	 [<ffffffff81124925>] ? alloc_pages_current+0x119/0x13e
	 [<ffffffff810ee5fd>] ? __page_cache_alloc+0xfb/0x10a
	 [<ffffffff810f87f8>] __do_page_cache_readahead+0x188/0x22c
	 [<ffffffff810f8b3a>] ondemand_readahead+0x29e/0x2af
	 [<ffffffff810f8c92>] page_cache_sync_readahead+0x38/0x3a
	 [<ffffffff810ef337>] generic_file_read_iter+0x1a2/0x55a
	 [<ffffffffa00a9dff>] ? nfs_revalidate_mapping+0xd6/0x288 [nfs]
	 [<ffffffffa00a6a23>] nfs_file_read+0x49/0x70 [nfs]
	 [<ffffffff811363be>] new_sync_read+0x78/0x9c
	 [<ffffffff81137164>] __vfs_read+0x13/0x38
	 [<ffffffff8113721e>] vfs_read+0x95/0x121
	 [<ffffffff811372f6>] SyS_read+0x4c/0x8a
	 [<ffffffff81557a52>] system_call_fastpath+0x12/0x17

The assertion is showing that the remaining number of pages (n_pages) is not 0
when the operation is being released.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Steve Dickson <steved@redhat.com>
Acked-by: Jeff Layton <jeff.layton@primarydata.com>

1 files changed, 24 insertions, 7 deletions

diff --git a/fs/fscache/operation.c b/fs/fscache/operation.c
index c76c097..57d4abb 100644
--- a/fs/fscache/operation.c
+++ b/fs/fscache/operation.c
@@ -20,6 +20,10 @@
 atomic_t fscache_op_debug_id;
 EXPORT_SYMBOL(fscache_op_debug_id);
 
+static void fscache_operation_dummy_cancel(struct fscache_operation *op)
+{
+}
+
 /**
  * fscache_operation_init - Do basic initialisation of an operation
  * @op: The operation to initialise
@@ -30,6 +34,7 @@ EXPORT_SYMBOL(fscache_op_debug_id);
  */
 void fscache_operation_init(struct fscache_operation *op,
 			    fscache_operation_processor_t processor,
+			    fscache_operation_cancel_t cancel,
 			    fscache_operation_release_t release)
 {
 	INIT_WORK(&op->work, fscache_op_work_func);
@@ -37,6 +42,7 @@ void fscache_operation_init(struct fscache_operation *op,
 	op->state = FSCACHE_OP_ST_INITIALISED;
 	op->debug_id = atomic_inc_return(&fscache_op_debug_id);
 	op->processor = processor;
+	op->cancel = cancel ?: fscache_operation_dummy_cancel;
 	op->release = release;
 	INIT_LIST_HEAD(&op->pend_link);
 	fscache_stat(&fscache_n_op_initialised);
@@ -164,9 +170,11 @@ int fscache_submit_exclusive_op(struct fscache_object *object,
 	flags = READ_ONCE(object->flags);
 	if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
 		fscache_stat(&fscache_n_op_rejected);
+		op->cancel(op);
 		op->state = FSCACHE_OP_ST_CANCELLED;
 		ret = -ENOBUFS;
 	} else if (unlikely(fscache_cache_is_broken(object))) {
+		op->cancel(op);
 		op->state = FSCACHE_OP_ST_CANCELLED;
 		ret = -EIO;
 	} else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
@@ -200,10 +208,12 @@ int fscache_submit_exclusive_op(struct fscache_object *object,
 		fscache_stat(&fscache_n_op_pend);
 		ret = 0;
 	} else if (flags & BIT(FSCACHE_OBJECT_KILLED_BY_CACHE)) {
+		op->cancel(op);
 		op->state = FSCACHE_OP_ST_CANCELLED;
 		ret = -ENOBUFS;
 	} else {
 		fscache_report_unexpected_submission(object, op, ostate);
+		op->cancel(op);
 		op->state = FSCACHE_OP_ST_CANCELLED;
 		ret = -ENOBUFS;
 	}
@@ -245,9 +255,11 @@ int fscache_submit_op(struct fscache_object *object,
 	flags = READ_ONCE(object->flags);
 	if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
 		fscache_stat(&fscache_n_op_rejected);
+		op->cancel(op);
 		op->state = FSCACHE_OP_ST_CANCELLED;
 		ret = -ENOBUFS;
 	} else if (unlikely(fscache_cache_is_broken(object))) {
+		op->cancel(op);
 		op->state = FSCACHE_OP_ST_CANCELLED;
 		ret = -EIO;
 	} else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
@@ -276,11 +288,13 @@ int fscache_submit_op(struct fscache_object *object,
 		fscache_stat(&fscache_n_op_pend);
 		ret = 0;
 	} else if (flags & BIT(FSCACHE_OBJECT_KILLED_BY_CACHE)) {
+		op->cancel(op);
 		op->state = FSCACHE_OP_ST_CANCELLED;
 		ret = -ENOBUFS;
 	} else {
 		fscache_report_unexpected_submission(object, op, ostate);
 		ASSERT(!fscache_object_is_active(object));
+		op->cancel(op);
 		op->state = FSCACHE_OP_ST_CANCELLED;
 		ret = -ENOBUFS;
 	}
@@ -335,7 +349,6 @@ 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,
-		      void (*do_cancel)(struct fscache_operation *),
 		      bool cancel_in_progress_op)
 {
 	struct fscache_object *object = op->object;
@@ -355,9 +368,9 @@ int fscache_cancel_op(struct fscache_operation *op,
 		ASSERT(!list_empty(&op->pend_link));
 		list_del_init(&op->pend_link);
 		put = true;
+
 		fscache_stat(&fscache_n_op_cancelled);
-		if (do_cancel)
-			do_cancel(op);
+		op->cancel(op);
 		op->state = FSCACHE_OP_ST_CANCELLED;
 		if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 			object->n_exclusive--;
@@ -373,8 +386,7 @@ int fscache_cancel_op(struct fscache_operation *op,
 			fscache_start_operations(object);
 
 		fscache_stat(&fscache_n_op_cancelled);
-		if (do_cancel)
-			do_cancel(op);
+		op->cancel(op);
 		op->state = FSCACHE_OP_ST_CANCELLED;
 		if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 			object->n_exclusive--;
@@ -408,6 +420,7 @@ void fscache_cancel_all_ops(struct fscache_object *object)
 		list_del_init(&op->pend_link);
 
 		ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
+		op->cancel(op);
 		op->state = FSCACHE_OP_ST_CANCELLED;
 
 		if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
@@ -440,8 +453,12 @@ void fscache_op_complete(struct fscache_operation *op, bool cancelled)
 
 	spin_lock(&object->lock);
 
-	op->state = cancelled ?
-		FSCACHE_OP_ST_CANCELLED : FSCACHE_OP_ST_COMPLETE;
+	if (!cancelled) {
+		op->state = FSCACHE_OP_ST_COMPLETE;
+	} else {
+		op->cancel(op);
+		op->state = FSCACHE_OP_ST_CANCELLED;
+	}
 
 	if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 		object->n_exclusive--;