Merge branch 'fscache' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs into linux-next

Pull fs-cache fixes from David Howells:

Can you pull these commits to fix an issue with NFS whereby caching can be
enabled on a file that is open for writing by subsequently opening it for
reading.  This can be made to crash by opening it for writing again if you're
quick enough.

The gist of the patchset is that the cookie should be acquired at inode
creation only and subsequently enabled and disabled as appropriate (which
dispenses with the backing objects when they're not needed).

The extra synchronisation that NFS does can then be dispensed with as it is
thenceforth managed by FS-Cache.

Could you send these on to Linus?

This likely will need fixing also in CIFS and 9P also once the FS-Cache
changes are upstream.  AFS and Ceph are probably safe.

* 'fscache' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  NFS: Use i_writecount to control whether to get an fscache cookie in nfs_open()
  FS-Cache: Provide the ability to enable/disable cookies
  FS-Cache: Add use/unuse/wake cookie wrappers

1 files changed, 42 insertions, 17 deletions

diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index 73899c1..7f5c658 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -163,12 +163,10 @@ static void fscache_attr_changed_op(struct fscache_operation *op)
 
 	fscache_stat(&fscache_n_attr_changed_calls);
 
-	if (fscache_object_is_active(object) &&
-	    fscache_use_cookie(object)) {
+	if (fscache_object_is_active(object)) {
 		fscache_stat(&fscache_n_cop_attr_changed);
 		ret = object->cache->ops->attr_changed(object);
 		fscache_stat_d(&fscache_n_cop_attr_changed);
-		fscache_unuse_cookie(object);
 		if (ret < 0)
 			fscache_abort_object(object);
 	}
@@ -184,6 +182,7 @@ int __fscache_attr_changed(struct fscache_cookie *cookie)
 {
 	struct fscache_operation *op;
 	struct fscache_object *object;
+	bool wake_cookie;
 
 	_enter("%p", cookie);
 
@@ -199,15 +198,19 @@ int __fscache_attr_changed(struct fscache_cookie *cookie)
 	}
 
 	fscache_operation_init(op, fscache_attr_changed_op, NULL);
-	op->flags = FSCACHE_OP_ASYNC | (1 << FSCACHE_OP_EXCLUSIVE);
+	op->flags = FSCACHE_OP_ASYNC |
+		(1 << FSCACHE_OP_EXCLUSIVE) |
+		(1 << FSCACHE_OP_UNUSE_COOKIE);
 
 	spin_lock(&cookie->lock);
 
-	if (hlist_empty(&cookie->backing_objects))
+	if (!fscache_cookie_enabled(cookie) ||
+	    hlist_empty(&cookie->backing_objects))
 		goto nobufs;
 	object = hlist_entry(cookie->backing_objects.first,
 			     struct fscache_object, cookie_link);
 
+	__fscache_use_cookie(cookie);
 	if (fscache_submit_exclusive_op(object, op) < 0)
 		goto nobufs;
 	spin_unlock(&cookie->lock);
@@ -217,8 +220,11 @@ int __fscache_attr_changed(struct fscache_cookie *cookie)
 	return 0;
 
 nobufs:
+	wake_cookie = __fscache_unuse_cookie(cookie);
 	spin_unlock(&cookie->lock);
 	kfree(op);
+	if (wake_cookie)
+		__fscache_wake_unused_cookie(cookie);
 	fscache_stat(&fscache_n_attr_changed_nobufs);
 	_leave(" = %d", -ENOBUFS);
 	return -ENOBUFS;
@@ -263,7 +269,6 @@ static struct fscache_retrieval *fscache_alloc_retrieval(
 	}
 
 	fscache_operation_init(&op->op, NULL, fscache_release_retrieval_op);
-	atomic_inc(&cookie->n_active);
 	op->op.flags	= FSCACHE_OP_MYTHREAD |
 		(1UL << FSCACHE_OP_WAITING) |
 		(1UL << FSCACHE_OP_UNUSE_COOKIE);
@@ -384,6 +389,7 @@ int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
 {
 	struct fscache_retrieval *op;
 	struct fscache_object *object;
+	bool wake_cookie = false;
 	int ret;
 
 	_enter("%p,%p,,,", cookie, page);
@@ -405,7 +411,7 @@ int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
 		return -ERESTARTSYS;
 
 	op = fscache_alloc_retrieval(cookie, page->mapping,
-				     end_io_func,context);
+				     end_io_func, context);
 	if (!op) {
 		_leave(" = -ENOMEM");
 		return -ENOMEM;
@@ -414,13 +420,15 @@ int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
 
 	spin_lock(&cookie->lock);
 
-	if (hlist_empty(&cookie->backing_objects))
+	if (!fscache_cookie_enabled(cookie) ||
+	    hlist_empty(&cookie->backing_objects))
 		goto nobufs_unlock;
 	object = hlist_entry(cookie->backing_objects.first,
 			     struct fscache_object, cookie_link);
 
 	ASSERT(test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags));
 
+	__fscache_use_cookie(cookie);
 	atomic_inc(&object->n_reads);
 	__set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
 
@@ -475,9 +483,11 @@ error:
 
 nobufs_unlock_dec:
 	atomic_dec(&object->n_reads);
+	wake_cookie = __fscache_unuse_cookie(cookie);
 nobufs_unlock:
 	spin_unlock(&cookie->lock);
-	atomic_dec(&cookie->n_active);
+	if (wake_cookie)
+		__fscache_wake_unused_cookie(cookie);
 	kfree(op);
 nobufs:
 	fscache_stat(&fscache_n_retrievals_nobufs);
@@ -514,6 +524,7 @@ int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
 {
 	struct fscache_retrieval *op;
 	struct fscache_object *object;
+	bool wake_cookie = false;
 	int ret;
 
 	_enter("%p,,%d,,,", cookie, *nr_pages);
@@ -542,11 +553,13 @@ int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
 
 	spin_lock(&cookie->lock);
 
-	if (hlist_empty(&cookie->backing_objects))
+	if (!fscache_cookie_enabled(cookie) ||
+	    hlist_empty(&cookie->backing_objects))
 		goto nobufs_unlock;
 	object = hlist_entry(cookie->backing_objects.first,
 			     struct fscache_object, cookie_link);
 
+	__fscache_use_cookie(cookie);
 	atomic_inc(&object->n_reads);
 	__set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
 
@@ -601,10 +614,12 @@ error:
 
 nobufs_unlock_dec:
 	atomic_dec(&object->n_reads);
+	wake_cookie = __fscache_unuse_cookie(cookie);
 nobufs_unlock:
 	spin_unlock(&cookie->lock);
-	atomic_dec(&cookie->n_active);
 	kfree(op);
+	if (wake_cookie)
+		__fscache_wake_unused_cookie(cookie);
 nobufs:
 	fscache_stat(&fscache_n_retrievals_nobufs);
 	_leave(" = -ENOBUFS");
@@ -626,6 +641,7 @@ int __fscache_alloc_page(struct fscache_cookie *cookie,
 {
 	struct fscache_retrieval *op;
 	struct fscache_object *object;
+	bool wake_cookie = false;
 	int ret;
 
 	_enter("%p,%p,,,", cookie, page);
@@ -653,13 +669,15 @@ int __fscache_alloc_page(struct fscache_cookie *cookie,
 
 	spin_lock(&cookie->lock);
 
-	if (hlist_empty(&cookie->backing_objects))
+	if (!fscache_cookie_enabled(cookie) ||
+	    hlist_empty(&cookie->backing_objects))
 		goto nobufs_unlock;
 	object = hlist_entry(cookie->backing_objects.first,
 			     struct fscache_object, cookie_link);
 
+	__fscache_use_cookie(cookie);
 	if (fscache_submit_op(object, &op->op) < 0)
-		goto nobufs_unlock;
+		goto nobufs_unlock_dec;
 	spin_unlock(&cookie->lock);
 
 	fscache_stat(&fscache_n_alloc_ops);
@@ -689,10 +707,13 @@ error:
 	_leave(" = %d", ret);
 	return ret;
 
+nobufs_unlock_dec:
+	wake_cookie = __fscache_unuse_cookie(cookie);
 nobufs_unlock:
 	spin_unlock(&cookie->lock);
-	atomic_dec(&cookie->n_active);
 	kfree(op);
+	if (wake_cookie)
+		__fscache_wake_unused_cookie(cookie);
 nobufs:
 	fscache_stat(&fscache_n_allocs_nobufs);
 	_leave(" = -ENOBUFS");
@@ -889,6 +910,7 @@ int __fscache_write_page(struct fscache_cookie *cookie,
 {
 	struct fscache_storage *op;
 	struct fscache_object *object;
+	bool wake_cookie = false;
 	int ret;
 
 	_enter("%p,%x,", cookie, (u32) page->flags);
@@ -920,7 +942,8 @@ int __fscache_write_page(struct fscache_cookie *cookie,
 	ret = -ENOBUFS;
 	spin_lock(&cookie->lock);
 
-	if (hlist_empty(&cookie->backing_objects))
+	if (!fscache_cookie_enabled(cookie) ||
+	    hlist_empty(&cookie->backing_objects))
 		goto nobufs;
 	object = hlist_entry(cookie->backing_objects.first,
 			     struct fscache_object, cookie_link);
@@ -957,7 +980,7 @@ int __fscache_write_page(struct fscache_cookie *cookie,
 	op->op.debug_id	= atomic_inc_return(&fscache_op_debug_id);
 	op->store_limit = object->store_limit;
 
-	atomic_inc(&cookie->n_active);
+	__fscache_use_cookie(cookie);
 	if (fscache_submit_op(object, &op->op) < 0)
 		goto submit_failed;
 
@@ -984,10 +1007,10 @@ already_pending:
 	return 0;
 
 submit_failed:
-	atomic_dec(&cookie->n_active);
 	spin_lock(&cookie->stores_lock);
 	radix_tree_delete(&cookie->stores, page->index);
 	spin_unlock(&cookie->stores_lock);
+	wake_cookie = __fscache_unuse_cookie(cookie);
 	page_cache_release(page);
 	ret = -ENOBUFS;
 	goto nobufs;
@@ -999,6 +1022,8 @@ nobufs:
 	spin_unlock(&cookie->lock);
 	radix_tree_preload_end();
 	kfree(op);
+	if (wake_cookie)
+		__fscache_wake_unused_cookie(cookie);
 	fscache_stat(&fscache_n_stores_nobufs);
 	_leave(" = -ENOBUFS");
 	return -ENOBUFS;