[PATCH v2 23/67] fscache: Provide a function to let the netfs update its coherency data

[David Howells <dhowells@redhat.com>]

Provide a function to let the netfs update its coherency data:

	void fscache_update_cookie(struct fscache_cookie *cookie,
				   const void *aux_data,
				   const loff_t *object_size);

This will update the auxiliary data and/or the size of the object attached
to a cookie if either pointer is not-NULL and flag that the disk needs to
be updated.

Note that fscache_unuse_cookie() also allows this to be done.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819610438.215744.4223265964131424954.stgit@warthog.procyon.org.uk/ # v1
---

 include/linux/fscache.h |   22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index 329ed9dcd22f..ceb1966acc52 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -334,6 +334,28 @@ void __fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data
 	set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags);
 }
 
+/**
+ * fscache_update_cookie - Request that a cache object be updated
+ * @cookie: The cookie representing the cache object
+ * @aux_data: The updated auxiliary data for the cookie (may be NULL)
+ * @object_size: The current size of the object (may be NULL)
+ *
+ * Request an update of the index data for the cache object associated with the
+ * cookie.  The auxiliary data on the cookie will be updated first if @aux_data
+ * is set and the object size will be updated and the object possibly trimmed
+ * if @object_size is set.
+ *
+ * See Documentation/filesystems/caching/netfs-api.rst for a complete
+ * description.
+ */
+static inline
+void fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data,
+			   const loff_t *object_size)
+{
+	if (fscache_cookie_enabled(cookie))
+		__fscache_update_cookie(cookie, aux_data, object_size);
+}
+
 /**
  * fscache_invalidate - Notify cache that an object needs invalidation
  * @cookie: The cookie representing the cache object