libceph: don't consume a ref on pagelist in ceph_msg_data_add_pagelist()

Because send_mds_reconnect() wants to send a message with a pagelist
and pass the ownership to the messenger, ceph_msg_data_add_pagelist()
consumes a ref which is then put in ceph_msg_data_destroy().  This
makes managing pagelists in the OSD client (where they are wrapped in
ceph_osd_data) unnecessarily hard because the handoff only happens in
ceph_osdc_start_request() instead of when the pagelist is passed to
ceph_osd_data_pagelist_init().  I counted several memory leaks on
various error paths.

Fix up ceph_msg_data_add_pagelist() and carry a pagelist ref in
ceph_osd_data.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

net/ceph/messenger.c

@@ -3313,6 +3313,7 @@ void ceph_msg_data_add_pagelist(struct ceph_msg *msg,
 
 	data = ceph_msg_data_create(CEPH_MSG_DATA_PAGELIST);
 	BUG_ON(!data);
+	refcount_inc(&pagelist->refcnt);
 	data->pagelist = pagelist;
 
 	list_add_tail(&data->links, &msg->data);

net/ceph/osd_client.c

@@ -126,6 +126,9 @@ static void ceph_osd_data_init(struct ceph_osd_data *osd_data)
 	osd_data->type = CEPH_OSD_DATA_TYPE_NONE;
 }
 
+/*
+ * Consumes @pages if @own_pages is true.
+ */
 static void ceph_osd_data_pages_init(struct ceph_osd_data *osd_data,
 			struct page **pages, u64 length, u32 alignment,
 			bool pages_from_pool, bool own_pages)
@@ -138,6 +141,9 @@ static void ceph_osd_data_pages_init(struct ceph_osd_data *osd_data,
 	osd_data->own_pages = own_pages;
 }
 
+/*
+ * Consumes a ref on @pagelist.
+ */
 static void ceph_osd_data_pagelist_init(struct ceph_osd_data *osd_data,
 			struct ceph_pagelist *pagelist)
 {
@@ -362,6 +368,8 @@ static void ceph_osd_data_release(struct ceph_osd_data *osd_data)
 		num_pages = calc_pages_for((u64)osd_data->alignment,
 						(u64)osd_data->length);
 		ceph_release_page_vector(osd_data->pages, num_pages);
+	} else if (osd_data->type == CEPH_OSD_DATA_TYPE_PAGELIST) {
+		ceph_pagelist_release(osd_data->pagelist);
 	}
 	ceph_osd_data_init(osd_data);
 }