libceph: reference counting pagelist

this allow pagelist to present data that may be sent multiple times.
Signed-off-by: Yan, Zheng <zyan@redhat.com>
Reviewed-by: Sage Weil <sage@redhat.com>

fs/ceph/mds_client.c

@@ -2865,7 +2865,6 @@ static void send_mds_reconnect(struct ceph_mds_client *mdsc,
 	mutex_unlock(&session->s_mutex);
 fail_nomsg:
 	ceph_pagelist_release(pagelist);
-	kfree(pagelist);
 fail_nopagelist:
 	pr_err("error %d preparing reconnect for mds%d\n", err, mds);
 	return;

include/linux/ceph/pagelist.h

@@ -2,6 +2,7 @@
 #define __FS_CEPH_PAGELIST_H
 
 #include <linux/list.h>
+#include <linux/atomic.h>
 
 struct ceph_pagelist {
 	struct list_head head;
@@ -10,6 +11,7 @@ struct ceph_pagelist {
 	size_t room;
 	struct list_head free_list;
 	size_t num_pages_free;
+	atomic_t refcnt;
 };
 
 struct ceph_pagelist_cursor {
@@ -26,9 +28,10 @@ static inline void ceph_pagelist_init(struct ceph_pagelist *pl)
 	pl->room = 0;
 	INIT_LIST_HEAD(&pl->free_list);
 	pl->num_pages_free = 0;
+	atomic_set(&pl->refcnt, 1);
 }
 
-extern int ceph_pagelist_release(struct ceph_pagelist *pl);
+extern void ceph_pagelist_release(struct ceph_pagelist *pl);
 
 extern int ceph_pagelist_append(struct ceph_pagelist *pl, const void *d, size_t l);
 

net/ceph/messenger.c

@@ -3071,10 +3071,8 @@ static void ceph_msg_data_destroy(struct ceph_msg_data *data)
 		return;
 
 	WARN_ON(!list_empty(&data->links));
-	if (data->type == CEPH_MSG_DATA_PAGELIST) {
+	if (data->type == CEPH_MSG_DATA_PAGELIST)
 		ceph_pagelist_release(data->pagelist);
-		kfree(data->pagelist);
-	}
 	kmem_cache_free(ceph_msg_data_cache, data);
 }
 

net/ceph/pagelist.c

 #include <linux/module.h>
 #include <linux/gfp.h>
+#include <linux/slab.h>
 #include <linux/pagemap.h>
 #include <linux/highmem.h>
 #include <linux/ceph/pagelist.h>
@@ -13,8 +14,10 @@ static void ceph_pagelist_unmap_tail(struct ceph_pagelist *pl)
 	}
 }
 
-int ceph_pagelist_release(struct ceph_pagelist *pl)
+void ceph_pagelist_release(struct ceph_pagelist *pl)
 {
+	if (!atomic_dec_and_test(&pl->refcnt))
+		return;
 	ceph_pagelist_unmap_tail(pl);
 	while (!list_empty(&pl->head)) {
 		struct page *page = list_first_entry(&pl->head, struct page,
@@ -23,7 +26,7 @@ int ceph_pagelist_release(struct ceph_pagelist *pl)
 		__free_page(page);
 	}
 	ceph_pagelist_free_reserve(pl);
-	return 0;
+	kfree(pl);
 }
 EXPORT_SYMBOL(ceph_pagelist_release);