libceph: use slab cache for osd client requests

Create a slab cache to manage allocation of ceph_osdc_request
structures.

This resolves:
    http://tracker.ceph.com/issues/3926

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

include/linux/ceph/osd_client.h

@@ -224,6 +224,9 @@ struct ceph_osd_client {
 	struct workqueue_struct	*notify_wq;
 };
 
+extern int ceph_osdc_setup(void);
+extern void ceph_osdc_cleanup(void);
+
 extern int ceph_osdc_init(struct ceph_osd_client *osdc,
 			  struct ceph_client *client);
 extern void ceph_osdc_stop(struct ceph_osd_client *osdc);

net/ceph/ceph_common.c

@@ -606,11 +606,17 @@ static int __init init_ceph_lib(void)
 	if (ret < 0)
 		goto out_crypto;
 
+	ret = ceph_osdc_setup();
+	if (ret < 0)
+		goto out_msgr;
+
 	pr_info("loaded (mon/osd proto %d/%d)\n",
 		CEPH_MONC_PROTOCOL, CEPH_OSDC_PROTOCOL);
 
 	return 0;
 
+out_msgr:
+	ceph_msgr_exit();
 out_crypto:
 	ceph_crypto_shutdown();
 out_debugfs:
@@ -622,6 +628,7 @@ out:
 static void __exit exit_ceph_lib(void)
 {
 	dout("exit_ceph_lib\n");
+	ceph_osdc_cleanup();
 	ceph_msgr_exit();
 	ceph_crypto_shutdown();
 	ceph_debugfs_cleanup();

net/ceph/osd_client.c

@@ -22,6 +22,8 @@
 #define OSD_OP_FRONT_LEN	4096
 #define OSD_OPREPLY_FRONT_LEN	512
 
+static struct kmem_cache	*ceph_osd_request_cache;
+
 static const struct ceph_connection_operations osd_con_ops;
 
 static void __send_queued(struct ceph_osd_client *osdc);
@@ -315,7 +317,8 @@ void ceph_osdc_release_request(struct kref *kref)
 	if (req->r_mempool)
 		mempool_free(req, req->r_osdc->req_mempool);
 	else
-		kfree(req);
+		kmem_cache_free(ceph_osd_request_cache, req);
+
 }
 EXPORT_SYMBOL(ceph_osdc_release_request);
 
@@ -346,7 +349,7 @@ struct ceph_osd_request *ceph_osdc_alloc_request(struct ceph_osd_client *osdc,
 		req = mempool_alloc(osdc->req_mempool, gfp_flags);
 		memset(req, 0, sizeof(*req));
 	} else {
-		req = kzalloc(sizeof(*req), gfp_flags);
+		req = kmem_cache_zalloc(ceph_osd_request_cache, gfp_flags);
 	}
 	if (req == NULL)
 		return NULL;
@@ -2365,6 +2368,26 @@ int ceph_osdc_writepages(struct ceph_osd_client *osdc, struct ceph_vino vino,
 }
 EXPORT_SYMBOL(ceph_osdc_writepages);
 
+int ceph_osdc_setup(void)
+{
+	BUG_ON(ceph_osd_request_cache);
+	ceph_osd_request_cache = kmem_cache_create("ceph_osd_request",
+					sizeof (struct ceph_osd_request),
+					__alignof__(struct ceph_osd_request),
+					0, NULL);
+
+	return ceph_osd_request_cache ? 0 : -ENOMEM;
+}
+EXPORT_SYMBOL(ceph_osdc_setup);
+
+void ceph_osdc_cleanup(void)
+{
+	BUG_ON(!ceph_osd_request_cache);
+	kmem_cache_destroy(ceph_osd_request_cache);
+	ceph_osd_request_cache = NULL;
+}
+EXPORT_SYMBOL(ceph_osdc_cleanup);
+
 /*
  * handle incoming message
  */