[PATCH v6 09/14] nvmet-fcloop: allocate/free fcloop_lsreq directly

[Daniel Wagner <wagi@kernel.org>]

fcloop depends on the host or the target to allocate the fcloop_lsreq
object. This means that the lifetime of the fcloop_lsreq is tied to
either the host or the target. Consequently, the host or the target must
cooperate during shutdown.

Unfortunately, this approach does not work well when the target forces a
shutdown, as there are dependencies that are difficult to resolve in a
clean way.

The simplest solution is to decouple the lifetime of the fcloop_lsreq
object by managing them directly within fcloop. Since this is not a
performance-critical path and only a small number of LS objects are used
during setup and cleanup, it does not significantly impact performance
to allocate them during normal operation.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Daniel Wagner <wagi@kernel.org>
---
 drivers/nvme/target/fcloop.c | 63 +++++++++++++++++++++++++++++++-------------
 1 file changed, 45 insertions(+), 18 deletions(-)

diff --git a/drivers/nvme/target/fcloop.c b/drivers/nvme/target/fcloop.c
index c74baa7f6e43c8bddd9e6948f806f27b032b1d4d..f999bd6513c19b19af64e0ea547db26b627aab69 100644
--- a/drivers/nvme/target/fcloop.c
+++ b/drivers/nvme/target/fcloop.c
@@ -293,6 +293,9 @@ struct fcloop_ini_fcpreq {
 	spinlock_t			inilock;
 };
 
+/* SLAB cache for fcloop_lsreq structures */
+static struct kmem_cache *lsreq_cache;
+
 static inline struct fcloop_lsreq *
 ls_rsp_to_lsreq(struct nvmefc_ls_rsp *lsrsp)
 {
@@ -343,6 +346,7 @@ fcloop_rport_lsrqst_work(struct work_struct *work)
 		 * callee may free memory containing tls_req.
 		 * do not reference lsreq after this.
 		 */
+		kmem_cache_free(lsreq_cache, tls_req);
 
 		spin_lock(&rport->lock);
 	}
@@ -354,10 +358,13 @@ fcloop_h2t_ls_req(struct nvme_fc_local_port *localport,
 			struct nvme_fc_remote_port *remoteport,
 			struct nvmefc_ls_req *lsreq)
 {
-	struct fcloop_lsreq *tls_req = lsreq->private;
 	struct fcloop_rport *rport = remoteport->private;
+	struct fcloop_lsreq *tls_req;
 	int ret = 0;
 
+	tls_req = kmem_cache_alloc(lsreq_cache, GFP_KERNEL);
+	if (!tls_req)
+		return -ENOMEM;
 	tls_req->lsreq = lsreq;
 	INIT_LIST_HEAD(&tls_req->ls_list);
 
@@ -394,14 +401,17 @@ fcloop_h2t_xmt_ls_rsp(struct nvmet_fc_target_port *targetport,
 
 	lsrsp->done(lsrsp);
 
-	if (remoteport) {
-		rport = remoteport->private;
-		spin_lock(&rport->lock);
-		list_add_tail(&tls_req->ls_list, &rport->ls_list);
-		spin_unlock(&rport->lock);
-		queue_work(nvmet_wq, &rport->ls_work);
+	if (!remoteport) {
+		kmem_cache_free(lsreq_cache, tls_req);
+		return 0;
 	}
 
+	rport = remoteport->private;
+	spin_lock(&rport->lock);
+	list_add_tail(&tls_req->ls_list, &rport->ls_list);
+	spin_unlock(&rport->lock);
+	queue_work(nvmet_wq, &rport->ls_work);
+
 	return 0;
 }
 
@@ -427,6 +437,7 @@ fcloop_tport_lsrqst_work(struct work_struct *work)
 		 * callee may free memory containing tls_req.
 		 * do not reference lsreq after this.
 		 */
+		kmem_cache_free(lsreq_cache, tls_req);
 
 		spin_lock(&tport->lock);
 	}
@@ -437,8 +448,8 @@ static int
 fcloop_t2h_ls_req(struct nvmet_fc_target_port *targetport, void *hosthandle,
 			struct nvmefc_ls_req *lsreq)
 {
-	struct fcloop_lsreq *tls_req = lsreq->private;
 	struct fcloop_tport *tport = targetport->private;
+	struct fcloop_lsreq *tls_req;
 	int ret = 0;
 
 	/*
@@ -446,6 +457,10 @@ fcloop_t2h_ls_req(struct nvmet_fc_target_port *targetport, void *hosthandle,
 	 * hosthandle ignored as fcloop currently is
 	 * 1:1 tgtport vs remoteport
 	 */
+
+	tls_req = kmem_cache_alloc(lsreq_cache, GFP_KERNEL);
+	if (!tls_req)
+		return -ENOMEM;
 	tls_req->lsreq = lsreq;
 	INIT_LIST_HEAD(&tls_req->ls_list);
 
@@ -462,6 +477,9 @@ fcloop_t2h_ls_req(struct nvmet_fc_target_port *targetport, void *hosthandle,
 	ret = nvme_fc_rcv_ls_req(tport->remoteport, &tls_req->ls_rsp,
 				 lsreq->rqstaddr, lsreq->rqstlen);
 
+	if (ret)
+		kmem_cache_free(lsreq_cache, tls_req);
+
 	return ret;
 }
 
@@ -481,14 +499,17 @@ fcloop_t2h_xmt_ls_rsp(struct nvme_fc_local_port *localport,
 				lsreq->rsplen : lsrsp->rsplen));
 	lsrsp->done(lsrsp);
 
-	if (targetport) {
-		tport = targetport->private;
-		spin_lock(&tport->lock);
-		list_add_tail(&tls_req->ls_list, &tport->ls_list);
-		spin_unlock(&tport->lock);
-		queue_work(nvmet_wq, &tport->ls_work);
+	if (!targetport) {
+		kmem_cache_free(lsreq_cache, tls_req);
+		return 0;
 	}
 
+	tport = targetport->private;
+	spin_lock(&tport->lock);
+	list_add_tail(&tls_req->ls_list, &tport->ls_list);
+	spin_unlock(&tport->lock);
+	queue_work(nvmet_wq, &tport->ls_work);
+
 	return 0;
 }
 
@@ -1127,7 +1148,6 @@ static struct nvme_fc_port_template fctemplate = {
 	/* sizes of additional private data for data structures */
 	.local_priv_sz		= sizeof(struct fcloop_lport_priv),
 	.remote_priv_sz		= sizeof(struct fcloop_rport),
-	.lsrqst_priv_sz		= sizeof(struct fcloop_lsreq),
 	.fcprqst_priv_sz	= sizeof(struct fcloop_ini_fcpreq),
 };
 
@@ -1150,7 +1170,6 @@ static struct nvmet_fc_target_template tgttemplate = {
 	.target_features	= 0,
 	/* sizes of additional private data for data structures */
 	.target_priv_sz		= sizeof(struct fcloop_tport),
-	.lsrqst_priv_sz		= sizeof(struct fcloop_lsreq),
 };
 
 static ssize_t
@@ -1670,15 +1689,20 @@ static const struct class fcloop_class = {
 };
 static struct device *fcloop_device;
 
-
 static int __init fcloop_init(void)
 {
 	int ret;
 
+	lsreq_cache = kmem_cache_create("lsreq_cache",
+				sizeof(struct fcloop_lsreq), 0,
+				0, NULL);
+	if (!lsreq_cache)
+		return -ENOMEM;
+
 	ret = class_register(&fcloop_class);
 	if (ret) {
 		pr_err("couldn't register class fcloop\n");
-		return ret;
+		goto out_destroy_cache;
 	}
 
 	fcloop_device = device_create_with_groups(
@@ -1696,6 +1720,8 @@ static int __init fcloop_init(void)
 
 out_destroy_class:
 	class_unregister(&fcloop_class);
+out_destroy_cache:
+	kmem_cache_destroy(lsreq_cache);
 	return ret;
 }
 
@@ -1761,6 +1787,7 @@ static void __exit fcloop_exit(void)
 
 	device_destroy(&fcloop_class, MKDEV(0, 0));
 	class_unregister(&fcloop_class);
+	kmem_cache_destroy(lsreq_cache);
 }
 
 module_init(fcloop_init);

-- 
2.49.0