nvmet: track and limit the number of namespaces per subsystem

TP 4004 introduces a new 'Maximum Number of Allocated Namespaces' field
in the Identify controller data to help the host size resources.  Put
an upper limit on the supported namespaces to be able to support this
value as supporting 32-bits worth of namespaces would lead to very
large buffers.  The limit is completely arbitrary at this point.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>

diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index 16a9b24..55f2bf4 100644 (file)
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -252,6 +252,7 @@ static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
        id->maxcmd = cpu_to_le16(NVMET_MAX_CMD);
 
        id->nn = cpu_to_le32(ctrl->subsys->max_nsid);
+       id->mnan = cpu_to_le32(NVMET_MAX_NAMESPACES);
        id->oncs = cpu_to_le16(NVME_CTRL_ONCS_DSM |
                        NVME_CTRL_ONCS_WRITE_ZEROES);
 

diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index cbcd19f..42e8565 100644 (file)
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -337,9 +337,13 @@ static void nvmet_ns_dev_disable(struct nvmet_ns *ns)
 int nvmet_ns_enable(struct nvmet_ns *ns)
 {
        struct nvmet_subsys *subsys = ns->subsys;
-       int ret = 0;
+       int ret;
 
        mutex_lock(&subsys->lock);
+       ret = -EMFILE;
+       if (subsys->nr_namespaces == NVMET_MAX_NAMESPACES)
+               goto out_unlock;
+       ret = 0;
        if (ns->enabled)
                goto out_unlock;
 
@@ -374,6 +378,7 @@ int nvmet_ns_enable(struct nvmet_ns *ns)
 
                list_add_tail_rcu(&ns->dev_link, &old->dev_link);
        }
+       subsys->nr_namespaces++;
 
        nvmet_ns_changed(subsys, ns->nsid);
        ns->enabled = true;
@@ -414,6 +419,7 @@ void nvmet_ns_disable(struct nvmet_ns *ns)
        percpu_ref_exit(&ns->ref);
 
        mutex_lock(&subsys->lock);
+       subsys->nr_namespaces--;
        nvmet_ns_changed(subsys, ns->nsid);
        nvmet_ns_dev_disable(ns);
 out_unlock:

diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index de12dcb..701017f 100644 (file)
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -170,6 +170,7 @@ struct nvmet_subsys {
        struct kref             ref;
 
        struct list_head        namespaces;
+       unsigned int            nr_namespaces;
        unsigned int            max_nsid;
 
        struct list_head        ctrls;
@@ -362,6 +363,13 @@ u32 nvmet_get_log_page_len(struct nvme_command *cmd);
 #define NVMET_QUEUE_SIZE       1024
 #define NVMET_NR_QUEUES                128
 #define NVMET_MAX_CMD          NVMET_QUEUE_SIZE
+
+/*
+ * Nice round number that makes a list of nsids fit into a page.
+ * Should become tunable at some point in the future.
+ */
+#define NVMET_MAX_NAMESPACES   1024
+
 #define NVMET_KAS              10
 #define NVMET_DISC_KATO                120