target: Convert se_node_acl->device_list[] to RCU hlist
This patch converts se_node_acl->device_list[] table for mappedluns
to modern RCU hlist_head usage in order to support an arbitrary number
of node_acl lun mappings.
It converts transport_lookup_*_lun() fast-path code to use RCU read path
primitives when looking up se_dev_entry. It adds a new hlist_head at
se_node_acl->lun_entry_hlist for this purpose.
For transport_lookup_cmd_lun() code, it works with existing per-cpu
se_lun->lun_ref when associating se_cmd with se_lun + se_device.
Also, go ahead and update core_create_device_list_for_node() +
core_free_device_list_for_node() to use ->lun_entry_hlist.
It also converts se_dev_entry->pr_ref_count access to use modern
struct kref counting, and updates core_disable_device_list_for_node()
to kref_put() and block on se_deve->pr_comp waiting for outstanding PR
special-case PR references to drop, then invoke kfree_rcu() to wait
for the RCU grace period to complete before releasing memory.
So now that se_node_acl->lun_entry_hlist fast path access uses RCU
protected pointers, go ahead and convert remaining non-fast path
RCU updater code using ->lun_entry_lock to struct mutex to allow
callers to block while walking se_node_acl->lun_entry_hlist.
Finally drop the left-over core_clear_initiator_node_from_tpg() that
originally cleared lun_access during se_node_acl shutdown, as post
RCU conversion it now becomes duplicated logic.
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/target_core_spc.c b/drivers/target/target_core_spc.c
index 78c0b40..9f995b87 100644
--- a/drivers/target/target_core_spc.c
+++ b/drivers/target/target_core_spc.c
@@ -981,6 +981,7 @@
int length = 0;
int ret;
int i;
+ bool read_only = target_lun_is_rdonly(cmd);;
memset(buf, 0, SE_MODE_PAGE_BUF);
@@ -991,9 +992,7 @@
length = ten ? 3 : 2;
/* DEVICE-SPECIFIC PARAMETER */
- if ((cmd->se_lun->lun_access & TRANSPORT_LUNFLAGS_READ_ONLY) ||
- (cmd->se_deve &&
- (cmd->se_deve->lun_flags & TRANSPORT_LUNFLAGS_READ_ONLY)))
+ if ((cmd->se_lun->lun_access & TRANSPORT_LUNFLAGS_READ_ONLY) || read_only)
spc_modesense_write_protect(&buf[length], type);
/*
@@ -1211,8 +1210,9 @@
{
struct se_dev_entry *deve;
struct se_session *sess = cmd->se_sess;
+ struct se_node_acl *nacl;
unsigned char *buf;
- u32 lun_count = 0, offset = 8, i;
+ u32 lun_count = 0, offset = 8;
if (cmd->data_length < 16) {
pr_warn("REPORT LUNS allocation length %u too small\n",
@@ -1234,12 +1234,10 @@
lun_count = 1;
goto done;
}
+ nacl = sess->se_node_acl;
- spin_lock_irq(&sess->se_node_acl->device_list_lock);
- for (i = 0; i < TRANSPORT_MAX_LUNS_PER_TPG; i++) {
- deve = sess->se_node_acl->device_list[i];
- if (!(deve->lun_flags & TRANSPORT_LUNFLAGS_INITIATOR_ACCESS))
- continue;
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link) {
/*
* We determine the correct LUN LIST LENGTH even once we
* have reached the initial allocation length.
@@ -1252,7 +1250,7 @@
int_to_scsilun(deve->mapped_lun, (struct scsi_lun *)&buf[offset]);
offset += 8;
}
- spin_unlock_irq(&sess->se_node_acl->device_list_lock);
+ rcu_read_unlock();
/*
* See SPC3 r07, page 159.