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Date: Tue, 12 May 2015 13:58:23 -0700
From: Andy Grover <agrover@...hat.com>
To: "Nicholas A. Bellinger" <nab@...erainc.com>,
target-devel <target-devel@...r.kernel.org>
CC: linux-scsi <linux-scsi@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Hannes Reinecke <hare@...e.de>, Christoph Hellwig <hch@....de>,
Sagi Grimberg <sagig@...lanox.com>,
Nicholas Bellinger <nab@...ux-iscsi.org>
Subject: Re: [PATCH 01/12] target: Convert se_node_acl->device_list[] to RCU
hlist
On 05/12/2015 02:25 AM, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@...ux-iscsi.org>
>
> 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.
>
> This includes changes to core_[enable,disable]_device_list_for_node()
> rcu_assign_pointer() and invokes call_rcu() for releasing memory, along
> with a number of RCU read path conversions in target_core_device.c code.
>
> Required for subsequent conversion of transport_lookup_cmd() to lock-less
> RCU read path.
>
> Cc: Hannes Reinecke <hare@...e.de>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Sagi Grimberg <sagig@...lanox.com>
> Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
> ---
> drivers/target/target_core_device.c | 218 +++++++++++++++++++---------------
> drivers/target/target_core_internal.h | 1 +
> drivers/target/target_core_tpg.c | 23 ++--
> include/target/target_core_base.h | 7 +-
> 4 files changed, 137 insertions(+), 112 deletions(-)
>
> diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
> index 6e58976..1df14ce 100644
> --- a/drivers/target/target_core_device.c
> +++ b/drivers/target/target_core_device.c
> @@ -198,12 +198,9 @@ struct se_dev_entry *core_get_se_deve_from_rtpi(
> struct se_lun *lun;
> struct se_port *port;
> struct se_portal_group *tpg = nacl->se_tpg;
> - u32 i;
> -
> - spin_lock_irq(&nacl->device_list_lock);
> - for (i = 0; i < TRANSPORT_MAX_LUNS_PER_TPG; i++) {
> - deve = nacl->device_list[i];
>
> + rcu_read_lock();
> + hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link) {
> if (!(deve->lun_flags & TRANSPORT_LUNFLAGS_INITIATOR_ACCESS))
> continue;
>
> @@ -225,11 +222,11 @@ struct se_dev_entry *core_get_se_deve_from_rtpi(
> continue;
>
> atomic_inc_mb(&deve->pr_ref_count);
> - spin_unlock_irq(&nacl->device_list_lock);
> + rcu_read_unlock();
>
> return deve;
> }
> - spin_unlock_irq(&nacl->device_list_lock);
> + rcu_read_unlock();
>
> return NULL;
> }
> @@ -240,18 +237,12 @@ int core_free_device_list_for_node(
> {
> struct se_dev_entry *deve;
> struct se_lun *lun;
> - u32 i;
> -
> - if (!nacl->device_list)
> - return 0;
> -
> - spin_lock_irq(&nacl->device_list_lock);
> - for (i = 0; i < TRANSPORT_MAX_LUNS_PER_TPG; i++) {
> - deve = nacl->device_list[i];
> + u32 mapped_lun;
>
> + rcu_read_lock();
> + hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link) {
> if (!(deve->lun_flags & TRANSPORT_LUNFLAGS_INITIATOR_ACCESS))
> continue;
> -
> if (!deve->se_lun) {
> pr_err("%s device entries device pointer is"
> " NULL, but Initiator has access.\n",
> @@ -259,16 +250,14 @@ int core_free_device_list_for_node(
> continue;
> }
> lun = deve->se_lun;
> + mapped_lun = deve->mapped_lun;
> + rcu_read_unlock();
>
> - spin_unlock_irq(&nacl->device_list_lock);
> - core_disable_device_list_for_node(lun, NULL, deve->mapped_lun,
> - TRANSPORT_LUNFLAGS_NO_ACCESS, nacl, tpg);
> - spin_lock_irq(&nacl->device_list_lock);
> + core_disable_device_list_for_node(lun, NULL, mapped_lun,
> + TRANSPORT_LUNFLAGS_NO_ACCESS, nacl, tpg);
> + rcu_read_lock();
> }
> - spin_unlock_irq(&nacl->device_list_lock);
> -
> - array_free(nacl->device_list, TRANSPORT_MAX_LUNS_PER_TPG);
> - nacl->device_list = NULL;
> + rcu_read_unlock();
>
> return 0;
> }
> @@ -280,18 +269,44 @@ void core_update_device_list_access(
> {
> struct se_dev_entry *deve;
>
> - spin_lock_irq(&nacl->device_list_lock);
> - deve = nacl->device_list[mapped_lun];
> - if (lun_access & TRANSPORT_LUNFLAGS_READ_WRITE) {
> - deve->lun_flags &= ~TRANSPORT_LUNFLAGS_READ_ONLY;
> - deve->lun_flags |= TRANSPORT_LUNFLAGS_READ_WRITE;
> - } else {
> - deve->lun_flags &= ~TRANSPORT_LUNFLAGS_READ_WRITE;
> - deve->lun_flags |= TRANSPORT_LUNFLAGS_READ_ONLY;
> + spin_lock_irq(&nacl->lun_entry_lock);
> + deve = target_nacl_find_deve(nacl, mapped_lun);
> + if (deve) {
> + if (lun_access & TRANSPORT_LUNFLAGS_READ_WRITE) {
> + deve->lun_flags &= ~TRANSPORT_LUNFLAGS_READ_ONLY;
> + deve->lun_flags |= TRANSPORT_LUNFLAGS_READ_WRITE;
> + } else {
> + deve->lun_flags &= ~TRANSPORT_LUNFLAGS_READ_WRITE;
> + deve->lun_flags |= TRANSPORT_LUNFLAGS_READ_ONLY;
> + }
> }
> - spin_unlock_irq(&nacl->device_list_lock);
> + spin_unlock_irq(&nacl->lun_entry_lock);
> +
> + synchronize_rcu();
> +}
> +
> +static void target_nacl_deve_callrcu(struct rcu_head *head)
> +{
> + struct se_dev_entry *deve = container_of(head, struct se_dev_entry,
> + rcu_head);
> + kfree(deve);
> }
>
> +/*
> + * Called with rcu_read_lock or nacl->device_list_lock held.
> + */
> +struct se_dev_entry *target_nacl_find_deve(struct se_node_acl *nacl, u32 mapped_lun)
> +{
> + struct se_dev_entry *deve;
> +
> + hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link)
> + if (deve->mapped_lun == mapped_lun)
> + return deve;
> +
> + return NULL;
> +}
> +EXPORT_SYMBOL(target_nacl_find_deve);
> +
> /* core_enable_device_list_for_node():
> *
> *
> @@ -305,67 +320,61 @@ int core_enable_device_list_for_node(
> struct se_portal_group *tpg)
> {
> struct se_port *port = lun->lun_sep;
> - struct se_dev_entry *deve;
> + struct se_dev_entry *orig, *new;
>
> - spin_lock_irq(&nacl->device_list_lock);
> + new = kzalloc(sizeof(*new), GFP_KERNEL);
> + if (!new) {
> + pr_err("Unable to allocate se_dev_entry memory\n");
> + return -ENOMEM;
> + }
>
> - deve = nacl->device_list[mapped_lun];
> + new->se_node_acl = nacl;
> + atomic_set(&new->ua_count, 0);
> + spin_lock_init(&new->ua_lock);
> + INIT_LIST_HEAD(&new->alua_port_list);
> + INIT_LIST_HEAD(&new->ua_list);
>
> - /*
> - * Check if the call is handling demo mode -> explicit LUN ACL
> - * transition. This transition must be for the same struct se_lun
> - * + mapped_lun that was setup in demo mode..
> - */
> - if (deve->lun_flags & TRANSPORT_LUNFLAGS_INITIATOR_ACCESS) {
> - if (deve->se_lun_acl != NULL) {
> - pr_err("struct se_dev_entry->se_lun_acl"
> - " already set for demo mode -> explicit"
> - " LUN ACL transition\n");
> - spin_unlock_irq(&nacl->device_list_lock);
> - return -EINVAL;
> - }
> - if (deve->se_lun != lun) {
> - pr_err("struct se_dev_entry->se_lun does"
> - " match passed struct se_lun for demo mode"
> - " -> explicit LUN ACL transition\n");
> - spin_unlock_irq(&nacl->device_list_lock);
> - return -EINVAL;
> - }
> - deve->se_lun_acl = lun_acl;
> + new->mapped_lun = mapped_lun;
> + new->lun_flags |= TRANSPORT_LUNFLAGS_INITIATOR_ACCESS;
>
> - if (lun_access & TRANSPORT_LUNFLAGS_READ_WRITE) {
> - deve->lun_flags &= ~TRANSPORT_LUNFLAGS_READ_ONLY;
> - deve->lun_flags |= TRANSPORT_LUNFLAGS_READ_WRITE;
> - } else {
> - deve->lun_flags &= ~TRANSPORT_LUNFLAGS_READ_WRITE;
> - deve->lun_flags |= TRANSPORT_LUNFLAGS_READ_ONLY;
> - }
> + if (lun_access & TRANSPORT_LUNFLAGS_READ_WRITE)
> + new->lun_flags |= TRANSPORT_LUNFLAGS_READ_WRITE;
> + else
> + new->lun_flags |= TRANSPORT_LUNFLAGS_READ_ONLY;
> +
> + new->creation_time = get_jiffies_64();
> + new->attach_count++;
>
> + spin_lock_irq(&nacl->device_list_lock);
> + orig = target_nacl_find_deve(nacl, mapped_lun);
> + if (orig && orig->lun_flags & TRANSPORT_LUNFLAGS_INITIATOR_ACCESS) {
> + BUG_ON(orig->se_lun_acl != NULL);
> + BUG_ON(orig->se_lun != lun);
> +
> + rcu_assign_pointer(new->se_lun, lun);
> + rcu_assign_pointer(new->se_lun_acl, lun_acl);
> + hlist_add_head_rcu(&new->link, &nacl->lun_entry_hlist);
> spin_unlock_irq(&nacl->device_list_lock);
> - return 0;
> - }
>
> - deve->se_lun = lun;
> - deve->se_lun_acl = lun_acl;
> - deve->mapped_lun = mapped_lun;
> - deve->lun_flags |= TRANSPORT_LUNFLAGS_INITIATOR_ACCESS;
> + spin_lock_bh(&port->sep_alua_lock);
> + list_del(&orig->alua_port_list);
> + list_add_tail(&new->alua_port_list, &port->sep_alua_list);
> + spin_unlock_bh(&port->sep_alua_lock);
>
> - if (lun_access & TRANSPORT_LUNFLAGS_READ_WRITE) {
> - deve->lun_flags &= ~TRANSPORT_LUNFLAGS_READ_ONLY;
> - deve->lun_flags |= TRANSPORT_LUNFLAGS_READ_WRITE;
> - } else {
> - deve->lun_flags &= ~TRANSPORT_LUNFLAGS_READ_WRITE;
> - deve->lun_flags |= TRANSPORT_LUNFLAGS_READ_ONLY;
> + call_rcu(&orig->rcu_head, target_nacl_deve_callrcu);
> + return 0;
> }
>
> - deve->creation_time = get_jiffies_64();
> - deve->attach_count++;
> + rcu_assign_pointer(new->se_lun, lun);
> + rcu_assign_pointer(new->se_lun_acl, lun_acl);
> + hlist_add_head_rcu(&new->link, &nacl->lun_entry_hlist);
> spin_unlock_irq(&nacl->device_list_lock);
>
> spin_lock_bh(&port->sep_alua_lock);
> - list_add_tail(&deve->alua_port_list, &port->sep_alua_list);
> + list_add_tail(&new->alua_port_list, &port->sep_alua_list);
> spin_unlock_bh(&port->sep_alua_lock);
>
> + synchronize_rcu();
> return 0;
> }
>
> @@ -382,8 +391,14 @@ int core_disable_device_list_for_node(
> struct se_portal_group *tpg)
> {
> struct se_port *port = lun->lun_sep;
> - struct se_dev_entry *deve = nacl->device_list[mapped_lun];
> + struct se_dev_entry *orig;
>
> + spin_lock_irq(&nacl->device_list_lock);
> + orig = target_nacl_find_deve(nacl, mapped_lun);
> + if (!orig) {
> + spin_unlock_irq(&nacl->device_list_lock);
> + return 0;
> + }
> /*
> * If the MappedLUN entry is being disabled, the entry in
> * port->sep_alua_list must be removed now before clearing the
> @@ -398,27 +413,33 @@ int core_disable_device_list_for_node(
> * MappedLUN *deve will be released below..
> */
> spin_lock_bh(&port->sep_alua_lock);
> - list_del(&deve->alua_port_list);
> + list_del(&orig->alua_port_list);
> spin_unlock_bh(&port->sep_alua_lock);
> /*
> * Wait for any in process SPEC_I_PT=1 or REGISTER_AND_MOVE
> * PR operation to complete.
> */
> - while (atomic_read(&deve->pr_ref_count) != 0)
> + while (atomic_read(&orig->pr_ref_count) != 0)
> cpu_relax();
>
> - spin_lock_irq(&nacl->device_list_lock);
> /*
> * Disable struct se_dev_entry LUN ACL mapping
> */
> - core_scsi3_ua_release_all(deve);
> - deve->se_lun = NULL;
> - deve->se_lun_acl = NULL;
> - deve->lun_flags = 0;
> - deve->creation_time = 0;
> - deve->attach_count--;
> + core_scsi3_ua_release_all(orig);
> + rcu_assign_pointer(orig->se_lun, NULL);
> + rcu_assign_pointer(orig->se_lun_acl, NULL);
> + orig->lun_flags = 0;
> + orig->creation_time = 0;
> + orig->attach_count--;
> + hlist_del_rcu(&orig->link);
> spin_unlock_irq(&nacl->device_list_lock);
>
> + /*
> + * Fire off RCU callback to wait for any in process SPEC_I_PT=1
> + * or REGISTER_AND_MOVE PR operation to complete.
> + */
> + call_rcu(&orig->rcu_head, target_nacl_deve_callrcu);
> +
> core_scsi3_free_pr_reg_from_nacl(lun->lun_se_dev, nacl);
> return 0;
> }
> @@ -431,26 +452,25 @@ void core_clear_lun_from_tpg(struct se_lun *lun, struct se_portal_group *tpg)
> {
> struct se_node_acl *nacl;
> struct se_dev_entry *deve;
> - u32 i;
> + u32 mapped_lun;
>
> spin_lock_irq(&tpg->acl_node_lock);
> list_for_each_entry(nacl, &tpg->acl_node_list, acl_list) {
> spin_unlock_irq(&tpg->acl_node_lock);
>
> - spin_lock_irq(&nacl->device_list_lock);
> - for (i = 0; i < TRANSPORT_MAX_LUNS_PER_TPG; i++) {
> - deve = nacl->device_list[i];
> + rcu_read_lock();
> + hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link) {
> if (lun != deve->se_lun)
> continue;
> - spin_unlock_irq(&nacl->device_list_lock);
>
> - core_disable_device_list_for_node(lun, NULL,
> - deve->mapped_lun, TRANSPORT_LUNFLAGS_NO_ACCESS,
> - nacl, tpg);
> + mapped_lun = deve->mapped_lun;
> + rcu_read_unlock();
>
> - spin_lock_irq(&nacl->device_list_lock);
> + core_disable_device_list_for_node(lun, NULL, mapped_lun,
> + TRANSPORT_LUNFLAGS_NO_ACCESS, nacl, tpg);
> + rcu_read_lock();
> }
> - spin_unlock_irq(&nacl->device_list_lock);
> + rcu_read_unlock();
>
> spin_lock_irq(&tpg->acl_node_lock);
> }
> diff --git a/drivers/target/target_core_internal.h b/drivers/target/target_core_internal.h
> index d0344ad..9c4bce0 100644
> --- a/drivers/target/target_core_internal.h
> +++ b/drivers/target/target_core_internal.h
> @@ -12,6 +12,7 @@ struct se_dev_entry *core_get_se_deve_from_rtpi(struct se_node_acl *, u16);
> int core_free_device_list_for_node(struct se_node_acl *,
> struct se_portal_group *);
> void core_update_device_list_access(u32, u32, struct se_node_acl *);
> +struct se_dev_entry *target_nacl_find_deve(struct se_node_acl *, u32);
> int core_enable_device_list_for_node(struct se_lun *, struct se_lun_acl *,
> u32, u32, struct se_node_acl *, struct se_portal_group *);
> int core_disable_device_list_for_node(struct se_lun *, struct se_lun_acl *,
> diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c
> index c0c1f67..dbdd3e3 100644
> --- a/drivers/target/target_core_tpg.c
> +++ b/drivers/target/target_core_tpg.c
> @@ -55,32 +55,29 @@ static void core_clear_initiator_node_from_tpg(
> struct se_node_acl *nacl,
> struct se_portal_group *tpg)
> {
> - int i;
> struct se_dev_entry *deve;
> struct se_lun *lun;
> + u32 mapped_lun;
>
> - spin_lock_irq(&nacl->device_list_lock);
> - for (i = 0; i < TRANSPORT_MAX_LUNS_PER_TPG; i++) {
> - deve = nacl->device_list[i];
> -
> + rcu_read_lock();
> + hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link) {
> if (!(deve->lun_flags & TRANSPORT_LUNFLAGS_INITIATOR_ACCESS))
> continue;
> -
> if (!deve->se_lun) {
> pr_err("%s device entries device pointer is"
> " NULL, but Initiator has access.\n",
> tpg->se_tpg_tfo->get_fabric_name());
> continue;
> }
> -
> lun = deve->se_lun;
> - spin_unlock_irq(&nacl->device_list_lock);
> - core_disable_device_list_for_node(lun, NULL, deve->mapped_lun,
> - TRANSPORT_LUNFLAGS_NO_ACCESS, nacl, tpg);
> + mapped_lun = deve->mapped_lun;
> + rcu_read_unlock();
>
> - spin_lock_irq(&nacl->device_list_lock);
> + core_disable_device_list_for_node(lun, NULL, mapped_lun,
> + TRANSPORT_LUNFLAGS_NO_ACCESS, nacl, tpg);
> + rcu_read_lock();
> }
> - spin_unlock_irq(&nacl->device_list_lock);
> + rcu_read_unlock();
> }
>
> /* __core_tpg_get_initiator_node_acl():
> @@ -266,10 +263,12 @@ static struct se_node_acl *target_alloc_node_acl(struct se_portal_group *tpg,
>
> INIT_LIST_HEAD(&acl->acl_list);
> INIT_LIST_HEAD(&acl->acl_sess_list);
> + INIT_HLIST_HEAD(&acl->lun_entry_hlist);
> kref_init(&acl->acl_kref);
> init_completion(&acl->acl_free_comp);
> spin_lock_init(&acl->device_list_lock);
> spin_lock_init(&acl->nacl_sess_lock);
> + spin_lock_init(&acl->lun_entry_lock);
> atomic_set(&acl->acl_pr_ref_count, 0);
> if (tpg->se_tpg_tfo->tpg_get_default_depth)
> acl->queue_depth = tpg->se_tpg_tfo->tpg_get_default_depth(tpg);
> diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
> index 042a734..6fb38df 100644
> --- a/include/target/target_core_base.h
> +++ b/include/target/target_core_base.h
> @@ -584,10 +584,12 @@ struct se_node_acl {
> char acl_tag[MAX_ACL_TAG_SIZE];
> /* Used for PR SPEC_I_PT=1 and REGISTER_AND_MOVE */
> atomic_t acl_pr_ref_count;
> + struct hlist_head lun_entry_hlist;
> struct se_dev_entry **device_list;
Very nice to see all this posted!
Patch 6 is where device_list is finally removed. Suggest squashing 1-6,
maybe after review, I'm guessing they're not bisectable.
-- Andy
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