Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted

Pull networking updates from Jakub Kicinski:
 "Core:

   - Add dedicated kmem_cache for typical/small skb->head, avoid having
     to access struct page at kfree time, and improve memory use.

   - Introduce sysctl to set default RPS configuration for new netdevs.

   - Define Netlink protocol specification format which can be used to
     describe messages used by each family and auto-generate parsers.
     Add tools for generating kernel data structures and uAPI headers.

   - Expose all net/core sysctls inside netns.

   - Remove 4s sleep in netpoll if carrier is instantly detected on
     boot.

   - Add configurable limit of MDB entries per port, and port-vlan.

   - Continue populating drop reasons throughout the stack.

   - Retire a handful of legacy Qdiscs and classifiers.

  Protocols:

   - Support IPv4 big TCP (TSO frames larger than 64kB).

   - Add IP_LOCAL_PORT_RANGE socket option, to control local port range
     on socket by socket basis.

   - Track and report in procfs number of MPTCP sockets used.

   - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
     manager.

   - IPv6: don't check net.ipv6.route.max_size and rely on garbage
     collection to free memory (similarly to IPv4).

   - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).

   - ICMP: add per-rate limit counters.

   - Add support for user scanning requests in ieee802154.

   - Remove static WEP support.

   - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
     reporting.

   - WiFi 7 EHT channel puncturing support (client & AP).

  BPF:

   - Add a rbtree data structure following the "next-gen data structure"
     precedent set by recently added linked list, that is, by using
     kfunc + kptr instead of adding a new BPF map type.

   - Expose XDP hints via kfuncs with initial support for RX hash and
     timestamp metadata.

   - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
     better support decap on GRE tunnel devices not operating in collect
     metadata.

   - Improve x86 JIT's codegen for PROBE_MEM runtime error checks.

   - Remove the need for trace_printk_lock for bpf_trace_printk and
     bpf_trace_vprintk helpers.

   - Extend libbpf's bpf_tracing.h support for tracing arguments of
     kprobes/uprobes and syscall as a special case.

   - Significantly reduce the search time for module symbols by
     livepatch and BPF.

   - Enable cpumasks to be used as kptrs, which is useful for tracing
     programs tracking which tasks end up running on which CPUs in
     different time intervals.

   - Add support for BPF trampoline on s390x and riscv64.

   - Add capability to export the XDP features supported by the NIC.

   - Add __bpf_kfunc tag for marking kernel functions as kfuncs.

   - Add cgroup.memory=nobpf kernel parameter option to disable BPF
     memory accounting for container environments.

  Netfilter:

   - Remove the CLUSTERIP target. It has been marked as obsolete for
     years, and we still have WARN splats wrt races of the out-of-band
     /proc interface installed by this target.

   - Add 'destroy' commands to nf_tables. They are identical to the
     existing 'delete' commands, but do not return an error if the
     referenced object (set, chain, rule...) did not exist.

  Driver API:

   - Improve cpumask_local_spread() locality to help NICs set the right
     IRQ affinity on AMD platforms.

   - Separate C22 and C45 MDIO bus transactions more clearly.

   - Introduce new DCB table to control DSCP rewrite on egress.

   - Support configuration of Physical Layer Collision Avoidance (PLCA)
     Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
     shared medium Ethernet.

   - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
     preemption of low priority frames by high priority frames.

   - Add support for controlling MACSec offload using netlink SET.

   - Rework devlink instance refcounts to allow registration and
     de-registration under the instance lock. Split the code into
     multiple files, drop some of the unnecessarily granular locks and
     factor out common parts of netlink operation handling.

   - Add TX frame aggregation parameters (for USB drivers).

   - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
     messages with notifications for debug.

   - Allow offloading of UDP NEW connections via act_ct.

   - Add support for per action HW stats in TC.

   - Support hardware miss to TC action (continue processing in SW from
     a specific point in the action chain).

   - Warn if old Wireless Extension user space interface is used with
     modern cfg80211/mac80211 drivers. Do not support Wireless
     Extensions for Wi-Fi 7 devices at all. Everyone should switch to
     using nl80211 interface instead.

   - Improve the CAN bit timing configuration. Use extack to return
     error messages directly to user space, update the SJW handling,
     including the definition of a new default value that will benefit
     CAN-FD controllers, by increasing their oscillator tolerance.

  New hardware / drivers:

   - Ethernet:
      - nVidia BlueField-3 support (control traffic driver)
      - Ethernet support for imx93 SoCs
      - Motorcomm yt8531 gigabit Ethernet PHY
      - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
      - Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
      - Amlogic gxl MDIO mux

   - WiFi:
      - RealTek RTL8188EU (rtl8xxxu)
      - Qualcomm Wi-Fi 7 devices (ath12k)

   - CAN:
      - Renesas R-Car V4H

  Drivers:

   - Bluetooth:
      - Set Per Platform Antenna Gain (PPAG) for Intel controllers.

   - Ethernet NICs:
      - Intel (1G, igc):
         - support TSN / Qbv / packet scheduling features of i226 model
      - Intel (100G, ice):
         - use GNSS subsystem instead of TTY
         - multi-buffer XDP support
         - extend support for GPIO pins to E823 devices
      - nVidia/Mellanox:
         - update the shared buffer configuration on PFC commands
         - implement PTP adjphase function for HW offset control
         - TC support for Geneve and GRE with VF tunnel offload
         - more efficient crypto key management method
         - multi-port eswitch support
      - Netronome/Corigine:
         - add DCB IEEE support
         - support IPsec offloading for NFP3800
      - Freescale/NXP (enetc):
         - support XDP_REDIRECT for XDP non-linear buffers
         - improve reconfig, avoid link flap and waiting for idle
         - support MAC Merge layer
      - Other NICs:
         - sfc/ef100: add basic devlink support for ef100
         - ionic: rx_push mode operation (writing descriptors via MMIO)
         - bnxt: use the auxiliary bus abstraction for RDMA
         - r8169: disable ASPM and reset bus in case of tx timeout
         - cpsw: support QSGMII mode for J721e CPSW9G
         - cpts: support pulse-per-second output
         - ngbe: add an mdio bus driver
         - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
         - r8152: handle devices with FW with NCM support
         - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
         - virtio-net: support multi buffer XDP
         - virtio/vsock: replace virtio_vsock_pkt with sk_buff
         - tsnep: XDP support

   - Ethernet high-speed switches:
      - nVidia/Mellanox (mlxsw):
         - add support for latency TLV (in FW control messages)
      - Microchip (sparx5):
         - separate explicit and implicit traffic forwarding rules, make
           the implicit rules always active
         - add support for egress DSCP rewrite
         - IS0 VCAP support (Ingress Classification)
         - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
           etc.)
         - ES2 VCAP support (Egress Access Control)
         - support for Per-Stream Filtering and Policing (802.1Q,
           8.6.5.1)

   - Ethernet embedded switches:
      - Marvell (mv88e6xxx):
         - add MAB (port auth) offload support
         - enable PTP receive for mv88e6390
      - NXP (ocelot):
         - support MAC Merge layer
         - support for the the vsc7512 internal copper phys
      - Microchip:
         - lan9303: convert to PHYLINK
         - lan966x: support TC flower filter statistics
         - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
         - lan937x: support Credit Based Shaper configuration
         - ksz9477: support Energy Efficient Ethernet
      - other:
         - qca8k: convert to regmap read/write API, use bulk operations
         - rswitch: Improve TX timestamp accuracy

   - Intel WiFi (iwlwifi):
      - EHT (Wi-Fi 7) rate reporting
      - STEP equalizer support: transfer some STEP (connection to radio
        on platforms with integrated wifi) related parameters from the
        BIOS to the firmware.

   - Qualcomm 802.11ax WiFi (ath11k):
      - IPQ5018 support
      - Fine Timing Measurement (FTM) responder role support
      - channel 177 support

   - MediaTek WiFi (mt76):
      - per-PHY LED support
      - mt7996: EHT (Wi-Fi 7) support
      - Wireless Ethernet Dispatch (WED) reset support
      - switch to using page pool allocator

   - RealTek WiFi (rtw89):
      - support new version of Bluetooth co-existance

   - Mobile:
      - rmnet: support TX aggregation"

* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
  page_pool: add a comment explaining the fragment counter usage
  net: ethtool: fix __ethtool_dev_mm_supported() implementation
  ethtool: pse-pd: Fix double word in comments
  xsk: add linux/vmalloc.h to xsk.c
  sefltests: netdevsim: wait for devlink instance after netns removal
  selftest: fib_tests: Always cleanup before exit
  net/mlx5e: Align IPsec ASO result memory to be as required by hardware
  net/mlx5e: TC, Set CT miss to the specific ct action instance
  net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
  net/mlx5: Refactor tc miss handling to a single function
  net/mlx5: Kconfig: Make tc offload depend on tc skb extension
  net/sched: flower: Support hardware miss to tc action
  net/sched: flower: Move filter handle initialization earlier
  net/sched: cls_api: Support hardware miss to tc action
  net/sched: Rename user cookie and act cookie
  sfc: fix builds without CONFIG_RTC_LIB
  sfc: clean up some inconsistent indentings
  net/mlx4_en: Introduce flexible array to silence overflow warning
  net: lan966x: Fix possible deadlock inside PTP
  net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
  ...

1 files changed, 1307 insertions, 0 deletions

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
new file mode 100644
index 000000000..29a2865b8
--- /dev/null
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -0,0 +1,1307 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Generic SCSI-3 ALUA SCSI Device Handler
+ *
+ * Copyright (C) 2007-2010 Hannes Reinecke, SUSE Linux Products GmbH.
+ * All rights reserved.
+ */
+#include <linux/slab.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <asm/unaligned.h>
+#include <scsi/scsi.h>
+#include <scsi/scsi_proto.h>
+#include <scsi/scsi_dbg.h>
+#include <scsi/scsi_eh.h>
+#include <scsi/scsi_dh.h>
+
+#define ALUA_DH_NAME "alua"
+#define ALUA_DH_VER "2.0"
+
+#define TPGS_SUPPORT_NONE		0x00
+#define TPGS_SUPPORT_OPTIMIZED		0x01
+#define TPGS_SUPPORT_NONOPTIMIZED	0x02
+#define TPGS_SUPPORT_STANDBY		0x04
+#define TPGS_SUPPORT_UNAVAILABLE	0x08
+#define TPGS_SUPPORT_LBA_DEPENDENT	0x10
+#define TPGS_SUPPORT_OFFLINE		0x40
+#define TPGS_SUPPORT_TRANSITION		0x80
+#define TPGS_SUPPORT_ALL		0xdf
+
+#define RTPG_FMT_MASK			0x70
+#define RTPG_FMT_EXT_HDR		0x10
+
+#define TPGS_MODE_UNINITIALIZED		 -1
+#define TPGS_MODE_NONE			0x0
+#define TPGS_MODE_IMPLICIT		0x1
+#define TPGS_MODE_EXPLICIT		0x2
+
+#define ALUA_RTPG_SIZE			128
+#define ALUA_FAILOVER_TIMEOUT		60
+#define ALUA_FAILOVER_RETRIES		5
+#define ALUA_RTPG_DELAY_MSECS		5
+#define ALUA_RTPG_RETRY_DELAY		2
+
+/* device handler flags */
+#define ALUA_OPTIMIZE_STPG		0x01
+#define ALUA_RTPG_EXT_HDR_UNSUPP	0x02
+/* State machine flags */
+#define ALUA_PG_RUN_RTPG		0x10
+#define ALUA_PG_RUN_STPG		0x20
+#define ALUA_PG_RUNNING			0x40
+
+static uint optimize_stpg;
+module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(optimize_stpg, "Allow use of a non-optimized path, rather than sending a STPG, when implicit TPGS is supported (0=No,1=Yes). Default is 0.");
+
+static LIST_HEAD(port_group_list);
+static DEFINE_SPINLOCK(port_group_lock);
+static struct workqueue_struct *kaluad_wq;
+
+struct alua_port_group {
+	struct kref		kref;
+	struct rcu_head		rcu;
+	struct list_head	node;
+	struct list_head	dh_list;
+	unsigned char		device_id_str[256];
+	int			device_id_len;
+	int			group_id;
+	int			tpgs;
+	int			state;
+	int			pref;
+	int			valid_states;
+	unsigned		flags; /* used for optimizing STPG */
+	unsigned char		transition_tmo;
+	unsigned long		expiry;
+	unsigned long		interval;
+	struct delayed_work	rtpg_work;
+	spinlock_t		lock;
+	struct list_head	rtpg_list;
+	struct scsi_device	*rtpg_sdev;
+};
+
+struct alua_dh_data {
+	struct list_head	node;
+	struct alua_port_group __rcu *pg;
+	int			group_id;
+	spinlock_t		pg_lock;
+	struct scsi_device	*sdev;
+	int			init_error;
+	struct mutex		init_mutex;
+	bool			disabled;
+};
+
+struct alua_queue_data {
+	struct list_head	entry;
+	activate_complete	callback_fn;
+	void			*callback_data;
+};
+
+#define ALUA_POLICY_SWITCH_CURRENT	0
+#define ALUA_POLICY_SWITCH_ALL		1
+
+static void alua_rtpg_work(struct work_struct *work);
+static bool alua_rtpg_queue(struct alua_port_group *pg,
+			    struct scsi_device *sdev,
+			    struct alua_queue_data *qdata, bool force);
+static void alua_check(struct scsi_device *sdev, bool force);
+
+static void release_port_group(struct kref *kref)
+{
+	struct alua_port_group *pg;
+
+	pg = container_of(kref, struct alua_port_group, kref);
+	if (pg->rtpg_sdev)
+		flush_delayed_work(&pg->rtpg_work);
+	spin_lock(&port_group_lock);
+	list_del(&pg->node);
+	spin_unlock(&port_group_lock);
+	kfree_rcu(pg, rcu);
+}
+
+/*
+ * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
+ * @sdev: sdev the command should be sent to
+ */
+static int submit_rtpg(struct scsi_device *sdev, unsigned char *buff,
+		       int bufflen, struct scsi_sense_hdr *sshdr, int flags)
+{
+	u8 cdb[MAX_COMMAND_SIZE];
+	blk_opf_t req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
+		REQ_FAILFAST_DRIVER;
+
+	/* Prepare the command. */
+	memset(cdb, 0x0, MAX_COMMAND_SIZE);
+	cdb[0] = MAINTENANCE_IN;
+	if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
+		cdb[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
+	else
+		cdb[1] = MI_REPORT_TARGET_PGS;
+	put_unaligned_be32(bufflen, &cdb[6]);
+
+	return scsi_execute(sdev, cdb, DMA_FROM_DEVICE, buff, bufflen, NULL,
+			sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
+			ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
+}
+
+/*
+ * submit_stpg - Issue a SET TARGET PORT GROUP command
+ *
+ * Currently we're only setting the current target port group state
+ * to 'active/optimized' and let the array firmware figure out
+ * the states of the remaining groups.
+ */
+static int submit_stpg(struct scsi_device *sdev, int group_id,
+		       struct scsi_sense_hdr *sshdr)
+{
+	u8 cdb[MAX_COMMAND_SIZE];
+	unsigned char stpg_data[8];
+	int stpg_len = 8;
+	blk_opf_t req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
+		REQ_FAILFAST_DRIVER;
+
+	/* Prepare the data buffer */
+	memset(stpg_data, 0, stpg_len);
+	stpg_data[4] = SCSI_ACCESS_STATE_OPTIMAL;
+	put_unaligned_be16(group_id, &stpg_data[6]);
+
+	/* Prepare the command. */
+	memset(cdb, 0x0, MAX_COMMAND_SIZE);
+	cdb[0] = MAINTENANCE_OUT;
+	cdb[1] = MO_SET_TARGET_PGS;
+	put_unaligned_be32(stpg_len, &cdb[6]);
+
+	return scsi_execute(sdev, cdb, DMA_TO_DEVICE, stpg_data, stpg_len, NULL,
+			sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
+			ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
+}
+
+static struct alua_port_group *alua_find_get_pg(char *id_str, size_t id_size,
+						int group_id)
+{
+	struct alua_port_group *pg;
+
+	if (!id_str || !id_size || !strlen(id_str))
+		return NULL;
+
+	list_for_each_entry(pg, &port_group_list, node) {
+		if (pg->group_id != group_id)
+			continue;
+		if (!pg->device_id_len || pg->device_id_len != id_size)
+			continue;
+		if (strncmp(pg->device_id_str, id_str, id_size))
+			continue;
+		if (!kref_get_unless_zero(&pg->kref))
+			continue;
+		return pg;
+	}
+
+	return NULL;
+}
+
+/*
+ * alua_alloc_pg - Allocate a new port_group structure
+ * @sdev: scsi device
+ * @group_id: port group id
+ * @tpgs: target port group settings
+ *
+ * Allocate a new port_group structure for a given
+ * device.
+ */
+static struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
+					     int group_id, int tpgs)
+{
+	struct alua_port_group *pg, *tmp_pg;
+
+	pg = kzalloc(sizeof(struct alua_port_group), GFP_KERNEL);
+	if (!pg)
+		return ERR_PTR(-ENOMEM);
+
+	pg->device_id_len = scsi_vpd_lun_id(sdev, pg->device_id_str,
+					    sizeof(pg->device_id_str));
+	if (pg->device_id_len <= 0) {
+		/*
+		 * TPGS supported but no device identification found.
+		 * Generate private device identification.
+		 */
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: No device descriptors found\n",
+			    ALUA_DH_NAME);
+		pg->device_id_str[0] = '\0';
+		pg->device_id_len = 0;
+	}
+	pg->group_id = group_id;
+	pg->tpgs = tpgs;
+	pg->state = SCSI_ACCESS_STATE_OPTIMAL;
+	pg->valid_states = TPGS_SUPPORT_ALL;
+	if (optimize_stpg)
+		pg->flags |= ALUA_OPTIMIZE_STPG;
+	kref_init(&pg->kref);
+	INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work);
+	INIT_LIST_HEAD(&pg->rtpg_list);
+	INIT_LIST_HEAD(&pg->node);
+	INIT_LIST_HEAD(&pg->dh_list);
+	spin_lock_init(&pg->lock);
+
+	spin_lock(&port_group_lock);
+	tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
+				  group_id);
+	if (tmp_pg) {
+		spin_unlock(&port_group_lock);
+		kfree(pg);
+		return tmp_pg;
+	}
+
+	list_add(&pg->node, &port_group_list);
+	spin_unlock(&port_group_lock);
+
+	return pg;
+}
+
+/*
+ * alua_check_tpgs - Evaluate TPGS setting
+ * @sdev: device to be checked
+ *
+ * Examine the TPGS setting of the sdev to find out if ALUA
+ * is supported.
+ */
+static int alua_check_tpgs(struct scsi_device *sdev)
+{
+	int tpgs = TPGS_MODE_NONE;
+
+	/*
+	 * ALUA support for non-disk devices is fraught with
+	 * difficulties, so disable it for now.
+	 */
+	if (sdev->type != TYPE_DISK) {
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: disable for non-disk devices\n",
+			    ALUA_DH_NAME);
+		return tpgs;
+	}
+
+	tpgs = scsi_device_tpgs(sdev);
+	switch (tpgs) {
+	case TPGS_MODE_EXPLICIT|TPGS_MODE_IMPLICIT:
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: supports implicit and explicit TPGS\n",
+			    ALUA_DH_NAME);
+		break;
+	case TPGS_MODE_EXPLICIT:
+		sdev_printk(KERN_INFO, sdev, "%s: supports explicit TPGS\n",
+			    ALUA_DH_NAME);
+		break;
+	case TPGS_MODE_IMPLICIT:
+		sdev_printk(KERN_INFO, sdev, "%s: supports implicit TPGS\n",
+			    ALUA_DH_NAME);
+		break;
+	case TPGS_MODE_NONE:
+		sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
+			    ALUA_DH_NAME);
+		break;
+	default:
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: unsupported TPGS setting %d\n",
+			    ALUA_DH_NAME, tpgs);
+		tpgs = TPGS_MODE_NONE;
+		break;
+	}
+
+	return tpgs;
+}
+
+/*
+ * alua_check_vpd - Evaluate INQUIRY vpd page 0x83
+ * @sdev: device to be checked
+ *
+ * Extract the relative target port and the target port group
+ * descriptor from the list of identificators.
+ */
+static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
+			  int tpgs)
+{
+	int rel_port = -1, group_id;
+	struct alua_port_group *pg, *old_pg = NULL;
+	bool pg_updated = false;
+	unsigned long flags;
+
+	group_id = scsi_vpd_tpg_id(sdev, &rel_port);
+	if (group_id < 0) {
+		/*
+		 * Internal error; TPGS supported but required
+		 * VPD identification descriptors not present.
+		 * Disable ALUA support
+		 */
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: No target port descriptors found\n",
+			    ALUA_DH_NAME);
+		return SCSI_DH_DEV_UNSUPP;
+	}
+
+	pg = alua_alloc_pg(sdev, group_id, tpgs);
+	if (IS_ERR(pg)) {
+		if (PTR_ERR(pg) == -ENOMEM)
+			return SCSI_DH_NOMEM;
+		return SCSI_DH_DEV_UNSUPP;
+	}
+	if (pg->device_id_len)
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: device %s port group %x rel port %x\n",
+			    ALUA_DH_NAME, pg->device_id_str,
+			    group_id, rel_port);
+	else
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: port group %x rel port %x\n",
+			    ALUA_DH_NAME, group_id, rel_port);
+
+	kref_get(&pg->kref);
+
+	/* Check for existing port group references */
+	spin_lock(&h->pg_lock);
+	old_pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
+	if (old_pg != pg) {
+		/* port group has changed. Update to new port group */
+		if (h->pg) {
+			spin_lock_irqsave(&old_pg->lock, flags);
+			list_del_rcu(&h->node);
+			spin_unlock_irqrestore(&old_pg->lock, flags);
+		}
+		rcu_assign_pointer(h->pg, pg);
+		pg_updated = true;
+	}
+
+	spin_lock_irqsave(&pg->lock, flags);
+	if (pg_updated)
+		list_add_rcu(&h->node, &pg->dh_list);
+	spin_unlock_irqrestore(&pg->lock, flags);
+
+	spin_unlock(&h->pg_lock);
+
+	alua_rtpg_queue(pg, sdev, NULL, true);
+	kref_put(&pg->kref, release_port_group);
+
+	if (old_pg)
+		kref_put(&old_pg->kref, release_port_group);
+
+	return SCSI_DH_OK;
+}
+
+static char print_alua_state(unsigned char state)
+{
+	switch (state) {
+	case SCSI_ACCESS_STATE_OPTIMAL:
+		return 'A';
+	case SCSI_ACCESS_STATE_ACTIVE:
+		return 'N';
+	case SCSI_ACCESS_STATE_STANDBY:
+		return 'S';
+	case SCSI_ACCESS_STATE_UNAVAILABLE:
+		return 'U';
+	case SCSI_ACCESS_STATE_LBA:
+		return 'L';
+	case SCSI_ACCESS_STATE_OFFLINE:
+		return 'O';
+	case SCSI_ACCESS_STATE_TRANSITIONING:
+		return 'T';
+	default:
+		return 'X';
+	}
+}
+
+static enum scsi_disposition alua_check_sense(struct scsi_device *sdev,
+					      struct scsi_sense_hdr *sense_hdr)
+{
+	struct alua_dh_data *h = sdev->handler_data;
+	struct alua_port_group *pg;
+
+	switch (sense_hdr->sense_key) {
+	case NOT_READY:
+		if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) {
+			/*
+			 * LUN Not Accessible - ALUA state transition
+			 */
+			rcu_read_lock();
+			pg = rcu_dereference(h->pg);
+			if (pg)
+				pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
+			rcu_read_unlock();
+			alua_check(sdev, false);
+			return NEEDS_RETRY;
+		}
+		break;
+	case UNIT_ATTENTION:
+		if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) {
+			/*
+			 * Power On, Reset, or Bus Device Reset.
+			 * Might have obscured a state transition,
+			 * so schedule a recheck.
+			 */
+			alua_check(sdev, true);
+			return ADD_TO_MLQUEUE;
+		}
+		if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
+			/*
+			 * Device internal reset
+			 */
+			return ADD_TO_MLQUEUE;
+		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01)
+			/*
+			 * Mode Parameters Changed
+			 */
+			return ADD_TO_MLQUEUE;
+		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
+			/*
+			 * ALUA state changed
+			 */
+			alua_check(sdev, true);
+			return ADD_TO_MLQUEUE;
+		}
+		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
+			/*
+			 * Implicit ALUA state transition failed
+			 */
+			alua_check(sdev, true);
+			return ADD_TO_MLQUEUE;
+		}
+		if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
+			/*
+			 * Inquiry data has changed
+			 */
+			return ADD_TO_MLQUEUE;
+		if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x0e)
+			/*
+			 * REPORTED_LUNS_DATA_HAS_CHANGED is reported
+			 * when switching controllers on targets like
+			 * Intel Multi-Flex. We can just retry.
+			 */
+			return ADD_TO_MLQUEUE;
+		break;
+	}
+
+	return SCSI_RETURN_NOT_HANDLED;
+}
+
+/*
+ * alua_tur - Send a TEST UNIT READY
+ * @sdev: device to which the TEST UNIT READY command should be send
+ *
+ * Send a TEST UNIT READY to @sdev to figure out the device state
+ * Returns SCSI_DH_RETRY if the sense code is NOT READY/ALUA TRANSITIONING,
+ * SCSI_DH_OK if no error occurred, and SCSI_DH_IO otherwise.
+ */
+static int alua_tur(struct scsi_device *sdev)
+{
+	struct scsi_sense_hdr sense_hdr;
+	int retval;
+
+	retval = scsi_test_unit_ready(sdev, ALUA_FAILOVER_TIMEOUT * HZ,
+				      ALUA_FAILOVER_RETRIES, &sense_hdr);
+	if (sense_hdr.sense_key == NOT_READY &&
+	    sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
+		return SCSI_DH_RETRY;
+	else if (retval)
+		return SCSI_DH_IO;
+	else
+		return SCSI_DH_OK;
+}
+
+/*
+ * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
+ * @sdev: the device to be evaluated.
+ *
+ * Evaluate the Target Port Group State.
+ * Returns SCSI_DH_DEV_OFFLINED if the path is
+ * found to be unusable.
+ */
+static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
+{
+	struct scsi_sense_hdr sense_hdr;
+	struct alua_port_group *tmp_pg;
+	int len, k, off, bufflen = ALUA_RTPG_SIZE;
+	int group_id_old, state_old, pref_old, valid_states_old;
+	unsigned char *desc, *buff;
+	unsigned err;
+	int retval;
+	unsigned int tpg_desc_tbl_off;
+	unsigned char orig_transition_tmo;
+	unsigned long flags;
+	bool transitioning_sense = false;
+
+	group_id_old = pg->group_id;
+	state_old = pg->state;
+	pref_old = pg->pref;
+	valid_states_old = pg->valid_states;
+
+	if (!pg->expiry) {
+		unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT * HZ;
+
+		if (pg->transition_tmo)
+			transition_tmo = pg->transition_tmo * HZ;
+
+		pg->expiry = round_jiffies_up(jiffies + transition_tmo);
+	}
+
+	buff = kzalloc(bufflen, GFP_KERNEL);
+	if (!buff)
+		return SCSI_DH_DEV_TEMP_BUSY;
+
+ retry:
+	err = 0;
+	retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
+
+	if (retval) {
+		/*
+		 * Some (broken) implementations have a habit of returning
+		 * an error during things like firmware update etc.
+		 * But if the target only supports active/optimized there's
+		 * not much we can do; it's not that we can switch paths
+		 * or anything.
+		 * So ignore any errors to avoid spurious failures during
+		 * path failover.
+		 */
+		if ((pg->valid_states & ~TPGS_SUPPORT_OPTIMIZED) == 0) {
+			sdev_printk(KERN_INFO, sdev,
+				    "%s: ignoring rtpg result %d\n",
+				    ALUA_DH_NAME, retval);
+			kfree(buff);
+			return SCSI_DH_OK;
+		}
+		if (retval < 0 || !scsi_sense_valid(&sense_hdr)) {
+			sdev_printk(KERN_INFO, sdev,
+				    "%s: rtpg failed, result %d\n",
+				    ALUA_DH_NAME, retval);
+			kfree(buff);
+			if (retval < 0)
+				return SCSI_DH_DEV_TEMP_BUSY;
+			if (host_byte(retval) == DID_NO_CONNECT)
+				return SCSI_DH_RES_TEMP_UNAVAIL;
+			return SCSI_DH_IO;
+		}
+
+		/*
+		 * submit_rtpg() has failed on existing arrays
+		 * when requesting extended header info, and
+		 * the array doesn't support extended headers,
+		 * even though it shouldn't according to T10.
+		 * The retry without rtpg_ext_hdr_req set
+		 * handles this.
+		 * Note:  some arrays return a sense key of ILLEGAL_REQUEST
+		 * with ASC 00h if they don't support the extended header.
+		 */
+		if (!(pg->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
+		    sense_hdr.sense_key == ILLEGAL_REQUEST) {
+			pg->flags |= ALUA_RTPG_EXT_HDR_UNSUPP;
+			goto retry;
+		}
+		/*
+		 * If the array returns with 'ALUA state transition'
+		 * sense code here it cannot return RTPG data during
+		 * transition. So set the state to 'transitioning' directly.
+		 */
+		if (sense_hdr.sense_key == NOT_READY &&
+		    sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a) {
+			transitioning_sense = true;
+			goto skip_rtpg;
+		}
+		/*
+		 * Retry on any other UNIT ATTENTION occurred.
+		 */
+		if (sense_hdr.sense_key == UNIT_ATTENTION)
+			err = SCSI_DH_RETRY;
+		if (err == SCSI_DH_RETRY &&
+		    pg->expiry != 0 && time_before(jiffies, pg->expiry)) {
+			sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
+				    ALUA_DH_NAME);
+			scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
+			kfree(buff);
+			return err;
+		}
+		sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
+			    ALUA_DH_NAME);
+		scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
+		kfree(buff);
+		pg->expiry = 0;
+		return SCSI_DH_IO;
+	}
+
+	len = get_unaligned_be32(&buff[0]) + 4;
+
+	if (len > bufflen) {
+		/* Resubmit with the correct length */
+		kfree(buff);
+		bufflen = len;
+		buff = kmalloc(bufflen, GFP_KERNEL);
+		if (!buff) {
+			sdev_printk(KERN_WARNING, sdev,
+				    "%s: kmalloc buffer failed\n",__func__);
+			/* Temporary failure, bypass */
+			pg->expiry = 0;
+			return SCSI_DH_DEV_TEMP_BUSY;
+		}
+		goto retry;
+	}
+
+	orig_transition_tmo = pg->transition_tmo;
+	if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && buff[5] != 0)
+		pg->transition_tmo = buff[5];
+	else
+		pg->transition_tmo = ALUA_FAILOVER_TIMEOUT;
+
+	if (orig_transition_tmo != pg->transition_tmo) {
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: transition timeout set to %d seconds\n",
+			    ALUA_DH_NAME, pg->transition_tmo);
+		pg->expiry = jiffies + pg->transition_tmo * HZ;
+	}
+
+	if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
+		tpg_desc_tbl_off = 8;
+	else
+		tpg_desc_tbl_off = 4;
+
+	for (k = tpg_desc_tbl_off, desc = buff + tpg_desc_tbl_off;
+	     k < len;
+	     k += off, desc += off) {
+		u16 group_id = get_unaligned_be16(&desc[2]);
+
+		spin_lock_irqsave(&port_group_lock, flags);
+		tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
+					  group_id);
+		spin_unlock_irqrestore(&port_group_lock, flags);
+		if (tmp_pg) {
+			if (spin_trylock_irqsave(&tmp_pg->lock, flags)) {
+				if ((tmp_pg == pg) ||
+				    !(tmp_pg->flags & ALUA_PG_RUNNING)) {
+					struct alua_dh_data *h;
+
+					tmp_pg->state = desc[0] & 0x0f;
+					tmp_pg->pref = desc[0] >> 7;
+					rcu_read_lock();
+					list_for_each_entry_rcu(h,
+						&tmp_pg->dh_list, node) {
+						if (!h->sdev)
+							continue;
+						h->sdev->access_state = desc[0];
+					}
+					rcu_read_unlock();
+				}
+				if (tmp_pg == pg)
+					tmp_pg->valid_states = desc[1];
+				spin_unlock_irqrestore(&tmp_pg->lock, flags);
+			}
+			kref_put(&tmp_pg->kref, release_port_group);
+		}
+		off = 8 + (desc[7] * 4);
+	}
+
+ skip_rtpg:
+	spin_lock_irqsave(&pg->lock, flags);
+	if (transitioning_sense)
+		pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
+
+	if (group_id_old != pg->group_id || state_old != pg->state ||
+		pref_old != pg->pref || valid_states_old != pg->valid_states)
+		sdev_printk(KERN_INFO, sdev,
+			"%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
+			ALUA_DH_NAME, pg->group_id, print_alua_state(pg->state),
+			pg->pref ? "preferred" : "non-preferred",
+			pg->valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
+			pg->valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
+			pg->valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
+			pg->valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u',
+			pg->valid_states&TPGS_SUPPORT_STANDBY?'S':'s',
+			pg->valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
+			pg->valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
+
+	switch (pg->state) {
+	case SCSI_ACCESS_STATE_TRANSITIONING:
+		if (time_before(jiffies, pg->expiry)) {
+			/* State transition, retry */
+			pg->interval = ALUA_RTPG_RETRY_DELAY;
+			err = SCSI_DH_RETRY;
+		} else {
+			struct alua_dh_data *h;
+
+			/* Transitioning time exceeded, set port to standby */
+			err = SCSI_DH_IO;
+			pg->state = SCSI_ACCESS_STATE_STANDBY;
+			pg->expiry = 0;
+			rcu_read_lock();
+			list_for_each_entry_rcu(h, &pg->dh_list, node) {
+				if (!h->sdev)
+					continue;
+				h->sdev->access_state =
+					(pg->state & SCSI_ACCESS_STATE_MASK);
+				if (pg->pref)
+					h->sdev->access_state |=
+						SCSI_ACCESS_STATE_PREFERRED;
+			}
+			rcu_read_unlock();
+		}
+		break;
+	case SCSI_ACCESS_STATE_OFFLINE:
+		/* Path unusable */
+		err = SCSI_DH_DEV_OFFLINED;
+		pg->expiry = 0;
+		break;
+	default:
+		/* Useable path if active */
+		err = SCSI_DH_OK;
+		pg->expiry = 0;
+		break;
+	}
+	spin_unlock_irqrestore(&pg->lock, flags);
+	kfree(buff);
+	return err;
+}
+
+/*
+ * alua_stpg - Issue a SET TARGET PORT GROUP command
+ *
+ * Issue a SET TARGET PORT GROUP command and evaluate the
+ * response. Returns SCSI_DH_RETRY per default to trigger
+ * a re-evaluation of the target group state or SCSI_DH_OK
+ * if no further action needs to be taken.
+ */
+static unsigned alua_stpg(struct scsi_device *sdev, struct alua_port_group *pg)
+{
+	int retval;
+	struct scsi_sense_hdr sense_hdr;
+
+	if (!(pg->tpgs & TPGS_MODE_EXPLICIT)) {
+		/* Only implicit ALUA supported, retry */
+		return SCSI_DH_RETRY;
+	}
+	switch (pg->state) {
+	case SCSI_ACCESS_STATE_OPTIMAL:
+		return SCSI_DH_OK;
+	case SCSI_ACCESS_STATE_ACTIVE:
+		if ((pg->flags & ALUA_OPTIMIZE_STPG) &&
+		    !pg->pref &&
+		    (pg->tpgs & TPGS_MODE_IMPLICIT))
+			return SCSI_DH_OK;
+		break;
+	case SCSI_ACCESS_STATE_STANDBY:
+	case SCSI_ACCESS_STATE_UNAVAILABLE:
+		break;
+	case SCSI_ACCESS_STATE_OFFLINE:
+		return SCSI_DH_IO;
+	case SCSI_ACCESS_STATE_TRANSITIONING:
+		break;
+	default:
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: stpg failed, unhandled TPGS state %d",
+			    ALUA_DH_NAME, pg->state);
+		return SCSI_DH_NOSYS;
+	}
+	retval = submit_stpg(sdev, pg->group_id, &sense_hdr);
+
+	if (retval) {
+		if (retval < 0 || !scsi_sense_valid(&sense_hdr)) {
+			sdev_printk(KERN_INFO, sdev,
+				    "%s: stpg failed, result %d",
+				    ALUA_DH_NAME, retval);
+			if (retval < 0)
+				return SCSI_DH_DEV_TEMP_BUSY;
+		} else {
+			sdev_printk(KERN_INFO, sdev, "%s: stpg failed\n",
+				    ALUA_DH_NAME);
+			scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
+		}
+	}
+	/* Retry RTPG */
+	return SCSI_DH_RETRY;
+}
+
+/*
+ * The caller must call scsi_device_put() on the returned pointer if it is not
+ * NULL.
+ */
+static struct scsi_device * __must_check
+alua_rtpg_select_sdev(struct alua_port_group *pg)
+{
+	struct alua_dh_data *h;
+	struct scsi_device *sdev = NULL, *prev_sdev;
+
+	lockdep_assert_held(&pg->lock);
+	if (WARN_ON(!pg->rtpg_sdev))
+		return NULL;
+
+	/*
+	 * RCU protection isn't necessary for dh_list here
+	 * as we hold pg->lock, but for access to h->pg.
+	 */
+	rcu_read_lock();
+	list_for_each_entry_rcu(h, &pg->dh_list, node) {
+		if (!h->sdev)
+			continue;
+		if (h->sdev == pg->rtpg_sdev) {
+			h->disabled = true;
+			continue;
+		}
+		if (rcu_dereference(h->pg) == pg &&
+		    !h->disabled &&
+		    !scsi_device_get(h->sdev)) {
+			sdev = h->sdev;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	if (!sdev) {
+		pr_warn("%s: no device found for rtpg\n",
+			(pg->device_id_len ?
+			 (char *)pg->device_id_str : "(nameless PG)"));
+		return NULL;
+	}
+
+	sdev_printk(KERN_INFO, sdev, "rtpg retry on different device\n");
+
+	prev_sdev = pg->rtpg_sdev;
+	pg->rtpg_sdev = sdev;
+
+	return prev_sdev;
+}
+
+static void alua_rtpg_work(struct work_struct *work)
+{
+	struct alua_port_group *pg =
+		container_of(work, struct alua_port_group, rtpg_work.work);
+	struct scsi_device *sdev, *prev_sdev = NULL;
+	LIST_HEAD(qdata_list);
+	int err = SCSI_DH_OK;
+	struct alua_queue_data *qdata, *tmp;
+	struct alua_dh_data *h;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pg->lock, flags);
+	sdev = pg->rtpg_sdev;
+	if (!sdev) {
+		WARN_ON(pg->flags & ALUA_PG_RUN_RTPG);
+		WARN_ON(pg->flags & ALUA_PG_RUN_STPG);
+		spin_unlock_irqrestore(&pg->lock, flags);
+		kref_put(&pg->kref, release_port_group);
+		return;
+	}
+	pg->flags |= ALUA_PG_RUNNING;
+	if (pg->flags & ALUA_PG_RUN_RTPG) {
+		int state = pg->state;
+
+		pg->flags &= ~ALUA_PG_RUN_RTPG;
+		spin_unlock_irqrestore(&pg->lock, flags);
+		if (state == SCSI_ACCESS_STATE_TRANSITIONING) {
+			if (alua_tur(sdev) == SCSI_DH_RETRY) {
+				spin_lock_irqsave(&pg->lock, flags);
+				pg->flags &= ~ALUA_PG_RUNNING;
+				pg->flags |= ALUA_PG_RUN_RTPG;
+				if (!pg->interval)
+					pg->interval = ALUA_RTPG_RETRY_DELAY;
+				spin_unlock_irqrestore(&pg->lock, flags);
+				queue_delayed_work(kaluad_wq, &pg->rtpg_work,
+						   pg->interval * HZ);
+				return;
+			}
+			/* Send RTPG on failure or if TUR indicates SUCCESS */
+		}
+		err = alua_rtpg(sdev, pg);
+		spin_lock_irqsave(&pg->lock, flags);
+
+		/* If RTPG failed on the current device, try using another */
+		if (err == SCSI_DH_RES_TEMP_UNAVAIL &&
+		    (prev_sdev = alua_rtpg_select_sdev(pg)))
+			err = SCSI_DH_IMM_RETRY;
+
+		if (err == SCSI_DH_RETRY || err == SCSI_DH_IMM_RETRY ||
+		    pg->flags & ALUA_PG_RUN_RTPG) {
+			pg->flags &= ~ALUA_PG_RUNNING;
+			if (err == SCSI_DH_IMM_RETRY)
+				pg->interval = 0;
+			else if (!pg->interval && !(pg->flags & ALUA_PG_RUN_RTPG))
+				pg->interval = ALUA_RTPG_RETRY_DELAY;
+			pg->flags |= ALUA_PG_RUN_RTPG;
+			spin_unlock_irqrestore(&pg->lock, flags);
+			goto queue_rtpg;
+		}
+		if (err != SCSI_DH_OK)
+			pg->flags &= ~ALUA_PG_RUN_STPG;
+	}
+	if (pg->flags & ALUA_PG_RUN_STPG) {
+		pg->flags &= ~ALUA_PG_RUN_STPG;
+		spin_unlock_irqrestore(&pg->lock, flags);
+		err = alua_stpg(sdev, pg);
+		spin_lock_irqsave(&pg->lock, flags);
+		if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
+			pg->flags |= ALUA_PG_RUN_RTPG;
+			pg->interval = 0;
+			pg->flags &= ~ALUA_PG_RUNNING;
+			spin_unlock_irqrestore(&pg->lock, flags);
+			goto queue_rtpg;
+		}
+	}
+
+	list_splice_init(&pg->rtpg_list, &qdata_list);
+	/*
+	 * We went through an RTPG, for good or bad.
+	 * Re-enable all devices for the next attempt.
+	 */
+	list_for_each_entry(h, &pg->dh_list, node)
+		h->disabled = false;
+	pg->rtpg_sdev = NULL;
+	spin_unlock_irqrestore(&pg->lock, flags);
+
+	if (prev_sdev)
+		scsi_device_put(prev_sdev);
+
+	list_for_each_entry_safe(qdata, tmp, &qdata_list, entry) {
+		list_del(&qdata->entry);
+		if (qdata->callback_fn)
+			qdata->callback_fn(qdata->callback_data, err);
+		kfree(qdata);
+	}
+	spin_lock_irqsave(&pg->lock, flags);
+	pg->flags &= ~ALUA_PG_RUNNING;
+	spin_unlock_irqrestore(&pg->lock, flags);
+	scsi_device_put(sdev);
+	kref_put(&pg->kref, release_port_group);
+	return;
+
+queue_rtpg:
+	if (prev_sdev)
+		scsi_device_put(prev_sdev);
+	queue_delayed_work(kaluad_wq, &pg->rtpg_work, pg->interval * HZ);
+}
+
+/**
+ * alua_rtpg_queue() - cause RTPG to be submitted asynchronously
+ * @pg: ALUA port group associated with @sdev.
+ * @sdev: SCSI device for which to submit an RTPG.
+ * @qdata: Information about the callback to invoke after the RTPG.
+ * @force: Whether or not to submit an RTPG if a work item that will submit an
+ *         RTPG already has been scheduled.
+ *
+ * Returns true if and only if alua_rtpg_work() will be called asynchronously.
+ * That function is responsible for calling @qdata->fn().
+ *
+ * Context: may be called from atomic context (alua_check()) only if the caller
+ *	holds an sdev reference.
+ */
+static bool alua_rtpg_queue(struct alua_port_group *pg,
+			    struct scsi_device *sdev,
+			    struct alua_queue_data *qdata, bool force)
+{
+	int start_queue = 0;
+	unsigned long flags;
+
+	if (WARN_ON_ONCE(!pg) || scsi_device_get(sdev))
+		return false;
+
+	spin_lock_irqsave(&pg->lock, flags);
+	if (qdata) {
+		list_add_tail(&qdata->entry, &pg->rtpg_list);
+		pg->flags |= ALUA_PG_RUN_STPG;
+		force = true;
+	}
+	if (pg->rtpg_sdev == NULL) {
+		struct alua_dh_data *h = sdev->handler_data;
+
+		rcu_read_lock();
+		if (h && rcu_dereference(h->pg) == pg) {
+			pg->interval = 0;
+			pg->flags |= ALUA_PG_RUN_RTPG;
+			kref_get(&pg->kref);
+			pg->rtpg_sdev = sdev;
+			start_queue = 1;
+		}
+		rcu_read_unlock();
+	} else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force) {
+		pg->flags |= ALUA_PG_RUN_RTPG;
+		/* Do not queue if the worker is already running */
+		if (!(pg->flags & ALUA_PG_RUNNING)) {
+			kref_get(&pg->kref);
+			start_queue = 1;
+		}
+	}
+
+	spin_unlock_irqrestore(&pg->lock, flags);
+
+	if (start_queue) {
+		if (queue_delayed_work(kaluad_wq, &pg->rtpg_work,
+				msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS)))
+			sdev = NULL;
+		else
+			kref_put(&pg->kref, release_port_group);
+	}
+	if (sdev)
+		scsi_device_put(sdev);
+
+	return true;
+}
+
+/*
+ * alua_initialize - Initialize ALUA state
+ * @sdev: the device to be initialized
+ *
+ * For the prep_fn to work correctly we have
+ * to initialize the ALUA state for the device.
+ */
+static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
+{
+	int err = SCSI_DH_DEV_UNSUPP, tpgs;
+
+	mutex_lock(&h->init_mutex);
+	h->disabled = false;
+	tpgs = alua_check_tpgs(sdev);
+	if (tpgs != TPGS_MODE_NONE)
+		err = alua_check_vpd(sdev, h, tpgs);
+	h->init_error = err;
+	mutex_unlock(&h->init_mutex);
+	return err;
+}
+/*
+ * alua_set_params - set/unset the optimize flag
+ * @sdev: device on the path to be activated
+ * params - parameters in the following format
+ *      "no_of_params\0param1\0param2\0param3\0...\0"
+ * For example, to set the flag pass the following parameters
+ * from multipath.conf
+ *     hardware_handler        "2 alua 1"
+ */
+static int alua_set_params(struct scsi_device *sdev, const char *params)
+{
+	struct alua_dh_data *h = sdev->handler_data;
+	struct alua_port_group *pg = NULL;
+	unsigned int optimize = 0, argc;
+	const char *p = params;
+	int result = SCSI_DH_OK;
+	unsigned long flags;
+
+	if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
+		return -EINVAL;
+
+	while (*p++)
+		;
+	if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
+		return -EINVAL;
+
+	rcu_read_lock();
+	pg = rcu_dereference(h->pg);
+	if (!pg) {
+		rcu_read_unlock();
+		return -ENXIO;
+	}
+	spin_lock_irqsave(&pg->lock, flags);
+	if (optimize)
+		pg->flags |= ALUA_OPTIMIZE_STPG;
+	else
+		pg->flags &= ~ALUA_OPTIMIZE_STPG;
+	spin_unlock_irqrestore(&pg->lock, flags);
+	rcu_read_unlock();
+
+	return result;
+}
+
+/*
+ * alua_activate - activate a path
+ * @sdev: device on the path to be activated
+ *
+ * We're currently switching the port group to be activated only and
+ * let the array figure out the rest.
+ * There may be other arrays which require us to switch all port groups
+ * based on a certain policy. But until we actually encounter them it
+ * should be okay.
+ */
+static int alua_activate(struct scsi_device *sdev,
+			activate_complete fn, void *data)
+{
+	struct alua_dh_data *h = sdev->handler_data;
+	int err = SCSI_DH_OK;
+	struct alua_queue_data *qdata;
+	struct alua_port_group *pg;
+
+	qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
+	if (!qdata) {
+		err = SCSI_DH_RES_TEMP_UNAVAIL;
+		goto out;
+	}
+	qdata->callback_fn = fn;
+	qdata->callback_data = data;
+
+	mutex_lock(&h->init_mutex);
+	rcu_read_lock();
+	pg = rcu_dereference(h->pg);
+	if (!pg || !kref_get_unless_zero(&pg->kref)) {
+		rcu_read_unlock();
+		kfree(qdata);
+		err = h->init_error;
+		mutex_unlock(&h->init_mutex);
+		goto out;
+	}
+	rcu_read_unlock();
+	mutex_unlock(&h->init_mutex);
+
+	if (alua_rtpg_queue(pg, sdev, qdata, true))
+		fn = NULL;
+	else
+		err = SCSI_DH_DEV_OFFLINED;
+	kref_put(&pg->kref, release_port_group);
+out:
+	if (fn)
+		fn(data, err);
+	return 0;
+}
+
+/*
+ * alua_check - check path status
+ * @sdev: device on the path to be checked
+ *
+ * Check the device status
+ */
+static void alua_check(struct scsi_device *sdev, bool force)
+{
+	struct alua_dh_data *h = sdev->handler_data;
+	struct alua_port_group *pg;
+
+	rcu_read_lock();
+	pg = rcu_dereference(h->pg);
+	if (!pg || !kref_get_unless_zero(&pg->kref)) {
+		rcu_read_unlock();
+		return;
+	}
+	rcu_read_unlock();
+	alua_rtpg_queue(pg, sdev, NULL, force);
+	kref_put(&pg->kref, release_port_group);
+}
+
+/*
+ * alua_prep_fn - request callback
+ *
+ * Fail I/O to all paths not in state
+ * active/optimized or active/non-optimized.
+ */
+static blk_status_t alua_prep_fn(struct scsi_device *sdev, struct request *req)
+{
+	struct alua_dh_data *h = sdev->handler_data;
+	struct alua_port_group *pg;
+	unsigned char state = SCSI_ACCESS_STATE_OPTIMAL;
+
+	rcu_read_lock();
+	pg = rcu_dereference(h->pg);
+	if (pg)
+		state = pg->state;
+	rcu_read_unlock();
+
+	switch (state) {
+	case SCSI_ACCESS_STATE_OPTIMAL:
+	case SCSI_ACCESS_STATE_ACTIVE:
+	case SCSI_ACCESS_STATE_LBA:
+	case SCSI_ACCESS_STATE_TRANSITIONING:
+		return BLK_STS_OK;
+	default:
+		req->rq_flags |= RQF_QUIET;
+		return BLK_STS_IOERR;
+	}
+}
+
+static void alua_rescan(struct scsi_device *sdev)
+{
+	struct alua_dh_data *h = sdev->handler_data;
+
+	alua_initialize(sdev, h);
+}
+
+/*
+ * alua_bus_attach - Attach device handler
+ * @sdev: device to be attached to
+ */
+static int alua_bus_attach(struct scsi_device *sdev)
+{
+	struct alua_dh_data *h;
+	int err;
+
+	h = kzalloc(sizeof(*h) , GFP_KERNEL);
+	if (!h)
+		return SCSI_DH_NOMEM;
+	spin_lock_init(&h->pg_lock);
+	rcu_assign_pointer(h->pg, NULL);
+	h->init_error = SCSI_DH_OK;
+	h->sdev = sdev;
+	INIT_LIST_HEAD(&h->node);
+
+	mutex_init(&h->init_mutex);
+	err = alua_initialize(sdev, h);
+	if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED)
+		goto failed;
+
+	sdev->handler_data = h;
+	return SCSI_DH_OK;
+failed:
+	kfree(h);
+	return err;
+}
+
+/*
+ * alua_bus_detach - Detach device handler
+ * @sdev: device to be detached from
+ */
+static void alua_bus_detach(struct scsi_device *sdev)
+{
+	struct alua_dh_data *h = sdev->handler_data;
+	struct alua_port_group *pg;
+
+	spin_lock(&h->pg_lock);
+	pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
+	rcu_assign_pointer(h->pg, NULL);
+	spin_unlock(&h->pg_lock);
+	if (pg) {
+		spin_lock_irq(&pg->lock);
+		list_del_rcu(&h->node);
+		spin_unlock_irq(&pg->lock);
+		kref_put(&pg->kref, release_port_group);
+	}
+	sdev->handler_data = NULL;
+	synchronize_rcu();
+	kfree(h);
+}
+
+static struct scsi_device_handler alua_dh = {
+	.name = ALUA_DH_NAME,
+	.module = THIS_MODULE,
+	.attach = alua_bus_attach,
+	.detach = alua_bus_detach,
+	.prep_fn = alua_prep_fn,
+	.check_sense = alua_check_sense,
+	.activate = alua_activate,
+	.rescan = alua_rescan,
+	.set_params = alua_set_params,
+};
+
+static int __init alua_init(void)
+{
+	int r;
+
+	kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM, 0);
+	if (!kaluad_wq)
+		return -ENOMEM;
+
+	r = scsi_register_device_handler(&alua_dh);
+	if (r != 0) {
+		printk(KERN_ERR "%s: Failed to register scsi device handler",
+			ALUA_DH_NAME);
+		destroy_workqueue(kaluad_wq);
+	}
+	return r;
+}
+
+static void __exit alua_exit(void)
+{
+	scsi_unregister_device_handler(&alua_dh);
+	destroy_workqueue(kaluad_wq);
+}
+
+module_init(alua_init);
+module_exit(alua_exit);
+
+MODULE_DESCRIPTION("DM Multipath ALUA support");
+MODULE_AUTHOR("Hannes Reinecke <hare@suse.de>");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(ALUA_DH_VER);