[SCSI] scsi_netlink: Add transport and LLD recieve and event support

This patch adds scsi netlink recieve and event support for transport
and scsi LLDD's.  It is a reimplementation of the patch posted last
week by David Somayajulu.
http://marc.info/?l=linux-scsi&m=121745486221819&w=2

There are a few things done differently:

- Transport support is included

- Event delivery is included

- The vendor message is now its own unique message type, considered
  part of the generic "SCSI Transport".

- LLDD entry points are now registered rather than included in the
  scsi_host_template.

  Background: When I started to implement the event handler via template,
  I had to either: muck up scsi_add_host and scsi_remove_host;  or have
  the event handler search all possible shosts. Neither was acceptable.
  Moving to a registration solves this, and also limits the scope of
  the changes to something that could be backported to a distro without
  breaking an already-released-distro kabi. However, I admit it isn't
  as elegant, as the passing of the LLDD host template in the
  registration and the complexity around dynamic add/remove shows.

- The receive path was augmented to require a unique identifier for
  the LLDD before the message was allowed to be handed off to the
  driver. Given how quickly very fatal errors occur if there's msg
  mismatches (which I saw in testing my own tools :), I believe this
  to be a very good thing. The id plays off the vendor id scheme already
  introduced for the vendor unique event messages used by FC.
  Additionally, the id use as the basis of the registration/deregistration.

- Send assist functions, for both the transport and LLDDs are included.

[fujita.tomonori@lab.ntt.co.jp: fix missing cast]
Signed-off-by: James Smart <james.smart@emulex.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 515 insertions, 8 deletions

diff --git a/drivers/scsi/scsi_netlink.c b/drivers/scsi/scsi_netlink.c
index ae7ed9a22662..b37e133de805 100644
--- a/drivers/scsi/scsi_netlink.c
+++ b/drivers/scsi/scsi_netlink.c
@@ -21,6 +21,7 @@
 #include <linux/time.h>
 #include <linux/jiffies.h>
 #include <linux/security.h>
+#include <linux/delay.h>
 #include <net/sock.h>
 #include <net/netlink.h>
 
@@ -30,6 +31,39 @@
 struct sock *scsi_nl_sock = NULL;
 EXPORT_SYMBOL_GPL(scsi_nl_sock);
 
+static DEFINE_SPINLOCK(scsi_nl_lock);
+static struct list_head scsi_nl_drivers;
+
+static u32      scsi_nl_state;
+#define STATE_EHANDLER_BSY              0x00000001
+
+struct scsi_nl_transport {
+        int (*msg_handler)(struct sk_buff *);
+        void (*event_handler)(struct notifier_block *, unsigned long, void *);
+        unsigned int refcnt;
+        int flags;
+};
+
+/* flags values (bit flags) */
+#define HANDLER_DELETING                0x1
+
+static struct scsi_nl_transport transports[SCSI_NL_MAX_TRANSPORTS] =
+        { {NULL, }, };
+
+
+struct scsi_nl_drvr {
+        struct list_head next;
+        int (*dmsg_handler)(struct Scsi_Host *shost, void *payload,
+                                 u32 len, u32 pid);
+        void (*devt_handler)(struct notifier_block *nb,
+                                 unsigned long event, void *notify_ptr);
+        struct scsi_host_template *hostt;
+        u64 vendor_id;
+        unsigned int refcnt;
+        int flags;
+};
+
+
 
 /**
  * scsi_nl_rcv_msg - Receive message handler.
@@ -45,8 +79,9 @@ scsi_nl_rcv_msg(struct sk_buff *skb)
 {
         struct nlmsghdr *nlh;
         struct scsi_nl_hdr *hdr;
-        uint32_t rlen;
-        int err;
+        unsigned long flags;
+        u32 rlen;
+        int err, tport;
 
         while (skb->len >= NLMSG_SPACE(0)) {
                 err = 0;
@@ -65,7 +100,7 @@ scsi_nl_rcv_msg(struct sk_buff *skb)
 
                 if (nlh->nlmsg_type != SCSI_TRANSPORT_MSG) {
                         err = -EBADMSG;
-                        return;
+                        goto next_msg;
                 }
 
                 hdr = NLMSG_DATA(nlh);
@@ -83,12 +118,27 @@ scsi_nl_rcv_msg(struct sk_buff *skb)
                 if (nlh->nlmsg_len < (sizeof(*nlh) + hdr->msglen)) {
                         printk(KERN_WARNING "%s: discarding partial message\n",
                                  __func__);
-                        return;
+                        goto next_msg;
                 }
 
                 /*
-                 * We currently don't support anyone sending us a message
+                 * Deliver message to the appropriate transport
                  */
+                spin_lock_irqsave(&scsi_nl_lock, flags);
+
+                tport = hdr->transport;
+                if ((tport < SCSI_NL_MAX_TRANSPORTS) &&
+                    !(transports[tport].flags & HANDLER_DELETING) &&
+                    (transports[tport].msg_handler)) {
+                        transports[tport].refcnt++;
+                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
+                        err = transports[tport].msg_handler(skb);
+                        spin_lock_irqsave(&scsi_nl_lock, flags);
+                        transports[tport].refcnt--;
+                } else
+                        err = -ENOENT;
+
+                spin_unlock_irqrestore(&scsi_nl_lock, flags);
 
 next_msg:
                 if ((err) || (nlh->nlmsg_flags & NLM_F_ACK))
@@ -110,14 +160,42 @@ static int
 scsi_nl_rcv_event(struct notifier_block *this, unsigned long event, void *ptr)
 {
         struct netlink_notify *n = ptr;
+        struct scsi_nl_drvr *driver;
+        unsigned long flags;
+        int tport;
 
         if (n->protocol != NETLINK_SCSITRANSPORT)
                 return NOTIFY_DONE;
 
+        spin_lock_irqsave(&scsi_nl_lock, flags);
+        scsi_nl_state |= STATE_EHANDLER_BSY;
+
         /*
-         * Currently, we are not tracking PID's, etc. There is nothing
-         * to handle.
+         * Pass event on to any transports that may be listening
          */
+        for (tport = 0; tport < SCSI_NL_MAX_TRANSPORTS; tport++) {
+                if (!(transports[tport].flags & HANDLER_DELETING) &&
+                    (transports[tport].event_handler)) {
+                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
+                        transports[tport].event_handler(this, event, ptr);
+                        spin_lock_irqsave(&scsi_nl_lock, flags);
+                }
+        }
+
+        /*
+         * Pass event on to any drivers that may be listening
+         */
+        list_for_each_entry(driver, &scsi_nl_drivers, next) {
+                if (!(driver->flags & HANDLER_DELETING) &&
+                    (driver->devt_handler)) {
+                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
+                        driver->devt_handler(this, event, ptr);
+                        spin_lock_irqsave(&scsi_nl_lock, flags);
+                }
+        }
+
+        scsi_nl_state &= ~STATE_EHANDLER_BSY;
+        spin_unlock_irqrestore(&scsi_nl_lock, flags);
 
         return NOTIFY_DONE;
 }
@@ -128,7 +206,281 @@ static struct notifier_block scsi_netlink_notifier = {
 
 
 /**
- * scsi_netlink_init - Called by SCSI subsystem to intialize the SCSI transport netlink interface
+ * GENERIC SCSI transport receive and event handlers
+ **/
+
+/**
+ * scsi_generic_msg_handler - receive message handler for GENERIC transport
+ *                       messages
+ *
+ * @skb:                socket receive buffer
+ *
+ **/
+static int
+scsi_generic_msg_handler(struct sk_buff *skb)
+{
+        struct nlmsghdr *nlh = nlmsg_hdr(skb);
+        struct scsi_nl_hdr *snlh = NLMSG_DATA(nlh);
+        struct scsi_nl_drvr *driver;
+        struct Scsi_Host *shost;
+        unsigned long flags;
+        int err = 0, match, pid;
+
+        pid = NETLINK_CREDS(skb)->pid;
+
+        switch (snlh->msgtype) {
+        case SCSI_NL_SHOST_VENDOR:
+                {
+                struct scsi_nl_host_vendor_msg *msg = NLMSG_DATA(nlh);
+
+                /* Locate the driver that corresponds to the message */
+                spin_lock_irqsave(&scsi_nl_lock, flags);
+                match = 0;
+                list_for_each_entry(driver, &scsi_nl_drivers, next) {
+                        if (driver->vendor_id == msg->vendor_id) {
+                                match = 1;
+                                break;
+                        }
+                }
+
+                if ((!match) || (!driver->dmsg_handler)) {
+                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
+                        err = -ESRCH;
+                        goto rcv_exit;
+                }
+
+                if (driver->flags & HANDLER_DELETING) {
+                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
+                        err = -ESHUTDOWN;
+                        goto rcv_exit;
+                }
+
+                driver->refcnt++;
+                spin_unlock_irqrestore(&scsi_nl_lock, flags);
+
+
+                /* if successful, scsi_host_lookup takes a shost reference */
+                shost = scsi_host_lookup(msg->host_no);
+                if (!shost) {
+                        err = -ENODEV;
+                        goto driver_exit;
+                }
+
+                /* is this host owned by the vendor ? */
+                if (shost->hostt != driver->hostt) {
+                        err = -EINVAL;
+                        goto vendormsg_put;
+                }
+
+                /* pass message on to the driver */
+                err = driver->dmsg_handler(shost, (void *)&msg[1],
+                                         msg->vmsg_datalen, pid);
+
+vendormsg_put:
+                /* release reference by scsi_host_lookup */
+                scsi_host_put(shost);
+
+driver_exit:
+                /* release our own reference on the registration object */
+                spin_lock_irqsave(&scsi_nl_lock, flags);
+                driver->refcnt--;
+                spin_unlock_irqrestore(&scsi_nl_lock, flags);
+                break;
+                }
+
+        default:
+                err = -EBADR;
+                break;
+        }
+
+rcv_exit:
+        if (err)
+                printk(KERN_WARNING "%s: Msgtype %d failed - err %d\n",
+                         __func__, snlh->msgtype, err);
+        return err;
+}
+
+
+/**
+ * scsi_nl_add_transport -
+ *    Registers message and event handlers for a transport. Enables
+ *    receipt of netlink messages and events to a transport.
+ *
+ * @tport:              transport registering handlers
+ * @msg_handler:        receive message handler callback
+ * @event_handler:      receive event handler callback
+ **/
+int
+scsi_nl_add_transport(u8 tport,
+        int (*msg_handler)(struct sk_buff *),
+        void (*event_handler)(struct notifier_block *, unsigned long, void *))
+{
+        unsigned long flags;
+        int err = 0;
+
+        if (tport >= SCSI_NL_MAX_TRANSPORTS)
+                return -EINVAL;
+
+        spin_lock_irqsave(&scsi_nl_lock, flags);
+
+        if (scsi_nl_state & STATE_EHANDLER_BSY) {
+                spin_unlock_irqrestore(&scsi_nl_lock, flags);
+                msleep(1);
+                spin_lock_irqsave(&scsi_nl_lock, flags);
+        }
+
+        if (transports[tport].msg_handler || transports[tport].event_handler) {
+                err = -EALREADY;
+                goto register_out;
+        }
+
+        transports[tport].msg_handler = msg_handler;
+        transports[tport].event_handler = event_handler;
+        transports[tport].flags = 0;
+        transports[tport].refcnt = 0;
+
+register_out:
+        spin_unlock_irqrestore(&scsi_nl_lock, flags);
+
+        return err;
+}
+EXPORT_SYMBOL_GPL(scsi_nl_add_transport);
+
+
+/**
+ * scsi_nl_remove_transport -
+ *    Disable transport receiption of messages and events
+ *
+ * @tport:              transport deregistering handlers
+ *
+ **/
+void
+scsi_nl_remove_transport(u8 tport)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&scsi_nl_lock, flags);
+        if (scsi_nl_state & STATE_EHANDLER_BSY) {
+                spin_unlock_irqrestore(&scsi_nl_lock, flags);
+                msleep(1);
+                spin_lock_irqsave(&scsi_nl_lock, flags);
+        }
+
+        if (tport < SCSI_NL_MAX_TRANSPORTS) {
+                transports[tport].flags |= HANDLER_DELETING;
+
+                while (transports[tport].refcnt != 0) {
+                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
+                        schedule_timeout_uninterruptible(HZ/4);
+                        spin_lock_irqsave(&scsi_nl_lock, flags);
+                }
+                transports[tport].msg_handler = NULL;
+                transports[tport].event_handler = NULL;
+                transports[tport].flags = 0;
+        }
+
+        spin_unlock_irqrestore(&scsi_nl_lock, flags);
+
+        return;
+}
+EXPORT_SYMBOL_GPL(scsi_nl_remove_transport);
+
+
+/**
+ * scsi_nl_add_driver -
+ *    A driver is registering its interfaces for SCSI netlink messages
+ *
+ * @vendor_id:          A unique identification value for the driver.
+ * @hostt:              address of the driver's host template. Used
+ *                      to verify an shost is bound to the driver
+ * @nlmsg_handler:      receive message handler callback
+ * @nlevt_handler:      receive event handler callback
+ *
+ * Returns:
+ *   0 on Success
+ *   error result otherwise
+ **/
+int
+scsi_nl_add_driver(u64 vendor_id, struct scsi_host_template *hostt,
+        int (*nlmsg_handler)(struct Scsi_Host *shost, void *payload,
+                                 u32 len, u32 pid),
+        void (*nlevt_handler)(struct notifier_block *nb,
+                                 unsigned long event, void *notify_ptr))
+{
+        struct scsi_nl_drvr *driver;
+        unsigned long flags;
+
+        driver = kzalloc(sizeof(*driver), GFP_KERNEL);
+        if (unlikely(!driver)) {
+                printk(KERN_ERR "%s: allocation failure\n", __func__);
+                return -ENOMEM;
+        }
+
+        driver->dmsg_handler = nlmsg_handler;
+        driver->devt_handler = nlevt_handler;
+        driver->hostt = hostt;
+        driver->vendor_id = vendor_id;
+
+        spin_lock_irqsave(&scsi_nl_lock, flags);
+        if (scsi_nl_state & STATE_EHANDLER_BSY) {
+                spin_unlock_irqrestore(&scsi_nl_lock, flags);
+                msleep(1);
+                spin_lock_irqsave(&scsi_nl_lock, flags);
+        }
+        list_add_tail(&driver->next, &scsi_nl_drivers);
+        spin_unlock_irqrestore(&scsi_nl_lock, flags);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(scsi_nl_add_driver);
+
+
+/**
+ * scsi_nl_remove_driver -
+ *    An driver is unregistering with the SCSI netlink messages
+ *
+ * @vendor_id:          The unique identification value for the driver.
+ **/
+void
+scsi_nl_remove_driver(u64 vendor_id)
+{
+        struct scsi_nl_drvr *driver;
+        unsigned long flags;
+
+        spin_lock_irqsave(&scsi_nl_lock, flags);
+        if (scsi_nl_state & STATE_EHANDLER_BSY) {
+                spin_unlock_irqrestore(&scsi_nl_lock, flags);
+                msleep(1);
+                spin_lock_irqsave(&scsi_nl_lock, flags);
+        }
+
+        list_for_each_entry(driver, &scsi_nl_drivers, next) {
+                if (driver->vendor_id == vendor_id) {
+                        driver->flags |= HANDLER_DELETING;
+                        while (driver->refcnt != 0) {
+                                spin_unlock_irqrestore(&scsi_nl_lock, flags);
+                                schedule_timeout_uninterruptible(HZ/4);
+                                spin_lock_irqsave(&scsi_nl_lock, flags);
+                        }
+                        list_del(&driver->next);
+                        kfree(driver);
+                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
+                        return;
+                }
+        }
+
+        spin_unlock_irqrestore(&scsi_nl_lock, flags);
+
+        printk(KERN_ERR "%s: removal of driver failed - vendor_id 0x%llx\n",
+               __func__, (unsigned long long)vendor_id);
+        return;
+}
+EXPORT_SYMBOL_GPL(scsi_nl_remove_driver);
+
+
+/**
+ * scsi_netlink_init - Called by SCSI subsystem to intialize
+ *      the SCSI transport netlink interface
  *
  **/
 void
@@ -136,6 +488,8 @@ scsi_netlink_init(void)
 {
         int error;
 
+        INIT_LIST_HEAD(&scsi_nl_drivers);
+
         error = netlink_register_notifier(&scsi_netlink_notifier);
         if (error) {
                 printk(KERN_ERR "%s: register of event handler failed - %d\n",
@@ -150,8 +504,15 @@ scsi_netlink_init(void)
                 printk(KERN_ERR "%s: register of recieve handler failed\n",
                                 __func__);
                 netlink_unregister_notifier(&scsi_netlink_notifier);
+                return;
         }
 
+        /* Register the entry points for the generic SCSI transport */
+        error = scsi_nl_add_transport(SCSI_NL_TRANSPORT,
+                                scsi_generic_msg_handler, NULL);
+        if (error)
+                printk(KERN_ERR "%s: register of GENERIC transport handler"
+                                "  failed - %d\n", __func__, error);
         return;
 }
 
@@ -163,6 +524,8 @@ scsi_netlink_init(void)
 void
 scsi_netlink_exit(void)
 {
+        scsi_nl_remove_transport(SCSI_NL_TRANSPORT);
+
         if (scsi_nl_sock) {
                 netlink_kernel_release(scsi_nl_sock);
                 netlink_unregister_notifier(&scsi_netlink_notifier);
@@ -172,3 +535,147 @@ scsi_netlink_exit(void)
 }
 
 
+/*
+ * Exported Interfaces
+ */
+
+/**
+ * scsi_nl_send_transport_msg -
+ *    Generic function to send a single message from a SCSI transport to
+ *    a single process
+ *
+ * @pid:                receiving pid
+ * @hdr:                message payload
+ *
+ **/
+void
+scsi_nl_send_transport_msg(u32 pid, struct scsi_nl_hdr *hdr)
+{
+        struct sk_buff *skb;
+        struct nlmsghdr *nlh;
+        const char *fn;
+        char *datab;
+        u32 len, skblen;
+        int err;
+
+        if (!scsi_nl_sock) {
+                err = -ENOENT;
+                fn = "netlink socket";
+                goto msg_fail;
+        }
+
+        len = NLMSG_SPACE(hdr->msglen);
+        skblen = NLMSG_SPACE(len);
+
+        skb = alloc_skb(skblen, GFP_KERNEL);
+        if (!skb) {
+                err = -ENOBUFS;
+                fn = "alloc_skb";
+                goto msg_fail;
+        }
+
+        nlh = nlmsg_put(skb, pid, 0, SCSI_TRANSPORT_MSG, len - sizeof(*nlh), 0);
+        if (!nlh) {
+                err = -ENOBUFS;
+                fn = "nlmsg_put";
+                goto msg_fail_skb;
+        }
+        datab = NLMSG_DATA(nlh);
+        memcpy(datab, hdr, hdr->msglen);
+
+        err = nlmsg_unicast(scsi_nl_sock, skb, pid);
+        if (err < 0) {
+                fn = "nlmsg_unicast";
+                /* nlmsg_unicast already kfree_skb'd */
+                goto msg_fail;
+        }
+
+        return;
+
+msg_fail_skb:
+        kfree_skb(skb);
+msg_fail:
+        printk(KERN_WARNING
+                "%s: Dropped Message : pid %d Transport %d, msgtype x%x, "
+                "msglen %d: %s : err %d\n",
+                __func__, pid, hdr->transport, hdr->msgtype, hdr->msglen,
+                fn, err);
+        return;
+}
+EXPORT_SYMBOL_GPL(scsi_nl_send_transport_msg);
+
+
+/**
+ * scsi_nl_send_vendor_msg - called to send a shost vendor unique message
+ *                      to a specific process id.
+ *
+ * @pid:                process id of the receiver
+ * @host_no:            host # sending the message
+ * @vendor_id:          unique identifier for the driver's vendor
+ * @data_len:           amount, in bytes, of vendor unique payload data
+ * @data_buf:           pointer to vendor unique data buffer
+ *
+ * Returns:
+ *   0 on succesful return
+ *   otherwise, failing error code
+ *
+ * Notes:
+ *      This routine assumes no locks are held on entry.
+ */
+int
+scsi_nl_send_vendor_msg(u32 pid, unsigned short host_no, u64 vendor_id,
+                         char *data_buf, u32 data_len)
+{
+        struct sk_buff *skb;
+        struct nlmsghdr *nlh;
+        struct scsi_nl_host_vendor_msg *msg;
+        u32 len, skblen;
+        int err;
+
+        if (!scsi_nl_sock) {
+                err = -ENOENT;
+                goto send_vendor_fail;
+        }
+
+        len = SCSI_NL_MSGALIGN(sizeof(*msg) + data_len);
+        skblen = NLMSG_SPACE(len);
+
+        skb = alloc_skb(skblen, GFP_KERNEL);
+        if (!skb) {
+                err = -ENOBUFS;
+                goto send_vendor_fail;
+        }
+
+        nlh = nlmsg_put(skb, 0, 0, SCSI_TRANSPORT_MSG,
+                                skblen - sizeof(*nlh), 0);
+        if (!nlh) {
+                err = -ENOBUFS;
+                goto send_vendor_fail_skb;
+        }
+        msg = NLMSG_DATA(nlh);
+
+        INIT_SCSI_NL_HDR(&msg->snlh, SCSI_NL_TRANSPORT,
+                                SCSI_NL_SHOST_VENDOR, len);
+        msg->vendor_id = vendor_id;
+        msg->host_no = host_no;
+        msg->vmsg_datalen = data_len;   /* bytes */
+        memcpy(&msg[1], data_buf, data_len);
+
+        err = nlmsg_unicast(scsi_nl_sock, skb, pid);
+        if (err)
+                /* nlmsg_multicast already kfree_skb'd */
+                goto send_vendor_fail;
+
+        return 0;
+
+send_vendor_fail_skb:
+        kfree_skb(skb);
+send_vendor_fail:
+        printk(KERN_WARNING
+                "%s: Dropped SCSI Msg : host %d vendor_unique - err %d\n",
+                __func__, host_no, err);
+        return err;
+}
+EXPORT_SYMBOL(scsi_nl_send_vendor_msg);
+
+