fc_exch.c

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/*
 * Copyright(c) 2007 Intel Corporation. All rights reserved.
 * Copyright(c) 2008 Red Hat, Inc.  All rights reserved.
 * Copyright(c) 2008 Mike Christie
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Maintained at www.Open-FCoE.org
 */

/*
 * Fibre Channel exchange and sequence handling.
 */

#include <linux/timer.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/export.h>

#include <scsi/fc/fc_fc2.h>

#include <scsi/libfc.h>
#include <scsi/fc_encode.h>

#include "fc_libfc.h"

u16 fc_cpu_mask;        /* cpu mask for possible cpus */
EXPORT_SYMBOL(fc_cpu_mask);
static u16  fc_cpu_order;   /* 2's power to represent total possible cpus */
static struct kmem_cache *fc_em_cachep;        /* cache for exchanges */
static struct workqueue_struct *fc_exch_workqueue;

/*
 * Structure and function definitions for managing Fibre Channel Exchanges
 * and Sequences.
 *
 * The three primary structures used here are fc_exch_mgr, fc_exch, and fc_seq.
 *
 * fc_exch_mgr holds the exchange state for an N port
 *
 * fc_exch holds state for one exchange and links to its active sequence.
 *
 * fc_seq holds the state for an individual sequence.
 */

struct fc_exch_pool {
    spinlock_t   lock;
    struct list_head ex_list;
    u16      next_index;
    u16      total_exches;

    /* two cache of free slot in exch array */
    u16      left;
    u16      right;
} ____cacheline_aligned_in_smp;

struct fc_exch_mgr {
    struct fc_exch_pool __percpu *pool;
    mempool_t   *ep_pool;
    enum fc_class   class;
    struct kref kref;
    u16     min_xid;
    u16     max_xid;
    u16     pool_max_index;

    struct {
        atomic_t no_free_exch;
        atomic_t no_free_exch_xid;
        atomic_t xid_not_found;
        atomic_t xid_busy;
        atomic_t seq_not_found;
        atomic_t non_bls_resp;
    } stats;
};

struct fc_exch_mgr_anchor {
    struct list_head ema_list;
    struct fc_exch_mgr *mp;
    bool (*match)(struct fc_frame *);
};

static void fc_exch_rrq(struct fc_exch *);
static void fc_seq_ls_acc(struct fc_frame *);
static void fc_seq_ls_rjt(struct fc_frame *, enum fc_els_rjt_reason,
              enum fc_els_rjt_explan);
static void fc_exch_els_rec(struct fc_frame *);
static void fc_exch_els_rrq(struct fc_frame *);

/*
 * Internal implementation notes.
 *
 * The exchange manager is one by default in libfc but LLD may choose
 * to have one per CPU. The sequence manager is one per exchange manager
 * and currently never separated.
 *
 * Section 9.8 in FC-FS-2 specifies:  "The SEQ_ID is a one-byte field
 * assigned by the Sequence Initiator that shall be unique for a specific
 * D_ID and S_ID pair while the Sequence is open."   Note that it isn't
 * qualified by exchange ID, which one might think it would be.
 * In practice this limits the number of open sequences and exchanges to 256
 * per session.  For most targets we could treat this limit as per exchange.
 *
 * The exchange and its sequence are freed when the last sequence is received.
 * It's possible for the remote port to leave an exchange open without
 * sending any sequences.
 *
 * Notes on reference counts:
 *
 * Exchanges are reference counted and exchange gets freed when the reference
 * count becomes zero.
 *
 * Timeouts:
 * Sequences are timed out for E_D_TOV and R_A_TOV.
 *
 * Sequence event handling:
 *
 * The following events may occur on initiator sequences:
 *
 *  Send.
 *      For now, the whole thing is sent.
 *  Receive ACK
 *      This applies only to class F.
 *      The sequence is marked complete.
 *  ULP completion.
 *      The upper layer calls fc_exch_done() when done
 *      with exchange and sequence tuple.
 *  RX-inferred completion.
 *      When we receive the next sequence on the same exchange, we can
 *      retire the previous sequence ID.  (XXX not implemented).
 *  Timeout.
 *      R_A_TOV frees the sequence ID.  If we're waiting for ACK,
 *      E_D_TOV causes abort and calls upper layer response handler
 *      with FC_EX_TIMEOUT error.
 *  Receive RJT
 *      XXX defer.
 *  Send ABTS
 *      On timeout.
 *
 * The following events may occur on recipient sequences:
 *
 *  Receive
 *      Allocate sequence for first frame received.
 *      Hold during receive handler.
 *      Release when final frame received.
 *      Keep status of last N of these for the ELS RES command.  XXX TBD.
 *  Receive ABTS
 *      Deallocate sequence
 *  Send RJT
 *      Deallocate
 *
 * For now, we neglect conditions where only part of a sequence was
 * received or transmitted, or where out-of-order receipt is detected.
 */

/*
 * Locking notes:
 *
 * The EM code run in a per-CPU worker thread.
 *
 * To protect against concurrency between a worker thread code and timers,
 * sequence allocation and deallocation must be locked.
 *  - exchange refcnt can be done atomicly without locks.
 *  - sequence allocation must be locked by exch lock.
 *  - If the EM pool lock and ex_lock must be taken at the same time, then the
 *    EM pool lock must be taken before the ex_lock.
 */

/*
 * opcode names for debugging.
 */
static char *fc_exch_rctl_names[] = FC_RCTL_NAMES_INIT;

static inline const char *fc_exch_name_lookup(unsigned int op, char **table,
                          unsigned int max_index)
{
    const char *name = NULL;

    if (op < max_index)
        name = table[op];
    if (!name)
        name = "unknown";
    return name;
}

static const char *fc_exch_rctl_name(unsigned int op)
{
    return fc_exch_name_lookup(op, fc_exch_rctl_names,
                   ARRAY_SIZE(fc_exch_rctl_names));
}

static inline void fc_exch_hold(struct fc_exch *ep)
{
    atomic_inc(&ep->ex_refcnt);
}

static void fc_exch_setup_hdr(struct fc_exch *ep, struct fc_frame *fp,
                  u32 f_ctl)
{
    struct fc_frame_header *fh = fc_frame_header_get(fp);
    u16 fill;

    fr_sof(fp) = ep->class;
    if (ep->seq.cnt)
        fr_sof(fp) = fc_sof_normal(ep->class);

    if (f_ctl & FC_FC_END_SEQ) {
        fr_eof(fp) = FC_EOF_T;
        if (fc_sof_needs_ack(ep->class))
            fr_eof(fp) = FC_EOF_N;
        /*
         * From F_CTL.
         * The number of fill bytes to make the length a 4-byte
         * multiple is the low order 2-bits of the f_ctl.
         * The fill itself will have been cleared by the frame
         * allocation.
         * After this, the length will be even, as expected by
         * the transport.
         */
        fill = fr_len(fp) & 3;
        if (fill) {
            fill = 4 - fill;
            /* TODO, this may be a problem with fragmented skb */
            skb_put(fp_skb(fp), fill);
            hton24(fh->fh_f_ctl, f_ctl | fill);
        }
    } else {
        WARN_ON(fr_len(fp) % 4 != 0);   /* no pad to non last frame */
        fr_eof(fp) = FC_EOF_N;
    }

    /*
     * Initialize remainig fh fields
     * from fc_fill_fc_hdr
     */
    fh->fh_ox_id = htons(ep->oxid);
    fh->fh_rx_id = htons(ep->rxid);
    fh->fh_seq_id = ep->seq.id;
    fh->fh_seq_cnt = htons(ep->seq.cnt);
}

static void fc_exch_release(struct fc_exch *ep)
{
    struct fc_exch_mgr *mp;

    if (atomic_dec_and_test(&ep->ex_refcnt)) {
        mp = ep->em;
        if (ep->destructor)
            ep->destructor(&ep->seq, ep->arg);
        WARN_ON(!(ep->esb_stat & ESB_ST_COMPLETE));
        mempool_free(ep, mp->ep_pool);
    }
}

static inline  void fc_exch_timer_cancel(struct fc_exch *ep)
{
    if (cancel_delayed_work(&ep->timeout_work)) {
        FC_EXCH_DBG(ep, "Exchange timer canceled\n");
        atomic_dec(&ep->ex_refcnt); /* drop hold for timer */
    }
}

static inline void fc_exch_timer_set_locked(struct fc_exch *ep,
                        unsigned int timer_msec)
{
    if (ep->state & (FC_EX_RST_CLEANUP | FC_EX_DONE))
        return;

    FC_EXCH_DBG(ep, "Exchange timer armed : %d msecs\n", timer_msec);

    if (queue_delayed_work(fc_exch_workqueue, &ep->timeout_work,
                   msecs_to_jiffies(timer_msec)))
        fc_exch_hold(ep);       /* hold for timer */
}

static void fc_exch_timer_set(struct fc_exch *ep, unsigned int timer_msec)
{
    spin_lock_bh(&ep->ex_lock);
    fc_exch_timer_set_locked(ep, timer_msec);
    spin_unlock_bh(&ep->ex_lock);
}

static int fc_exch_done_locked(struct fc_exch *ep)
{
    int rc = 1;

    /*
     * We must check for completion in case there are two threads
     * tyring to complete this. But the rrq code will reuse the
     * ep, and in that case we only clear the resp and set it as
     * complete, so it can be reused by the timer to send the rrq.
     */
    ep->resp = NULL;
    if (ep->state & FC_EX_DONE)
        return rc;
    ep->esb_stat |= ESB_ST_COMPLETE;

    if (!(ep->esb_stat & ESB_ST_REC_QUAL)) {
        ep->state |= FC_EX_DONE;
        fc_exch_timer_cancel(ep);
        rc = 0;
    }
    return rc;
}

static inline struct fc_exch *fc_exch_ptr_get(struct fc_exch_pool *pool,
                          u16 index)
{
    struct fc_exch **exches = (struct fc_exch **)(pool + 1);
    return exches[index];
}

static inline void fc_exch_ptr_set(struct fc_exch_pool *pool, u16 index,
                   struct fc_exch *ep)
{
    ((struct fc_exch **)(pool + 1))[index] = ep;
}

static void fc_exch_delete(struct fc_exch *ep)
{
    struct fc_exch_pool *pool;
    u16 index;

    pool = ep->pool;
    spin_lock_bh(&pool->lock);
    WARN_ON(pool->total_exches <= 0);
    pool->total_exches--;

    /* update cache of free slot */
    index = (ep->xid - ep->em->min_xid) >> fc_cpu_order;
    if (pool->left == FC_XID_UNKNOWN)
        pool->left = index;
    else if (pool->right == FC_XID_UNKNOWN)
        pool->right = index;
    else
        pool->next_index = index;

    fc_exch_ptr_set(pool, index, NULL);
    list_del(&ep->ex_list);
    spin_unlock_bh(&pool->lock);
    fc_exch_release(ep);    /* drop hold for exch in mp */
}

static int fc_seq_send(struct fc_lport *lport, struct fc_seq *sp,
               struct fc_frame *fp)
{
    struct fc_exch *ep;
    struct fc_frame_header *fh = fc_frame_header_get(fp);
    int error;
    u32 f_ctl;
    u8 fh_type = fh->fh_type;

    ep = fc_seq_exch(sp);
    WARN_ON((ep->esb_stat & ESB_ST_SEQ_INIT) != ESB_ST_SEQ_INIT);

    f_ctl = ntoh24(fh->fh_f_ctl);
    fc_exch_setup_hdr(ep, fp, f_ctl);
    fr_encaps(fp) = ep->encaps;

    /*
     * update sequence count if this frame is carrying
     * multiple FC frames when sequence offload is enabled
     * by LLD.
     */
    if (fr_max_payload(fp))
        sp->cnt += DIV_ROUND_UP((fr_len(fp) - sizeof(*fh)),
                    fr_max_payload(fp));
    else
        sp->cnt++;

    /*
     * Send the frame.
     */
    error = lport->tt.frame_send(lport, fp);

    if (fh_type == FC_TYPE_BLS)
        return error;

    /*
     * Update the exchange and sequence flags,
     * assuming all frames for the sequence have been sent.
     * We can only be called to send once for each sequence.
     */
    spin_lock_bh(&ep->ex_lock);
    ep->f_ctl = f_ctl & ~FC_FC_FIRST_SEQ;   /* not first seq */
    if (f_ctl & FC_FC_SEQ_INIT)
        ep->esb_stat &= ~ESB_ST_SEQ_INIT;
    spin_unlock_bh(&ep->ex_lock);
    return error;
}

static struct fc_seq *fc_seq_alloc(struct fc_exch *ep, u8 seq_id)
{
    struct fc_seq *sp;

    sp = &ep->seq;
    sp->ssb_stat = 0;
    sp->cnt = 0;
    sp->id = seq_id;
    return sp;
}

static struct fc_seq *fc_seq_start_next_locked(struct fc_seq *sp)
{
    struct fc_exch *ep = fc_seq_exch(sp);

    sp = fc_seq_alloc(ep, ep->seq_id++);
    FC_EXCH_DBG(ep, "f_ctl %6x seq %2x\n",
            ep->f_ctl, sp->id);
    return sp;
}

static struct fc_seq *fc_seq_start_next(struct fc_seq *sp)
{
    struct fc_exch *ep = fc_seq_exch(sp);

    spin_lock_bh(&ep->ex_lock);
    sp = fc_seq_start_next_locked(sp);
    spin_unlock_bh(&ep->ex_lock);

    return sp;
}

/*
 * Set the response handler for the exchange associated with a sequence.
 */
static void fc_seq_set_resp(struct fc_seq *sp,
                void (*resp)(struct fc_seq *, struct fc_frame *,
                     void *),
                void *arg)
{
    struct fc_exch *ep = fc_seq_exch(sp);

    spin_lock_bh(&ep->ex_lock);
    ep->resp = resp;
    ep->arg = arg;
    spin_unlock_bh(&ep->ex_lock);
}

static int fc_exch_abort_locked(struct fc_exch *ep,
                unsigned int timer_msec)
{
    struct fc_seq *sp;
    struct fc_frame *fp;
    int error;

    if (ep->esb_stat & (ESB_ST_COMPLETE | ESB_ST_ABNORMAL) ||
        ep->state & (FC_EX_DONE | FC_EX_RST_CLEANUP))
        return -ENXIO;

    /*
     * Send the abort on a new sequence if possible.
     */
    sp = fc_seq_start_next_locked(&ep->seq);
    if (!sp)
        return -ENOMEM;

    ep->esb_stat |= ESB_ST_SEQ_INIT | ESB_ST_ABNORMAL;
    if (timer_msec)
        fc_exch_timer_set_locked(ep, timer_msec);

    /*
     * If not logged into the fabric, don't send ABTS but leave
     * sequence active until next timeout.
     */
    if (!ep->sid)
        return 0;

    /*
     * Send an abort for the sequence that timed out.
     */
    fp = fc_frame_alloc(ep->lp, 0);
    if (fp) {
        fc_fill_fc_hdr(fp, FC_RCTL_BA_ABTS, ep->did, ep->sid,
                   FC_TYPE_BLS, FC_FC_END_SEQ | FC_FC_SEQ_INIT, 0);
        error = fc_seq_send(ep->lp, sp, fp);
    } else
        error = -ENOBUFS;
    return error;
}

static int fc_seq_exch_abort(const struct fc_seq *req_sp,
                 unsigned int timer_msec)
{
    struct fc_exch *ep;
    int error;

    ep = fc_seq_exch(req_sp);
    spin_lock_bh(&ep->ex_lock);
    error = fc_exch_abort_locked(ep, timer_msec);
    spin_unlock_bh(&ep->ex_lock);
    return error;
}

static void fc_exch_timeout(struct work_struct *work)
{
    struct fc_exch *ep = container_of(work, struct fc_exch,
                      timeout_work.work);
    struct fc_seq *sp = &ep->seq;
    void (*resp)(struct fc_seq *, struct fc_frame *fp, void *arg);
    void *arg;
    u32 e_stat;
    int rc = 1;

    FC_EXCH_DBG(ep, "Exchange timed out\n");

    spin_lock_bh(&ep->ex_lock);
    if (ep->state & (FC_EX_RST_CLEANUP | FC_EX_DONE))
        goto unlock;

    e_stat = ep->esb_stat;
    if (e_stat & ESB_ST_COMPLETE) {
        ep->esb_stat = e_stat & ~ESB_ST_REC_QUAL;
        spin_unlock_bh(&ep->ex_lock);
        if (e_stat & ESB_ST_REC_QUAL)
            fc_exch_rrq(ep);
        goto done;
    } else {
        resp = ep->resp;
        arg = ep->arg;
        ep->resp = NULL;
        if (e_stat & ESB_ST_ABNORMAL)
            rc = fc_exch_done_locked(ep);
        spin_unlock_bh(&ep->ex_lock);
        if (!rc)
            fc_exch_delete(ep);
        if (resp)
            resp(sp, ERR_PTR(-FC_EX_TIMEOUT), arg);
        fc_seq_exch_abort(sp, 2 * ep->r_a_tov);
        goto done;
    }
unlock:
    spin_unlock_bh(&ep->ex_lock);
done:
    /*
     * This release matches the hold taken when the timer was set.
     */
    fc_exch_release(ep);
}

static struct fc_exch *fc_exch_em_alloc(struct fc_lport *lport,
                    struct fc_exch_mgr *mp)
{
    struct fc_exch *ep;
    unsigned int cpu;
    u16 index;
    struct fc_exch_pool *pool;

    /* allocate memory for exchange */
    ep = mempool_alloc(mp->ep_pool, GFP_ATOMIC);
    if (!ep) {
        atomic_inc(&mp->stats.no_free_exch);
        goto out;
    }
    memset(ep, 0, sizeof(*ep));

    cpu = get_cpu();
    pool = per_cpu_ptr(mp->pool, cpu);
    spin_lock_bh(&pool->lock);
    put_cpu();

    /* peek cache of free slot */
    if (pool->left != FC_XID_UNKNOWN) {
        index = pool->left;
        pool->left = FC_XID_UNKNOWN;
        goto hit;
    }
    if (pool->right != FC_XID_UNKNOWN) {
        index = pool->right;
        pool->right = FC_XID_UNKNOWN;
        goto hit;
    }

    index = pool->next_index;
    /* allocate new exch from pool */
    while (fc_exch_ptr_get(pool, index)) {
        index = index == mp->pool_max_index ? 0 : index + 1;
        if (index == pool->next_index)
            goto err;
    }
    pool->next_index = index == mp->pool_max_index ? 0 : index + 1;
hit:
    fc_exch_hold(ep);   /* hold for exch in mp */
    spin_lock_init(&ep->ex_lock);
    /*
     * Hold exch lock for caller to prevent fc_exch_reset()
     * from releasing exch  while fc_exch_alloc() caller is
     * still working on exch.
     */
    spin_lock_bh(&ep->ex_lock);

    fc_exch_ptr_set(pool, index, ep);
    list_add_tail(&ep->ex_list, &pool->ex_list);
    fc_seq_alloc(ep, ep->seq_id++);
    pool->total_exches++;
    spin_unlock_bh(&pool->lock);

    /*
     *  update exchange
     */
    ep->oxid = ep->xid = (index << fc_cpu_order | cpu) + mp->min_xid;
    ep->em = mp;
    ep->pool = pool;
    ep->lp = lport;
    ep->f_ctl = FC_FC_FIRST_SEQ;    /* next seq is first seq */
    ep->rxid = FC_XID_UNKNOWN;
    ep->class = mp->class;
    INIT_DELAYED_WORK(&ep->timeout_work, fc_exch_timeout);
out:
    return ep;
err:
    spin_unlock_bh(&pool->lock);
    atomic_inc(&mp->stats.no_free_exch_xid);
    mempool_free(ep, mp->ep_pool);
    return NULL;
}

static inline struct fc_exch *fc_exch_alloc(struct fc_lport *lport,
                        struct fc_frame *fp)
{
    struct fc_exch_mgr_anchor *ema;

    list_for_each_entry(ema, &lport->ema_list, ema_list)
        if (!ema->match || ema->match(fp))
            return fc_exch_em_alloc(lport, ema->mp);
    return NULL;
}

static struct fc_exch *fc_exch_find(struct fc_exch_mgr *mp, u16 xid)
{
    struct fc_exch_pool *pool;
    struct fc_exch *ep = NULL;

    if ((xid >= mp->min_xid) && (xid <= mp->max_xid)) {
        pool = per_cpu_ptr(mp->pool, xid & fc_cpu_mask);
        spin_lock_bh(&pool->lock);
        ep = fc_exch_ptr_get(pool, (xid - mp->min_xid) >> fc_cpu_order);
        if (ep && ep->xid == xid)
            fc_exch_hold(ep);
        spin_unlock_bh(&pool->lock);
    }
    return ep;
}


static void fc_exch_done(struct fc_seq *sp)
{
    struct fc_exch *ep = fc_seq_exch(sp);
    int rc;

    spin_lock_bh(&ep->ex_lock);
    rc = fc_exch_done_locked(ep);
    spin_unlock_bh(&ep->ex_lock);
    if (!rc)
        fc_exch_delete(ep);
}

static struct fc_exch *fc_exch_resp(struct fc_lport *lport,
                    struct fc_exch_mgr *mp,
                    struct fc_frame *fp)
{
    struct fc_exch *ep;
    struct fc_frame_header *fh;

    ep = fc_exch_alloc(lport, fp);
    if (ep) {
        ep->class = fc_frame_class(fp);

        /*
         * Set EX_CTX indicating we're responding on this exchange.
         */
        ep->f_ctl |= FC_FC_EX_CTX;  /* we're responding */
        ep->f_ctl &= ~FC_FC_FIRST_SEQ;  /* not new */
        fh = fc_frame_header_get(fp);
        ep->sid = ntoh24(fh->fh_d_id);
        ep->did = ntoh24(fh->fh_s_id);
        ep->oid = ep->did;

        /*
         * Allocated exchange has placed the XID in the
         * originator field. Move it to the responder field,
         * and set the originator XID from the frame.
         */
        ep->rxid = ep->xid;
        ep->oxid = ntohs(fh->fh_ox_id);
        ep->esb_stat |= ESB_ST_RESP | ESB_ST_SEQ_INIT;
        if ((ntoh24(fh->fh_f_ctl) & FC_FC_SEQ_INIT) == 0)
            ep->esb_stat &= ~ESB_ST_SEQ_INIT;

        fc_exch_hold(ep);   /* hold for caller */
        spin_unlock_bh(&ep->ex_lock);   /* lock from fc_exch_alloc */
    }
    return ep;
}

static enum fc_pf_rjt_reason fc_seq_lookup_recip(struct fc_lport *lport,
                         struct fc_exch_mgr *mp,
                         struct fc_frame *fp)
{
    struct fc_frame_header *fh = fc_frame_header_get(fp);
    struct fc_exch *ep = NULL;
    struct fc_seq *sp = NULL;
    enum fc_pf_rjt_reason reject = FC_RJT_NONE;
    u32 f_ctl;
    u16 xid;

    f_ctl = ntoh24(fh->fh_f_ctl);
    WARN_ON((f_ctl & FC_FC_SEQ_CTX) != 0);

    /*
     * Lookup or create the exchange if we will be creating the sequence.
     */
    if (f_ctl & FC_FC_EX_CTX) {
        xid = ntohs(fh->fh_ox_id);  /* we originated exch */
        ep = fc_exch_find(mp, xid);
        if (!ep) {
            atomic_inc(&mp->stats.xid_not_found);
            reject = FC_RJT_OX_ID;
            goto out;
        }
        if (ep->rxid == FC_XID_UNKNOWN)
            ep->rxid = ntohs(fh->fh_rx_id);
        else if (ep->rxid != ntohs(fh->fh_rx_id)) {
            reject = FC_RJT_OX_ID;
            goto rel;
        }
    } else {
        xid = ntohs(fh->fh_rx_id);  /* we are the responder */

        /*
         * Special case for MDS issuing an ELS TEST with a
         * bad rxid of 0.
         * XXX take this out once we do the proper reject.
         */
        if (xid == 0 && fh->fh_r_ctl == FC_RCTL_ELS_REQ &&
            fc_frame_payload_op(fp) == ELS_TEST) {
            fh->fh_rx_id = htons(FC_XID_UNKNOWN);
            xid = FC_XID_UNKNOWN;
        }

        /*
         * new sequence - find the exchange
         */
        ep = fc_exch_find(mp, xid);
        if ((f_ctl & FC_FC_FIRST_SEQ) && fc_sof_is_init(fr_sof(fp))) {
            if (ep) {
                atomic_inc(&mp->stats.xid_busy);
                reject = FC_RJT_RX_ID;
                goto rel;
            }
            ep = fc_exch_resp(lport, mp, fp);
            if (!ep) {
                reject = FC_RJT_EXCH_EST;   /* XXX */
                goto out;
            }
            xid = ep->xid;  /* get our XID */
        } else if (!ep) {
            atomic_inc(&mp->stats.xid_not_found);
            reject = FC_RJT_RX_ID;  /* XID not found */
            goto out;
        }
    }

    /*
     * At this point, we have the exchange held.
     * Find or create the sequence.
     */
    if (fc_sof_is_init(fr_sof(fp))) {
        sp = &ep->seq;
        sp->ssb_stat |= SSB_ST_RESP;
        sp->id = fh->fh_seq_id;
    } else {
        sp = &ep->seq;
        if (sp->id != fh->fh_seq_id) {
            atomic_inc(&mp->stats.seq_not_found);
            if (f_ctl & FC_FC_END_SEQ) {
                /*
                 * Update sequence_id based on incoming last
                 * frame of sequence exchange. This is needed
                 * for FC target where DDP has been used
                 * on target where, stack is indicated only
                 * about last frame's (payload _header) header.
                 * Whereas "seq_id" which is part of
                 * frame_header is allocated by initiator
                 * which is totally different from "seq_id"
                 * allocated when XFER_RDY was sent by target.
                 * To avoid false -ve which results into not
                 * sending RSP, hence write request on other
                 * end never finishes.
                 */
                spin_lock_bh(&ep->ex_lock);
                sp->ssb_stat |= SSB_ST_RESP;
                sp->id = fh->fh_seq_id;
                spin_unlock_bh(&ep->ex_lock);
            } else {
                /* sequence/exch should exist */
                reject = FC_RJT_SEQ_ID;
                goto rel;
            }
        }
    }
    WARN_ON(ep != fc_seq_exch(sp));

    if (f_ctl & FC_FC_SEQ_INIT)
        ep->esb_stat |= ESB_ST_SEQ_INIT;

    fr_seq(fp) = sp;
out:
    return reject;
rel:
    fc_exch_done(&ep->seq);
    fc_exch_release(ep);    /* hold from fc_exch_find/fc_exch_resp */
    return reject;
}

static struct fc_seq *fc_seq_lookup_orig(struct fc_exch_mgr *mp,
                     struct fc_frame *fp)
{
    struct fc_frame_header *fh = fc_frame_header_get(fp);
    struct fc_exch *ep;
    struct fc_seq *sp = NULL;
    u32 f_ctl;
    u16 xid;

    f_ctl = ntoh24(fh->fh_f_ctl);
    WARN_ON((f_ctl & FC_FC_SEQ_CTX) != FC_FC_SEQ_CTX);
    xid = ntohs((f_ctl & FC_FC_EX_CTX) ? fh->fh_ox_id : fh->fh_rx_id);
    ep = fc_exch_find(mp, xid);
    if (!ep)
        return NULL;
    if (ep->seq.id == fh->fh_seq_id) {
        /*
         * Save the RX_ID if we didn't previously know it.
         */
        sp = &ep->seq;
        if ((f_ctl & FC_FC_EX_CTX) != 0 &&
            ep->rxid == FC_XID_UNKNOWN) {
            ep->rxid = ntohs(fh->fh_rx_id);
        }
    }
    fc_exch_release(ep);
    return sp;
}

static void fc_exch_set_addr(struct fc_exch *ep,
                 u32 orig_id, u32 resp_id)
{
    ep->oid = orig_id;
    if (ep->esb_stat & ESB_ST_RESP) {
        ep->sid = resp_id;
        ep->did = orig_id;
    } else {
        ep->sid = orig_id;
        ep->did = resp_id;
    }
}

static void fc_seq_els_rsp_send(struct fc_frame *fp, enum fc_els_cmd els_cmd,
                struct fc_seq_els_data *els_data)
{
    switch (els_cmd) {
    case ELS_LS_RJT:
        fc_seq_ls_rjt(fp, els_data->reason, els_data->explan);
        break;
    case ELS_LS_ACC:
        fc_seq_ls_acc(fp);
        break;
    case ELS_RRQ:
        fc_exch_els_rrq(fp);
        break;
    case ELS_REC:
        fc_exch_els_rec(fp);
        break;
    default:
        FC_LPORT_DBG(fr_dev(fp), "Invalid ELS CMD:%x\n", els_cmd);
    }
}

static void fc_seq_send_last(struct fc_seq *sp, struct fc_frame *fp,
                 enum fc_rctl rctl, enum fc_fh_type fh_type)
{
    u32 f_ctl;
    struct fc_exch *ep = fc_seq_exch(sp);

    f_ctl = FC_FC_LAST_SEQ | FC_FC_END_SEQ | FC_FC_SEQ_INIT;
    f_ctl |= ep->f_ctl;
    fc_fill_fc_hdr(fp, rctl, ep->did, ep->sid, fh_type, f_ctl, 0);
    fc_seq_send(ep->lp, sp, fp);
}

static void fc_seq_send_ack(struct fc_seq *sp, const struct fc_frame *rx_fp)
{
    struct fc_frame *fp;
    struct fc_frame_header *rx_fh;
    struct fc_frame_header *fh;
    struct fc_exch *ep = fc_seq_exch(sp);
    struct fc_lport *lport = ep->lp;
    unsigned int f_ctl;

    /*
     * Don't send ACKs for class 3.
     */
    if (fc_sof_needs_ack(fr_sof(rx_fp))) {
        fp = fc_frame_alloc(lport, 0);
        if (!fp)
            return;

        fh = fc_frame_header_get(fp);
        fh->fh_r_ctl = FC_RCTL_ACK_1;
        fh->fh_type = FC_TYPE_BLS;

        /*
         * Form f_ctl by inverting EX_CTX and SEQ_CTX (bits 23, 22).
         * Echo FIRST_SEQ, LAST_SEQ, END_SEQ, END_CONN, SEQ_INIT.
         * Bits 9-8 are meaningful (retransmitted or unidirectional).
         * Last ACK uses bits 7-6 (continue sequence),
         * bits 5-4 are meaningful (what kind of ACK to use).
         */
        rx_fh = fc_frame_header_get(rx_fp);
        f_ctl = ntoh24(rx_fh->fh_f_ctl);
        f_ctl &= FC_FC_EX_CTX | FC_FC_SEQ_CTX |
            FC_FC_FIRST_SEQ | FC_FC_LAST_SEQ |
            FC_FC_END_SEQ | FC_FC_END_CONN | FC_FC_SEQ_INIT |
            FC_FC_RETX_SEQ | FC_FC_UNI_TX;
        f_ctl ^= FC_FC_EX_CTX | FC_FC_SEQ_CTX;
        hton24(fh->fh_f_ctl, f_ctl);

        fc_exch_setup_hdr(ep, fp, f_ctl);
        fh->fh_seq_id = rx_fh->fh_seq_id;
        fh->fh_seq_cnt = rx_fh->fh_seq_cnt;
        fh->fh_parm_offset = htonl(1);  /* ack single frame */

        fr_sof(fp) = fr_sof(rx_fp);
        if (f_ctl & FC_FC_END_SEQ)
            fr_eof(fp) = FC_EOF_T;
        else
            fr_eof(fp) = FC_EOF_N;

        lport->tt.frame_send(lport, fp);
    }
}

static void fc_exch_send_ba_rjt(struct fc_frame *rx_fp,
                enum fc_ba_rjt_reason reason,
                enum fc_ba_rjt_explan explan)
{
    struct fc_frame *fp;
    struct fc_frame_header *rx_fh;
    struct fc_frame_header *fh;
    struct fc_ba_rjt *rp;
    struct fc_lport *lport;
    unsigned int f_ctl;

    lport = fr_dev(rx_fp);
    fp = fc_frame_alloc(lport, sizeof(*rp));
    if (!fp)
        return;
    fh = fc_frame_header_get(fp);
    rx_fh = fc_frame_header_get(rx_fp);

    memset(fh, 0, sizeof(*fh) + sizeof(*rp));

    rp = fc_frame_payload_get(fp, sizeof(*rp));
    rp->br_reason = reason;
    rp->br_explan = explan;

    /*
     * seq_id, cs_ctl, df_ctl and param/offset are zero.
     */
    memcpy(fh->fh_s_id, rx_fh->fh_d_id, 3);
    memcpy(fh->fh_d_id, rx_fh->fh_s_id, 3);
    fh->fh_ox_id = rx_fh->fh_ox_id;
    fh->fh_rx_id = rx_fh->fh_rx_id;
    fh->fh_seq_cnt = rx_fh->fh_seq_cnt;
    fh->fh_r_ctl = FC_RCTL_BA_RJT;
    fh->fh_type = FC_TYPE_BLS;

    /*
     * Form f_ctl by inverting EX_CTX and SEQ_CTX (bits 23, 22).
     * Echo FIRST_SEQ, LAST_SEQ, END_SEQ, END_CONN, SEQ_INIT.
     * Bits 9-8 are meaningful (retransmitted or unidirectional).
     * Last ACK uses bits 7-6 (continue sequence),
     * bits 5-4 are meaningful (what kind of ACK to use).
     * Always set LAST_SEQ, END_SEQ.
     */
    f_ctl = ntoh24(rx_fh->fh_f_ctl);
    f_ctl &= FC_FC_EX_CTX | FC_FC_SEQ_CTX |
        FC_FC_END_CONN | FC_FC_SEQ_INIT |
        FC_FC_RETX_SEQ | FC_FC_UNI_TX;
    f_ctl ^= FC_FC_EX_CTX | FC_FC_SEQ_CTX;
    f_ctl |= FC_FC_LAST_SEQ | FC_FC_END_SEQ;
    f_ctl &= ~FC_FC_FIRST_SEQ;
    hton24(fh->fh_f_ctl, f_ctl);

    fr_sof(fp) = fc_sof_class(fr_sof(rx_fp));
    fr_eof(fp) = FC_EOF_T;
    if (fc_sof_needs_ack(fr_sof(fp)))
        fr_eof(fp) = FC_EOF_N;

    lport->tt.frame_send(lport, fp);
}

static void fc_exch_recv_abts(struct fc_exch *ep, struct fc_frame *rx_fp)
{
    struct fc_frame *fp;
    struct fc_ba_acc *ap;
    struct fc_frame_header *fh;
    struct fc_seq *sp;

    if (!ep)
        goto reject;
    spin_lock_bh(&ep->ex_lock);
    if (ep->esb_stat & ESB_ST_COMPLETE) {
        spin_unlock_bh(&ep->ex_lock);
        goto reject;
    }
    if (!(ep->esb_stat & ESB_ST_REC_QUAL))
        fc_exch_hold(ep);       /* hold for REC_QUAL */
    ep->esb_stat |= ESB_ST_ABNORMAL | ESB_ST_REC_QUAL;
    fc_exch_timer_set_locked(ep, ep->r_a_tov);

    fp = fc_frame_alloc(ep->lp, sizeof(*ap));
    if (!fp) {
        spin_unlock_bh(&ep->ex_lock);
        goto free;
    }
    fh = fc_frame_header_get(fp);
    ap = fc_frame_payload_get(fp, sizeof(*ap));
    memset(ap, 0, sizeof(*ap));
    sp = &ep->seq;
    ap->ba_high_seq_cnt = htons(0xffff);
    if (sp->ssb_stat & SSB_ST_RESP) {
        ap->ba_seq_id = sp->id;
        ap->ba_seq_id_val = FC_BA_SEQ_ID_VAL;
        ap->ba_high_seq_cnt = fh->fh_seq_cnt;
        ap->ba_low_seq_cnt = htons(sp->cnt);
    }
    sp = fc_seq_start_next_locked(sp);
    spin_unlock_bh(&ep->ex_lock);
    fc_seq_send_last(sp, fp, FC_RCTL_BA_ACC, FC_TYPE_BLS);
    fc_frame_free(rx_fp);
    return;

reject:
    fc_exch_send_ba_rjt(rx_fp, FC_BA_RJT_UNABLE, FC_BA_RJT_INV_XID);
free:
    fc_frame_free(rx_fp);
}

static struct fc_seq *fc_seq_assign(struct fc_lport *lport, struct fc_frame *fp)
{
    struct fc_exch_mgr_anchor *ema;

    WARN_ON(lport != fr_dev(fp));
    WARN_ON(fr_seq(fp));
    fr_seq(fp) = NULL;

    list_for_each_entry(ema, &lport->ema_list, ema_list)
        if ((!ema->match || ema->match(fp)) &&
            fc_seq_lookup_recip(lport, ema->mp, fp) == FC_RJT_NONE)
            break;
    return fr_seq(fp);
}

static void fc_seq_release(struct fc_seq *sp)
{
    fc_exch_release(fc_seq_exch(sp));
}

static void fc_exch_recv_req(struct fc_lport *lport, struct fc_exch_mgr *mp,
                 struct fc_frame *fp)
{
    struct fc_frame_header *fh = fc_frame_header_get(fp);
    struct fc_seq *sp = NULL;
    struct fc_exch *ep = NULL;
    enum fc_pf_rjt_reason reject;

    /* We can have the wrong fc_lport at this point with NPIV, which is a
     * problem now that we know a new exchange needs to be allocated
     */
    lport = fc_vport_id_lookup(lport, ntoh24(fh->fh_d_id));
    if (!lport) {
        fc_frame_free(fp);
        return;
    }
    fr_dev(fp) = lport;

    BUG_ON(fr_seq(fp));     /* XXX remove later */

    /*
     * If the RX_ID is 0xffff, don't allocate an exchange.
     * The upper-level protocol may request one later, if needed.
     */
    if (fh->fh_rx_id == htons(FC_XID_UNKNOWN))
        return lport->tt.lport_recv(lport, fp);

    reject = fc_seq_lookup_recip(lport, mp, fp);
    if (reject == FC_RJT_NONE) {
        sp = fr_seq(fp);    /* sequence will be held */
        ep = fc_seq_exch(sp);
        fc_seq_send_ack(sp, fp);
        ep->encaps = fr_encaps(fp);

        /*
         * Call the receive function.
         *
         * The receive function may allocate a new sequence
         * over the old one, so we shouldn't change the
         * sequence after this.
         *
         * The frame will be freed by the receive function.
         * If new exch resp handler is valid then call that
         * first.
         */
        if (ep->resp)
            ep->resp(sp, fp, ep->arg);
        else
            lport->tt.lport_recv(lport, fp);
        fc_exch_release(ep);    /* release from lookup */
    } else {
        FC_LPORT_DBG(lport, "exch/seq lookup failed: reject %x\n",
                 reject);
        fc_frame_free(fp);
    }
}

static void fc_exch_recv_seq_resp(struct fc_exch_mgr *mp, struct fc_frame *fp)
{
    struct fc_frame_header *fh = fc_frame_header_get(fp);
    struct fc_seq *sp;
    struct fc_exch *ep;
    enum fc_sof sof;
    u32 f_ctl;
    void (*resp)(struct fc_seq *, struct fc_frame *fp, void *arg);
    void *ex_resp_arg;
    int rc;

    ep = fc_exch_find(mp, ntohs(fh->fh_ox_id));
    if (!ep) {
        atomic_inc(&mp->stats.xid_not_found);
        goto out;
    }
    if (ep->esb_stat & ESB_ST_COMPLETE) {
        atomic_inc(&mp->stats.xid_not_found);
        goto rel;
    }
    if (ep->rxid == FC_XID_UNKNOWN)
        ep->rxid = ntohs(fh->fh_rx_id);
    if (ep->sid != 0 && ep->sid != ntoh24(fh->fh_d_id)) {
        atomic_inc(&mp->stats.xid_not_found);
        goto rel;
    }
    if (ep->did != ntoh24(fh->fh_s_id) &&
        ep->did != FC_FID_FLOGI) {
        atomic_inc(&mp->stats.xid_not_found);
        goto rel;
    }
    sof = fr_sof(fp);
    sp = &ep->seq;
    if (fc_sof_is_init(sof)) {
        sp->ssb_stat |= SSB_ST_RESP;
        sp->id = fh->fh_seq_id;
    } else if (sp->id != fh->fh_seq_id) {
        atomic_inc(&mp->stats.seq_not_found);
        goto rel;
    }

    f_ctl = ntoh24(fh->fh_f_ctl);
    fr_seq(fp) = sp;
    if (f_ctl & FC_FC_SEQ_INIT)
        ep->esb_stat |= ESB_ST_SEQ_INIT;

    if (fc_sof_needs_ack(sof))
        fc_seq_send_ack(sp, fp);
    resp = ep->resp;
    ex_resp_arg = ep->arg;

    if (fh->fh_type != FC_TYPE_FCP && fr_eof(fp) == FC_EOF_T &&
        (f_ctl & (FC_FC_LAST_SEQ | FC_FC_END_SEQ)) ==
        (FC_FC_LAST_SEQ | FC_FC_END_SEQ)) {
        spin_lock_bh(&ep->ex_lock);
        resp = ep->resp;
        rc = fc_exch_done_locked(ep);
        WARN_ON(fc_seq_exch(sp) != ep);
        spin_unlock_bh(&ep->ex_lock);
        if (!rc)
            fc_exch_delete(ep);
    }

    /*
     * Call the receive function.
     * The sequence is held (has a refcnt) for us,
     * but not for the receive function.
     *
     * The receive function may allocate a new sequence
     * over the old one, so we shouldn't change the
     * sequence after this.
     *
     * The frame will be freed by the receive function.
     * If new exch resp handler is valid then call that
     * first.
     */
    if (resp)
        resp(sp, fp, ex_resp_arg);
    else
        fc_frame_free(fp);
    fc_exch_release(ep);
    return;
rel:
    fc_exch_release(ep);
out:
    fc_frame_free(fp);
}

static void fc_exch_recv_resp(struct fc_exch_mgr *mp, struct fc_frame *fp)
{
    struct fc_seq *sp;

    sp = fc_seq_lookup_orig(mp, fp);    /* doesn't hold sequence */

    if (!sp)
        atomic_inc(&mp->stats.xid_not_found);
    else
        atomic_inc(&mp->stats.non_bls_resp);

    fc_frame_free(fp);
}

static void fc_exch_abts_resp(struct fc_exch *ep, struct fc_frame *fp)
{
    void (*resp)(struct fc_seq *, struct fc_frame *fp, void *arg);
    void *ex_resp_arg;
    struct fc_frame_header *fh;
    struct fc_ba_acc *ap;
    struct fc_seq *sp;
    u16 low;
    u16 high;
    int rc = 1, has_rec = 0;

    fh = fc_frame_header_get(fp);
    FC_EXCH_DBG(ep, "exch: BLS rctl %x - %s\n", fh->fh_r_ctl,
            fc_exch_rctl_name(fh->fh_r_ctl));

    if (cancel_delayed_work_sync(&ep->timeout_work)) {
        FC_EXCH_DBG(ep, "Exchange timer canceled\n");
        fc_exch_release(ep);    /* release from pending timer hold */
    }

    spin_lock_bh(&ep->ex_lock);
    switch (fh->fh_r_ctl) {
    case FC_RCTL_BA_ACC:
        ap = fc_frame_payload_get(fp, sizeof(*ap));
        if (!ap)
            break;

        /*
         * Decide whether to establish a Recovery Qualifier.
         * We do this if there is a non-empty SEQ_CNT range and
         * SEQ_ID is the same as the one we aborted.
         */
        low = ntohs(ap->ba_low_seq_cnt);
        high = ntohs(ap->ba_high_seq_cnt);
        if ((ep->esb_stat & ESB_ST_REC_QUAL) == 0 &&
            (ap->ba_seq_id_val != FC_BA_SEQ_ID_VAL ||
             ap->ba_seq_id == ep->seq_id) && low != high) {
            ep->esb_stat |= ESB_ST_REC_QUAL;
            fc_exch_hold(ep);  /* hold for recovery qualifier */
            has_rec = 1;
        }
        break;
    case FC_RCTL_BA_RJT:
        break;
    default:
        break;
    }

    resp = ep->resp;
    ex_resp_arg = ep->arg;

    /* do we need to do some other checks here. Can we reuse more of
     * fc_exch_recv_seq_resp
     */
    sp = &ep->seq;
    /*
     * do we want to check END_SEQ as well as LAST_SEQ here?
     */
    if (ep->fh_type != FC_TYPE_FCP &&
        ntoh24(fh->fh_f_ctl) & FC_FC_LAST_SEQ)
        rc = fc_exch_done_locked(ep);
    spin_unlock_bh(&ep->ex_lock);
    if (!rc)
        fc_exch_delete(ep);

    if (resp)
        resp(sp, fp, ex_resp_arg);
    else
        fc_frame_free(fp);

    if (has_rec)
        fc_exch_timer_set(ep, ep->r_a_tov);

}

static void fc_exch_recv_bls(struct fc_exch_mgr *mp, struct fc_frame *fp)
{
    struct fc_frame_header *fh;
    struct fc_exch *ep;
    u32 f_ctl;

    fh = fc_frame_header_get(fp);
    f_ctl = ntoh24(fh->fh_f_ctl);
    fr_seq(fp) = NULL;

    ep = fc_exch_find(mp, (f_ctl & FC_FC_EX_CTX) ?
              ntohs(fh->fh_ox_id) : ntohs(fh->fh_rx_id));
    if (ep && (f_ctl & FC_FC_SEQ_INIT)) {
        spin_lock_bh(&ep->ex_lock);
        ep->esb_stat |= ESB_ST_SEQ_INIT;
        spin_unlock_bh(&ep->ex_lock);
    }
    if (f_ctl & FC_FC_SEQ_CTX) {
        /*
         * A response to a sequence we initiated.
         * This should only be ACKs for class 2 or F.
         */
        switch (fh->fh_r_ctl) {
        case FC_RCTL_ACK_1:
        case FC_RCTL_ACK_0:
            break;
        default:
            if (ep)
                FC_EXCH_DBG(ep, "BLS rctl %x - %s received",
                        fh->fh_r_ctl,
                        fc_exch_rctl_name(fh->fh_r_ctl));
            break;
        }
        fc_frame_free(fp);
    } else {
        switch (fh->fh_r_ctl) {
        case FC_RCTL_BA_RJT:
        case FC_RCTL_BA_ACC:
            if (ep)
                fc_exch_abts_resp(ep, fp);
            else
                fc_frame_free(fp);
            break;
        case FC_RCTL_BA_ABTS:
            fc_exch_recv_abts(ep, fp);
            break;
        default:            /* ignore junk */
            fc_frame_free(fp);
            break;
        }
    }
    if (ep)
        fc_exch_release(ep);    /* release hold taken by fc_exch_find */
}

static void fc_seq_ls_acc(struct fc_frame *rx_fp)
{
    struct fc_lport *lport;
    struct fc_els_ls_acc *acc;
    struct fc_frame *fp;

    lport = fr_dev(rx_fp);
    fp = fc_frame_alloc(lport, sizeof(*acc));
    if (!fp)
        return;
    acc = fc_frame_payload_get(fp, sizeof(*acc));
    memset(acc, 0, sizeof(*acc));
    acc->la_cmd = ELS_LS_ACC;
    fc_fill_reply_hdr(fp, rx_fp, FC_RCTL_ELS_REP, 0);
    lport->tt.frame_send(lport, fp);
}

static void fc_seq_ls_rjt(struct fc_frame *rx_fp, enum fc_els_rjt_reason reason,
              enum fc_els_rjt_explan explan)
{
    struct fc_lport *lport;
    struct fc_els_ls_rjt *rjt;
    struct fc_frame *fp;

    lport = fr_dev(rx_fp);
    fp = fc_frame_alloc(lport, sizeof(*rjt));
    if (!fp)
        return;
    rjt = fc_frame_payload_get(fp, sizeof(*rjt));
    memset(rjt, 0, sizeof(*rjt));
    rjt->er_cmd = ELS_LS_RJT;
    rjt->er_reason = reason;
    rjt->er_explan = explan;
    fc_fill_reply_hdr(fp, rx_fp, FC_RCTL_ELS_REP, 0);
    lport->tt.frame_send(lport, fp);
}

static void fc_exch_reset(struct fc_exch *ep)
{
    struct fc_seq *sp;
    void (*resp)(struct fc_seq *, struct fc_frame *, void *);
    void *arg;
    int rc = 1;

    spin_lock_bh(&ep->ex_lock);
    fc_exch_abort_locked(ep, 0);
    ep->state |= FC_EX_RST_CLEANUP;
    fc_exch_timer_cancel(ep);
    resp = ep->resp;
    ep->resp = NULL;
    if (ep->esb_stat & ESB_ST_REC_QUAL)
        atomic_dec(&ep->ex_refcnt); /* drop hold for rec_qual */
    ep->esb_stat &= ~ESB_ST_REC_QUAL;
    arg = ep->arg;
    sp = &ep->seq;
    rc = fc_exch_done_locked(ep);
    spin_unlock_bh(&ep->ex_lock);
    if (!rc)
        fc_exch_delete(ep);

    if (resp)
        resp(sp, ERR_PTR(-FC_EX_CLOSED), arg);
}

static void fc_exch_pool_reset(struct fc_lport *lport,
                   struct fc_exch_pool *pool,
                   u32 sid, u32 did)
{
    struct fc_exch *ep;
    struct fc_exch *next;

    spin_lock_bh(&pool->lock);
restart:
    list_for_each_entry_safe(ep, next, &pool->ex_list, ex_list) {
        if ((lport == ep->lp) &&
            (sid == 0 || sid == ep->sid) &&
            (did == 0 || did == ep->did)) {
            fc_exch_hold(ep);
            spin_unlock_bh(&pool->lock);

            fc_exch_reset(ep);

            fc_exch_release(ep);
            spin_lock_bh(&pool->lock);

            /*
             * must restart loop incase while lock
             * was down multiple eps were released.
             */
            goto restart;
        }
    }
    pool->next_index = 0;
    pool->left = FC_XID_UNKNOWN;
    pool->right = FC_XID_UNKNOWN;
    spin_unlock_bh(&pool->lock);
}

void fc_exch_mgr_reset(struct fc_lport *lport, u32 sid, u32 did)
{
    struct fc_exch_mgr_anchor *ema;
    unsigned int cpu;

    list_for_each_entry(ema, &lport->ema_list, ema_list) {
        for_each_possible_cpu(cpu)
            fc_exch_pool_reset(lport,
                       per_cpu_ptr(ema->mp->pool, cpu),
                       sid, did);
    }
}
EXPORT_SYMBOL(fc_exch_mgr_reset);

static struct fc_exch *fc_exch_lookup(struct fc_lport *lport, u32 xid)
{
    struct fc_exch_mgr_anchor *ema;

    list_for_each_entry(ema, &lport->ema_list, ema_list)
        if (ema->mp->min_xid <= xid && xid <= ema->mp->max_xid)
            return fc_exch_find(ema->mp, xid);
    return NULL;
}

static void fc_exch_els_rec(struct fc_frame *rfp)
{
    struct fc_lport *lport;
    struct fc_frame *fp;
    struct fc_exch *ep;
    struct fc_els_rec *rp;
    struct fc_els_rec_acc *acc;
    enum fc_els_rjt_reason reason = ELS_RJT_LOGIC;
    enum fc_els_rjt_explan explan;
    u32 sid;
    u16 rxid;
    u16 oxid;

    lport = fr_dev(rfp);
    rp = fc_frame_payload_get(rfp, sizeof(*rp));
    explan = ELS_EXPL_INV_LEN;
    if (!rp)
        goto reject;
    sid = ntoh24(rp->rec_s_id);
    rxid = ntohs(rp->rec_rx_id);
    oxid = ntohs(rp->rec_ox_id);

    ep = fc_exch_lookup(lport,
                sid == fc_host_port_id(lport->host) ? oxid : rxid);
    explan = ELS_EXPL_OXID_RXID;
    if (!ep)
        goto reject;
    if (ep->oid != sid || oxid != ep->oxid)
        goto rel;
    if (rxid != FC_XID_UNKNOWN && rxid != ep->rxid)
        goto rel;
    fp = fc_frame_alloc(lport, sizeof(*acc));
    if (!fp)
        goto out;

    acc = fc_frame_payload_get(fp, sizeof(*acc));
    memset(acc, 0, sizeof(*acc));
    acc->reca_cmd = ELS_LS_ACC;
    acc->reca_ox_id = rp->rec_ox_id;
    memcpy(acc->reca_ofid, rp->rec_s_id, 3);
    acc->reca_rx_id = htons(ep->rxid);
    if (ep->sid == ep->oid)
        hton24(acc->reca_rfid, ep->did);
    else
        hton24(acc->reca_rfid, ep->sid);
    acc->reca_fc4value = htonl(ep->seq.rec_data);
    acc->reca_e_stat = htonl(ep->esb_stat & (ESB_ST_RESP |
                         ESB_ST_SEQ_INIT |
                         ESB_ST_COMPLETE));
    fc_fill_reply_hdr(fp, rfp, FC_RCTL_ELS_REP, 0);
    lport->tt.frame_send(lport, fp);
out:
    fc_exch_release(ep);
    return;

rel:
    fc_exch_release(ep);
reject:
    fc_seq_ls_rjt(rfp, reason, explan);
}

static void fc_exch_rrq_resp(struct fc_seq *sp, struct fc_frame *fp, void *arg)
{
    struct fc_exch *aborted_ep = arg;
    unsigned int op;

    if (IS_ERR(fp)) {
        int err = PTR_ERR(fp);

        if (err == -FC_EX_CLOSED || err == -FC_EX_TIMEOUT)
            goto cleanup;
        FC_EXCH_DBG(aborted_ep, "Cannot process RRQ, "
                "frame error %d\n", err);
        return;
    }

    op = fc_frame_payload_op(fp);
    fc_frame_free(fp);

    switch (op) {
    case ELS_LS_RJT:
        FC_EXCH_DBG(aborted_ep, "LS_RJT for RRQ");
        /* fall through */
    case ELS_LS_ACC:
        goto cleanup;
    default:
        FC_EXCH_DBG(aborted_ep, "unexpected response op %x "
                "for RRQ", op);
        return;
    }

cleanup:
    fc_exch_done(&aborted_ep->seq);
    /* drop hold for rec qual */
    fc_exch_release(aborted_ep);
}


static struct fc_seq *fc_exch_seq_send(struct fc_lport *lport,
                       struct fc_frame *fp,
                       void (*resp)(struct fc_seq *,
                            struct fc_frame *fp,
                            void *arg),
                       void (*destructor)(struct fc_seq *,
                              void *),
                       void *arg, u32 timer_msec)
{
    struct fc_exch *ep;
    struct fc_seq *sp = NULL;
    struct fc_frame_header *fh;
    struct fc_fcp_pkt *fsp = NULL;
    int rc = 1;

    ep = fc_exch_alloc(lport, fp);
    if (!ep) {
        fc_frame_free(fp);
        return NULL;
    }
    ep->esb_stat |= ESB_ST_SEQ_INIT;
    fh = fc_frame_header_get(fp);
    fc_exch_set_addr(ep, ntoh24(fh->fh_s_id), ntoh24(fh->fh_d_id));
    ep->resp = resp;
    ep->destructor = destructor;
    ep->arg = arg;
    ep->r_a_tov = FC_DEF_R_A_TOV;
    ep->lp = lport;
    sp = &ep->seq;

    ep->fh_type = fh->fh_type; /* save for possbile timeout handling */
    ep->f_ctl = ntoh24(fh->fh_f_ctl);
    fc_exch_setup_hdr(ep, fp, ep->f_ctl);
    sp->cnt++;

    if (ep->xid <= lport->lro_xid && fh->fh_r_ctl == FC_RCTL_DD_UNSOL_CMD) {
        fsp = fr_fsp(fp);
        fc_fcp_ddp_setup(fr_fsp(fp), ep->xid);
    }

    if (unlikely(lport->tt.frame_send(lport, fp)))
        goto err;

    if (timer_msec)
        fc_exch_timer_set_locked(ep, timer_msec);
    ep->f_ctl &= ~FC_FC_FIRST_SEQ;  /* not first seq */

    if (ep->f_ctl & FC_FC_SEQ_INIT)
        ep->esb_stat &= ~ESB_ST_SEQ_INIT;
    spin_unlock_bh(&ep->ex_lock);
    return sp;
err:
    if (fsp)
        fc_fcp_ddp_done(fsp);
    rc = fc_exch_done_locked(ep);
    spin_unlock_bh(&ep->ex_lock);
    if (!rc)
        fc_exch_delete(ep);
    return NULL;
}

static void fc_exch_rrq(struct fc_exch *ep)
{
    struct fc_lport *lport;
    struct fc_els_rrq *rrq;
    struct fc_frame *fp;
    u32 did;

    lport = ep->lp;

    fp = fc_frame_alloc(lport, sizeof(*rrq));
    if (!fp)
        goto retry;

    rrq = fc_frame_payload_get(fp, sizeof(*rrq));
    memset(rrq, 0, sizeof(*rrq));
    rrq->rrq_cmd = ELS_RRQ;
    hton24(rrq->rrq_s_id, ep->sid);
    rrq->rrq_ox_id = htons(ep->oxid);
    rrq->rrq_rx_id = htons(ep->rxid);

    did = ep->did;
    if (ep->esb_stat & ESB_ST_RESP)
        did = ep->sid;

    fc_fill_fc_hdr(fp, FC_RCTL_ELS_REQ, did,
               lport->port_id, FC_TYPE_ELS,
               FC_FC_FIRST_SEQ | FC_FC_END_SEQ | FC_FC_SEQ_INIT, 0);

    if (fc_exch_seq_send(lport, fp, fc_exch_rrq_resp, NULL, ep,
                 lport->e_d_tov))
        return;

retry:
    spin_lock_bh(&ep->ex_lock);
    if (ep->state & (FC_EX_RST_CLEANUP | FC_EX_DONE)) {
        spin_unlock_bh(&ep->ex_lock);
        /* drop hold for rec qual */
        fc_exch_release(ep);
        return;
    }
    ep->esb_stat |= ESB_ST_REC_QUAL;
    fc_exch_timer_set_locked(ep, ep->r_a_tov);
    spin_unlock_bh(&ep->ex_lock);
}

static void fc_exch_els_rrq(struct fc_frame *fp)
{
    struct fc_lport *lport;
    struct fc_exch *ep = NULL;  /* request or subject exchange */
    struct fc_els_rrq *rp;
    u32 sid;
    u16 xid;
    enum fc_els_rjt_explan explan;

    lport = fr_dev(fp);
    rp = fc_frame_payload_get(fp, sizeof(*rp));
    explan = ELS_EXPL_INV_LEN;
    if (!rp)
        goto reject;

    /*
     * lookup subject exchange.
     */
    sid = ntoh24(rp->rrq_s_id);     /* subject source */
    xid = fc_host_port_id(lport->host) == sid ?
            ntohs(rp->rrq_ox_id) : ntohs(rp->rrq_rx_id);
    ep = fc_exch_lookup(lport, xid);
    explan = ELS_EXPL_OXID_RXID;
    if (!ep)
        goto reject;
    spin_lock_bh(&ep->ex_lock);
    if (ep->oxid != ntohs(rp->rrq_ox_id))
        goto unlock_reject;
    if (ep->rxid != ntohs(rp->rrq_rx_id) &&
        ep->rxid != FC_XID_UNKNOWN)
        goto unlock_reject;
    explan = ELS_EXPL_SID;
    if (ep->sid != sid)
        goto unlock_reject;

    /*
     * Clear Recovery Qualifier state, and cancel timer if complete.
     */
    if (ep->esb_stat & ESB_ST_REC_QUAL) {
        ep->esb_stat &= ~ESB_ST_REC_QUAL;
        atomic_dec(&ep->ex_refcnt); /* drop hold for rec qual */
    }
    if (ep->esb_stat & ESB_ST_COMPLETE)
        fc_exch_timer_cancel(ep);

    spin_unlock_bh(&ep->ex_lock);

    /*
     * Send LS_ACC.
     */
    fc_seq_ls_acc(fp);
    goto out;

unlock_reject:
    spin_unlock_bh(&ep->ex_lock);
reject:
    fc_seq_ls_rjt(fp, ELS_RJT_LOGIC, explan);
out:
    if (ep)
        fc_exch_release(ep);    /* drop hold from fc_exch_find */
}

void fc_exch_update_stats(struct fc_lport *lport)
{
    struct fc_host_statistics *st;
    struct fc_exch_mgr_anchor *ema;
    struct fc_exch_mgr *mp;

    st = &lport->host_stats;

    list_for_each_entry(ema, &lport->ema_list, ema_list) {
        mp = ema->mp;
        st->fc_no_free_exch += atomic_read(&mp->stats.no_free_exch);
        st->fc_no_free_exch_xid +=
                atomic_read(&mp->stats.no_free_exch_xid);
        st->fc_xid_not_found += atomic_read(&mp->stats.xid_not_found);
        st->fc_xid_busy += atomic_read(&mp->stats.xid_busy);
        st->fc_seq_not_found += atomic_read(&mp->stats.seq_not_found);
        st->fc_non_bls_resp += atomic_read(&mp->stats.non_bls_resp);
    }
}
EXPORT_SYMBOL(fc_exch_update_stats);

struct fc_exch_mgr_anchor *fc_exch_mgr_add(struct fc_lport *lport,
                       struct fc_exch_mgr *mp,
                       bool (*match)(struct fc_frame *))
{
    struct fc_exch_mgr_anchor *ema;

    ema = kmalloc(sizeof(*ema), GFP_ATOMIC);
    if (!ema)
        return ema;

    ema->mp = mp;
    ema->match = match;
    /* add EM anchor to EM anchors list */
    list_add_tail(&ema->ema_list, &lport->ema_list);
    kref_get(&mp->kref);
    return ema;
}
EXPORT_SYMBOL(fc_exch_mgr_add);

static void fc_exch_mgr_destroy(struct kref *kref)
{
    struct fc_exch_mgr *mp = container_of(kref, struct fc_exch_mgr, kref);

    mempool_destroy(mp->ep_pool);
    free_percpu(mp->pool);
    kfree(mp);
}

void fc_exch_mgr_del(struct fc_exch_mgr_anchor *ema)
{
    /* remove EM anchor from EM anchors list */
    list_del(&ema->ema_list);
    kref_put(&ema->mp->kref, fc_exch_mgr_destroy);
    kfree(ema);
}
EXPORT_SYMBOL(fc_exch_mgr_del);

int fc_exch_mgr_list_clone(struct fc_lport *src, struct fc_lport *dst)
{
    struct fc_exch_mgr_anchor *ema, *tmp;

    list_for_each_entry(ema, &src->ema_list, ema_list) {
        if (!fc_exch_mgr_add(dst, ema->mp, ema->match))
            goto err;
    }
    return 0;
err:
    list_for_each_entry_safe(ema, tmp, &dst->ema_list, ema_list)
        fc_exch_mgr_del(ema);
    return -ENOMEM;
}
EXPORT_SYMBOL(fc_exch_mgr_list_clone);

struct fc_exch_mgr *fc_exch_mgr_alloc(struct fc_lport *lport,
                      enum fc_class class,
                      u16 min_xid, u16 max_xid,
                      bool (*match)(struct fc_frame *))
{
    struct fc_exch_mgr *mp;
    u16 pool_exch_range;
    size_t pool_size;
    unsigned int cpu;
    struct fc_exch_pool *pool;

    if (max_xid <= min_xid || max_xid == FC_XID_UNKNOWN ||
        (min_xid & fc_cpu_mask) != 0) {
        FC_LPORT_DBG(lport, "Invalid min_xid 0x:%x and max_xid 0x:%x\n",
                 min_xid, max_xid);
        return NULL;
    }

    /*
     * allocate memory for EM
     */
    mp = kzalloc(sizeof(struct fc_exch_mgr), GFP_ATOMIC);
    if (!mp)
        return NULL;

    mp->class = class;
    /* adjust em exch xid range for offload */
    mp->min_xid = min_xid;

       /* reduce range so per cpu pool fits into PCPU_MIN_UNIT_SIZE pool */
    pool_exch_range = (PCPU_MIN_UNIT_SIZE - sizeof(*pool)) /
        sizeof(struct fc_exch *);
    if ((max_xid - min_xid + 1) / (fc_cpu_mask + 1) > pool_exch_range) {
        mp->max_xid = pool_exch_range * (fc_cpu_mask + 1) +
            min_xid - 1;
    } else {
        mp->max_xid = max_xid;
        pool_exch_range = (mp->max_xid - mp->min_xid + 1) /
            (fc_cpu_mask + 1);
    }

    mp->ep_pool = mempool_create_slab_pool(2, fc_em_cachep);
    if (!mp->ep_pool)
        goto free_mp;

    /*
     * Setup per cpu exch pool with entire exchange id range equally
     * divided across all cpus. The exch pointers array memory is
     * allocated for exch range per pool.
     */
    mp->pool_max_index = pool_exch_range - 1;

    /*
     * Allocate and initialize per cpu exch pool
     */
    pool_size = sizeof(*pool) + pool_exch_range * sizeof(struct fc_exch *);
    mp->pool = __alloc_percpu(pool_size, __alignof__(struct fc_exch_pool));
    if (!mp->pool)
        goto free_mempool;
    for_each_possible_cpu(cpu) {
        pool = per_cpu_ptr(mp->pool, cpu);
        pool->next_index = 0;
        pool->left = FC_XID_UNKNOWN;
        pool->right = FC_XID_UNKNOWN;
        spin_lock_init(&pool->lock);
        INIT_LIST_HEAD(&pool->ex_list);
    }

    kref_init(&mp->kref);
    if (!fc_exch_mgr_add(lport, mp, match)) {
        free_percpu(mp->pool);
        goto free_mempool;
    }

    /*
     * Above kref_init() sets mp->kref to 1 and then
     * call to fc_exch_mgr_add incremented mp->kref again,
     * so adjust that extra increment.
     */
    kref_put(&mp->kref, fc_exch_mgr_destroy);
    return mp;

free_mempool:
    mempool_destroy(mp->ep_pool);
free_mp:
    kfree(mp);
    return NULL;
}
EXPORT_SYMBOL(fc_exch_mgr_alloc);

void fc_exch_mgr_free(struct fc_lport *lport)
{
    struct fc_exch_mgr_anchor *ema, *next;

    flush_workqueue(fc_exch_workqueue);
    list_for_each_entry_safe(ema, next, &lport->ema_list, ema_list)
        fc_exch_mgr_del(ema);
}
EXPORT_SYMBOL(fc_exch_mgr_free);

static struct fc_exch_mgr_anchor *fc_find_ema(u32 f_ctl,
                          struct fc_lport *lport,
                          struct fc_frame_header *fh)
{
    struct fc_exch_mgr_anchor *ema;
    u16 xid;

    if (f_ctl & FC_FC_EX_CTX)
        xid = ntohs(fh->fh_ox_id);
    else {
        xid = ntohs(fh->fh_rx_id);
        if (xid == FC_XID_UNKNOWN)
            return list_entry(lport->ema_list.prev,
                      typeof(*ema), ema_list);
    }

    list_for_each_entry(ema, &lport->ema_list, ema_list) {
        if ((xid >= ema->mp->min_xid) &&
            (xid <= ema->mp->max_xid))
            return ema;
    }
    return NULL;
}
void fc_exch_recv(struct fc_lport *lport, struct fc_frame *fp)
{
    struct fc_frame_header *fh = fc_frame_header_get(fp);
    struct fc_exch_mgr_anchor *ema;
    u32 f_ctl;

    /* lport lock ? */
    if (!lport || lport->state == LPORT_ST_DISABLED) {
        FC_LPORT_DBG(lport, "Receiving frames for an lport that "
                 "has not been initialized correctly\n");
        fc_frame_free(fp);
        return;
    }

    f_ctl = ntoh24(fh->fh_f_ctl);
    ema = fc_find_ema(f_ctl, lport, fh);
    if (!ema) {
        FC_LPORT_DBG(lport, "Unable to find Exchange Manager Anchor,"
                    "fc_ctl <0x%x>, xid <0x%x>\n",
                     f_ctl,
                     (f_ctl & FC_FC_EX_CTX) ?
                     ntohs(fh->fh_ox_id) :
                     ntohs(fh->fh_rx_id));
        fc_frame_free(fp);
        return;
    }

    /*
     * If frame is marked invalid, just drop it.
     */
    switch (fr_eof(fp)) {
    case FC_EOF_T:
        if (f_ctl & FC_FC_END_SEQ)
            skb_trim(fp_skb(fp), fr_len(fp) - FC_FC_FILL(f_ctl));
        /* fall through */
    case FC_EOF_N:
        if (fh->fh_type == FC_TYPE_BLS)
            fc_exch_recv_bls(ema->mp, fp);
        else if ((f_ctl & (FC_FC_EX_CTX | FC_FC_SEQ_CTX)) ==
             FC_FC_EX_CTX)
            fc_exch_recv_seq_resp(ema->mp, fp);
        else if (f_ctl & FC_FC_SEQ_CTX)
            fc_exch_recv_resp(ema->mp, fp);
        else    /* no EX_CTX and no SEQ_CTX */
            fc_exch_recv_req(lport, ema->mp, fp);
        break;
    default:
        FC_LPORT_DBG(lport, "dropping invalid frame (eof %x)",
                 fr_eof(fp));
        fc_frame_free(fp);
    }
}
EXPORT_SYMBOL(fc_exch_recv);

int fc_exch_init(struct fc_lport *lport)
{
    if (!lport->tt.seq_start_next)
        lport->tt.seq_start_next = fc_seq_start_next;

    if (!lport->tt.seq_set_resp)
        lport->tt.seq_set_resp = fc_seq_set_resp;

    if (!lport->tt.exch_seq_send)
        lport->tt.exch_seq_send = fc_exch_seq_send;

    if (!lport->tt.seq_send)
        lport->tt.seq_send = fc_seq_send;

    if (!lport->tt.seq_els_rsp_send)
        lport->tt.seq_els_rsp_send = fc_seq_els_rsp_send;

    if (!lport->tt.exch_done)
        lport->tt.exch_done = fc_exch_done;

    if (!lport->tt.exch_mgr_reset)
        lport->tt.exch_mgr_reset = fc_exch_mgr_reset;

    if (!lport->tt.seq_exch_abort)
        lport->tt.seq_exch_abort = fc_seq_exch_abort;

    if (!lport->tt.seq_assign)
        lport->tt.seq_assign = fc_seq_assign;

    if (!lport->tt.seq_release)
        lport->tt.seq_release = fc_seq_release;

    return 0;
}
EXPORT_SYMBOL(fc_exch_init);

int fc_setup_exch_mgr(void)
{
    fc_em_cachep = kmem_cache_create("libfc_em", sizeof(struct fc_exch),
                     0, SLAB_HWCACHE_ALIGN, NULL);
    if (!fc_em_cachep)
        return -ENOMEM;

    /*
     * Initialize fc_cpu_mask and fc_cpu_order. The
     * fc_cpu_mask is set for nr_cpu_ids rounded up
     * to order of 2's * power and order is stored
     * in fc_cpu_order as this is later required in
     * mapping between an exch id and exch array index
     * in per cpu exch pool.
     *
     * This round up is required to align fc_cpu_mask
     * to exchange id's lower bits such that all incoming
     * frames of an exchange gets delivered to the same
     * cpu on which exchange originated by simple bitwise
     * AND operation between fc_cpu_mask and exchange id.
     */
    fc_cpu_mask = 1;
    fc_cpu_order = 0;
    while (fc_cpu_mask < nr_cpu_ids) {
        fc_cpu_mask <<= 1;
        fc_cpu_order++;
    }
    fc_cpu_mask--;

    fc_exch_workqueue = create_singlethread_workqueue("fc_exch_workqueue");
    if (!fc_exch_workqueue)
        goto err;
    return 0;
err:
    kmem_cache_destroy(fc_em_cachep);
    return -ENOMEM;
}

void fc_destroy_exch_mgr(void)
{
    destroy_workqueue(fc_exch_workqueue);
    kmem_cache_destroy(fc_em_cachep);
}