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[linux-rt-nao.git] / drivers / scsi / libfc / fc_exch.c

/*
 * 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/gfp.h>
#include <linux/err.h>

#include <scsi/fc/fc_fc2.h>

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

/*
 * fc_exch_debug can be set in debugger or at compile time to get more logs.
 */
static int fc_exch_debug;

#define FC_DEBUG_EXCH(fmt...)                   \
        do {                                    \
                if (fc_exch_debug)              \
                        FC_DBG(fmt);            \
        } while (0)

static struct kmem_cache *fc_em_cachep; /* cache for exchanges */

/*
 * 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.
 */

/*
 * Exchange manager.
 *
 * This structure is the center for creating exchanges and sequences.
 * It manages the allocation of exchange IDs.
 */
struct fc_exch_mgr {
        enum fc_class   class;          /* default class for sequences */
        spinlock_t      em_lock;        /* exchange manager lock,
                                           must be taken before ex_lock */
        u16             last_xid;       /* last allocated exchange ID */
        u16             min_xid;        /* min exchange ID */
        u16             max_xid;        /* max exchange ID */
        u16             max_read;       /* max exchange ID for read */
        u16             last_read;      /* last xid allocated for read */
        u32     total_exches;           /* total allocated exchanges */
        struct list_head        ex_list;        /* allocated exchanges list */
        struct fc_lport *lp;            /* fc device instance */
        mempool_t       *ep_pool;       /* reserve ep's */

        /*
         * currently exchange mgr stats are updated but not used.
         * either stats can be expose via sysfs or remove them
         * all together if not used XXX
         */
        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 **exches;        /* for exch pointers indexed by xid */
};
#define fc_seq_exch(sp) container_of(sp, struct fc_exch, seq)

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

/*
 * 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_lock and ex_lock must be taken at the same time, then the
 *    em_lock must be taken before the ex_lock.
 */

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

#define FC_TABLE_SIZE(x)   (sizeof(x) / sizeof(x[0]))

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,
                                   FC_TABLE_SIZE(fc_exch_rctl_names));
}

/*
 * Hold an exchange - keep it from being freed.
 */
static void fc_exch_hold(struct fc_exch *ep)
{
        atomic_inc(&ep->ex_refcnt);
}

/*
 * setup fc hdr by initializing few more FC header fields and sof/eof.
 * Initialized fields by this func:
 *      - fh_ox_id, fh_rx_id, fh_seq_id, fh_seq_cnt
 *      - sof and eof
 */
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;
                /*
                 * Form 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);
}


/*
 * Release a reference to an exchange.
 * If the refcnt goes to zero and the exchange is complete, it is freed.
 */
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);
                if (ep->lp->tt.exch_put)
                        ep->lp->tt.exch_put(ep->lp, mp, ep->xid);
                WARN_ON(!ep->esb_stat & ESB_ST_COMPLETE);
                mempool_free(ep, mp->ep_pool);
        }
}

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;
                if (cancel_delayed_work(&ep->timeout_work))
                        atomic_dec(&ep->ex_refcnt); /* drop hold for timer */
                rc = 0;
        }
        return rc;
}

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

        mp = ep->em;
        spin_lock_bh(&mp->em_lock);
        WARN_ON(mp->total_exches <= 0);
        mp->total_exches--;
        mp->exches[ep->xid - mp->min_xid] = NULL;
        list_del(&ep->ex_list);
        spin_unlock_bh(&mp->em_lock);
        fc_exch_release(ep);    /* drop hold for exch in mp */
}

/*
 * Internal version of fc_exch_timer_set - used with lock held.
 */
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_DEBUG_EXCH("Exchange (%4x) timed out, notifying the upper layer\n",
                      ep->xid);
        if (schedule_delayed_work(&ep->timeout_work,
                                  msecs_to_jiffies(timer_msec)))
                fc_exch_hold(ep);               /* hold for timer */
}

/*
 * Set timer for an exchange.
 * The time is a minimum delay in milliseconds until the timer fires.
 * Used for upper level protocols to time out the exchange.
 * The timer is cancelled when it fires or when the exchange completes.
 * Returns non-zero if a timer couldn't be allocated.
 */
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);
}

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

        ep = fc_seq_exch(req_sp);

        spin_lock_bh(&ep->ex_lock);
        if (ep->esb_stat & (ESB_ST_COMPLETE | ESB_ST_ABNORMAL) ||
            ep->state & (FC_EX_DONE | FC_EX_RST_CLEANUP)) {
                spin_unlock_bh(&ep->ex_lock);
                return -ENXIO;
        }

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

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

        /*
         * 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;
}
EXPORT_SYMBOL(fc_seq_exch_abort);

/*
 * Exchange timeout - handle exchange timer expiration.
 * The timer will have been cancelled before this is called.
 */
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;

        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;
                if (e_stat & ESB_ST_REC_QUAL)
                        fc_exch_rrq(ep);
                spin_unlock_bh(&ep->ex_lock);
                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_mgr_delete_ep(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);
}

/*
 * Allocate a sequence.
 *
 * We don't support multiple originated sequences on the same exchange.
 * By implication, any previously originated sequence on this exchange
 * is complete, and we reallocate the same sequence.
 */
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;
}

/*
 * fc_em_alloc_xid - returns an xid based on request type
 * @lp : ptr to associated lport
 * @fp : ptr to the assocated frame
 *
 * check the associated fc_fsp_pkt to get scsi command type and
 * command direction to decide from which range this exch id
 * will be allocated from.
 *
 * Returns : 0 or an valid xid
 */
static u16 fc_em_alloc_xid(struct fc_exch_mgr *mp, const struct fc_frame *fp)
{
        u16 xid, min, max;
        u16 *plast;
        struct fc_exch *ep = NULL;

        if (mp->max_read) {
                if (fc_frame_is_read(fp)) {
                        min = mp->min_xid;
                        max = mp->max_read;
                        plast = &mp->last_read;
                } else {
                        min = mp->max_read + 1;
                        max = mp->max_xid;
                        plast = &mp->last_xid;
                }
        } else {
                min = mp->min_xid;
                max = mp->max_xid;
                plast = &mp->last_xid;
        }
        xid = *plast;
        do {
                xid = (xid == max) ? min : xid + 1;
                ep = mp->exches[xid - mp->min_xid];
        } while ((ep != NULL) && (xid != *plast));

        if (unlikely(ep))
                xid = 0;
        else
                *plast = xid;

        return xid;
}

/*
 * fc_exch_alloc - allocate an exchange.
 * @mp : ptr to the exchange manager
 * @xid: input xid
 *
 * if xid is supplied zero then assign next free exchange ID
 * from exchange manager, otherwise use supplied xid.
 * Returns with exch lock held.
 */
struct fc_exch *fc_exch_alloc(struct fc_exch_mgr *mp,
                              struct fc_frame *fp, u16 xid)
{
        struct fc_exch *ep;

        /* 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));

        spin_lock_bh(&mp->em_lock);
        /* alloc xid if input xid 0 */
        if (!xid) {
                /* alloc a new xid */
                xid = fc_em_alloc_xid(mp, fp);
                if (!xid) {
                        printk(KERN_ERR "fc_em_alloc_xid() failed\n");
                        goto err;
                }
        }

        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);

        mp->exches[xid - mp->min_xid] = ep;
        list_add_tail(&ep->ex_list, &mp->ex_list);
        fc_seq_alloc(ep, ep->seq_id++);
        mp->total_exches++;
        spin_unlock_bh(&mp->em_lock);

        /*
         *  update exchange
         */
        ep->oxid = ep->xid = xid;
        ep->em = mp;
        ep->lp = mp->lp;
        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(&mp->em_lock);
        atomic_inc(&mp->stats.no_free_exch_xid);
        mempool_free(ep, mp->ep_pool);
        return NULL;
}
EXPORT_SYMBOL(fc_exch_alloc);

/*
 * Lookup and hold an exchange.
 */
static struct fc_exch *fc_exch_find(struct fc_exch_mgr *mp, u16 xid)
{
        struct fc_exch *ep = NULL;

        if ((xid >= mp->min_xid) && (xid <= mp->max_xid)) {
                spin_lock_bh(&mp->em_lock);
                ep = mp->exches[xid - mp->min_xid];
                if (ep) {
                        fc_exch_hold(ep);
                        WARN_ON(ep->xid != xid);
                }
                spin_unlock_bh(&mp->em_lock);
        }
        return ep;
}

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_mgr_delete_ep(ep);
}
EXPORT_SYMBOL(fc_exch_done);

/*
 * Allocate a new exchange as responder.
 * Sets the responder ID in the frame header.
 */
static struct fc_exch *fc_exch_resp(struct fc_exch_mgr *mp, struct fc_frame *fp)
{
        struct fc_exch *ep;
        struct fc_frame_header *fh;

        ep = mp->lp->tt.exch_get(mp->lp, 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 exch_get */
        }
        return ep;
}

/*
 * Find a sequence for receive where the other end is originating the sequence.
 * If fc_pf_rjt_reason is FC_RJT_NONE then this function will have a hold
 * on the ep that should be released by the caller.
 */
static enum fc_pf_rjt_reason fc_seq_lookup_recip(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(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 = fc_seq_start_next(&ep->seq);
                if (!sp) {
                        reject = FC_RJT_SEQ_XS; /* exchange shortage */
                        goto rel;
                }
                sp->id = fh->fh_seq_id;
                sp->ssb_stat |= SSB_ST_RESP;
        } else {
                sp = &ep->seq;
                if (sp->id != fh->fh_seq_id) {
                        atomic_inc(&mp->stats.seq_not_found);
                        reject = FC_RJT_SEQ_ID; /* sequence/exch should exist */
                        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;
}

/*
 * Find the sequence for a frame being received.
 * We originated the sequence, so it should be found.
 * We may or may not have originated the exchange.
 * Does not hold the sequence for the caller.
 */
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;
}

/*
 * Set addresses for an exchange.
 * Note this must be done before the first sequence of the exchange is sent.
 */
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 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_DEBUG_EXCH("exch %4x f_ctl %6x seq %2x\n",
                      ep->xid, ep->f_ctl, sp->id);
        return sp;
}
/*
 * Allocate a new sequence on the same exchange as the supplied sequence.
 * This will never return NULL.
 */
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);
        WARN_ON((ep->esb_stat & ESB_ST_COMPLETE) != 0);
        sp = fc_seq_start_next_locked(sp);
        spin_unlock_bh(&ep->ex_lock);

        return sp;
}
EXPORT_SYMBOL(fc_seq_start_next);

int fc_seq_send(struct fc_lport *lp, 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;

        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);

        /*
         * 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 = lp->tt.frame_send(lp, fp);

        /*
         * 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_END_SEQ | FC_FC_SEQ_INIT))
                ep->esb_stat &= ~ESB_ST_SEQ_INIT;
        spin_unlock_bh(&ep->ex_lock);
        return error;
}
EXPORT_SYMBOL(fc_seq_send);

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

/*
 * Send a sequence, which is also the last sequence in the exchange.
 */
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);
}

/*
 * Send ACK_1 (or equiv.) indicating we received something.
 * The frame we're acking is supplied.
 */
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 *lp = 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(lp, 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;

                (void) lp->tt.frame_send(lp, fp);
        }
}

/*
 * Send BLS Reject.
 * This is for rejecting BA_ABTS only.
 */
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 *lp;
        unsigned int f_ctl;

        lp = fr_dev(rx_fp);
        fp = fc_frame_alloc(lp, 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_rx_id;
        fh->fh_rx_id = rx_fh->fh_ox_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;

        (void) lp->tt.frame_send(lp, fp);
}

/*
 * Handle an incoming ABTS.  This would be for target mode usually,
 * but could be due to lost FCP transfer ready, confirm or RRQ.
 * We always handle this as an exchange abort, ignoring the parameter.
 */
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);
}

/*
 * Handle receive where the other end is originating the sequence.
 */
static void fc_exch_recv_req(struct fc_lport *lp, 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_sof sof;
        enum fc_eof eof;
        u32 f_ctl;
        enum fc_pf_rjt_reason reject;

        fr_seq(fp) = NULL;
        reject = fc_seq_lookup_recip(mp, fp);
        if (reject == FC_RJT_NONE) {
                sp = fr_seq(fp);        /* sequence will be held */
                ep = fc_seq_exch(sp);
                sof = fr_sof(fp);
                eof = fr_eof(fp);
                f_ctl = ntoh24(fh->fh_f_ctl);
                fc_seq_send_ack(sp, 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
                        lp->tt.lport_recv(lp, sp, fp);
                fc_exch_release(ep);    /* release from lookup */
        } else {
                FC_DEBUG_EXCH("exch/seq lookup failed: reject %x\n", reject);
                fc_frame_free(fp);
        }
}

/*
 * Handle receive where the other end is originating the sequence in
 * response to our exchange.
 */
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->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);
        if (fc_sof_is_init(sof)) {
                sp = fc_seq_start_next(&ep->seq);
                sp->id = fh->fh_seq_id;
                sp->ssb_stat |= SSB_ST_RESP;
        } else {
                sp = &ep->seq;
                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);
                rc = fc_exch_done_locked(ep);
                WARN_ON(fc_seq_exch(sp) != ep);
                spin_unlock_bh(&ep->ex_lock);
                if (!rc)
                        fc_exch_mgr_delete_ep(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);
}

/*
 * Handle receive for a sequence where other end is responding to our sequence.
 */
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);
                FC_DEBUG_EXCH("seq lookup failed\n");
        } else {
                atomic_inc(&mp->stats.non_bls_resp);
                FC_DEBUG_EXCH("non-BLS response to sequence");
        }
        fc_frame_free(fp);
}

/*
 * Handle the response to an ABTS for exchange or sequence.
 * This can be BA_ACC or BA_RJT.
 */
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_DEBUG_EXCH("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_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_mgr_delete_ep(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);

}

/*
 * Receive BLS sequence.
 * This is always a sequence initiated by the remote side.
 * We may be either the originator or recipient of the exchange.
 */
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:
                        FC_DEBUG_EXCH("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 */
}

/*
 * Accept sequence with LS_ACC.
 * If this fails due to allocation or transmit congestion, assume the
 * originator will repeat the sequence.
 */
static void fc_seq_ls_acc(struct fc_seq *req_sp)
{
        struct fc_seq *sp;
        struct fc_els_ls_acc *acc;
        struct fc_frame *fp;

        sp = fc_seq_start_next(req_sp);
        fp = fc_frame_alloc(fc_seq_exch(sp)->lp, sizeof(*acc));
        if (fp) {
                acc = fc_frame_payload_get(fp, sizeof(*acc));
                memset(acc, 0, sizeof(*acc));
                acc->la_cmd = ELS_LS_ACC;
                fc_seq_send_last(sp, fp, FC_RCTL_ELS_REP, FC_TYPE_ELS);
        }
}

/*
 * Reject sequence with ELS LS_RJT.
 * If this fails due to allocation or transmit congestion, assume the
 * originator will repeat the sequence.
 */
static void fc_seq_ls_rjt(struct fc_seq *req_sp, enum fc_els_rjt_reason reason,
                          enum fc_els_rjt_explan explan)
{
        struct fc_seq *sp;
        struct fc_els_ls_rjt *rjt;
        struct fc_frame *fp;

        sp = fc_seq_start_next(req_sp);
        fp = fc_frame_alloc(fc_seq_exch(sp)->lp, sizeof(*rjt));
        if (fp) {
                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_seq_send_last(sp, fp, FC_RCTL_ELS_REP, FC_TYPE_ELS);
        }
}

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);
        ep->state |= FC_EX_RST_CLEANUP;
        /*
         * we really want to call del_timer_sync, but cannot due
         * to the lport calling with the lport lock held (some resp
         * functions can also grab the lport lock which could cause
         * a deadlock).
         */
        if (cancel_delayed_work(&ep->timeout_work))
                atomic_dec(&ep->ex_refcnt);     /* drop hold for timer */
        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_mgr_delete_ep(ep);

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

/*
 * Reset an exchange manager, releasing all sequences and exchanges.
 * If sid is non-zero, reset only exchanges we source from that FID.
 * If did is non-zero, reset only exchanges destined to that FID.
 */
void fc_exch_mgr_reset(struct fc_lport *lp, u32 sid, u32 did)
{
        struct fc_exch *ep;
        struct fc_exch *next;
        struct fc_exch_mgr *mp = lp->emp;

        spin_lock_bh(&mp->em_lock);
restart:
        list_for_each_entry_safe(ep, next, &mp->ex_list, ex_list) {
                if ((sid == 0 || sid == ep->sid) &&
                    (did == 0 || did == ep->did)) {
                        fc_exch_hold(ep);
                        spin_unlock_bh(&mp->em_lock);

                        fc_exch_reset(ep);

                        fc_exch_release(ep);
                        spin_lock_bh(&mp->em_lock);

                        /*
                         * must restart loop incase while lock was down
                         * multiple eps were released.
                         */
                        goto restart;
                }
        }
        spin_unlock_bh(&mp->em_lock);
}
EXPORT_SYMBOL(fc_exch_mgr_reset);

/*
 * Handle incoming ELS REC - Read Exchange Concise.
 * Note that the requesting port may be different than the S_ID in the request.
 */
static void fc_exch_els_rec(struct fc_seq *sp, struct fc_frame *rfp)
{
        struct fc_frame *fp;
        struct fc_exch *ep;
        struct fc_exch_mgr *em;
        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;

        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);

        /*
         * Currently it's hard to find the local S_ID from the exchange
         * manager.  This will eventually be fixed, but for now it's easier
         * to lookup the subject exchange twice, once as if we were
         * the initiator, and then again if we weren't.
         */
        em = fc_seq_exch(sp)->em;
        ep = fc_exch_find(em, oxid);
        explan = ELS_EXPL_OXID_RXID;
        if (ep && ep->oid == sid) {
                if (ep->rxid != FC_XID_UNKNOWN &&
                    rxid != FC_XID_UNKNOWN &&
                    ep->rxid != rxid)
                        goto rel;
        } else {
                if (ep)
                        fc_exch_release(ep);
                ep = NULL;
                if (rxid != FC_XID_UNKNOWN)
                        ep = fc_exch_find(em, rxid);
                if (!ep)
                        goto reject;
        }

        fp = fc_frame_alloc(fc_seq_exch(sp)->lp, sizeof(*acc));
        if (!fp) {
                fc_exch_done(sp);
                goto out;
        }
        sp = fc_seq_start_next(sp);
        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));
        sp = fc_seq_start_next(sp);
        fc_seq_send_last(sp, fp, FC_RCTL_ELS_REP, FC_TYPE_ELS);
out:
        fc_exch_release(ep);
        fc_frame_free(rfp);
        return;

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

/*
 * Handle response from RRQ.
 * Not much to do here, really.
 * Should report errors.
 *
 * TODO: fix error handler.
 */
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_DBG("Cannot process RRQ, because of frame error %d\n", err);
                return;
        }

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

        switch (op) {
        case ELS_LS_RJT:
                FC_DBG("LS_RJT for RRQ");
                /* fall through */
        case ELS_LS_ACC:
                goto cleanup;
        default:
                FC_DBG("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);
}

/*
 * Send ELS RRQ - Reinstate Recovery Qualifier.
 * This tells the remote port to stop blocking the use of
 * the exchange and the seq_cnt range.
 */
static void fc_exch_rrq(struct fc_exch *ep)
{
        struct fc_lport *lp;
        struct fc_els_rrq *rrq;
        struct fc_frame *fp;
        struct fc_seq *rrq_sp;
        u32 did;

        lp = ep->lp;

        fp = fc_frame_alloc(lp, sizeof(*rrq));
        if (!fp)
                return;
        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,
                       fc_host_port_id(lp->host), FC_TYPE_ELS,
                       FC_FC_FIRST_SEQ | FC_FC_END_SEQ | FC_FC_SEQ_INIT, 0);

        rrq_sp = fc_exch_seq_send(lp, fp, fc_exch_rrq_resp, NULL, ep,
                                  lp->e_d_tov);
        if (!rrq_sp) {
                ep->esb_stat |= ESB_ST_REC_QUAL;
                fc_exch_timer_set_locked(ep, ep->r_a_tov);
                return;
        }
}


/*
 * Handle incoming ELS RRQ - Reset Recovery Qualifier.
 */
static void fc_exch_els_rrq(struct fc_seq *sp, struct fc_frame *fp)
{
        struct fc_exch *ep;             /* request or subject exchange */
        struct fc_els_rrq *rp;
        u32 sid;
        u16 xid;
        enum fc_els_rjt_explan explan;

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

        /*
         * lookup subject exchange.
         */
        ep = fc_seq_exch(sp);
        sid = ntoh24(rp->rrq_s_id);             /* subject source */
        xid = ep->did == sid ? ntohs(rp->rrq_ox_id) : ntohs(rp->rrq_rx_id);
        ep = fc_exch_find(ep->em, 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) {
                if (cancel_delayed_work(&ep->timeout_work))
                        atomic_dec(&ep->ex_refcnt);     /* drop timer hold */
        }

        spin_unlock_bh(&ep->ex_lock);

        /*
         * Send LS_ACC.
         */
        fc_seq_ls_acc(sp);
        fc_frame_free(fp);
        return;

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

struct fc_exch_mgr *fc_exch_mgr_alloc(struct fc_lport *lp,
                                      enum fc_class class,
                                      u16 min_xid, u16 max_xid)
{
        struct fc_exch_mgr *mp;
        size_t len;

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

        /*
         * Memory need for EM
         */
#define xid_ok(i, m1, m2) (((i) >= (m1)) && ((i) <= (m2)))
        len = (max_xid - min_xid + 1) * (sizeof(struct fc_exch *));
        len += sizeof(struct fc_exch_mgr);

        mp = kzalloc(len, GFP_ATOMIC);
        if (!mp)
                return NULL;

        mp->class = class;
        mp->total_exches = 0;
        mp->exches = (struct fc_exch **)(mp + 1);
        mp->lp = lp;
        /* adjust em exch xid range for offload */
        mp->min_xid = min_xid;
        mp->max_xid = max_xid;
        mp->last_xid = min_xid - 1;
        mp->max_read = 0;
        mp->last_read = 0;
        if (lp->lro_enabled && xid_ok(lp->lro_xid, min_xid, max_xid)) {
                mp->max_read = lp->lro_xid;
                mp->last_read = min_xid - 1;
                mp->last_xid = mp->max_read;
        } else {
                /* disable lro if no xid control over read */
                lp->lro_enabled = 0;
        }

        INIT_LIST_HEAD(&mp->ex_list);
        spin_lock_init(&mp->em_lock);

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

        return mp;

free_mp:
        kfree(mp);
        return NULL;
}
EXPORT_SYMBOL(fc_exch_mgr_alloc);

void fc_exch_mgr_free(struct fc_exch_mgr *mp)
{
        WARN_ON(!mp);
        /*
         * The total exch count must be zero
         * before freeing exchange manager.
         */
        WARN_ON(mp->total_exches != 0);
        mempool_destroy(mp->ep_pool);
        kfree(mp);
}
EXPORT_SYMBOL(fc_exch_mgr_free);

struct fc_exch *fc_exch_get(struct fc_lport *lp, struct fc_frame *fp)
{
        if (!lp || !lp->emp)
                return NULL;

        return fc_exch_alloc(lp->emp, fp, 0);
}
EXPORT_SYMBOL(fc_exch_get);

struct fc_seq *fc_exch_seq_send(struct fc_lport *lp,
                                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;
        int rc = 1;

        ep = lp->tt.exch_get(lp, 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 = lp;
        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 (unlikely(lp->tt.frame_send(lp, 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:
        rc = fc_exch_done_locked(ep);
        spin_unlock_bh(&ep->ex_lock);
        if (!rc)
                fc_exch_mgr_delete_ep(ep);
        return NULL;
}
EXPORT_SYMBOL(fc_exch_seq_send);

/*
 * Receive a frame
 */
void fc_exch_recv(struct fc_lport *lp, struct fc_exch_mgr *mp,
                  struct fc_frame *fp)
{
        struct fc_frame_header *fh = fc_frame_header_get(fp);
        u32 f_ctl;

        /* lport lock ? */
        if (!lp || !mp || (lp->state == LPORT_ST_NONE)) {
                FC_DBG("fc_lport or EM is not allocated and configured");
                fc_frame_free(fp);
                return;
        }

        /*
         * If frame is marked invalid, just drop it.
         */
        f_ctl = ntoh24(fh->fh_f_ctl);
        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(mp, fp);
                else if ((f_ctl & (FC_FC_EX_CTX | FC_FC_SEQ_CTX)) ==
                         FC_FC_EX_CTX)
                        fc_exch_recv_seq_resp(mp, fp);
                else if (f_ctl & FC_FC_SEQ_CTX)
                        fc_exch_recv_resp(mp, fp);
                else
                        fc_exch_recv_req(lp, mp, fp);
                break;
        default:
                FC_DBG("dropping invalid frame (eof %x)", fr_eof(fp));
                fc_frame_free(fp);
                break;
        }
}
EXPORT_SYMBOL(fc_exch_recv);

int fc_exch_init(struct fc_lport *lp)
{
        if (!lp->tt.exch_get) {
                /*
                 *  exch_put() should be NULL if
                 *  exch_get() is NULL
                 */
                WARN_ON(lp->tt.exch_put);
                lp->tt.exch_get = fc_exch_get;
        }

        if (!lp->tt.seq_start_next)
                lp->tt.seq_start_next = fc_seq_start_next;

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

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

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

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

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

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

        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;
        return 0;
}

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