/*
 * Copyright (c) 2010 Cisco Systems, Inc.
 *
 * Portions based on tcm_loop_fabric_scsi.c and libfc/fc_fcp.c
 *
 * Copyright (c) 2007 Intel Corporation. All rights reserved.
 * Copyright (c) 2008 Red Hat, Inc.  All rights reserved.
 * Copyright (c) 2008 Mike Christie
 * Copyright (c) 2009 Rising Tide, Inc.
 * Copyright (c) 2009 Linux-iSCSI.org
 * Copyright (c) 2009 Nicholas A. Bellinger <nab@linux-iscsi.org>
 *
 * 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.
 */

/* XXX TBD some includes may be extraneous */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/utsname.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/kthread.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/configfs.h>
#include <linux/ctype.h>
#include <linux/hash.h>
#include <linux/ratelimit.h>
#include <asm/unaligned.h>
#include <scsi/scsi.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/libfc.h>
#include <scsi/fc_encode.h>

#include <target/target_core_base.h>
#include <target/target_core_fabric.h>

#include "tcm_fc.h"

/*
 * Deliver read data back to initiator.
 * XXX TBD handle resource problems later.
 */
int ft_queue_data_in(struct se_cmd *se_cmd)
{
        struct ft_cmd *cmd = container_of(se_cmd, struct ft_cmd, se_cmd);
        struct fc_frame *fp = NULL;
        struct fc_exch *ep;
        struct fc_lport *lport;
        struct scatterlist *sg = NULL;
        size_t remaining;
        u32 f_ctl = FC_FC_EX_CTX | FC_FC_REL_OFF;
        u32 mem_off = 0;
        u32 fh_off = 0;
        u32 frame_off = 0;
        size_t frame_len = 0;
        size_t mem_len = 0;
        size_t tlen;
        size_t off_in_page;
        struct page *page = NULL;
        int use_sg;
        int error;
        void *page_addr;
        void *from;
        void *to = NULL;

        if (cmd->aborted)
                return 0;

        if (se_cmd->scsi_status == SAM_STAT_TASK_SET_FULL)
                goto queue_status;

        ep = fc_seq_exch(cmd->seq);
        lport = ep->lp;
        cmd->seq = lport->tt.seq_start_next(cmd->seq);

        remaining = se_cmd->data_length;

        /*
         * Setup to use first mem list entry, unless no data.
         */
        BUG_ON(remaining && !se_cmd->t_data_sg);
        if (remaining) {
                sg = se_cmd->t_data_sg;
                mem_len = sg->length;
                mem_off = sg->offset;
                page = sg_page(sg);
        }

        /* no scatter/gather in skb for odd word length due to fc_seq_send() */
        use_sg = !(remaining % 4);

        while (remaining) {
                struct fc_seq *seq = cmd->seq;

                if (!seq) {
                        pr_debug("%s: Command aborted, xid 0x%x\n",
                                 __func__, ep->xid);
                        break;
                }
                if (!mem_len) {
                        sg = sg_next(sg);
                        mem_len = min((size_t)sg->length, remaining);
                        mem_off = sg->offset;
                        page = sg_page(sg);
                }
                if (!frame_len) {
                        /*
                         * If lport's has capability of Large Send Offload LSO)
                         * , then allow 'frame_len' to be as big as 'lso_max'
                         * if indicated transfer length is >= lport->lso_max
                         */
                        frame_len = (lport->seq_offload) ? lport->lso_max :
                                                          cmd->sess->max_frame;
                        frame_len = min(frame_len, remaining);
                        fp = fc_frame_alloc(lport, use_sg ? 0 : frame_len);
                        if (!fp)
                                return -ENOMEM;
                        to = fc_frame_payload_get(fp, 0);
                        fh_off = frame_off;
                        frame_off += frame_len;
                        /*
                         * Setup the frame's max payload which is used by base
                         * driver to indicate HW about max frame size, so that
                         * HW can do fragmentation appropriately based on
                         * "gso_max_size" of underline netdev.
                         */
                        fr_max_payload(fp) = cmd->sess->max_frame;
                }
                tlen = min(mem_len, frame_len);

                if (use_sg) {
                        off_in_page = mem_off;
                        BUG_ON(!page);
                        get_page(page);
                        skb_fill_page_desc(fp_skb(fp),
                                           skb_shinfo(fp_skb(fp))->nr_frags,
                                           page, off_in_page, tlen);
                        fr_len(fp) += tlen;
                        fp_skb(fp)->data_len += tlen;
                        fp_skb(fp)->truesize +=
                                        PAGE_SIZE << compound_order(page);
                } else {
                        BUG_ON(!page);
                        from = kmap_atomic(page + (mem_off >> PAGE_SHIFT));
                        page_addr = from;
                        from += offset_in_page(mem_off);
                        tlen = min(tlen, (size_t)(PAGE_SIZE -
                                                offset_in_page(mem_off)));
                        memcpy(to, from, tlen);
                        kunmap_atomic(page_addr);
                        to += tlen;
                }

                mem_off += tlen;
                mem_len -= tlen;
                frame_len -= tlen;
                remaining -= tlen;

                if (frame_len &&
                    (skb_shinfo(fp_skb(fp))->nr_frags < FC_FRAME_SG_LEN))
                        continue;
                if (!remaining)
                        f_ctl |= FC_FC_END_SEQ;
                fc_fill_fc_hdr(fp, FC_RCTL_DD_SOL_DATA, ep->did, ep->sid,
                               FC_TYPE_FCP, f_ctl, fh_off);
                error = lport->tt.seq_send(lport, seq, fp);
                if (error) {
                        pr_info_ratelimited("%s: Failed to send frame %p, "
                                                "xid <0x%x>, remaining %zu, "
                                                "lso_max <0x%x>\n",
                                                __func__, fp, ep->xid,
                                                remaining, lport->lso_max);
                        /*
                         * Go ahead and set TASK_SET_FULL status ignoring the
                         * rest of the DataIN, and immediately attempt to
                         * send the response via ft_queue_status() in order
                         * to notify the initiator that it should reduce it's
                         * per LUN queue_depth.
                         */
                        se_cmd->scsi_status = SAM_STAT_TASK_SET_FULL;
                        break;
                }
        }
queue_status:
        return ft_queue_status(se_cmd);
}

static void ft_execute_work(struct work_struct *work)
{
        struct ft_cmd *cmd = container_of(work, struct ft_cmd, work);

        target_execute_cmd(&cmd->se_cmd);
}

/*
 * Receive write data frame.
 */
void ft_recv_write_data(struct ft_cmd *cmd, struct fc_frame *fp)
{
        struct se_cmd *se_cmd = &cmd->se_cmd;
        struct fc_seq *seq = cmd->seq;
        struct fc_exch *ep;
        struct fc_lport *lport;
        struct fc_frame_header *fh;
        struct scatterlist *sg = NULL;
        u32 mem_off = 0;
        u32 rel_off;
        size_t frame_len;
        size_t mem_len = 0;
        size_t tlen;
        struct page *page = NULL;
        void *page_addr;
        void *from;
        void *to;
        u32 f_ctl;
        void *buf;

        fh = fc_frame_header_get(fp);
        if (!(ntoh24(fh->fh_f_ctl) & FC_FC_REL_OFF))
                goto drop;

        f_ctl = ntoh24(fh->fh_f_ctl);
        ep = fc_seq_exch(seq);
        lport = ep->lp;
        if (cmd->was_ddp_setup) {
                BUG_ON(!ep);
                BUG_ON(!lport);
                /*
                 * Since DDP (Large Rx offload) was setup for this request,
                 * payload is expected to be copied directly to user buffers.
                 */
                buf = fc_frame_payload_get(fp, 1);
                if (buf)
                        pr_err("%s: xid 0x%x, f_ctl 0x%x, cmd->sg %p, "
                                "cmd->sg_cnt 0x%x. DDP was setup"
                                " hence not expected to receive frame with "
                                "payload, Frame will be dropped if"
                                "'Sequence Initiative' bit in f_ctl is"
                                "not set\n", __func__, ep->xid, f_ctl,
                                se_cmd->t_data_sg, se_cmd->t_data_nents);
                /*
                 * Invalidate HW DDP context if it was setup for respective
                 * command. Invalidation of HW DDP context is requited in both
                 * situation (success and error).
                 */
                ft_invl_hw_context(cmd);

                /*
                 * If "Sequence Initiative (TSI)" bit set in f_ctl, means last
                 * write data frame is received successfully where payload is
                 * posted directly to user buffer and only the last frame's
                 * header is posted in receive queue.
                 *
                 * If "Sequence Initiative (TSI)" bit is not set, means error
                 * condition w.r.t. DDP, hence drop the packet and let explict
                 * ABORTS from other end of exchange timer trigger the recovery.
                 */
                if (f_ctl & FC_FC_SEQ_INIT)
                        goto last_frame;
                else
                        goto drop;
        }

        rel_off = ntohl(fh->fh_parm_offset);
        frame_len = fr_len(fp);
        if (frame_len <= sizeof(*fh))
                goto drop;
        frame_len -= sizeof(*fh);
        from = fc_frame_payload_get(fp, 0);
        if (rel_off >= se_cmd->data_length)
                goto drop;
        if (frame_len + rel_off > se_cmd->data_length)
                frame_len = se_cmd->data_length - rel_off;

        /*
         * Setup to use first mem list entry, unless no data.
         */
        BUG_ON(frame_len && !se_cmd->t_data_sg);
        if (frame_len) {
                sg = se_cmd->t_data_sg;
                mem_len = sg->length;
                mem_off = sg->offset;
                page = sg_page(sg);
        }

        while (frame_len) {
                if (!mem_len) {
                        sg = sg_next(sg);
                        mem_len = sg->length;
                        mem_off = sg->offset;
                        page = sg_page(sg);
                }
                if (rel_off >= mem_len) {
                        rel_off -= mem_len;
                        mem_len = 0;
                        continue;
                }
                mem_off += rel_off;
                mem_len -= rel_off;
                rel_off = 0;

                tlen = min(mem_len, frame_len);

                to = kmap_atomic(page + (mem_off >> PAGE_SHIFT));
                page_addr = to;
                to += offset_in_page(mem_off);
                tlen = min(tlen, (size_t)(PAGE_SIZE -
                                          offset_in_page(mem_off)));
                memcpy(to, from, tlen);
                kunmap_atomic(page_addr);

                from += tlen;
                frame_len -= tlen;
                mem_off += tlen;
                mem_len -= tlen;
                cmd->write_data_len += tlen;
        }
last_frame:
        if (cmd->write_data_len == se_cmd->data_length) {
                INIT_WORK(&cmd->work, ft_execute_work);
                queue_work(cmd->sess->tport->tpg->workqueue, &cmd->work);
        }
drop:
        fc_frame_free(fp);
}

/*
 * Handle and cleanup any HW specific resources if
 * received ABORTS, errors, timeouts.
 */
void ft_invl_hw_context(struct ft_cmd *cmd)
{
        struct fc_seq *seq;
        struct fc_exch *ep = NULL;
        struct fc_lport *lport = NULL;

        BUG_ON(!cmd);
        seq = cmd->seq;

        /* Cleanup the DDP context in HW if DDP was setup */
        if (cmd->was_ddp_setup && seq) {
                ep = fc_seq_exch(seq);
                if (ep) {
                        lport = ep->lp;
                        if (lport && (ep->xid <= lport->lro_xid)) {
                                /*
                                 * "ddp_done" trigger invalidation of HW
                                 * specific DDP context
                                 */
                                cmd->write_data_len = lport->tt.ddp_done(lport,
                                                                      ep->xid);

                                /*
                                 * Resetting same variable to indicate HW's
                                 * DDP context has been invalidated to avoid
                                 * re_invalidation of same context (context is
                                 * identified using ep->xid)
                                 */
                                cmd->was_ddp_setup = 0;
                        }
                }
        }
}