/*
 * Copyright (c) 2015 Oracle.  All rights reserved.
 * Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
 */

/* Lightweight memory registration using Fast Registration Work
 * Requests (FRWR). Also referred to sometimes as FRMR mode.
 *
 * FRWR features ordered asynchronous registration and deregistration
 * of arbitrarily sized memory regions. This is the fastest and safest
 * but most complex memory registration mode.
 */

/* Normal operation
 *
 * A Memory Region is prepared for RDMA READ or WRITE using a FAST_REG
 * Work Request (frmr_op_map). When the RDMA operation is finished, this
 * Memory Region is invalidated using a LOCAL_INV Work Request
 * (frmr_op_unmap).
 *
 * Typically these Work Requests are not signaled, and neither are RDMA
 * SEND Work Requests (with the exception of signaling occasionally to
 * prevent provider work queue overflows). This greatly reduces HCA
 * interrupt workload.
 *
 * As an optimization, frwr_op_unmap marks MRs INVALID before the
 * LOCAL_INV WR is posted. If posting succeeds, the MR is placed on
 * rb_mws immediately so that no work (like managing a linked list
 * under a spinlock) is needed in the completion upcall.
 *
 * But this means that frwr_op_map() can occasionally encounter an MR
 * that is INVALID but the LOCAL_INV WR has not completed. Work Queue
 * ordering prevents a subsequent FAST_REG WR from executing against
 * that MR while it is still being invalidated.
 */

/* Transport recovery
 *
 * ->op_map and the transport connect worker cannot run at the same
 * time, but ->op_unmap can fire while the transport connect worker
 * is running. Thus MR recovery is handled in ->op_map, to guarantee
 * that recovered MRs are owned by a sending RPC, and not one where
 * ->op_unmap could fire at the same time transport reconnect is
 * being done.
 *
 * When the underlying transport disconnects, MRs are left in one of
 * three states:
 *
 * INVALID:     The MR was not in use before the QP entered ERROR state.
 *              (Or, the LOCAL_INV WR has not completed or flushed yet).
 *
 * STALE:       The MR was being registered or unregistered when the QP
 *              entered ERROR state, and the pending WR was flushed.
 *
 * VALID:       The MR was registered before the QP entered ERROR state.
 *
 * When frwr_op_map encounters STALE and VALID MRs, they are recovered
 * with ib_dereg_mr and then are re-initialized. Beause MR recovery
 * allocates fresh resources, it is deferred to a workqueue, and the
 * recovered MRs are placed back on the rb_mws list when recovery is
 * complete. frwr_op_map allocates another MR for the current RPC while
 * the broken MR is reset.
 *
 * To ensure that frwr_op_map doesn't encounter an MR that is marked
 * INVALID but that is about to be flushed due to a previous transport
 * disconnect, the transport connect worker attempts to drain all
 * pending send queue WRs before the transport is reconnected.
 */

#include "xprt_rdma.h"

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
# define RPCDBG_FACILITY        RPCDBG_TRANS
#endif

static struct workqueue_struct *frwr_recovery_wq;

#define FRWR_RECOVERY_WQ_FLAGS          (WQ_UNBOUND | WQ_MEM_RECLAIM)

int
frwr_alloc_recovery_wq(void)
{
        frwr_recovery_wq = alloc_workqueue("frwr_recovery",
                                           FRWR_RECOVERY_WQ_FLAGS, 0);
        return !frwr_recovery_wq ? -ENOMEM : 0;
}

void
frwr_destroy_recovery_wq(void)
{
        struct workqueue_struct *wq;

        if (!frwr_recovery_wq)
                return;

        wq = frwr_recovery_wq;
        frwr_recovery_wq = NULL;
        destroy_workqueue(wq);
}

/* Deferred reset of a single FRMR. Generate a fresh rkey by
 * replacing the MR.
 *
 * There's no recovery if this fails. The FRMR is abandoned, but
 * remains in rb_all. It will be cleaned up when the transport is
 * destroyed.
 */
static void
__frwr_recovery_worker(struct work_struct *work)
{
        struct rpcrdma_mw *r = container_of(work, struct rpcrdma_mw,
                                            frmr.fr_work);
        struct rpcrdma_xprt *r_xprt = r->frmr.fr_xprt;
        unsigned int depth = r_xprt->rx_ia.ri_max_frmr_depth;
        struct ib_pd *pd = r_xprt->rx_ia.ri_pd;

        if (ib_dereg_mr(r->frmr.fr_mr))
                goto out_fail;

        r->frmr.fr_mr = ib_alloc_mr(pd, IB_MR_TYPE_MEM_REG, depth);
        if (IS_ERR(r->frmr.fr_mr))
                goto out_fail;

        dprintk("RPC:       %s: recovered FRMR %p\n", __func__, r);
        r->frmr.fr_state = FRMR_IS_INVALID;
        rpcrdma_put_mw(r_xprt, r);
        return;

out_fail:
        pr_warn("RPC:       %s: FRMR %p unrecovered\n",
                __func__, r);
}

/* A broken MR was discovered in a context that can't sleep.
 * Defer recovery to the recovery worker.
 */
static void
__frwr_queue_recovery(struct rpcrdma_mw *r)
{
        INIT_WORK(&r->frmr.fr_work, __frwr_recovery_worker);
        queue_work(frwr_recovery_wq, &r->frmr.fr_work);
}

static int
__frwr_init(struct rpcrdma_mw *r, struct ib_pd *pd, struct ib_device *device,
            unsigned int depth)
{
        struct rpcrdma_frmr *f = &r->frmr;
        int rc;

        f->fr_mr = ib_alloc_mr(pd, IB_MR_TYPE_MEM_REG, depth);
        if (IS_ERR(f->fr_mr))
                goto out_mr_err;

        f->sg = kcalloc(depth, sizeof(*f->sg), GFP_KERNEL);
        if (!f->sg)
                goto out_list_err;

        sg_init_table(f->sg, depth);

        init_completion(&f->fr_linv_done);

        return 0;

out_mr_err:
        rc = PTR_ERR(f->fr_mr);
        dprintk("RPC:       %s: ib_alloc_mr status %i\n",
                __func__, rc);
        return rc;

out_list_err:
        rc = -ENOMEM;
        dprintk("RPC:       %s: sg allocation failure\n",
                __func__);
        ib_dereg_mr(f->fr_mr);
        return rc;
}

static void
__frwr_release(struct rpcrdma_mw *r)
{
        int rc;

        rc = ib_dereg_mr(r->frmr.fr_mr);
        if (rc)
                dprintk("RPC:       %s: ib_dereg_mr status %i\n",
                        __func__, rc);
        kfree(r->frmr.sg);
}

static int
frwr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
             struct rpcrdma_create_data_internal *cdata)
{
        int depth, delta;

        ia->ri_max_frmr_depth =
                        min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
                              ia->ri_device->attrs.max_fast_reg_page_list_len);
        dprintk("RPC:       %s: device's max FR page list len = %u\n",
                __func__, ia->ri_max_frmr_depth);

        /* Add room for frmr register and invalidate WRs.
         * 1. FRMR reg WR for head
         * 2. FRMR invalidate WR for head
         * 3. N FRMR reg WRs for pagelist
         * 4. N FRMR invalidate WRs for pagelist
         * 5. FRMR reg WR for tail
         * 6. FRMR invalidate WR for tail
         * 7. The RDMA_SEND WR
         */
        depth = 7;

        /* Calculate N if the device max FRMR depth is smaller than
         * RPCRDMA_MAX_DATA_SEGS.
         */
        if (ia->ri_max_frmr_depth < RPCRDMA_MAX_DATA_SEGS) {
                delta = RPCRDMA_MAX_DATA_SEGS - ia->ri_max_frmr_depth;
                do {
                        depth += 2; /* FRMR reg + invalidate */
                        delta -= ia->ri_max_frmr_depth;
                } while (delta > 0);
        }

        ep->rep_attr.cap.max_send_wr *= depth;
        if (ep->rep_attr.cap.max_send_wr > ia->ri_device->attrs.max_qp_wr) {
                cdata->max_requests = ia->ri_device->attrs.max_qp_wr / depth;
                if (!cdata->max_requests)
                        return -EINVAL;
                ep->rep_attr.cap.max_send_wr = cdata->max_requests *
                                               depth;
        }

        return 0;
}

/* FRWR mode conveys a list of pages per chunk segment. The
 * maximum length of that list is the FRWR page list depth.
 */
static size_t
frwr_op_maxpages(struct rpcrdma_xprt *r_xprt)
{
        struct rpcrdma_ia *ia = &r_xprt->rx_ia;

        return min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
                     rpcrdma_max_segments(r_xprt) * ia->ri_max_frmr_depth);
}

static void
__frwr_sendcompletion_flush(struct ib_wc *wc, struct rpcrdma_frmr *frmr,
                            const char *wr)
{
        frmr->fr_state = FRMR_IS_STALE;
        if (wc->status != IB_WC_WR_FLUSH_ERR)
                pr_err("rpcrdma: %s: %s (%u/0x%x)\n",
                       wr, ib_wc_status_msg(wc->status),
                       wc->status, wc->vendor_err);
}

/**
 * frwr_wc_fastreg - Invoked by RDMA provider for each polled FastReg WC
 * @cq: completion queue (ignored)
 * @wc: completed WR
 *
 */
static void
frwr_wc_fastreg(struct ib_cq *cq, struct ib_wc *wc)
{
        struct rpcrdma_frmr *frmr;
        struct ib_cqe *cqe;

        /* WARNING: Only wr_cqe and status are reliable at this point */
        if (wc->status != IB_WC_SUCCESS) {
                cqe = wc->wr_cqe;
                frmr = container_of(cqe, struct rpcrdma_frmr, fr_cqe);
                __frwr_sendcompletion_flush(wc, frmr, "fastreg");
        }
}

/**
 * frwr_wc_localinv - Invoked by RDMA provider for each polled LocalInv WC
 * @cq: completion queue (ignored)
 * @wc: completed WR
 *
 */
static void
frwr_wc_localinv(struct ib_cq *cq, struct ib_wc *wc)
{
        struct rpcrdma_frmr *frmr;
        struct ib_cqe *cqe;

        /* WARNING: Only wr_cqe and status are reliable at this point */
        if (wc->status != IB_WC_SUCCESS) {
                cqe = wc->wr_cqe;
                frmr = container_of(cqe, struct rpcrdma_frmr, fr_cqe);
                __frwr_sendcompletion_flush(wc, frmr, "localinv");
        }
}

/**
 * frwr_wc_localinv - Invoked by RDMA provider for each polled LocalInv WC
 * @cq: completion queue (ignored)
 * @wc: completed WR
 *
 * Awaken anyone waiting for an MR to finish being fenced.
 */
static void
frwr_wc_localinv_wake(struct ib_cq *cq, struct ib_wc *wc)
{
        struct rpcrdma_frmr *frmr;
        struct ib_cqe *cqe;

        /* WARNING: Only wr_cqe and status are reliable at this point */
        cqe = wc->wr_cqe;
        frmr = container_of(cqe, struct rpcrdma_frmr, fr_cqe);
        if (wc->status != IB_WC_SUCCESS)
                __frwr_sendcompletion_flush(wc, frmr, "localinv");
        complete_all(&frmr->fr_linv_done);
}

static int
frwr_op_init(struct rpcrdma_xprt *r_xprt)
{
        struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
        struct ib_device *device = r_xprt->rx_ia.ri_device;
        unsigned int depth = r_xprt->rx_ia.ri_max_frmr_depth;
        struct ib_pd *pd = r_xprt->rx_ia.ri_pd;
        int i;

        spin_lock_init(&buf->rb_mwlock);
        INIT_LIST_HEAD(&buf->rb_mws);
        INIT_LIST_HEAD(&buf->rb_all);

        i = max_t(int, RPCRDMA_MAX_DATA_SEGS / depth, 1);
        i += 2;                         /* head + tail */
        i *= buf->rb_max_requests;      /* one set for each RPC slot */
        dprintk("RPC:       %s: initalizing %d FRMRs\n", __func__, i);

        while (i--) {
                struct rpcrdma_mw *r;
                int rc;

                r = kzalloc(sizeof(*r), GFP_KERNEL);
                if (!r)
                        return -ENOMEM;

                rc = __frwr_init(r, pd, device, depth);
                if (rc) {
                        kfree(r);
                        return rc;
                }

                list_add(&r->mw_list, &buf->rb_mws);
                list_add(&r->mw_all, &buf->rb_all);
                r->frmr.fr_xprt = r_xprt;
        }

        return 0;
}

/* Post a FAST_REG Work Request to register a memory region
 * for remote access via RDMA READ or RDMA WRITE.
 */
static int
frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
            int nsegs, bool writing)
{
        struct rpcrdma_ia *ia = &r_xprt->rx_ia;
        struct ib_device *device = ia->ri_device;
        enum dma_data_direction direction = rpcrdma_data_dir(writing);
        struct rpcrdma_mr_seg *seg1 = seg;
        struct rpcrdma_mw *mw;
        struct rpcrdma_frmr *frmr;
        struct ib_mr *mr;
        struct ib_reg_wr *reg_wr;
        struct ib_send_wr *bad_wr;
        int rc, i, n, dma_nents;
        u8 key;

        mw = seg1->rl_mw;
        seg1->rl_mw = NULL;
        do {
                if (mw)
                        __frwr_queue_recovery(mw);
                mw = rpcrdma_get_mw(r_xprt);
                if (!mw)
                        return -ENOMEM;
        } while (mw->frmr.fr_state != FRMR_IS_INVALID);
        frmr = &mw->frmr;
        frmr->fr_state = FRMR_IS_VALID;
        mr = frmr->fr_mr;
        reg_wr = &frmr->fr_regwr;

        if (nsegs > ia->ri_max_frmr_depth)
                nsegs = ia->ri_max_frmr_depth;

        for (i = 0; i < nsegs;) {
                if (seg->mr_page)
                        sg_set_page(&frmr->sg[i],
                                    seg->mr_page,
                                    seg->mr_len,
                                    offset_in_page(seg->mr_offset));
                else
                        sg_set_buf(&frmr->sg[i], seg->mr_offset,
                                   seg->mr_len);

                ++seg;
                ++i;

                /* Check for holes */
                if ((i < nsegs && offset_in_page(seg->mr_offset)) ||
                    offset_in_page((seg-1)->mr_offset + (seg-1)->mr_len))
                        break;
        }
        frmr->sg_nents = i;

        dma_nents = ib_dma_map_sg(device, frmr->sg, frmr->sg_nents, direction);
        if (!dma_nents) {
                pr_err("RPC:       %s: failed to dma map sg %p sg_nents %u\n",
                       __func__, frmr->sg, frmr->sg_nents);
                return -ENOMEM;
        }

        n = ib_map_mr_sg(mr, frmr->sg, frmr->sg_nents, PAGE_SIZE);
        if (unlikely(n != frmr->sg_nents)) {
                pr_err("RPC:       %s: failed to map mr %p (%u/%u)\n",
                       __func__, frmr->fr_mr, n, frmr->sg_nents);
                rc = n < 0 ? n : -EINVAL;
                goto out_senderr;
        }

        dprintk("RPC:       %s: Using frmr %p to map %u segments (%u bytes)\n",
                __func__, mw, frmr->sg_nents, mr->length);

        key = (u8)(mr->rkey & 0x000000FF);
        ib_update_fast_reg_key(mr, ++key);

        reg_wr->wr.next = NULL;
        reg_wr->wr.opcode = IB_WR_REG_MR;
        frmr->fr_cqe.done = frwr_wc_fastreg;
        reg_wr->wr.wr_cqe = &frmr->fr_cqe;
        reg_wr->wr.num_sge = 0;
        reg_wr->wr.send_flags = 0;
        reg_wr->mr = mr;
        reg_wr->key = mr->rkey;
        reg_wr->access = writing ?
                         IB_ACCESS_REMOTE_WRITE | IB_ACCESS_LOCAL_WRITE :
                         IB_ACCESS_REMOTE_READ;

        DECR_CQCOUNT(&r_xprt->rx_ep);
        rc = ib_post_send(ia->ri_id->qp, &reg_wr->wr, &bad_wr);
        if (rc)
                goto out_senderr;

        seg1->mr_dir = direction;
        seg1->rl_mw = mw;
        seg1->mr_rkey = mr->rkey;
        seg1->mr_base = mr->iova;
        seg1->mr_nsegs = frmr->sg_nents;
        seg1->mr_len = mr->length;

        return frmr->sg_nents;

out_senderr:
        dprintk("RPC:       %s: ib_post_send status %i\n", __func__, rc);
        ib_dma_unmap_sg(device, frmr->sg, dma_nents, direction);
        __frwr_queue_recovery(mw);
        return rc;
}

static struct ib_send_wr *
__frwr_prepare_linv_wr(struct rpcrdma_mr_seg *seg)
{
        struct rpcrdma_mw *mw = seg->rl_mw;
        struct rpcrdma_frmr *f = &mw->frmr;
        struct ib_send_wr *invalidate_wr;

        f->fr_state = FRMR_IS_INVALID;
        invalidate_wr = &f->fr_invwr;

        memset(invalidate_wr, 0, sizeof(*invalidate_wr));
        f->fr_cqe.done = frwr_wc_localinv;
        invalidate_wr->wr_cqe = &f->fr_cqe;
        invalidate_wr->opcode = IB_WR_LOCAL_INV;
        invalidate_wr->ex.invalidate_rkey = f->fr_mr->rkey;

        return invalidate_wr;
}

static void
__frwr_dma_unmap(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
                 int rc)
{
        struct ib_device *device = r_xprt->rx_ia.ri_device;
        struct rpcrdma_mw *mw = seg->rl_mw;
        struct rpcrdma_frmr *f = &mw->frmr;

        seg->rl_mw = NULL;

        ib_dma_unmap_sg(device, f->sg, f->sg_nents, seg->mr_dir);

        if (!rc)
                rpcrdma_put_mw(r_xprt, mw);
        else
                __frwr_queue_recovery(mw);
}

/* Invalidate all memory regions that were registered for "req".
 *
 * Sleeps until it is safe for the host CPU to access the
 * previously mapped memory regions.
 */
static void
frwr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
{
        struct ib_send_wr *invalidate_wrs, *pos, *prev, *bad_wr;
        struct rpcrdma_ia *ia = &r_xprt->rx_ia;
        struct rpcrdma_mr_seg *seg;
        unsigned int i, nchunks;
        struct rpcrdma_frmr *f;
        int rc;

        dprintk("RPC:       %s: req %p\n", __func__, req);

        /* ORDER: Invalidate all of the req's MRs first
         *
         * Chain the LOCAL_INV Work Requests and post them with
         * a single ib_post_send() call.
         */
        invalidate_wrs = pos = prev = NULL;
        seg = NULL;
        for (i = 0, nchunks = req->rl_nchunks; nchunks; nchunks--) {
                seg = &req->rl_segments[i];

                pos = __frwr_prepare_linv_wr(seg);

                if (!invalidate_wrs)
                        invalidate_wrs = pos;
                else
                        prev->next = pos;
                prev = pos;

                i += seg->mr_nsegs;
        }
        f = &seg->rl_mw->frmr;

        /* Strong send queue ordering guarantees that when the
         * last WR in the chain completes, all WRs in the chain
         * are complete.
         */
        f->fr_invwr.send_flags = IB_SEND_SIGNALED;
        f->fr_cqe.done = frwr_wc_localinv_wake;
        reinit_completion(&f->fr_linv_done);
        INIT_CQCOUNT(&r_xprt->rx_ep);

        /* Transport disconnect drains the receive CQ before it
         * replaces the QP. The RPC reply handler won't call us
         * unless ri_id->qp is a valid pointer.
         */
        rc = ib_post_send(ia->ri_id->qp, invalidate_wrs, &bad_wr);
        if (rc) {
                pr_warn("%s: ib_post_send failed %i\n", __func__, rc);
                rdma_disconnect(ia->ri_id);
                goto unmap;
        }

        wait_for_completion(&f->fr_linv_done);

        /* ORDER: Now DMA unmap all of the req's MRs, and return
         * them to the free MW list.
         */
unmap:
        for (i = 0, nchunks = req->rl_nchunks; nchunks; nchunks--) {
                seg = &req->rl_segments[i];

                __frwr_dma_unmap(r_xprt, seg, rc);

                i += seg->mr_nsegs;
                seg->mr_nsegs = 0;
        }

        req->rl_nchunks = 0;
}

/* Post a LOCAL_INV Work Request to prevent further remote access
 * via RDMA READ or RDMA WRITE.
 */
static int
frwr_op_unmap(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg)
{
        struct rpcrdma_mr_seg *seg1 = seg;
        struct rpcrdma_ia *ia = &r_xprt->rx_ia;
        struct rpcrdma_mw *mw = seg1->rl_mw;
        struct rpcrdma_frmr *frmr = &mw->frmr;
        struct ib_send_wr *invalidate_wr, *bad_wr;
        int rc, nsegs = seg->mr_nsegs;

        dprintk("RPC:       %s: FRMR %p\n", __func__, mw);

        seg1->rl_mw = NULL;
        frmr->fr_state = FRMR_IS_INVALID;
        invalidate_wr = &mw->frmr.fr_invwr;

        memset(invalidate_wr, 0, sizeof(*invalidate_wr));
        frmr->fr_cqe.done = frwr_wc_localinv;
        invalidate_wr->wr_cqe = &frmr->fr_cqe;
        invalidate_wr->opcode = IB_WR_LOCAL_INV;
        invalidate_wr->ex.invalidate_rkey = frmr->fr_mr->rkey;
        DECR_CQCOUNT(&r_xprt->rx_ep);

        ib_dma_unmap_sg(ia->ri_device, frmr->sg, frmr->sg_nents, seg1->mr_dir);
        read_lock(&ia->ri_qplock);
        rc = ib_post_send(ia->ri_id->qp, invalidate_wr, &bad_wr);
        read_unlock(&ia->ri_qplock);
        if (rc)
                goto out_err;

        rpcrdma_put_mw(r_xprt, mw);
        return nsegs;

out_err:
        dprintk("RPC:       %s: ib_post_send status %i\n", __func__, rc);
        __frwr_queue_recovery(mw);
        return nsegs;
}

static void
frwr_op_destroy(struct rpcrdma_buffer *buf)
{
        struct rpcrdma_mw *r;

        /* Ensure stale MWs for "buf" are no longer in flight */
        flush_workqueue(frwr_recovery_wq);

        while (!list_empty(&buf->rb_all)) {
                r = list_entry(buf->rb_all.next, struct rpcrdma_mw, mw_all);
                list_del(&r->mw_all);
                __frwr_release(r);
                kfree(r);
        }
}

const struct rpcrdma_memreg_ops rpcrdma_frwr_memreg_ops = {
        .ro_map                         = frwr_op_map,
        .ro_unmap_sync                  = frwr_op_unmap_sync,
        .ro_unmap                       = frwr_op_unmap,
        .ro_open                        = frwr_op_open,
        .ro_maxpages                    = frwr_op_maxpages,
        .ro_init                        = frwr_op_init,
        .ro_destroy                     = frwr_op_destroy,
        .ro_displayname                 = "frwr",
};