// SPDX-License-Identifier: GPL-2.0
/*
 * 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
 * four states:
 *
 * INVALID:     The MR was not in use before the QP entered ERROR state.
 *
 * VALID:       The MR was registered before the QP entered ERROR state.
 *
 * FLUSHED_FR:  The MR was being registered when the QP entered ERROR
 *              state, and the pending WR was flushed.
 *
 * FLUSHED_LI:  The MR was being invalidated when the QP entered ERROR
 *              state, and the pending WR was flushed.
 *
 * When frwr_op_map encounters FLUSHED and VALID MRs, they are recovered
 * with ib_dereg_mr and then are re-initialized. Because 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 <linux/sunrpc/rpc_rdma.h>

#include "xprt_rdma.h"

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

bool
frwr_is_supported(struct rpcrdma_ia *ia)
{
        struct ib_device_attr *attrs = &ia->ri_device->attrs;

        if (!(attrs->device_cap_flags & IB_DEVICE_MEM_MGT_EXTENSIONS))
                goto out_not_supported;
        if (attrs->max_fast_reg_page_list_len == 0)
                goto out_not_supported;
        return true;

out_not_supported:
        pr_info("rpcrdma: 'frwr' mode is not supported by device %s\n",
                ia->ri_device->name);
        return false;
}

static int
frwr_op_init_mr(struct rpcrdma_ia *ia, struct rpcrdma_mw *r)
{
        unsigned int depth = ia->ri_max_frmr_depth;
        struct rpcrdma_frmr *f = &r->frmr;
        int rc;

        f->fr_mr = ib_alloc_mr(ia->ri_pd, ia->ri_mrtype, depth);
        if (IS_ERR(f->fr_mr))
                goto out_mr_err;

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

        sg_init_table(r->mw_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_op_release_mr(struct rpcrdma_mw *r)
{
        int rc;

        /* Ensure MW is not on any rl_registered list */
        if (!list_empty(&r->mw_list))
                list_del(&r->mw_list);

        rc = ib_dereg_mr(r->frmr.fr_mr);
        if (rc)
                pr_err("rpcrdma: final ib_dereg_mr for %p returned %i\n",
                       r, rc);
        kfree(r->mw_sg);
        kfree(r);
}

static int
__frwr_reset_mr(struct rpcrdma_ia *ia, struct rpcrdma_mw *r)
{
        struct rpcrdma_frmr *f = &r->frmr;
        int rc;

        rc = ib_dereg_mr(f->fr_mr);
        if (rc) {
                pr_warn("rpcrdma: ib_dereg_mr status %d, frwr %p orphaned\n",
                        rc, r);
                return rc;
        }

        f->fr_mr = ib_alloc_mr(ia->ri_pd, ia->ri_mrtype,
                               ia->ri_max_frmr_depth);
        if (IS_ERR(f->fr_mr)) {
                pr_warn("rpcrdma: ib_alloc_mr status %ld, frwr %p orphaned\n",
                        PTR_ERR(f->fr_mr), r);
                return PTR_ERR(f->fr_mr);
        }

        dprintk("RPC:       %s: recovered FRMR %p\n", __func__, f);
        f->fr_state = FRMR_IS_INVALID;
        return 0;
}

/* Reset of a single FRMR. Generate a fresh rkey by replacing the MR.
 */
static void
frwr_op_recover_mr(struct rpcrdma_mw *mw)
{
        enum rpcrdma_frmr_state state = mw->frmr.fr_state;
        struct rpcrdma_xprt *r_xprt = mw->mw_xprt;
        struct rpcrdma_ia *ia = &r_xprt->rx_ia;
        int rc;

        rc = __frwr_reset_mr(ia, mw);
        if (state != FRMR_FLUSHED_LI)
                ib_dma_unmap_sg(ia->ri_device,
                                mw->mw_sg, mw->mw_nents, mw->mw_dir);
        if (rc)
                goto out_release;

        rpcrdma_put_mw(r_xprt, mw);
        r_xprt->rx_stats.mrs_recovered++;
        return;

out_release:
        pr_err("rpcrdma: FRMR reset failed %d, %p release\n", rc, mw);
        r_xprt->rx_stats.mrs_orphaned++;

        spin_lock(&r_xprt->rx_buf.rb_mwlock);
        list_del(&mw->mw_all);
        spin_unlock(&r_xprt->rx_buf.rb_mwlock);

        frwr_op_release_mr(mw);
}

static int
frwr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
             struct rpcrdma_create_data_internal *cdata)
{
        struct ib_device_attr *attrs = &ia->ri_device->attrs;
        int depth, delta;

        ia->ri_mrtype = IB_MR_TYPE_MEM_REG;
        if (attrs->device_cap_flags & IB_DEVICE_SG_GAPS_REG)
                ia->ri_mrtype = IB_MR_TYPE_SG_GAPS;

        ia->ri_max_frmr_depth =
                        min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
                              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 > attrs->max_qp_wr) {
                cdata->max_requests = attrs->max_qp_wr / depth;
                if (!cdata->max_requests)
                        return -EINVAL;
                ep->rep_attr.cap.max_send_wr = cdata->max_requests *
                                               depth;
        }

        ia->ri_max_segs = max_t(unsigned int, 1, RPCRDMA_MAX_DATA_SEGS /
                                ia->ri_max_frmr_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_HDR_SEGS * ia->ri_max_frmr_depth);
}

static void
__frwr_sendcompletion_flush(struct ib_wc *wc, const char *wr)
{
        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 a flushed 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);
                frmr->fr_state = FRMR_FLUSHED_FR;
                __frwr_sendcompletion_flush(wc, "fastreg");
        }
}

/**
 * frwr_wc_localinv - Invoked by RDMA provider for a flushed 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);
                frmr->fr_state = FRMR_FLUSHED_LI;
                __frwr_sendcompletion_flush(wc, "localinv");
        }
}

/**
 * frwr_wc_localinv_wake - Invoked by RDMA provider for a signaled 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) {
                frmr->fr_state = FRMR_FLUSHED_LI;
                __frwr_sendcompletion_flush(wc, "localinv");
        }
        complete(&frmr->fr_linv_done);
}

/* Post a REG_MR Work Request to register a memory region
 * for remote access via RDMA READ or RDMA WRITE.
 */
static struct rpcrdma_mr_seg *
frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
            int nsegs, bool writing, struct rpcrdma_mw **out)
{
        struct rpcrdma_ia *ia = &r_xprt->rx_ia;
        bool holes_ok = ia->ri_mrtype == IB_MR_TYPE_SG_GAPS;
        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;
        u8 key;

        mw = NULL;
        do {
                if (mw)
                        rpcrdma_defer_mr_recovery(mw);
                mw = rpcrdma_get_mw(r_xprt);
                if (!mw)
                        return ERR_PTR(-ENOBUFS);
        } 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(&mw->mw_sg[i],
                                    seg->mr_page,
                                    seg->mr_len,
                                    offset_in_page(seg->mr_offset));
                else
                        sg_set_buf(&mw->mw_sg[i], seg->mr_offset,
                                   seg->mr_len);

                ++seg;
                ++i;
                if (holes_ok)
                        continue;
                if ((i < nsegs && offset_in_page(seg->mr_offset)) ||
                    offset_in_page((seg-1)->mr_offset + (seg-1)->mr_len))
                        break;
        }
        mw->mw_dir = rpcrdma_data_dir(writing);

        mw->mw_nents = ib_dma_map_sg(ia->ri_device, mw->mw_sg, i, mw->mw_dir);
        if (!mw->mw_nents)
                goto out_dmamap_err;

        n = ib_map_mr_sg(mr, mw->mw_sg, mw->mw_nents, NULL, PAGE_SIZE);
        if (unlikely(n != mw->mw_nents))
                goto out_mapmr_err;

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

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

        mw->mw_handle = mr->rkey;
        mw->mw_length = mr->length;
        mw->mw_offset = mr->iova;

        *out = mw;
        return seg;

out_dmamap_err:
        pr_err("rpcrdma: failed to DMA map sg %p sg_nents %d\n",
               mw->mw_sg, i);
        frmr->fr_state = FRMR_IS_INVALID;
        rpcrdma_put_mw(r_xprt, mw);
        return ERR_PTR(-EIO);

out_mapmr_err:
        pr_err("rpcrdma: failed to map mr %p (%d/%d)\n",
               frmr->fr_mr, n, mw->mw_nents);
        rpcrdma_defer_mr_recovery(mw);
        return ERR_PTR(-EIO);

out_senderr:
        pr_err("rpcrdma: FRMR registration ib_post_send returned %i\n", rc);
        rpcrdma_defer_mr_recovery(mw);
        return ERR_PTR(-ENOTCONN);
}

/* 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.
 *
 * Caller ensures that @mws is not empty before the call. This
 * function empties the list.
 */
static void
frwr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct list_head *mws)
{
        struct ib_send_wr *first, **prev, *last, *bad_wr;
        struct rpcrdma_ia *ia = &r_xprt->rx_ia;
        struct rpcrdma_frmr *f;
        struct rpcrdma_mw *mw;
        int count, rc;

        /* ORDER: Invalidate all of the MRs first
         *
         * Chain the LOCAL_INV Work Requests and post them with
         * a single ib_post_send() call.
         */
        f = NULL;
        count = 0;
        prev = &first;
        list_for_each_entry(mw, mws, mw_list) {
                mw->frmr.fr_state = FRMR_IS_INVALID;

                if (mw->mw_flags & RPCRDMA_MW_F_RI)
                        continue;

                f = &mw->frmr;
                dprintk("RPC:       %s: invalidating frmr %p\n",
                        __func__, f);

                f->fr_cqe.done = frwr_wc_localinv;
                last = &f->fr_invwr;
                memset(last, 0, sizeof(*last));
                last->wr_cqe = &f->fr_cqe;
                last->opcode = IB_WR_LOCAL_INV;
                last->ex.invalidate_rkey = mw->mw_handle;
                count++;

                *prev = last;
                prev = &last->next;
        }
        if (!f)
                goto unmap;

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

        /* Initialize CQ count, since there is always a signaled
         * WR being posted here.  The new cqcount depends on how
         * many SQEs are about to be consumed.
         */
        rpcrdma_init_cqcount(&r_xprt->rx_ep, count);

        /* 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.
         */
        r_xprt->rx_stats.local_inv_needed++;
        bad_wr = NULL;
        rc = ib_post_send(ia->ri_id->qp, first, &bad_wr);
        if (bad_wr != first)
                wait_for_completion(&f->fr_linv_done);
        if (rc)
                goto reset_mrs;

        /* ORDER: Now DMA unmap all of the MRs, and return
         * them to the free MW list.
         */
unmap:
        while (!list_empty(mws)) {
                mw = rpcrdma_pop_mw(mws);
                dprintk("RPC:       %s: DMA unmapping frmr %p\n",
                        __func__, &mw->frmr);
                ib_dma_unmap_sg(ia->ri_device,
                                mw->mw_sg, mw->mw_nents, mw->mw_dir);
                rpcrdma_put_mw(r_xprt, mw);
        }
        return;

reset_mrs:
        pr_err("rpcrdma: FRMR invalidate ib_post_send returned %i\n", rc);

        /* Find and reset the MRs in the LOCAL_INV WRs that did not
         * get posted.
         */
        rpcrdma_init_cqcount(&r_xprt->rx_ep, -count);
        while (bad_wr) {
                f = container_of(bad_wr, struct rpcrdma_frmr,
                                 fr_invwr);
                mw = container_of(f, struct rpcrdma_mw, frmr);

                __frwr_reset_mr(ia, mw);

                bad_wr = bad_wr->next;
        }
        goto unmap;
}

/* Use a slow, safe mechanism to invalidate all memory regions
 * that were registered for "req".
 */
static void
frwr_op_unmap_safe(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
                   bool sync)
{
        struct rpcrdma_mw *mw;

        while (!list_empty(&req->rl_registered)) {
                mw = rpcrdma_pop_mw(&req->rl_registered);
                if (sync)
                        frwr_op_recover_mr(mw);
                else
                        rpcrdma_defer_mr_recovery(mw);
        }
}

const struct rpcrdma_memreg_ops rpcrdma_frwr_memreg_ops = {
        .ro_map                         = frwr_op_map,
        .ro_unmap_sync                  = frwr_op_unmap_sync,
        .ro_unmap_safe                  = frwr_op_unmap_safe,
        .ro_recover_mr                  = frwr_op_recover_mr,
        .ro_open                        = frwr_op_open,
        .ro_maxpages                    = frwr_op_maxpages,
        .ro_init_mr                     = frwr_op_init_mr,
        .ro_release_mr                  = frwr_op_release_mr,
        .ro_displayname                 = "frwr",
        .ro_send_w_inv_ok               = RPCRDMA_CMP_F_SND_W_INV_OK,
};