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

/* Lightweight memory registration using Fast Memory Regions (FMR).
 * Referred to sometimes as MTHCAFMR mode.
 *
 * FMR uses synchronous memory registration and deregistration.
 * FMR registration is known to be fast, but FMR deregistration
 * can take tens of usecs to complete.
 */

/* Normal operation
 *
 * A Memory Region is prepared for RDMA READ or WRITE using the
 * ib_map_phys_fmr verb (fmr_op_map). When the RDMA operation is
 * finished, the Memory Region is unmapped using the ib_unmap_fmr
 * verb (fmr_op_unmap).
 */

#include "xprt_rdma.h"

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

/* Maximum scatter/gather per FMR */
#define RPCRDMA_MAX_FMR_SGES    (64)

/* Access mode of externally registered pages */
enum {
        RPCRDMA_FMR_ACCESS_FLAGS        = IB_ACCESS_REMOTE_WRITE |
                                          IB_ACCESS_REMOTE_READ,
};

bool
fmr_is_supported(struct rpcrdma_ia *ia)
{
        if (!ia->ri_device->alloc_fmr) {
                pr_info("rpcrdma: 'fmr' mode is not supported by device %s\n",
                        ia->ri_device->name);
                return false;
        }
        return true;
}

static int
fmr_op_init_mr(struct rpcrdma_ia *ia, struct rpcrdma_mw *mw)
{
        static struct ib_fmr_attr fmr_attr = {
                .max_pages      = RPCRDMA_MAX_FMR_SGES,
                .max_maps       = 1,
                .page_shift     = PAGE_SHIFT
        };

        mw->fmr.fm_physaddrs = kcalloc(RPCRDMA_MAX_FMR_SGES,
                                       sizeof(u64), GFP_KERNEL);
        if (!mw->fmr.fm_physaddrs)
                goto out_free;

        mw->mw_sg = kcalloc(RPCRDMA_MAX_FMR_SGES,
                            sizeof(*mw->mw_sg), GFP_KERNEL);
        if (!mw->mw_sg)
                goto out_free;

        sg_init_table(mw->mw_sg, RPCRDMA_MAX_FMR_SGES);

        mw->fmr.fm_mr = ib_alloc_fmr(ia->ri_pd, RPCRDMA_FMR_ACCESS_FLAGS,
                                     &fmr_attr);
        if (IS_ERR(mw->fmr.fm_mr))
                goto out_fmr_err;

        return 0;

out_fmr_err:
        dprintk("RPC:       %s: ib_alloc_fmr returned %ld\n", __func__,
                PTR_ERR(mw->fmr.fm_mr));

out_free:
        kfree(mw->mw_sg);
        kfree(mw->fmr.fm_physaddrs);
        return -ENOMEM;
}

static int
__fmr_unmap(struct rpcrdma_mw *mw)
{
        LIST_HEAD(l);
        int rc;

        list_add(&mw->fmr.fm_mr->list, &l);
        rc = ib_unmap_fmr(&l);
        list_del_init(&mw->fmr.fm_mr->list);
        return rc;
}

static void
fmr_op_release_mr(struct rpcrdma_mw *r)
{
        LIST_HEAD(unmap_list);
        int rc;

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

        kfree(r->fmr.fm_physaddrs);
        kfree(r->mw_sg);

        /* In case this one was left mapped, try to unmap it
         * to prevent dealloc_fmr from failing with EBUSY
         */
        rc = __fmr_unmap(r);
        if (rc)
                pr_err("rpcrdma: final ib_unmap_fmr for %p failed %i\n",
                       r, rc);

        rc = ib_dealloc_fmr(r->fmr.fm_mr);
        if (rc)
                pr_err("rpcrdma: final ib_dealloc_fmr for %p returned %i\n",
                       r, rc);

        kfree(r);
}

/* Reset of a single FMR.
 */
static void
fmr_op_recover_mr(struct rpcrdma_mw *mw)
{
        struct rpcrdma_xprt *r_xprt = mw->mw_xprt;
        int rc;

        /* ORDER: invalidate first */
        rc = __fmr_unmap(mw);

        /* ORDER: then DMA unmap */
        ib_dma_unmap_sg(r_xprt->rx_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: FMR reset failed (%d), %p released\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);

        fmr_op_release_mr(mw);
}

static int
fmr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
            struct rpcrdma_create_data_internal *cdata)
{
        ia->ri_max_segs = max_t(unsigned int, 1, RPCRDMA_MAX_DATA_SEGS /
                                RPCRDMA_MAX_FMR_SGES);
        return 0;
}

/* FMR mode conveys up to 64 pages of payload per chunk segment.
 */
static size_t
fmr_op_maxpages(struct rpcrdma_xprt *r_xprt)
{
        return min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
                     RPCRDMA_MAX_HDR_SEGS * RPCRDMA_MAX_FMR_SGES);
}

/* Use the ib_map_phys_fmr() verb to register a memory region
 * for remote access via RDMA READ or RDMA WRITE.
 */
static int
fmr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
           int nsegs, bool writing, struct rpcrdma_mw **out)
{
        struct rpcrdma_mr_seg *seg1 = seg;
        int len, pageoff, i, rc;
        struct rpcrdma_mw *mw;
        u64 *dma_pages;

        mw = rpcrdma_get_mw(r_xprt);
        if (!mw)
                return -ENOBUFS;

        pageoff = offset_in_page(seg1->mr_offset);
        seg1->mr_offset -= pageoff;     /* start of page */
        seg1->mr_len += pageoff;
        len = -pageoff;
        if (nsegs > RPCRDMA_MAX_FMR_SGES)
                nsegs = RPCRDMA_MAX_FMR_SGES;
        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);
                len += 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;
        }
        mw->mw_nents = i;
        mw->mw_dir = rpcrdma_data_dir(writing);
        if (i == 0)
                goto out_dmamap_err;

        if (!ib_dma_map_sg(r_xprt->rx_ia.ri_device,
                           mw->mw_sg, mw->mw_nents, mw->mw_dir))
                goto out_dmamap_err;

        for (i = 0, dma_pages = mw->fmr.fm_physaddrs; i < mw->mw_nents; i++)
                dma_pages[i] = sg_dma_address(&mw->mw_sg[i]);
        rc = ib_map_phys_fmr(mw->fmr.fm_mr, dma_pages, mw->mw_nents,
                             dma_pages[0]);
        if (rc)
                goto out_maperr;

        mw->mw_handle = mw->fmr.fm_mr->rkey;
        mw->mw_length = len;
        mw->mw_offset = dma_pages[0] + pageoff;

        *out = mw;
        return mw->mw_nents;

out_dmamap_err:
        pr_err("rpcrdma: failed to dma map sg %p sg_nents %u\n",
               mw->mw_sg, mw->mw_nents);
        rpcrdma_defer_mr_recovery(mw);
        return -EIO;

out_maperr:
        pr_err("rpcrdma: ib_map_phys_fmr %u@0x%llx+%i (%d) status %i\n",
               len, (unsigned long long)dma_pages[0],
               pageoff, mw->mw_nents, rc);
        rpcrdma_defer_mr_recovery(mw);
        return -EIO;
}

/* 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 req->rl_registered is not empty.
 */
static void
fmr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
{
        struct rpcrdma_mw *mw, *tmp;
        LIST_HEAD(unmap_list);
        int rc;

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

        /* ORDER: Invalidate all of the req's MRs first
         *
         * ib_unmap_fmr() is slow, so use a single call instead
         * of one call per mapped FMR.
         */
        list_for_each_entry(mw, &req->rl_registered, mw_list)
                list_add_tail(&mw->fmr.fm_mr->list, &unmap_list);
        r_xprt->rx_stats.local_inv_needed++;
        rc = ib_unmap_fmr(&unmap_list);
        if (rc)
                goto out_reset;

        /* ORDER: Now DMA unmap all of the req's MRs, and return
         * them to the free MW list.
         */
        list_for_each_entry_safe(mw, tmp, &req->rl_registered, mw_list) {
                list_del_init(&mw->mw_list);
                list_del_init(&mw->fmr.fm_mr->list);
                ib_dma_unmap_sg(r_xprt->rx_ia.ri_device,
                                mw->mw_sg, mw->mw_nents, mw->mw_dir);
                rpcrdma_put_mw(r_xprt, mw);
        }

        return;

out_reset:
        pr_err("rpcrdma: ib_unmap_fmr failed (%i)\n", rc);

        list_for_each_entry_safe(mw, tmp, &req->rl_registered, mw_list) {
                list_del_init(&mw->fmr.fm_mr->list);
                fmr_op_recover_mr(mw);
        }
}

/* Use a slow, safe mechanism to invalidate all memory regions
 * that were registered for "req".
 */
static void
fmr_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 = list_first_entry(&req->rl_registered,
                                      struct rpcrdma_mw, mw_list);
                list_del_init(&mw->mw_list);

                if (sync)
                        fmr_op_recover_mr(mw);
                else
                        rpcrdma_defer_mr_recovery(mw);
        }
}

const struct rpcrdma_memreg_ops rpcrdma_fmr_memreg_ops = {
        .ro_map                         = fmr_op_map,
        .ro_unmap_sync                  = fmr_op_unmap_sync,
        .ro_unmap_safe                  = fmr_op_unmap_safe,
        .ro_recover_mr                  = fmr_op_recover_mr,
        .ro_open                        = fmr_op_open,
        .ro_maxpages                    = fmr_op_maxpages,
        .ro_init_mr                     = fmr_op_init_mr,
        .ro_release_mr                  = fmr_op_release_mr,
        .ro_displayname                 = "fmr",
        .ro_send_w_inv_ok               = 0,
};