// SPDX-License-Identifier: GPL-2.0
/*
 * Shared Memory Communications over RDMA (SMC-R) and RoCE
 *
 * Manage RMBE
 * copy new RMBE data into user space
 *
 * Copyright IBM Corp. 2016
 *
 * Author(s):  Ursula Braun <ubraun@linux.vnet.ibm.com>
 */

#include <linux/net.h>
#include <linux/rcupdate.h>
#include <linux/sched/signal.h>
#include <linux/splice.h>

#include <net/sock.h>
#include <trace/events/sock.h>

#include "smc.h"
#include "smc_core.h"
#include "smc_cdc.h"
#include "smc_tx.h" /* smc_tx_consumer_update() */
#include "smc_rx.h"
#include "smc_stats.h"
#include "smc_tracepoint.h"

/* callback implementation to wakeup consumers blocked with smc_rx_wait().
 * indirectly called by smc_cdc_msg_recv_action().
 */
static void smc_rx_wake_up(struct sock *sk)
{
        struct socket_wq *wq;

        trace_sk_data_ready(sk);

        /* derived from sock_def_readable() */
        /* called already in smc_listen_work() */
        rcu_read_lock();
        wq = rcu_dereference(sk->sk_wq);
        if (skwq_has_sleeper(wq))
                wake_up_interruptible_sync_poll(&wq->wait, EPOLLIN | EPOLLPRI |
                                                EPOLLRDNORM | EPOLLRDBAND);
        sk_wake_async_rcu(sk, SOCK_WAKE_WAITD, POLL_IN);
        if ((sk->sk_shutdown == SHUTDOWN_MASK) ||
            (sk->sk_state == SMC_CLOSED))
                sk_wake_async_rcu(sk, SOCK_WAKE_WAITD, POLL_HUP);
        rcu_read_unlock();
}

/* Update consumer cursor
 *   @conn   connection to update
 *   @cons   consumer cursor
 *   @len    number of Bytes consumed
 *   Returns:
 *   1 if we should end our receive, 0 otherwise
 */
static int smc_rx_update_consumer(struct smc_sock *smc,
                                  union smc_host_cursor cons, size_t len)
{
        struct smc_connection *conn = &smc->conn;
        struct sock *sk = &smc->sk;
        bool force = false;
        int diff, rc = 0;

        smc_curs_add(conn->rmb_desc->len, &cons, len);

        /* did we process urgent data? */
        if (conn->urg_state == SMC_URG_VALID || conn->urg_rx_skip_pend) {
                diff = smc_curs_comp(conn->rmb_desc->len, &cons,
                                     &conn->urg_curs);
                if (sock_flag(sk, SOCK_URGINLINE)) {
                        if (diff == 0) {
                                force = true;
                                rc = 1;
                                conn->urg_state = SMC_URG_READ;
                        }
                } else {
                        if (diff == 1) {
                                /* skip urgent byte */
                                force = true;
                                smc_curs_add(conn->rmb_desc->len, &cons, 1);
                                conn->urg_rx_skip_pend = false;
                        } else if (diff < -1)
                                /* we read past urgent byte */
                                conn->urg_state = SMC_URG_READ;
                }
        }

        smc_curs_copy(&conn->local_tx_ctrl.cons, &cons, conn);

        /* send consumer cursor update if required */
        /* similar to advertising new TCP rcv_wnd if required */
        smc_tx_consumer_update(conn, force);

        return rc;
}

static void smc_rx_update_cons(struct smc_sock *smc, size_t len)
{
        struct smc_connection *conn = &smc->conn;
        union smc_host_cursor cons;

        smc_curs_copy(&cons, &conn->local_tx_ctrl.cons, conn);
        smc_rx_update_consumer(smc, cons, len);
}

struct smc_spd_priv {
        struct smc_sock *smc;
        size_t           len;
};

static void smc_rx_pipe_buf_release(struct pipe_inode_info *pipe,
                                    struct pipe_buffer *buf)
{
        struct smc_spd_priv *priv = (struct smc_spd_priv *)buf->private;
        struct smc_sock *smc = priv->smc;
        struct smc_connection *conn;
        struct sock *sk = &smc->sk;

        if (sk->sk_state == SMC_CLOSED ||
            sk->sk_state == SMC_PEERFINCLOSEWAIT ||
            sk->sk_state == SMC_APPFINCLOSEWAIT)
                goto out;
        conn = &smc->conn;
        lock_sock(sk);
        smc_rx_update_cons(smc, priv->len);
        release_sock(sk);
        if (atomic_sub_and_test(priv->len, &conn->splice_pending))
                smc_rx_wake_up(sk);
out:
        kfree(priv);
        put_page(buf->page);
        sock_put(sk);
}

static bool smc_rx_pipe_buf_get(struct pipe_inode_info *pipe,
                                struct pipe_buffer *buf)
{
        /* smc_spd_priv in buf->private is not shareable; disallow cloning. */
        return false;
}

static const struct pipe_buf_operations smc_pipe_ops = {
        .release = smc_rx_pipe_buf_release,
        .get     = smc_rx_pipe_buf_get,
};

static void smc_rx_spd_release(struct splice_pipe_desc *spd,
                               unsigned int i)
{
        put_page(spd->pages[i]);
}

static int smc_rx_splice(struct pipe_inode_info *pipe, char *src, size_t len,
                         struct smc_sock *smc)
{
        struct smc_link_group *lgr = smc->conn.lgr;
        int offset = offset_in_page(src);
        struct partial_page *partial;
        struct splice_pipe_desc spd;
        struct smc_spd_priv **priv;
        struct page **pages;
        int bytes, nr_pages;
        int i;

        nr_pages = !lgr->is_smcd && smc->conn.rmb_desc->is_vm ?
                   PAGE_ALIGN(len + offset) / PAGE_SIZE : 1;

        pages = kzalloc_objs(*pages, nr_pages);
        if (!pages)
                goto out;
        partial = kzalloc_objs(*partial, nr_pages);
        if (!partial)
                goto out_page;
        priv = kzalloc_objs(*priv, nr_pages);
        if (!priv)
                goto out_part;
        for (i = 0; i < nr_pages; i++) {
                priv[i] = kzalloc_obj(**priv);
                if (!priv[i])
                        goto out_priv;
        }

        if (lgr->is_smcd ||
            (!lgr->is_smcd && !smc->conn.rmb_desc->is_vm)) {
                /* smcd or smcr that uses physically contiguous RMBs */
                priv[0]->len = len;
                priv[0]->smc = smc;
                partial[0].offset = src - (char *)smc->conn.rmb_desc->cpu_addr;
                partial[0].len = len;
                partial[0].private = (unsigned long)priv[0];
                pages[0] = smc->conn.rmb_desc->pages;
        } else {
                int size, left = len;
                void *buf = src;
                /* smcr that uses virtually contiguous RMBs*/
                for (i = 0; i < nr_pages; i++) {
                        size = min_t(int, PAGE_SIZE - offset, left);
                        priv[i]->len = size;
                        priv[i]->smc = smc;
                        pages[i] = vmalloc_to_page(buf);
                        partial[i].offset = offset;
                        partial[i].len = size;
                        partial[i].private = (unsigned long)priv[i];
                        buf += size;
                        left -= size;
                        offset = 0;
                }
        }
        spd.nr_pages_max = nr_pages;
        spd.nr_pages = nr_pages;
        spd.pages = pages;
        spd.partial = partial;
        spd.ops = &smc_pipe_ops;
        spd.spd_release = smc_rx_spd_release;

        bytes = splice_to_pipe(pipe, &spd);
        if (bytes > 0) {
                sock_hold(&smc->sk);
                if (!lgr->is_smcd && smc->conn.rmb_desc->is_vm) {
                        for (i = 0; i < PAGE_ALIGN(bytes + offset) / PAGE_SIZE; i++)
                                get_page(pages[i]);
                } else {
                        get_page(smc->conn.rmb_desc->pages);
                }
                atomic_add(bytes, &smc->conn.splice_pending);
        }
        kfree(priv);
        kfree(partial);
        kfree(pages);

        return bytes;

out_priv:
        for (i = (i - 1); i >= 0; i--)
                kfree(priv[i]);
        kfree(priv);
out_part:
        kfree(partial);
out_page:
        kfree(pages);
out:
        return -ENOMEM;
}

static int smc_rx_data_available_and_no_splice_pend(struct smc_connection *conn, size_t peeked)
{
        return smc_rx_data_available(conn, peeked) &&
               !atomic_read(&conn->splice_pending);
}

/* blocks rcvbuf consumer until >=len bytes available or timeout or interrupted
 *   @smc    smc socket
 *   @timeo  pointer to max seconds to wait, pointer to value 0 for no timeout
 *   @peeked  number of bytes already peeked
 *   @fcrit  add'l criterion to evaluate as function pointer
 * Returns:
 * 1 if at least 1 byte available in rcvbuf or if socket error/shutdown.
 * 0 otherwise (nothing in rcvbuf nor timeout, e.g. interrupted).
 */
int smc_rx_wait(struct smc_sock *smc, long *timeo, size_t peeked,
                int (*fcrit)(struct smc_connection *conn, size_t baseline))
{
        DEFINE_WAIT_FUNC(wait, woken_wake_function);
        struct smc_connection *conn = &smc->conn;
        struct smc_cdc_conn_state_flags *cflags =
                                        &conn->local_tx_ctrl.conn_state_flags;
        struct sock *sk = &smc->sk;
        int rc;

        if (fcrit(conn, peeked))
                return 1;
        sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
        add_wait_queue(sk_sleep(sk), &wait);
        rc = sk_wait_event(sk, timeo,
                           READ_ONCE(sk->sk_err) ||
                           cflags->peer_conn_abort ||
                           READ_ONCE(sk->sk_shutdown) & RCV_SHUTDOWN ||
                           conn->killed ||
                           fcrit(conn, peeked),
                           &wait);
        remove_wait_queue(sk_sleep(sk), &wait);
        sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
        return rc;
}

static int smc_rx_recv_urg(struct smc_sock *smc, struct msghdr *msg, int len,
                           int flags)
{
        struct smc_connection *conn = &smc->conn;
        union smc_host_cursor cons;
        struct sock *sk = &smc->sk;
        int rc = 0;

        if (sock_flag(sk, SOCK_URGINLINE) ||
            !(conn->urg_state == SMC_URG_VALID) ||
            conn->urg_state == SMC_URG_READ)
                return -EINVAL;

        SMC_STAT_INC(smc, urg_data_cnt);
        if (conn->urg_state == SMC_URG_VALID) {
                if (!(flags & MSG_PEEK))
                        smc->conn.urg_state = SMC_URG_READ;
                msg->msg_flags |= MSG_OOB;
                if (len > 0) {
                        if (!(flags & MSG_TRUNC))
                                rc = memcpy_to_msg(msg, &conn->urg_rx_byte, 1);
                        len = 1;
                        smc_curs_copy(&cons, &conn->local_tx_ctrl.cons, conn);
                        if (smc_curs_diff(conn->rmb_desc->len, &cons,
                                          &conn->urg_curs) > 1)
                                conn->urg_rx_skip_pend = true;
                        /* Urgent Byte was already accounted for, but trigger
                         * skipping the urgent byte in non-inline case
                         */
                        if (!(flags & MSG_PEEK))
                                smc_rx_update_consumer(smc, cons, 0);
                } else {
                        msg->msg_flags |= MSG_TRUNC;
                }

                return rc ? -EFAULT : len;
        }

        if (sk->sk_state == SMC_CLOSED || sk->sk_shutdown & RCV_SHUTDOWN)
                return 0;

        return -EAGAIN;
}

static bool smc_rx_recvmsg_data_available(struct smc_sock *smc, size_t peeked)
{
        struct smc_connection *conn = &smc->conn;

        if (smc_rx_data_available(conn, peeked))
                return true;
        else if (conn->urg_state == SMC_URG_VALID)
                /* we received a single urgent Byte - skip */
                smc_rx_update_cons(smc, 0);
        return false;
}

/* smc_rx_recvmsg - receive data from RMBE
 * @msg:        copy data to receive buffer
 * @pipe:       copy data to pipe if set - indicates splice() call
 *
 * rcvbuf consumer: main API called by socket layer.
 * Called under sk lock.
 */
int smc_rx_recvmsg(struct smc_sock *smc, struct msghdr *msg,
                   struct pipe_inode_info *pipe, size_t len, int flags)
{
        size_t copylen, read_done = 0, read_remaining = len, peeked_bytes = 0;
        size_t chunk_len, chunk_off, chunk_len_sum;
        struct smc_connection *conn = &smc->conn;
        int (*func)(struct smc_connection *conn, size_t baseline);
        union smc_host_cursor cons;
        int readable, chunk;
        char *rcvbuf_base;
        struct sock *sk;
        int splbytes;
        long timeo;
        int target;             /* Read at least these many bytes */
        int rc;

        if (unlikely(flags & MSG_ERRQUEUE))
                return -EINVAL; /* future work for sk.sk_family == AF_SMC */

        sk = &smc->sk;
        if (sk->sk_state == SMC_LISTEN)
                return -ENOTCONN;
        if (flags & MSG_OOB)
                return smc_rx_recv_urg(smc, msg, len, flags);
        timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
        target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);

        readable = atomic_read(&conn->bytes_to_rcv);
        if (readable >= conn->rmb_desc->len)
                SMC_STAT_RMB_RX_FULL(smc, !conn->lnk);

        if (len < readable)
                SMC_STAT_RMB_RX_SIZE_SMALL(smc, !conn->lnk);
        /* we currently use 1 RMBE per RMB, so RMBE == RMB base addr */
        rcvbuf_base = conn->rx_off + conn->rmb_desc->cpu_addr;

        do { /* while (read_remaining) */
                if (read_done >= target || (pipe && read_done))
                        break;

                if (conn->killed)
                        break;

                if (smc_rx_recvmsg_data_available(smc, peeked_bytes))
                        goto copy;

                if (sk->sk_shutdown & RCV_SHUTDOWN) {
                        /* smc_cdc_msg_recv_action() could have run after
                         * above smc_rx_recvmsg_data_available()
                         */
                        if (smc_rx_recvmsg_data_available(smc, peeked_bytes))
                                goto copy;
                        break;
                }

                if (read_done) {
                        if (sk->sk_err ||
                            sk->sk_state == SMC_CLOSED ||
                            !timeo ||
                            signal_pending(current))
                                break;
                } else {
                        if (sk->sk_err) {
                                read_done = sock_error(sk);
                                break;
                        }
                        if (sk->sk_state == SMC_CLOSED) {
                                if (!sock_flag(sk, SOCK_DONE)) {
                                        /* This occurs when user tries to read
                                         * from never connected socket.
                                         */
                                        read_done = -ENOTCONN;
                                        break;
                                }
                                break;
                        }
                        if (!timeo)
                                return -EAGAIN;
                        if (signal_pending(current)) {
                                read_done = sock_intr_errno(timeo);
                                break;
                        }
                }

                if (!smc_rx_data_available(conn, peeked_bytes)) {
                        smc_rx_wait(smc, &timeo, peeked_bytes, smc_rx_data_available);
                        continue;
                }

copy:
                /* initialize variables for 1st iteration of subsequent loop */
                /* could be just 1 byte, even after waiting on data above */
                readable = smc_rx_data_available(conn, peeked_bytes);
                splbytes = atomic_read(&conn->splice_pending);
                if (!readable || (msg && splbytes)) {
                        if (splbytes)
                                func = smc_rx_data_available_and_no_splice_pend;
                        else
                                func = smc_rx_data_available;
                        smc_rx_wait(smc, &timeo, peeked_bytes, func);
                        continue;
                }

                smc_curs_copy(&cons, &conn->local_tx_ctrl.cons, conn);
                if ((flags & MSG_PEEK) && peeked_bytes)
                        smc_curs_add(conn->rmb_desc->len, &cons, peeked_bytes);
                /* subsequent splice() calls pick up where previous left */
                if (splbytes)
                        smc_curs_add(conn->rmb_desc->len, &cons, splbytes);
                if (conn->urg_state == SMC_URG_VALID &&
                    sock_flag(&smc->sk, SOCK_URGINLINE) &&
                    readable > 1)
                        readable--;     /* always stop at urgent Byte */
                /* not more than what user space asked for */
                copylen = min_t(size_t, read_remaining, readable);
                /* determine chunks where to read from rcvbuf */
                /* either unwrapped case, or 1st chunk of wrapped case */
                chunk_len = min_t(size_t, copylen, conn->rmb_desc->len -
                                  cons.count);
                chunk_len_sum = chunk_len;
                chunk_off = cons.count;
                smc_rmb_sync_sg_for_cpu(conn);
                for (chunk = 0; chunk < 2; chunk++) {
                        if (!(flags & MSG_TRUNC)) {
                                if (msg) {
                                        rc = memcpy_to_msg(msg, rcvbuf_base +
                                                           chunk_off,
                                                           chunk_len);
                                } else {
                                        rc = smc_rx_splice(pipe, rcvbuf_base +
                                                        chunk_off, chunk_len,
                                                        smc);
                                }
                                if (rc < 0) {
                                        if (!read_done)
                                                read_done = -EFAULT;
                                        goto out;
                                }
                        }
                        read_remaining -= chunk_len;
                        read_done += chunk_len;
                        if (flags & MSG_PEEK)
                                peeked_bytes += chunk_len;

                        if (chunk_len_sum == copylen)
                                break; /* either on 1st or 2nd iteration */
                        /* prepare next (== 2nd) iteration */
                        chunk_len = copylen - chunk_len; /* remainder */
                        chunk_len_sum += chunk_len;
                        chunk_off = 0; /* modulo offset in recv ring buffer */
                }

                /* update cursors */
                if (!(flags & MSG_PEEK)) {
                        /* increased in recv tasklet smc_cdc_msg_rcv() */
                        smp_mb__before_atomic();
                        atomic_sub(copylen, &conn->bytes_to_rcv);
                        /* guarantee 0 <= bytes_to_rcv <= rmb_desc->len */
                        smp_mb__after_atomic();
                        if (msg && smc_rx_update_consumer(smc, cons, copylen))
                                goto out;
                }

                trace_smc_rx_recvmsg(smc, copylen);
        } while (read_remaining);
out:
        return read_done;
}

/* Initialize receive properties on connection establishment. NB: not __init! */
void smc_rx_init(struct smc_sock *smc)
{
        smc->sk.sk_data_ready = smc_rx_wake_up;
        atomic_set(&smc->conn.splice_pending, 0);
        smc->conn.urg_state = SMC_URG_READ;
}