tcp_recv.c

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/*
 * Copyright (c) 2006 Oracle.  All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */
#include <linux/kernel.h>
#include <linux/slab.h>
#include <net/tcp.h>

#include "rds.h"
#include "tcp.h"

static struct kmem_cache *rds_tcp_incoming_slab;

static void rds_tcp_inc_purge(struct rds_incoming *inc)
{
    struct rds_tcp_incoming *tinc;
    tinc = container_of(inc, struct rds_tcp_incoming, ti_inc);
    rdsdebug("purging tinc %p inc %p\n", tinc, inc);
    skb_queue_purge(&tinc->ti_skb_list);
}

void rds_tcp_inc_free(struct rds_incoming *inc)
{
    struct rds_tcp_incoming *tinc;
    tinc = container_of(inc, struct rds_tcp_incoming, ti_inc);
    rds_tcp_inc_purge(inc);
    rdsdebug("freeing tinc %p inc %p\n", tinc, inc);
    kmem_cache_free(rds_tcp_incoming_slab, tinc);
}

/*
 * this is pretty lame, but, whatever.
 */
int rds_tcp_inc_copy_to_user(struct rds_incoming *inc, struct iovec *first_iov,
                 size_t size)
{
    struct rds_tcp_incoming *tinc;
    struct iovec *iov, tmp;
    struct sk_buff *skb;
    unsigned long to_copy, skb_off;
    int ret = 0;

    if (size == 0)
        goto out;

    tinc = container_of(inc, struct rds_tcp_incoming, ti_inc);
    iov = first_iov;
    tmp = *iov;

    skb_queue_walk(&tinc->ti_skb_list, skb) {
        skb_off = 0;
        while (skb_off < skb->len) {
            while (tmp.iov_len == 0) {
                iov++;
                tmp = *iov;
            }

            to_copy = min(tmp.iov_len, size);
            to_copy = min(to_copy, skb->len - skb_off);

            rdsdebug("ret %d size %zu skb %p skb_off %lu "
                 "skblen %d iov_base %p iov_len %zu cpy %lu\n",
                 ret, size, skb, skb_off, skb->len,
                 tmp.iov_base, tmp.iov_len, to_copy);

            /* modifies tmp as it copies */
            if (skb_copy_datagram_iovec(skb, skb_off, &tmp,
                            to_copy)) {
                ret = -EFAULT;
                goto out;
            }

            rds_stats_add(s_copy_to_user, to_copy);
            size -= to_copy;
            ret += to_copy;
            skb_off += to_copy;
            if (size == 0)
                goto out;
        }
    }
out:
    return ret;
}

/*
 * We have a series of skbs that have fragmented pieces of the congestion
 * bitmap.  They must add up to the exact size of the congestion bitmap.  We
 * use the skb helpers to copy those into the pages that make up the in-memory
 * congestion bitmap for the remote address of this connection.  We then tell
 * the congestion core that the bitmap has been changed so that it can wake up
 * sleepers.
 *
 * This is racing with sending paths which are using test_bit to see if the
 * bitmap indicates that their recipient is congested.
 */

static void rds_tcp_cong_recv(struct rds_connection *conn,
                  struct rds_tcp_incoming *tinc)
{
    struct sk_buff *skb;
    unsigned int to_copy, skb_off;
    unsigned int map_off;
    unsigned int map_page;
    struct rds_cong_map *map;
    int ret;

    /* catch completely corrupt packets */
    if (be32_to_cpu(tinc->ti_inc.i_hdr.h_len) != RDS_CONG_MAP_BYTES)
        return;

    map_page = 0;
    map_off = 0;
    map = conn->c_fcong;

    skb_queue_walk(&tinc->ti_skb_list, skb) {
        skb_off = 0;
        while (skb_off < skb->len) {
            to_copy = min_t(unsigned int, PAGE_SIZE - map_off,
                    skb->len - skb_off);

            BUG_ON(map_page >= RDS_CONG_MAP_PAGES);

            /* only returns 0 or -error */
            ret = skb_copy_bits(skb, skb_off,
                (void *)map->m_page_addrs[map_page] + map_off,
                to_copy);
            BUG_ON(ret != 0);

            skb_off += to_copy;
            map_off += to_copy;
            if (map_off == PAGE_SIZE) {
                map_off = 0;
                map_page++;
            }
        }
    }

    rds_cong_map_updated(map, ~(u64) 0);
}

struct rds_tcp_desc_arg {
    struct rds_connection *conn;
    gfp_t gfp;
};

static int rds_tcp_data_recv(read_descriptor_t *desc, struct sk_buff *skb,
                 unsigned int offset, size_t len)
{
    struct rds_tcp_desc_arg *arg = desc->arg.data;
    struct rds_connection *conn = arg->conn;
    struct rds_tcp_connection *tc = conn->c_transport_data;
    struct rds_tcp_incoming *tinc = tc->t_tinc;
    struct sk_buff *clone;
    size_t left = len, to_copy;

    rdsdebug("tcp data tc %p skb %p offset %u len %zu\n", tc, skb, offset,
         len);

    /*
     * tcp_read_sock() interprets partial progress as an indication to stop
     * processing.
     */
    while (left) {
        if (!tinc) {
            tinc = kmem_cache_alloc(rds_tcp_incoming_slab,
                            arg->gfp);
            if (!tinc) {
                desc->error = -ENOMEM;
                goto out;
            }
            tc->t_tinc = tinc;
            rdsdebug("alloced tinc %p\n", tinc);
            rds_inc_init(&tinc->ti_inc, conn, conn->c_faddr);
            /*
             * XXX * we might be able to use the __ variants when
             * we've already serialized at a higher level.
             */
            skb_queue_head_init(&tinc->ti_skb_list);
        }

        if (left && tc->t_tinc_hdr_rem) {
            to_copy = min(tc->t_tinc_hdr_rem, left);
            rdsdebug("copying %zu header from skb %p\n", to_copy,
                 skb);
            skb_copy_bits(skb, offset,
                      (char *)&tinc->ti_inc.i_hdr +
                        sizeof(struct rds_header) -
                        tc->t_tinc_hdr_rem,
                      to_copy);
            tc->t_tinc_hdr_rem -= to_copy;
            left -= to_copy;
            offset += to_copy;

            if (tc->t_tinc_hdr_rem == 0) {
                /* could be 0 for a 0 len message */
                tc->t_tinc_data_rem =
                    be32_to_cpu(tinc->ti_inc.i_hdr.h_len);
            }
        }

        if (left && tc->t_tinc_data_rem) {
            clone = skb_clone(skb, arg->gfp);
            if (!clone) {
                desc->error = -ENOMEM;
                goto out;
            }

            to_copy = min(tc->t_tinc_data_rem, left);
            pskb_pull(clone, offset);
            pskb_trim(clone, to_copy);
            skb_queue_tail(&tinc->ti_skb_list, clone);

            rdsdebug("skb %p data %p len %d off %u to_copy %zu -> "
                 "clone %p data %p len %d\n",
                 skb, skb->data, skb->len, offset, to_copy,
                 clone, clone->data, clone->len);

            tc->t_tinc_data_rem -= to_copy;
            left -= to_copy;
            offset += to_copy;
        }

        if (tc->t_tinc_hdr_rem == 0 && tc->t_tinc_data_rem == 0) {
            if (tinc->ti_inc.i_hdr.h_flags == RDS_FLAG_CONG_BITMAP)
                rds_tcp_cong_recv(conn, tinc);
            else
                rds_recv_incoming(conn, conn->c_faddr,
                          conn->c_laddr, &tinc->ti_inc,
                          arg->gfp);

            tc->t_tinc_hdr_rem = sizeof(struct rds_header);
            tc->t_tinc_data_rem = 0;
            tc->t_tinc = NULL;
            rds_inc_put(&tinc->ti_inc);
            tinc = NULL;
        }
    }
out:
    rdsdebug("returning len %zu left %zu skb len %d rx queue depth %d\n",
         len, left, skb->len,
         skb_queue_len(&tc->t_sock->sk->sk_receive_queue));
    return len - left;
}

/* the caller has to hold the sock lock */
static int rds_tcp_read_sock(struct rds_connection *conn, gfp_t gfp)
{
    struct rds_tcp_connection *tc = conn->c_transport_data;
    struct socket *sock = tc->t_sock;
    read_descriptor_t desc;
    struct rds_tcp_desc_arg arg;

    /* It's like glib in the kernel! */
    arg.conn = conn;
    arg.gfp = gfp;
    desc.arg.data = &arg;
    desc.error = 0;
    desc.count = 1; /* give more than one skb per call */

    tcp_read_sock(sock->sk, &desc, rds_tcp_data_recv);
    rdsdebug("tcp_read_sock for tc %p gfp 0x%x returned %d\n", tc, gfp,
         desc.error);

    return desc.error;
}

/*
 * We hold the sock lock to serialize our rds_tcp_recv->tcp_read_sock from
 * data_ready.
 *
 * if we fail to allocate we're in trouble.. blindly wait some time before
 * trying again to see if the VM can free up something for us.
 */
int rds_tcp_recv(struct rds_connection *conn)
{
    struct rds_tcp_connection *tc = conn->c_transport_data;
    struct socket *sock = tc->t_sock;
    int ret = 0;

    rdsdebug("recv worker conn %p tc %p sock %p\n", conn, tc, sock);

    lock_sock(sock->sk);
    ret = rds_tcp_read_sock(conn, GFP_KERNEL);
    release_sock(sock->sk);

    return ret;
}

void rds_tcp_data_ready(struct sock *sk, int bytes)
{
    void (*ready)(struct sock *sk, int bytes);
    struct rds_connection *conn;
    struct rds_tcp_connection *tc;

    rdsdebug("data ready sk %p bytes %d\n", sk, bytes);

    read_lock(&sk->sk_callback_lock);
    conn = sk->sk_user_data;
    if (!conn) { /* check for teardown race */
        ready = sk->sk_data_ready;
        goto out;
    }

    tc = conn->c_transport_data;
    ready = tc->t_orig_data_ready;
    rds_tcp_stats_inc(s_tcp_data_ready_calls);

    if (rds_tcp_read_sock(conn, GFP_ATOMIC) == -ENOMEM)
        queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
out:
    read_unlock(&sk->sk_callback_lock);
    ready(sk, bytes);
}

int rds_tcp_recv_init(void)
{
    rds_tcp_incoming_slab = kmem_cache_create("rds_tcp_incoming",
                    sizeof(struct rds_tcp_incoming),
                    0, 0, NULL);
    if (!rds_tcp_incoming_slab)
        return -ENOMEM;
    return 0;
}

void rds_tcp_recv_exit(void)
{
    kmem_cache_destroy(rds_tcp_incoming_slab);
}