Merge branch 'x86/rdrand' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

[wandboard.git] / net / ceph / messenger.c

#include <linux/ceph/ceph_debug.h>

#include <linux/crc32c.h>
#include <linux/ctype.h>
#include <linux/highmem.h>
#include <linux/inet.h>
#include <linux/kthread.h>
#include <linux/net.h>
#include <linux/slab.h>
#include <linux/socket.h>
#include <linux/string.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/dns_resolver.h>
#include <net/tcp.h>

#include <linux/ceph/libceph.h>
#include <linux/ceph/messenger.h>
#include <linux/ceph/decode.h>
#include <linux/ceph/pagelist.h>
#include <linux/export.h>

/*
 * Ceph uses the messenger to exchange ceph_msg messages with other
 * hosts in the system.  The messenger provides ordered and reliable
 * delivery.  We tolerate TCP disconnects by reconnecting (with
 * exponential backoff) in the case of a fault (disconnection, bad
 * crc, protocol error).  Acks allow sent messages to be discarded by
 * the sender.
 */

/* static tag bytes (protocol control messages) */
static char tag_msg = CEPH_MSGR_TAG_MSG;
static char tag_ack = CEPH_MSGR_TAG_ACK;
static char tag_keepalive = CEPH_MSGR_TAG_KEEPALIVE;

#ifdef CONFIG_LOCKDEP
static struct lock_class_key socket_class;
#endif


static void queue_con(struct ceph_connection *con);
static void con_work(struct work_struct *);
static void ceph_fault(struct ceph_connection *con);

/*
 * nicely render a sockaddr as a string.
 */
#define MAX_ADDR_STR 20
#define MAX_ADDR_STR_LEN 60
static char addr_str[MAX_ADDR_STR][MAX_ADDR_STR_LEN];
static DEFINE_SPINLOCK(addr_str_lock);
static int last_addr_str;

const char *ceph_pr_addr(const struct sockaddr_storage *ss)
{
        int i;
        char *s;
        struct sockaddr_in *in4 = (void *)ss;
        struct sockaddr_in6 *in6 = (void *)ss;

        spin_lock(&addr_str_lock);
        i = last_addr_str++;
        if (last_addr_str == MAX_ADDR_STR)
                last_addr_str = 0;
        spin_unlock(&addr_str_lock);
        s = addr_str[i];

        switch (ss->ss_family) {
        case AF_INET:
                snprintf(s, MAX_ADDR_STR_LEN, "%pI4:%u", &in4->sin_addr,
                         (unsigned int)ntohs(in4->sin_port));
                break;

        case AF_INET6:
                snprintf(s, MAX_ADDR_STR_LEN, "[%pI6c]:%u", &in6->sin6_addr,
                         (unsigned int)ntohs(in6->sin6_port));
                break;

        default:
                snprintf(s, MAX_ADDR_STR_LEN, "(unknown sockaddr family %d)",
                         (int)ss->ss_family);
        }

        return s;
}
EXPORT_SYMBOL(ceph_pr_addr);

static void encode_my_addr(struct ceph_messenger *msgr)
{
        memcpy(&msgr->my_enc_addr, &msgr->inst.addr, sizeof(msgr->my_enc_addr));
        ceph_encode_addr(&msgr->my_enc_addr);
}

/*
 * work queue for all reading and writing to/from the socket.
 */
struct workqueue_struct *ceph_msgr_wq;

int ceph_msgr_init(void)
{
        ceph_msgr_wq = alloc_workqueue("ceph-msgr", WQ_NON_REENTRANT, 0);
        if (!ceph_msgr_wq) {
                pr_err("msgr_init failed to create workqueue\n");
                return -ENOMEM;
        }
        return 0;
}
EXPORT_SYMBOL(ceph_msgr_init);

void ceph_msgr_exit(void)
{
        destroy_workqueue(ceph_msgr_wq);
}
EXPORT_SYMBOL(ceph_msgr_exit);

void ceph_msgr_flush(void)
{
        flush_workqueue(ceph_msgr_wq);
}
EXPORT_SYMBOL(ceph_msgr_flush);


/*
 * socket callback functions
 */

/* data available on socket, or listen socket received a connect */
static void ceph_data_ready(struct sock *sk, int count_unused)
{
        struct ceph_connection *con =
                (struct ceph_connection *)sk->sk_user_data;
        if (sk->sk_state != TCP_CLOSE_WAIT) {
                dout("ceph_data_ready on %p state = %lu, queueing work\n",
                     con, con->state);
                queue_con(con);
        }
}

/* socket has buffer space for writing */
static void ceph_write_space(struct sock *sk)
{
        struct ceph_connection *con =
                (struct ceph_connection *)sk->sk_user_data;

        /* only queue to workqueue if there is data we want to write. */
        if (test_bit(WRITE_PENDING, &con->state)) {
                dout("ceph_write_space %p queueing write work\n", con);
                queue_con(con);
        } else {
                dout("ceph_write_space %p nothing to write\n", con);
        }

        /* since we have our own write_space, clear the SOCK_NOSPACE flag */
        clear_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
}

/* socket's state has changed */
static void ceph_state_change(struct sock *sk)
{
        struct ceph_connection *con =
                (struct ceph_connection *)sk->sk_user_data;

        dout("ceph_state_change %p state = %lu sk_state = %u\n",
             con, con->state, sk->sk_state);

        if (test_bit(CLOSED, &con->state))
                return;

        switch (sk->sk_state) {
        case TCP_CLOSE:
                dout("ceph_state_change TCP_CLOSE\n");
        case TCP_CLOSE_WAIT:
                dout("ceph_state_change TCP_CLOSE_WAIT\n");
                if (test_and_set_bit(SOCK_CLOSED, &con->state) == 0) {
                        if (test_bit(CONNECTING, &con->state))
                                con->error_msg = "connection failed";
                        else
                                con->error_msg = "socket closed";
                        queue_con(con);
                }
                break;
        case TCP_ESTABLISHED:
                dout("ceph_state_change TCP_ESTABLISHED\n");
                queue_con(con);
                break;
        }
}

/*
 * set up socket callbacks
 */
static void set_sock_callbacks(struct socket *sock,
                               struct ceph_connection *con)
{
        struct sock *sk = sock->sk;
        sk->sk_user_data = (void *)con;
        sk->sk_data_ready = ceph_data_ready;
        sk->sk_write_space = ceph_write_space;
        sk->sk_state_change = ceph_state_change;
}


/*
 * socket helpers
 */

/*
 * initiate connection to a remote socket.
 */
static struct socket *ceph_tcp_connect(struct ceph_connection *con)
{
        struct sockaddr_storage *paddr = &con->peer_addr.in_addr;
        struct socket *sock;
        int ret;

        BUG_ON(con->sock);
        ret = sock_create_kern(con->peer_addr.in_addr.ss_family, SOCK_STREAM,
                               IPPROTO_TCP, &sock);
        if (ret)
                return ERR_PTR(ret);
        con->sock = sock;
        sock->sk->sk_allocation = GFP_NOFS;

#ifdef CONFIG_LOCKDEP
        lockdep_set_class(&sock->sk->sk_lock, &socket_class);
#endif

        set_sock_callbacks(sock, con);

        dout("connect %s\n", ceph_pr_addr(&con->peer_addr.in_addr));

        ret = sock->ops->connect(sock, (struct sockaddr *)paddr, sizeof(*paddr),
                                 O_NONBLOCK);
        if (ret == -EINPROGRESS) {
                dout("connect %s EINPROGRESS sk_state = %u\n",
                     ceph_pr_addr(&con->peer_addr.in_addr),
                     sock->sk->sk_state);
                ret = 0;
        }
        if (ret < 0) {
                pr_err("connect %s error %d\n",
                       ceph_pr_addr(&con->peer_addr.in_addr), ret);
                sock_release(sock);
                con->sock = NULL;
                con->error_msg = "connect error";
        }

        if (ret < 0)
                return ERR_PTR(ret);
        return sock;
}

static int ceph_tcp_recvmsg(struct socket *sock, void *buf, size_t len)
{
        struct kvec iov = {buf, len};
        struct msghdr msg = { .msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL };
        int r;

        r = kernel_recvmsg(sock, &msg, &iov, 1, len, msg.msg_flags);
        if (r == -EAGAIN)
                r = 0;
        return r;
}

/*
 * write something.  @more is true if caller will be sending more data
 * shortly.
 */
static int ceph_tcp_sendmsg(struct socket *sock, struct kvec *iov,
                     size_t kvlen, size_t len, int more)
{
        struct msghdr msg = { .msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL };
        int r;

        if (more)
                msg.msg_flags |= MSG_MORE;
        else
                msg.msg_flags |= MSG_EOR;  /* superfluous, but what the hell */

        r = kernel_sendmsg(sock, &msg, iov, kvlen, len);
        if (r == -EAGAIN)
                r = 0;
        return r;
}


/*
 * Shutdown/close the socket for the given connection.
 */
static int con_close_socket(struct ceph_connection *con)
{
        int rc;

        dout("con_close_socket on %p sock %p\n", con, con->sock);
        if (!con->sock)
                return 0;
        set_bit(SOCK_CLOSED, &con->state);
        rc = con->sock->ops->shutdown(con->sock, SHUT_RDWR);
        sock_release(con->sock);
        con->sock = NULL;
        clear_bit(SOCK_CLOSED, &con->state);
        return rc;
}

/*
 * Reset a connection.  Discard all incoming and outgoing messages
 * and clear *_seq state.
 */
static void ceph_msg_remove(struct ceph_msg *msg)
{
        list_del_init(&msg->list_head);
        ceph_msg_put(msg);
}
static void ceph_msg_remove_list(struct list_head *head)
{
        while (!list_empty(head)) {
                struct ceph_msg *msg = list_first_entry(head, struct ceph_msg,
                                                        list_head);
                ceph_msg_remove(msg);
        }
}

static void reset_connection(struct ceph_connection *con)
{
        /* reset connection, out_queue, msg_ and connect_seq */
        /* discard existing out_queue and msg_seq */
        ceph_msg_remove_list(&con->out_queue);
        ceph_msg_remove_list(&con->out_sent);

        if (con->in_msg) {
                ceph_msg_put(con->in_msg);
                con->in_msg = NULL;
        }

        con->connect_seq = 0;
        con->out_seq = 0;
        if (con->out_msg) {
                ceph_msg_put(con->out_msg);
                con->out_msg = NULL;
        }
        con->in_seq = 0;
        con->in_seq_acked = 0;
}

/*
 * mark a peer down.  drop any open connections.
 */
void ceph_con_close(struct ceph_connection *con)
{
        dout("con_close %p peer %s\n", con,
             ceph_pr_addr(&con->peer_addr.in_addr));
        set_bit(CLOSED, &con->state);  /* in case there's queued work */
        clear_bit(STANDBY, &con->state);  /* avoid connect_seq bump */
        clear_bit(LOSSYTX, &con->state);  /* so we retry next connect */
        clear_bit(KEEPALIVE_PENDING, &con->state);
        clear_bit(WRITE_PENDING, &con->state);
        mutex_lock(&con->mutex);
        reset_connection(con);
        con->peer_global_seq = 0;
        cancel_delayed_work(&con->work);
        mutex_unlock(&con->mutex);
        queue_con(con);
}
EXPORT_SYMBOL(ceph_con_close);

/*
 * Reopen a closed connection, with a new peer address.
 */
void ceph_con_open(struct ceph_connection *con, struct ceph_entity_addr *addr)
{
        dout("con_open %p %s\n", con, ceph_pr_addr(&addr->in_addr));
        set_bit(OPENING, &con->state);
        clear_bit(CLOSED, &con->state);
        memcpy(&con->peer_addr, addr, sizeof(*addr));
        con->delay = 0;      /* reset backoff memory */
        queue_con(con);
}
EXPORT_SYMBOL(ceph_con_open);

/*
 * return true if this connection ever successfully opened
 */
bool ceph_con_opened(struct ceph_connection *con)
{
        return con->connect_seq > 0;
}

/*
 * generic get/put
 */
struct ceph_connection *ceph_con_get(struct ceph_connection *con)
{
        dout("con_get %p nref = %d -> %d\n", con,
             atomic_read(&con->nref), atomic_read(&con->nref) + 1);
        if (atomic_inc_not_zero(&con->nref))
                return con;
        return NULL;
}

void ceph_con_put(struct ceph_connection *con)
{
        dout("con_put %p nref = %d -> %d\n", con,
             atomic_read(&con->nref), atomic_read(&con->nref) - 1);
        BUG_ON(atomic_read(&con->nref) == 0);
        if (atomic_dec_and_test(&con->nref)) {
                BUG_ON(con->sock);
                kfree(con);
        }
}

/*
 * initialize a new connection.
 */
void ceph_con_init(struct ceph_messenger *msgr, struct ceph_connection *con)
{
        dout("con_init %p\n", con);
        memset(con, 0, sizeof(*con));
        atomic_set(&con->nref, 1);
        con->msgr = msgr;
        mutex_init(&con->mutex);
        INIT_LIST_HEAD(&con->out_queue);
        INIT_LIST_HEAD(&con->out_sent);
        INIT_DELAYED_WORK(&con->work, con_work);
}
EXPORT_SYMBOL(ceph_con_init);


/*
 * We maintain a global counter to order connection attempts.  Get
 * a unique seq greater than @gt.
 */
static u32 get_global_seq(struct ceph_messenger *msgr, u32 gt)
{
        u32 ret;

        spin_lock(&msgr->global_seq_lock);
        if (msgr->global_seq < gt)
                msgr->global_seq = gt;
        ret = ++msgr->global_seq;
        spin_unlock(&msgr->global_seq_lock);
        return ret;
}


/*
 * Prepare footer for currently outgoing message, and finish things
 * off.  Assumes out_kvec* are already valid.. we just add on to the end.
 */
static void prepare_write_message_footer(struct ceph_connection *con, int v)
{
        struct ceph_msg *m = con->out_msg;

        dout("prepare_write_message_footer %p\n", con);
        con->out_kvec_is_msg = true;
        con->out_kvec[v].iov_base = &m->footer;
        con->out_kvec[v].iov_len = sizeof(m->footer);
        con->out_kvec_bytes += sizeof(m->footer);
        con->out_kvec_left++;
        con->out_more = m->more_to_follow;
        con->out_msg_done = true;
}

/*
 * Prepare headers for the next outgoing message.
 */
static void prepare_write_message(struct ceph_connection *con)
{
        struct ceph_msg *m;
        int v = 0;

        con->out_kvec_bytes = 0;
        con->out_kvec_is_msg = true;
        con->out_msg_done = false;

        /* Sneak an ack in there first?  If we can get it into the same
         * TCP packet that's a good thing. */
        if (con->in_seq > con->in_seq_acked) {
                con->in_seq_acked = con->in_seq;
                con->out_kvec[v].iov_base = &tag_ack;
                con->out_kvec[v++].iov_len = 1;
                con->out_temp_ack = cpu_to_le64(con->in_seq_acked);
                con->out_kvec[v].iov_base = &con->out_temp_ack;
                con->out_kvec[v++].iov_len = sizeof(con->out_temp_ack);
                con->out_kvec_bytes = 1 + sizeof(con->out_temp_ack);
        }

        m = list_first_entry(&con->out_queue,
                       struct ceph_msg, list_head);
        con->out_msg = m;

        /* put message on sent list */
        ceph_msg_get(m);
        list_move_tail(&m->list_head, &con->out_sent);

        /*
         * only assign outgoing seq # if we haven't sent this message
         * yet.  if it is requeued, resend with it's original seq.
         */
        if (m->needs_out_seq) {
                m->hdr.seq = cpu_to_le64(++con->out_seq);
                m->needs_out_seq = false;
        }

        dout("prepare_write_message %p seq %lld type %d len %d+%d+%d %d pgs\n",
             m, con->out_seq, le16_to_cpu(m->hdr.type),
             le32_to_cpu(m->hdr.front_len), le32_to_cpu(m->hdr.middle_len),
             le32_to_cpu(m->hdr.data_len),
             m->nr_pages);
        BUG_ON(le32_to_cpu(m->hdr.front_len) != m->front.iov_len);

        /* tag + hdr + front + middle */
        con->out_kvec[v].iov_base = &tag_msg;
        con->out_kvec[v++].iov_len = 1;
        con->out_kvec[v].iov_base = &m->hdr;
        con->out_kvec[v++].iov_len = sizeof(m->hdr);
        con->out_kvec[v++] = m->front;
        if (m->middle)
                con->out_kvec[v++] = m->middle->vec;
        con->out_kvec_left = v;
        con->out_kvec_bytes += 1 + sizeof(m->hdr) + m->front.iov_len +
                (m->middle ? m->middle->vec.iov_len : 0);
        con->out_kvec_cur = con->out_kvec;

        /* fill in crc (except data pages), footer */
        con->out_msg->hdr.crc =
                cpu_to_le32(crc32c(0, (void *)&m->hdr,
                                      sizeof(m->hdr) - sizeof(m->hdr.crc)));
        con->out_msg->footer.flags = CEPH_MSG_FOOTER_COMPLETE;
        con->out_msg->footer.front_crc =
                cpu_to_le32(crc32c(0, m->front.iov_base, m->front.iov_len));
        if (m->middle)
                con->out_msg->footer.middle_crc =
                        cpu_to_le32(crc32c(0, m->middle->vec.iov_base,
                                           m->middle->vec.iov_len));
        else
                con->out_msg->footer.middle_crc = 0;
        con->out_msg->footer.data_crc = 0;
        dout("prepare_write_message front_crc %u data_crc %u\n",
             le32_to_cpu(con->out_msg->footer.front_crc),
             le32_to_cpu(con->out_msg->footer.middle_crc));

        /* is there a data payload? */
        if (le32_to_cpu(m->hdr.data_len) > 0) {
                /* initialize page iterator */
                con->out_msg_pos.page = 0;
                if (m->pages)
                        con->out_msg_pos.page_pos = m->page_alignment;
                else
                        con->out_msg_pos.page_pos = 0;
                con->out_msg_pos.data_pos = 0;
                con->out_msg_pos.did_page_crc = 0;
                con->out_more = 1;  /* data + footer will follow */
        } else {
                /* no, queue up footer too and be done */
                prepare_write_message_footer(con, v);
        }

        set_bit(WRITE_PENDING, &con->state);
}

/*
 * Prepare an ack.
 */
static void prepare_write_ack(struct ceph_connection *con)
{
        dout("prepare_write_ack %p %llu -> %llu\n", con,
             con->in_seq_acked, con->in_seq);
        con->in_seq_acked = con->in_seq;

        con->out_kvec[0].iov_base = &tag_ack;
        con->out_kvec[0].iov_len = 1;
        con->out_temp_ack = cpu_to_le64(con->in_seq_acked);
        con->out_kvec[1].iov_base = &con->out_temp_ack;
        con->out_kvec[1].iov_len = sizeof(con->out_temp_ack);
        con->out_kvec_left = 2;
        con->out_kvec_bytes = 1 + sizeof(con->out_temp_ack);
        con->out_kvec_cur = con->out_kvec;
        con->out_more = 1;  /* more will follow.. eventually.. */
        set_bit(WRITE_PENDING, &con->state);
}

/*
 * Prepare to write keepalive byte.
 */
static void prepare_write_keepalive(struct ceph_connection *con)
{
        dout("prepare_write_keepalive %p\n", con);
        con->out_kvec[0].iov_base = &tag_keepalive;
        con->out_kvec[0].iov_len = 1;
        con->out_kvec_left = 1;
        con->out_kvec_bytes = 1;
        con->out_kvec_cur = con->out_kvec;
        set_bit(WRITE_PENDING, &con->state);
}

/*
 * Connection negotiation.
 */

static int prepare_connect_authorizer(struct ceph_connection *con)
{
        void *auth_buf;
        int auth_len = 0;
        int auth_protocol = 0;

        mutex_unlock(&con->mutex);
        if (con->ops->get_authorizer)
                con->ops->get_authorizer(con, &auth_buf, &auth_len,
                                         &auth_protocol, &con->auth_reply_buf,
                                         &con->auth_reply_buf_len,
                                         con->auth_retry);
        mutex_lock(&con->mutex);

        if (test_bit(CLOSED, &con->state) ||
            test_bit(OPENING, &con->state))
                return -EAGAIN;

        con->out_connect.authorizer_protocol = cpu_to_le32(auth_protocol);
        con->out_connect.authorizer_len = cpu_to_le32(auth_len);

        if (auth_len) {
                con->out_kvec[con->out_kvec_left].iov_base = auth_buf;
                con->out_kvec[con->out_kvec_left].iov_len = auth_len;
                con->out_kvec_left++;
                con->out_kvec_bytes += auth_len;
        }
        return 0;
}

/*
 * We connected to a peer and are saying hello.
 */
static void prepare_write_banner(struct ceph_messenger *msgr,
                                 struct ceph_connection *con)
{
        int len = strlen(CEPH_BANNER);

        con->out_kvec[0].iov_base = CEPH_BANNER;
        con->out_kvec[0].iov_len = len;
        con->out_kvec[1].iov_base = &msgr->my_enc_addr;
        con->out_kvec[1].iov_len = sizeof(msgr->my_enc_addr);
        con->out_kvec_left = 2;
        con->out_kvec_bytes = len + sizeof(msgr->my_enc_addr);
        con->out_kvec_cur = con->out_kvec;
        con->out_more = 0;
        set_bit(WRITE_PENDING, &con->state);
}

static int prepare_write_connect(struct ceph_messenger *msgr,
                                 struct ceph_connection *con,
                                 int after_banner)
{
        unsigned global_seq = get_global_seq(con->msgr, 0);
        int proto;

        switch (con->peer_name.type) {
        case CEPH_ENTITY_TYPE_MON:
                proto = CEPH_MONC_PROTOCOL;
                break;
        case CEPH_ENTITY_TYPE_OSD:
                proto = CEPH_OSDC_PROTOCOL;
                break;
        case CEPH_ENTITY_TYPE_MDS:
                proto = CEPH_MDSC_PROTOCOL;
                break;
        default:
                BUG();
        }

        dout("prepare_write_connect %p cseq=%d gseq=%d proto=%d\n", con,
             con->connect_seq, global_seq, proto);

        con->out_connect.features = cpu_to_le64(msgr->supported_features);
        con->out_connect.host_type = cpu_to_le32(CEPH_ENTITY_TYPE_CLIENT);
        con->out_connect.connect_seq = cpu_to_le32(con->connect_seq);
        con->out_connect.global_seq = cpu_to_le32(global_seq);
        con->out_connect.protocol_version = cpu_to_le32(proto);
        con->out_connect.flags = 0;

        if (!after_banner) {
                con->out_kvec_left = 0;
                con->out_kvec_bytes = 0;
        }
        con->out_kvec[con->out_kvec_left].iov_base = &con->out_connect;
        con->out_kvec[con->out_kvec_left].iov_len = sizeof(con->out_connect);
        con->out_kvec_left++;
        con->out_kvec_bytes += sizeof(con->out_connect);
        con->out_kvec_cur = con->out_kvec;
        con->out_more = 0;
        set_bit(WRITE_PENDING, &con->state);

        return prepare_connect_authorizer(con);
}


/*
 * write as much of pending kvecs to the socket as we can.
 *  1 -> done
 *  0 -> socket full, but more to do
 * <0 -> error
 */
static int write_partial_kvec(struct ceph_connection *con)
{
        int ret;

        dout("write_partial_kvec %p %d left\n", con, con->out_kvec_bytes);
        while (con->out_kvec_bytes > 0) {
                ret = ceph_tcp_sendmsg(con->sock, con->out_kvec_cur,
                                       con->out_kvec_left, con->out_kvec_bytes,
                                       con->out_more);
                if (ret <= 0)
                        goto out;
                con->out_kvec_bytes -= ret;
                if (con->out_kvec_bytes == 0)
                        break;            /* done */
                while (ret > 0) {
                        if (ret >= con->out_kvec_cur->iov_len) {
                                ret -= con->out_kvec_cur->iov_len;
                                con->out_kvec_cur++;
                                con->out_kvec_left--;
                        } else {
                                con->out_kvec_cur->iov_len -= ret;
                                con->out_kvec_cur->iov_base += ret;
                                ret = 0;
                                break;
                        }
                }
        }
        con->out_kvec_left = 0;
        con->out_kvec_is_msg = false;
        ret = 1;
out:
        dout("write_partial_kvec %p %d left in %d kvecs ret = %d\n", con,
             con->out_kvec_bytes, con->out_kvec_left, ret);
        return ret;  /* done! */
}

#ifdef CONFIG_BLOCK
static void init_bio_iter(struct bio *bio, struct bio **iter, int *seg)
{
        if (!bio) {
                *iter = NULL;
                *seg = 0;
                return;
        }
        *iter = bio;
        *seg = bio->bi_idx;
}

static void iter_bio_next(struct bio **bio_iter, int *seg)
{
        if (*bio_iter == NULL)
                return;

        BUG_ON(*seg >= (*bio_iter)->bi_vcnt);

        (*seg)++;
        if (*seg == (*bio_iter)->bi_vcnt)
                init_bio_iter((*bio_iter)->bi_next, bio_iter, seg);
}
#endif

/*
 * Write as much message data payload as we can.  If we finish, queue
 * up the footer.
 *  1 -> done, footer is now queued in out_kvec[].
 *  0 -> socket full, but more to do
 * <0 -> error
 */
static int write_partial_msg_pages(struct ceph_connection *con)
{
        struct ceph_msg *msg = con->out_msg;
        unsigned data_len = le32_to_cpu(msg->hdr.data_len);
        size_t len;
        int crc = con->msgr->nocrc;
        int ret;
        int total_max_write;
        int in_trail = 0;
        size_t trail_len = (msg->trail ? msg->trail->length : 0);

        dout("write_partial_msg_pages %p msg %p page %d/%d offset %d\n",
             con, con->out_msg, con->out_msg_pos.page, con->out_msg->nr_pages,
             con->out_msg_pos.page_pos);

#ifdef CONFIG_BLOCK
        if (msg->bio && !msg->bio_iter)
                init_bio_iter(msg->bio, &msg->bio_iter, &msg->bio_seg);
#endif

        while (data_len > con->out_msg_pos.data_pos) {
                struct page *page = NULL;
                void *kaddr = NULL;
                int max_write = PAGE_SIZE;
                int page_shift = 0;

                total_max_write = data_len - trail_len -
                        con->out_msg_pos.data_pos;

                /*
                 * if we are calculating the data crc (the default), we need
                 * to map the page.  if our pages[] has been revoked, use the
                 * zero page.
                 */

                /* have we reached the trail part of the data? */
                if (con->out_msg_pos.data_pos >= data_len - trail_len) {
                        in_trail = 1;

                        total_max_write = data_len - con->out_msg_pos.data_pos;

                        page = list_first_entry(&msg->trail->head,
                                                struct page, lru);
                        if (crc)
                                kaddr = kmap(page);
                        max_write = PAGE_SIZE;
                } else if (msg->pages) {
                        page = msg->pages[con->out_msg_pos.page];
                        if (crc)
                                kaddr = kmap(page);
                } else if (msg->pagelist) {
                        page = list_first_entry(&msg->pagelist->head,
                                                struct page, lru);
                        if (crc)
                                kaddr = kmap(page);
#ifdef CONFIG_BLOCK
                } else if (msg->bio) {
                        struct bio_vec *bv;

                        bv = bio_iovec_idx(msg->bio_iter, msg->bio_seg);
                        page = bv->bv_page;
                        page_shift = bv->bv_offset;
                        if (crc)
                                kaddr = kmap(page) + page_shift;
                        max_write = bv->bv_len;
#endif
                } else {
                        page = con->msgr->zero_page;
                        if (crc)
                                kaddr = page_address(con->msgr->zero_page);
                }
                len = min_t(int, max_write - con->out_msg_pos.page_pos,
                            total_max_write);

                if (crc && !con->out_msg_pos.did_page_crc) {
                        void *base = kaddr + con->out_msg_pos.page_pos;
                        u32 tmpcrc = le32_to_cpu(con->out_msg->footer.data_crc);

                        BUG_ON(kaddr == NULL);
                        con->out_msg->footer.data_crc =
                                cpu_to_le32(crc32c(tmpcrc, base, len));
                        con->out_msg_pos.did_page_crc = 1;
                }
                ret = kernel_sendpage(con->sock, page,
                                      con->out_msg_pos.page_pos + page_shift,
                                      len,
                                      MSG_DONTWAIT | MSG_NOSIGNAL |
                                      MSG_MORE);

                if (crc &&
                    (msg->pages || msg->pagelist || msg->bio || in_trail))
                        kunmap(page);

                if (ret == -EAGAIN)
                        ret = 0;
                if (ret <= 0)
                        goto out;

                con->out_msg_pos.data_pos += ret;
                con->out_msg_pos.page_pos += ret;
                if (ret == len) {
                        con->out_msg_pos.page_pos = 0;
                        con->out_msg_pos.page++;
                        con->out_msg_pos.did_page_crc = 0;
                        if (in_trail)
                                list_move_tail(&page->lru,
                                               &msg->trail->head);
                        else if (msg->pagelist)
                                list_move_tail(&page->lru,
                                               &msg->pagelist->head);
#ifdef CONFIG_BLOCK
                        else if (msg->bio)
                                iter_bio_next(&msg->bio_iter, &msg->bio_seg);
#endif
                }
        }

        dout("write_partial_msg_pages %p msg %p done\n", con, msg);

        /* prepare and queue up footer, too */
        if (!crc)
                con->out_msg->footer.flags |= CEPH_MSG_FOOTER_NOCRC;
        con->out_kvec_bytes = 0;
        con->out_kvec_left = 0;
        con->out_kvec_cur = con->out_kvec;
        prepare_write_message_footer(con, 0);
        ret = 1;
out:
        return ret;
}

/*
 * write some zeros
 */
static int write_partial_skip(struct ceph_connection *con)
{
        int ret;

        while (con->out_skip > 0) {
                struct kvec iov = {
                        .iov_base = page_address(con->msgr->zero_page),
                        .iov_len = min(con->out_skip, (int)PAGE_CACHE_SIZE)
                };

                ret = ceph_tcp_sendmsg(con->sock, &iov, 1, iov.iov_len, 1);
                if (ret <= 0)
                        goto out;
                con->out_skip -= ret;
        }
        ret = 1;
out:
        return ret;
}

/*
 * Prepare to read connection handshake, or an ack.
 */
static void prepare_read_banner(struct ceph_connection *con)
{
        dout("prepare_read_banner %p\n", con);
        con->in_base_pos = 0;
}

static void prepare_read_connect(struct ceph_connection *con)
{
        dout("prepare_read_connect %p\n", con);
        con->in_base_pos = 0;
}

static void prepare_read_ack(struct ceph_connection *con)
{
        dout("prepare_read_ack %p\n", con);
        con->in_base_pos = 0;
}

static void prepare_read_tag(struct ceph_connection *con)
{
        dout("prepare_read_tag %p\n", con);
        con->in_base_pos = 0;
        con->in_tag = CEPH_MSGR_TAG_READY;
}

/*
 * Prepare to read a message.
 */
static int prepare_read_message(struct ceph_connection *con)
{
        dout("prepare_read_message %p\n", con);
        BUG_ON(con->in_msg != NULL);
        con->in_base_pos = 0;
        con->in_front_crc = con->in_middle_crc = con->in_data_crc = 0;
        return 0;
}


static int read_partial(struct ceph_connection *con,
                        int *to, int size, void *object)
{
        *to += size;
        while (con->in_base_pos < *to) {
                int left = *to - con->in_base_pos;
                int have = size - left;
                int ret = ceph_tcp_recvmsg(con->sock, object + have, left);
                if (ret <= 0)
                        return ret;
                con->in_base_pos += ret;
        }
        return 1;
}


/*
 * Read all or part of the connect-side handshake on a new connection
 */
static int read_partial_banner(struct ceph_connection *con)
{
        int ret, to = 0;

        dout("read_partial_banner %p at %d\n", con, con->in_base_pos);

        /* peer's banner */
        ret = read_partial(con, &to, strlen(CEPH_BANNER), con->in_banner);
        if (ret <= 0)
                goto out;
        ret = read_partial(con, &to, sizeof(con->actual_peer_addr),
                           &con->actual_peer_addr);
        if (ret <= 0)
                goto out;
        ret = read_partial(con, &to, sizeof(con->peer_addr_for_me),
                           &con->peer_addr_for_me);
        if (ret <= 0)
                goto out;
out:
        return ret;
}

static int read_partial_connect(struct ceph_connection *con)
{
        int ret, to = 0;

        dout("read_partial_connect %p at %d\n", con, con->in_base_pos);

        ret = read_partial(con, &to, sizeof(con->in_reply), &con->in_reply);
        if (ret <= 0)
                goto out;
        ret = read_partial(con, &to, le32_to_cpu(con->in_reply.authorizer_len),
                           con->auth_reply_buf);
        if (ret <= 0)
                goto out;

        dout("read_partial_connect %p tag %d, con_seq = %u, g_seq = %u\n",
             con, (int)con->in_reply.tag,
             le32_to_cpu(con->in_reply.connect_seq),
             le32_to_cpu(con->in_reply.global_seq));
out:
        return ret;

}

/*
 * Verify the hello banner looks okay.
 */
static int verify_hello(struct ceph_connection *con)
{
        if (memcmp(con->in_banner, CEPH_BANNER, strlen(CEPH_BANNER))) {
                pr_err("connect to %s got bad banner\n",
                       ceph_pr_addr(&con->peer_addr.in_addr));
                con->error_msg = "protocol error, bad banner";
                return -1;
        }
        return 0;
}

static bool addr_is_blank(struct sockaddr_storage *ss)
{
        switch (ss->ss_family) {
        case AF_INET:
                return ((struct sockaddr_in *)ss)->sin_addr.s_addr == 0;
        case AF_INET6:
                return
                     ((struct sockaddr_in6 *)ss)->sin6_addr.s6_addr32[0] == 0 &&
                     ((struct sockaddr_in6 *)ss)->sin6_addr.s6_addr32[1] == 0 &&
                     ((struct sockaddr_in6 *)ss)->sin6_addr.s6_addr32[2] == 0 &&
                     ((struct sockaddr_in6 *)ss)->sin6_addr.s6_addr32[3] == 0;
        }
        return false;
}

static int addr_port(struct sockaddr_storage *ss)
{
        switch (ss->ss_family) {
        case AF_INET:
                return ntohs(((struct sockaddr_in *)ss)->sin_port);
        case AF_INET6:
                return ntohs(((struct sockaddr_in6 *)ss)->sin6_port);
        }
        return 0;
}

static void addr_set_port(struct sockaddr_storage *ss, int p)
{
        switch (ss->ss_family) {
        case AF_INET:
                ((struct sockaddr_in *)ss)->sin_port = htons(p);
                break;
        case AF_INET6:
                ((struct sockaddr_in6 *)ss)->sin6_port = htons(p);
                break;
        }
}

/*
 * Unlike other *_pton function semantics, zero indicates success.
 */
static int ceph_pton(const char *str, size_t len, struct sockaddr_storage *ss,
                char delim, const char **ipend)
{
        struct sockaddr_in *in4 = (void *)ss;
        struct sockaddr_in6 *in6 = (void *)ss;

        memset(ss, 0, sizeof(*ss));

        if (in4_pton(str, len, (u8 *)&in4->sin_addr.s_addr, delim, ipend)) {
                ss->ss_family = AF_INET;
                return 0;
        }

        if (in6_pton(str, len, (u8 *)&in6->sin6_addr.s6_addr, delim, ipend)) {
                ss->ss_family = AF_INET6;
                return 0;
        }

        return -EINVAL;
}

/*
 * Extract hostname string and resolve using kernel DNS facility.
 */
#ifdef CONFIG_CEPH_LIB_USE_DNS_RESOLVER
static int ceph_dns_resolve_name(const char *name, size_t namelen,
                struct sockaddr_storage *ss, char delim, const char **ipend)
{
        const char *end, *delim_p;
        char *colon_p, *ip_addr = NULL;
        int ip_len, ret;

        /*
         * The end of the hostname occurs immediately preceding the delimiter or
         * the port marker (':') where the delimiter takes precedence.
         */
        delim_p = memchr(name, delim, namelen);
        colon_p = memchr(name, ':', namelen);

        if (delim_p && colon_p)
                end = delim_p < colon_p ? delim_p : colon_p;
        else if (!delim_p && colon_p)
                end = colon_p;
        else {
                end = delim_p;
                if (!end) /* case: hostname:/ */
                        end = name + namelen;
        }

        if (end <= name)
                return -EINVAL;

        /* do dns_resolve upcall */
        ip_len = dns_query(NULL, name, end - name, NULL, &ip_addr, NULL);
        if (ip_len > 0)
                ret = ceph_pton(ip_addr, ip_len, ss, -1, NULL);
        else
                ret = -ESRCH;

        kfree(ip_addr);

        *ipend = end;

        pr_info("resolve '%.*s' (ret=%d): %s\n", (int)(end - name), name,
                        ret, ret ? "failed" : ceph_pr_addr(ss));

        return ret;
}
#else
static inline int ceph_dns_resolve_name(const char *name, size_t namelen,
                struct sockaddr_storage *ss, char delim, const char **ipend)
{
        return -EINVAL;
}
#endif

/*
 * Parse a server name (IP or hostname). If a valid IP address is not found
 * then try to extract a hostname to resolve using userspace DNS upcall.
 */
static int ceph_parse_server_name(const char *name, size_t namelen,
                        struct sockaddr_storage *ss, char delim, const char **ipend)
{
        int ret;

        ret = ceph_pton(name, namelen, ss, delim, ipend);
        if (ret)
                ret = ceph_dns_resolve_name(name, namelen, ss, delim, ipend);

        return ret;
}

/*
 * Parse an ip[:port] list into an addr array.  Use the default
 * monitor port if a port isn't specified.
 */
int ceph_parse_ips(const char *c, const char *end,
                   struct ceph_entity_addr *addr,
                   int max_count, int *count)
{
        int i, ret = -EINVAL;
        const char *p = c;

        dout("parse_ips on '%.*s'\n", (int)(end-c), c);
        for (i = 0; i < max_count; i++) {
                const char *ipend;
                struct sockaddr_storage *ss = &addr[i].in_addr;
                int port;
                char delim = ',';

                if (*p == '[') {
                        delim = ']';
                        p++;
                }

                ret = ceph_parse_server_name(p, end - p, ss, delim, &ipend);
                if (ret)
                        goto bad;
                ret = -EINVAL;

                p = ipend;

                if (delim == ']') {
                        if (*p != ']') {
                                dout("missing matching ']'\n");
                                goto bad;
                        }
                        p++;
                }

                /* port? */
                if (p < end && *p == ':') {
                        port = 0;
                        p++;
                        while (p < end && *p >= '0' && *p <= '9') {
                                port = (port * 10) + (*p - '0');
                                p++;
                        }
                        if (port > 65535 || port == 0)
                                goto bad;
                } else {
                        port = CEPH_MON_PORT;
                }

                addr_set_port(ss, port);

                dout("parse_ips got %s\n", ceph_pr_addr(ss));

                if (p == end)
                        break;
                if (*p != ',')
                        goto bad;
                p++;
        }

        if (p != end)
                goto bad;

        if (count)
                *count = i + 1;
        return 0;

bad:
        pr_err("parse_ips bad ip '%.*s'\n", (int)(end - c), c);
        return ret;
}
EXPORT_SYMBOL(ceph_parse_ips);

static int process_banner(struct ceph_connection *con)
{
        dout("process_banner on %p\n", con);

        if (verify_hello(con) < 0)
                return -1;

        ceph_decode_addr(&con->actual_peer_addr);
        ceph_decode_addr(&con->peer_addr_for_me);

        /*
         * Make sure the other end is who we wanted.  note that the other
         * end may not yet know their ip address, so if it's 0.0.0.0, give
         * them the benefit of the doubt.
         */
        if (memcmp(&con->peer_addr, &con->actual_peer_addr,
                   sizeof(con->peer_addr)) != 0 &&
            !(addr_is_blank(&con->actual_peer_addr.in_addr) &&
              con->actual_peer_addr.nonce == con->peer_addr.nonce)) {
                pr_warning("wrong peer, want %s/%d, got %s/%d\n",
                           ceph_pr_addr(&con->peer_addr.in_addr),
                           (int)le32_to_cpu(con->peer_addr.nonce),
                           ceph_pr_addr(&con->actual_peer_addr.in_addr),
                           (int)le32_to_cpu(con->actual_peer_addr.nonce));
                con->error_msg = "wrong peer at address";
                return -1;
        }

        /*
         * did we learn our address?
         */
        if (addr_is_blank(&con->msgr->inst.addr.in_addr)) {
                int port = addr_port(&con->msgr->inst.addr.in_addr);

                memcpy(&con->msgr->inst.addr.in_addr,
                       &con->peer_addr_for_me.in_addr,
                       sizeof(con->peer_addr_for_me.in_addr));
                addr_set_port(&con->msgr->inst.addr.in_addr, port);
                encode_my_addr(con->msgr);
                dout("process_banner learned my addr is %s\n",
                     ceph_pr_addr(&con->msgr->inst.addr.in_addr));
        }

        set_bit(NEGOTIATING, &con->state);
        prepare_read_connect(con);
        return 0;
}

static void fail_protocol(struct ceph_connection *con)
{
        reset_connection(con);
        set_bit(CLOSED, &con->state);  /* in case there's queued work */

        mutex_unlock(&con->mutex);
        if (con->ops->bad_proto)
                con->ops->bad_proto(con);
        mutex_lock(&con->mutex);
}

static int process_connect(struct ceph_connection *con)
{
        u64 sup_feat = con->msgr->supported_features;
        u64 req_feat = con->msgr->required_features;
        u64 server_feat = le64_to_cpu(con->in_reply.features);
        int ret;

        dout("process_connect on %p tag %d\n", con, (int)con->in_tag);

        switch (con->in_reply.tag) {
        case CEPH_MSGR_TAG_FEATURES:
                pr_err("%s%lld %s feature set mismatch,"
                       " my %llx < server's %llx, missing %llx\n",
                       ENTITY_NAME(con->peer_name),
                       ceph_pr_addr(&con->peer_addr.in_addr),
                       sup_feat, server_feat, server_feat & ~sup_feat);
                con->error_msg = "missing required protocol features";
                fail_protocol(con);
                return -1;

        case CEPH_MSGR_TAG_BADPROTOVER:
                pr_err("%s%lld %s protocol version mismatch,"
                       " my %d != server's %d\n",
                       ENTITY_NAME(con->peer_name),
                       ceph_pr_addr(&con->peer_addr.in_addr),
                       le32_to_cpu(con->out_connect.protocol_version),
                       le32_to_cpu(con->in_reply.protocol_version));
                con->error_msg = "protocol version mismatch";
                fail_protocol(con);
                return -1;

        case CEPH_MSGR_TAG_BADAUTHORIZER:
                con->auth_retry++;
                dout("process_connect %p got BADAUTHORIZER attempt %d\n", con,
                     con->auth_retry);
                if (con->auth_retry == 2) {
                        con->error_msg = "connect authorization failure";
                        return -1;
                }
                con->auth_retry = 1;
                ret = prepare_write_connect(con->msgr, con, 0);
                if (ret < 0)
                        return ret;
                prepare_read_connect(con);
                break;

        case CEPH_MSGR_TAG_RESETSESSION:
                /*
                 * If we connected with a large connect_seq but the peer
                 * has no record of a session with us (no connection, or
                 * connect_seq == 0), they will send RESETSESION to indicate
                 * that they must have reset their session, and may have
                 * dropped messages.
                 */
                dout("process_connect got RESET peer seq %u\n",
                     le32_to_cpu(con->in_connect.connect_seq));
                pr_err("%s%lld %s connection reset\n",
                       ENTITY_NAME(con->peer_name),
                       ceph_pr_addr(&con->peer_addr.in_addr));
                reset_connection(con);
                prepare_write_connect(con->msgr, con, 0);
                prepare_read_connect(con);

                /* Tell ceph about it. */
                mutex_unlock(&con->mutex);
                pr_info("reset on %s%lld\n", ENTITY_NAME(con->peer_name));
                if (con->ops->peer_reset)
                        con->ops->peer_reset(con);
                mutex_lock(&con->mutex);
                if (test_bit(CLOSED, &con->state) ||
                    test_bit(OPENING, &con->state))
                        return -EAGAIN;
                break;

        case CEPH_MSGR_TAG_RETRY_SESSION:
                /*
                 * If we sent a smaller connect_seq than the peer has, try
                 * again with a larger value.
                 */
                dout("process_connect got RETRY my seq = %u, peer_seq = %u\n",
                     le32_to_cpu(con->out_connect.connect_seq),
                     le32_to_cpu(con->in_connect.connect_seq));
                con->connect_seq = le32_to_cpu(con->in_connect.connect_seq);
                prepare_write_connect(con->msgr, con, 0);
                prepare_read_connect(con);
                break;

        case CEPH_MSGR_TAG_RETRY_GLOBAL:
                /*
                 * If we sent a smaller global_seq than the peer has, try
                 * again with a larger value.
                 */
                dout("process_connect got RETRY_GLOBAL my %u peer_gseq %u\n",
                     con->peer_global_seq,
                     le32_to_cpu(con->in_connect.global_seq));
                get_global_seq(con->msgr,
                               le32_to_cpu(con->in_connect.global_seq));
                prepare_write_connect(con->msgr, con, 0);
                prepare_read_connect(con);
                break;

        case CEPH_MSGR_TAG_READY:
                if (req_feat & ~server_feat) {
                        pr_err("%s%lld %s protocol feature mismatch,"
                               " my required %llx > server's %llx, need %llx\n",
                               ENTITY_NAME(con->peer_name),
                               ceph_pr_addr(&con->peer_addr.in_addr),
                               req_feat, server_feat, req_feat & ~server_feat);
                        con->error_msg = "missing required protocol features";
                        fail_protocol(con);
                        return -1;
                }
                clear_bit(CONNECTING, &con->state);
                con->peer_global_seq = le32_to_cpu(con->in_reply.global_seq);
                con->connect_seq++;
                con->peer_features = server_feat;
                dout("process_connect got READY gseq %d cseq %d (%d)\n",
                     con->peer_global_seq,
                     le32_to_cpu(con->in_reply.connect_seq),
                     con->connect_seq);
                WARN_ON(con->connect_seq !=
                        le32_to_cpu(con->in_reply.connect_seq));

                if (con->in_reply.flags & CEPH_MSG_CONNECT_LOSSY)
                        set_bit(LOSSYTX, &con->state);

                prepare_read_tag(con);
                break;

        case CEPH_MSGR_TAG_WAIT:
                /*
                 * If there is a connection race (we are opening
                 * connections to each other), one of us may just have
                 * to WAIT.  This shouldn't happen if we are the
                 * client.
                 */
                pr_err("process_connect got WAIT as client\n");
                con->error_msg = "protocol error, got WAIT as client";
                return -1;

        default:
                pr_err("connect protocol error, will retry\n");
                con->error_msg = "protocol error, garbage tag during connect";
                return -1;
        }
        return 0;
}


/*
 * read (part of) an ack
 */
static int read_partial_ack(struct ceph_connection *con)
{
        int to = 0;

        return read_partial(con, &to, sizeof(con->in_temp_ack),
                            &con->in_temp_ack);
}


/*
 * We can finally discard anything that's been acked.
 */
static void process_ack(struct ceph_connection *con)
{
        struct ceph_msg *m;
        u64 ack = le64_to_cpu(con->in_temp_ack);
        u64 seq;

        while (!list_empty(&con->out_sent)) {
                m = list_first_entry(&con->out_sent, struct ceph_msg,
                                     list_head);
                seq = le64_to_cpu(m->hdr.seq);
                if (seq > ack)
                        break;
                dout("got ack for seq %llu type %d at %p\n", seq,
                     le16_to_cpu(m->hdr.type), m);
                m->ack_stamp = jiffies;
                ceph_msg_remove(m);
        }
        prepare_read_tag(con);
}




static int read_partial_message_section(struct ceph_connection *con,
                                        struct kvec *section,
                                        unsigned int sec_len, u32 *crc)
{
        int ret, left;

        BUG_ON(!section);

        while (section->iov_len < sec_len) {
                BUG_ON(section->iov_base == NULL);
                left = sec_len - section->iov_len;
                ret = ceph_tcp_recvmsg(con->sock, (char *)section->iov_base +
                                       section->iov_len, left);
                if (ret <= 0)
                        return ret;
                section->iov_len += ret;
                if (section->iov_len == sec_len)
                        *crc = crc32c(0, section->iov_base,
                                      section->iov_len);
        }

        return 1;
}

static struct ceph_msg *ceph_alloc_msg(struct ceph_connection *con,
                                struct ceph_msg_header *hdr,
                                int *skip);


static int read_partial_message_pages(struct ceph_connection *con,
                                      struct page **pages,
                                      unsigned data_len, int datacrc)
{
        void *p;
        int ret;
        int left;

        left = min((int)(data_len - con->in_msg_pos.data_pos),
                   (int)(PAGE_SIZE - con->in_msg_pos.page_pos));
        /* (page) data */
        BUG_ON(pages == NULL);
        p = kmap(pages[con->in_msg_pos.page]);
        ret = ceph_tcp_recvmsg(con->sock, p + con->in_msg_pos.page_pos,
                               left);
        if (ret > 0 && datacrc)
                con->in_data_crc =
                        crc32c(con->in_data_crc,
                                  p + con->in_msg_pos.page_pos, ret);
        kunmap(pages[con->in_msg_pos.page]);
        if (ret <= 0)
                return ret;
        con->in_msg_pos.data_pos += ret;
        con->in_msg_pos.page_pos += ret;
        if (con->in_msg_pos.page_pos == PAGE_SIZE) {
                con->in_msg_pos.page_pos = 0;
                con->in_msg_pos.page++;
        }

        return ret;
}

#ifdef CONFIG_BLOCK
static int read_partial_message_bio(struct ceph_connection *con,
                                    struct bio **bio_iter, int *bio_seg,
                                    unsigned data_len, int datacrc)
{
        struct bio_vec *bv = bio_iovec_idx(*bio_iter, *bio_seg);
        void *p;
        int ret, left;

        if (IS_ERR(bv))
                return PTR_ERR(bv);

        left = min((int)(data_len - con->in_msg_pos.data_pos),
                   (int)(bv->bv_len - con->in_msg_pos.page_pos));

        p = kmap(bv->bv_page) + bv->bv_offset;

        ret = ceph_tcp_recvmsg(con->sock, p + con->in_msg_pos.page_pos,
                               left);
        if (ret > 0 && datacrc)
                con->in_data_crc =
                        crc32c(con->in_data_crc,
                                  p + con->in_msg_pos.page_pos, ret);
        kunmap(bv->bv_page);
        if (ret <= 0)
                return ret;
        con->in_msg_pos.data_pos += ret;
        con->in_msg_pos.page_pos += ret;
        if (con->in_msg_pos.page_pos == bv->bv_len) {
                con->in_msg_pos.page_pos = 0;
                iter_bio_next(bio_iter, bio_seg);
        }

        return ret;
}
#endif

/*
 * read (part of) a message.
 */
static int read_partial_message(struct ceph_connection *con)
{
        struct ceph_msg *m = con->in_msg;
        int ret;
        int to, left;
        unsigned front_len, middle_len, data_len;
        int datacrc = con->msgr->nocrc;
        int skip;
        u64 seq;

        dout("read_partial_message con %p msg %p\n", con, m);

        /* header */
        while (con->in_base_pos < sizeof(con->in_hdr)) {
                left = sizeof(con->in_hdr) - con->in_base_pos;
                ret = ceph_tcp_recvmsg(con->sock,
                                       (char *)&con->in_hdr + con->in_base_pos,
                                       left);
                if (ret <= 0)
                        return ret;
                con->in_base_pos += ret;
                if (con->in_base_pos == sizeof(con->in_hdr)) {
                        u32 crc = crc32c(0, (void *)&con->in_hdr,
                                 sizeof(con->in_hdr) - sizeof(con->in_hdr.crc));
                        if (crc != le32_to_cpu(con->in_hdr.crc)) {
                                pr_err("read_partial_message bad hdr "
                                       " crc %u != expected %u\n",
                                       crc, con->in_hdr.crc);
                                return -EBADMSG;
                        }
                }
        }
        front_len = le32_to_cpu(con->in_hdr.front_len);
        if (front_len > CEPH_MSG_MAX_FRONT_LEN)
                return -EIO;
        middle_len = le32_to_cpu(con->in_hdr.middle_len);
        if (middle_len > CEPH_MSG_MAX_DATA_LEN)
                return -EIO;
        data_len = le32_to_cpu(con->in_hdr.data_len);
        if (data_len > CEPH_MSG_MAX_DATA_LEN)
                return -EIO;

        /* verify seq# */
        seq = le64_to_cpu(con->in_hdr.seq);
        if ((s64)seq - (s64)con->in_seq < 1) {
                pr_info("skipping %s%lld %s seq %lld expected %lld\n",
                        ENTITY_NAME(con->peer_name),
                        ceph_pr_addr(&con->peer_addr.in_addr),
                        seq, con->in_seq + 1);
                con->in_base_pos = -front_len - middle_len - data_len -
                        sizeof(m->footer);
                con->in_tag = CEPH_MSGR_TAG_READY;
                return 0;
        } else if ((s64)seq - (s64)con->in_seq > 1) {
                pr_err("read_partial_message bad seq %lld expected %lld\n",
                       seq, con->in_seq + 1);
                con->error_msg = "bad message sequence # for incoming message";
                return -EBADMSG;
        }

        /* allocate message? */
        if (!con->in_msg) {
                dout("got hdr type %d front %d data %d\n", con->in_hdr.type,
                     con->in_hdr.front_len, con->in_hdr.data_len);
                skip = 0;
                con->in_msg = ceph_alloc_msg(con, &con->in_hdr, &skip);
                if (skip) {
                        /* skip this message */
                        dout("alloc_msg said skip message\n");
                        BUG_ON(con->in_msg);
                        con->in_base_pos = -front_len - middle_len - data_len -
                                sizeof(m->footer);
                        con->in_tag = CEPH_MSGR_TAG_READY;
                        con->in_seq++;
                        return 0;
                }
                if (!con->in_msg) {
                        con->error_msg =
                                "error allocating memory for incoming message";
                        return -ENOMEM;
                }
                m = con->in_msg;
                m->front.iov_len = 0;    /* haven't read it yet */
                if (m->middle)
                        m->middle->vec.iov_len = 0;

                con->in_msg_pos.page = 0;
                if (m->pages)
                        con->in_msg_pos.page_pos = m->page_alignment;
                else
                        con->in_msg_pos.page_pos = 0;
                con->in_msg_pos.data_pos = 0;
        }

        /* front */
        ret = read_partial_message_section(con, &m->front, front_len,
                                           &con->in_front_crc);
        if (ret <= 0)
                return ret;

        /* middle */
        if (m->middle) {
                ret = read_partial_message_section(con, &m->middle->vec,
                                                   middle_len,
                                                   &con->in_middle_crc);
                if (ret <= 0)
                        return ret;
        }
#ifdef CONFIG_BLOCK
        if (m->bio && !m->bio_iter)
                init_bio_iter(m->bio, &m->bio_iter, &m->bio_seg);
#endif

        /* (page) data */
        while (con->in_msg_pos.data_pos < data_len) {
                if (m->pages) {
                        ret = read_partial_message_pages(con, m->pages,
                                                 data_len, datacrc);
                        if (ret <= 0)
                                return ret;
#ifdef CONFIG_BLOCK
                } else if (m->bio) {

                        ret = read_partial_message_bio(con,
                                                 &m->bio_iter, &m->bio_seg,
                                                 data_len, datacrc);
                        if (ret <= 0)
                                return ret;
#endif
                } else {
                        BUG_ON(1);
                }
        }

        /* footer */
        to = sizeof(m->hdr) + sizeof(m->footer);
        while (con->in_base_pos < to) {
                left = to - con->in_base_pos;
                ret = ceph_tcp_recvmsg(con->sock, (char *)&m->footer +
                                       (con->in_base_pos - sizeof(m->hdr)),
                                       left);
                if (ret <= 0)
                        return ret;
                con->in_base_pos += ret;
        }
        dout("read_partial_message got msg %p %d (%u) + %d (%u) + %d (%u)\n",
             m, front_len, m->footer.front_crc, middle_len,
             m->footer.middle_crc, data_len, m->footer.data_crc);

        /* crc ok? */
        if (con->in_front_crc != le32_to_cpu(m->footer.front_crc)) {
                pr_err("read_partial_message %p front crc %u != exp. %u\n",
                       m, con->in_front_crc, m->footer.front_crc);
                return -EBADMSG;
        }
        if (con->in_middle_crc != le32_to_cpu(m->footer.middle_crc)) {
                pr_err("read_partial_message %p middle crc %u != exp %u\n",
                       m, con->in_middle_crc, m->footer.middle_crc);
                return -EBADMSG;
        }
        if (datacrc &&
            (m->footer.flags & CEPH_MSG_FOOTER_NOCRC) == 0 &&
            con->in_data_crc != le32_to_cpu(m->footer.data_crc)) {
                pr_err("read_partial_message %p data crc %u != exp. %u\n", m,
                       con->in_data_crc, le32_to_cpu(m->footer.data_crc));
                return -EBADMSG;
        }

        return 1; /* done! */
}

/*
 * Process message.  This happens in the worker thread.  The callback should
 * be careful not to do anything that waits on other incoming messages or it
 * may deadlock.
 */
static void process_message(struct ceph_connection *con)
{
        struct ceph_msg *msg;

        msg = con->in_msg;
        con->in_msg = NULL;

        /* if first message, set peer_name */
        if (con->peer_name.type == 0)
                con->peer_name = msg->hdr.src;

        con->in_seq++;
        mutex_unlock(&con->mutex);

        dout("===== %p %llu from %s%lld %d=%s len %d+%d (%u %u %u) =====\n",
             msg, le64_to_cpu(msg->hdr.seq),
             ENTITY_NAME(msg->hdr.src),
             le16_to_cpu(msg->hdr.type),
             ceph_msg_type_name(le16_to_cpu(msg->hdr.type)),
             le32_to_cpu(msg->hdr.front_len),
             le32_to_cpu(msg->hdr.data_len),
             con->in_front_crc, con->in_middle_crc, con->in_data_crc);
        con->ops->dispatch(con, msg);

        mutex_lock(&con->mutex);
        prepare_read_tag(con);
}


/*
 * Write something to the socket.  Called in a worker thread when the
 * socket appears to be writeable and we have something ready to send.
 */
static int try_write(struct ceph_connection *con)
{
        struct ceph_messenger *msgr = con->msgr;
        int ret = 1;

        dout("try_write start %p state %lu nref %d\n", con, con->state,
             atomic_read(&con->nref));

more:
        dout("try_write out_kvec_bytes %d\n", con->out_kvec_bytes);

        /* open the socket first? */
        if (con->sock == NULL) {
                prepare_write_banner(msgr, con);
                prepare_write_connect(msgr, con, 1);
                prepare_read_banner(con);
                set_bit(CONNECTING, &con->state);
                clear_bit(NEGOTIATING, &con->state);

                BUG_ON(con->in_msg);
                con->in_tag = CEPH_MSGR_TAG_READY;
                dout("try_write initiating connect on %p new state %lu\n",
                     con, con->state);
                con->sock = ceph_tcp_connect(con);
                if (IS_ERR(con->sock)) {
                        con->sock = NULL;
                        con->error_msg = "connect error";
                        ret = -1;
                        goto out;
                }
        }

more_kvec:
        /* kvec data queued? */
        if (con->out_skip) {
                ret = write_partial_skip(con);
                if (ret <= 0)
                        goto out;
        }
        if (con->out_kvec_left) {
                ret = write_partial_kvec(con);
                if (ret <= 0)
                        goto out;
        }

        /* msg pages? */
        if (con->out_msg) {
                if (con->out_msg_done) {
                        ceph_msg_put(con->out_msg);
                        con->out_msg = NULL;   /* we're done with this one */
                        goto do_next;
                }

                ret = write_partial_msg_pages(con);
                if (ret == 1)
                        goto more_kvec;  /* we need to send the footer, too! */
                if (ret == 0)
                        goto out;
                if (ret < 0) {
                        dout("try_write write_partial_msg_pages err %d\n",
                             ret);
                        goto out;
                }
        }

do_next:
        if (!test_bit(CONNECTING, &con->state)) {
                /* is anything else pending? */
                if (!list_empty(&con->out_queue)) {
                        prepare_write_message(con);
                        goto more;
                }
                if (con->in_seq > con->in_seq_acked) {
                        prepare_write_ack(con);
                        goto more;
                }
                if (test_and_clear_bit(KEEPALIVE_PENDING, &con->state)) {
                        prepare_write_keepalive(con);
                        goto more;
                }
        }

        /* Nothing to do! */
        clear_bit(WRITE_PENDING, &con->state);
        dout("try_write nothing else to write.\n");
        ret = 0;
out:
        dout("try_write done on %p ret %d\n", con, ret);
        return ret;
}



/*
 * Read what we can from the socket.
 */
static int try_read(struct ceph_connection *con)
{
        int ret = -1;

        if (!con->sock)
                return 0;

        if (test_bit(STANDBY, &con->state))
                return 0;

        dout("try_read start on %p\n", con);

more:
        dout("try_read tag %d in_base_pos %d\n", (int)con->in_tag,
             con->in_base_pos);

        /*
         * process_connect and process_message drop and re-take
         * con->mutex.  make sure we handle a racing close or reopen.
         */
        if (test_bit(CLOSED, &con->state) ||
            test_bit(OPENING, &con->state)) {
                ret = -EAGAIN;
                goto out;
        }

        if (test_bit(CONNECTING, &con->state)) {
                if (!test_bit(NEGOTIATING, &con->state)) {
                        dout("try_read connecting\n");
                        ret = read_partial_banner(con);
                        if (ret <= 0)
                                goto out;
                        ret = process_banner(con);
                        if (ret < 0)
                                goto out;
                }
                ret = read_partial_connect(con);
                if (ret <= 0)
                        goto out;
                ret = process_connect(con);
                if (ret < 0)
                        goto out;
                goto more;
        }

        if (con->in_base_pos < 0) {
                /*
                 * skipping + discarding content.
                 *
                 * FIXME: there must be a better way to do this!
                 */
                static char buf[1024];
                int skip = min(1024, -con->in_base_pos);
                dout("skipping %d / %d bytes\n", skip, -con->in_base_pos);
                ret = ceph_tcp_recvmsg(con->sock, buf, skip);
                if (ret <= 0)
                        goto out;
                con->in_base_pos += ret;
                if (con->in_base_pos)
                        goto more;
        }
        if (con->in_tag == CEPH_MSGR_TAG_READY) {
                /*
                 * what's next?
                 */
                ret = ceph_tcp_recvmsg(con->sock, &con->in_tag, 1);
                if (ret <= 0)
                        goto out;
                dout("try_read got tag %d\n", (int)con->in_tag);
                switch (con->in_tag) {
                case CEPH_MSGR_TAG_MSG:
                        prepare_read_message(con);
                        break;
                case CEPH_MSGR_TAG_ACK:
                        prepare_read_ack(con);
                        break;
                case CEPH_MSGR_TAG_CLOSE:
                        set_bit(CLOSED, &con->state);   /* fixme */
                        goto out;
                default:
                        goto bad_tag;
                }
        }
        if (con->in_tag == CEPH_MSGR_TAG_MSG) {
                ret = read_partial_message(con);
                if (ret <= 0) {
                        switch (ret) {
                        case -EBADMSG:
                                con->error_msg = "bad crc";
                                ret = -EIO;
                                break;
                        case -EIO:
                                con->error_msg = "io error";
                                break;
                        }
                        goto out;
                }
                if (con->in_tag == CEPH_MSGR_TAG_READY)
                        goto more;
                process_message(con);
                goto more;
        }
        if (con->in_tag == CEPH_MSGR_TAG_ACK) {
                ret = read_partial_ack(con);
                if (ret <= 0)
                        goto out;
                process_ack(con);
                goto more;
        }

out:
        dout("try_read done on %p ret %d\n", con, ret);
        return ret;

bad_tag:
        pr_err("try_read bad con->in_tag = %d\n", (int)con->in_tag);
        con->error_msg = "protocol error, garbage tag";
        ret = -1;
        goto out;
}


/*
 * Atomically queue work on a connection.  Bump @con reference to
 * avoid races with connection teardown.
 */
static void queue_con(struct ceph_connection *con)
{
        if (test_bit(DEAD, &con->state)) {
                dout("queue_con %p ignoring: DEAD\n",
                     con);
                return;
        }

        if (!con->ops->get(con)) {
                dout("queue_con %p ref count 0\n", con);
                return;
        }

        if (!queue_delayed_work(ceph_msgr_wq, &con->work, 0)) {
                dout("queue_con %p - already queued\n", con);
                con->ops->put(con);
        } else {
                dout("queue_con %p\n", con);
        }
}

/*
 * Do some work on a connection.  Drop a connection ref when we're done.
 */
static void con_work(struct work_struct *work)
{
        struct ceph_connection *con = container_of(work, struct ceph_connection,
                                                   work.work);
        int ret;

        mutex_lock(&con->mutex);
restart:
        if (test_and_clear_bit(BACKOFF, &con->state)) {
                dout("con_work %p backing off\n", con);
                if (queue_delayed_work(ceph_msgr_wq, &con->work,
                                       round_jiffies_relative(con->delay))) {
                        dout("con_work %p backoff %lu\n", con, con->delay);
                        mutex_unlock(&con->mutex);
                        return;
                } else {
                        con->ops->put(con);
                        dout("con_work %p FAILED to back off %lu\n", con,
                             con->delay);
                }
        }

        if (test_bit(STANDBY, &con->state)) {
                dout("con_work %p STANDBY\n", con);
                goto done;
        }
        if (test_bit(CLOSED, &con->state)) { /* e.g. if we are replaced */
                dout("con_work CLOSED\n");
                con_close_socket(con);
                goto done;
        }
        if (test_and_clear_bit(OPENING, &con->state)) {
                /* reopen w/ new peer */
                dout("con_work OPENING\n");
                con_close_socket(con);
        }

        if (test_and_clear_bit(SOCK_CLOSED, &con->state))
                goto fault;

        ret = try_read(con);
        if (ret == -EAGAIN)
                goto restart;
        if (ret < 0)
                goto fault;

        ret = try_write(con);
        if (ret == -EAGAIN)
                goto restart;
        if (ret < 0)
                goto fault;

done:
        mutex_unlock(&con->mutex);
done_unlocked:
        con->ops->put(con);
        return;

fault:
        mutex_unlock(&con->mutex);
        ceph_fault(con);     /* error/fault path */
        goto done_unlocked;
}


/*
 * Generic error/fault handler.  A retry mechanism is used with
 * exponential backoff
 */
static void ceph_fault(struct ceph_connection *con)
{
        pr_err("%s%lld %s %s\n", ENTITY_NAME(con->peer_name),
               ceph_pr_addr(&con->peer_addr.in_addr), con->error_msg);
        dout("fault %p state %lu to peer %s\n",
             con, con->state, ceph_pr_addr(&con->peer_addr.in_addr));

        if (test_bit(LOSSYTX, &con->state)) {
                dout("fault on LOSSYTX channel\n");
                goto out;
        }

        mutex_lock(&con->mutex);
        if (test_bit(CLOSED, &con->state))
                goto out_unlock;

        con_close_socket(con);

        if (con->in_msg) {
                ceph_msg_put(con->in_msg);
                con->in_msg = NULL;
        }

        /* Requeue anything that hasn't been acked */
        list_splice_init(&con->out_sent, &con->out_queue);

        /* If there are no messages queued or keepalive pending, place
         * the connection in a STANDBY state */
        if (list_empty(&con->out_queue) &&
            !test_bit(KEEPALIVE_PENDING, &con->state)) {
                dout("fault %p setting STANDBY clearing WRITE_PENDING\n", con);
                clear_bit(WRITE_PENDING, &con->state);
                set_bit(STANDBY, &con->state);
        } else {
                /* retry after a delay. */
                if (con->delay == 0)
                        con->delay = BASE_DELAY_INTERVAL;
                else if (con->delay < MAX_DELAY_INTERVAL)
                        con->delay *= 2;
                con->ops->get(con);
                if (queue_delayed_work(ceph_msgr_wq, &con->work,
                                       round_jiffies_relative(con->delay))) {
                        dout("fault queued %p delay %lu\n", con, con->delay);
                } else {
                        con->ops->put(con);
                        dout("fault failed to queue %p delay %lu, backoff\n",
                             con, con->delay);
                        /*
                         * In many cases we see a socket state change
                         * while con_work is running and end up
                         * queuing (non-delayed) work, such that we
                         * can't backoff with a delay.  Set a flag so
                         * that when con_work restarts we schedule the
                         * delay then.
                         */
                        set_bit(BACKOFF, &con->state);
                }
        }

out_unlock:
        mutex_unlock(&con->mutex);
out:
        /*
         * in case we faulted due to authentication, invalidate our
         * current tickets so that we can get new ones.
         */
        if (con->auth_retry && con->ops->invalidate_authorizer) {
                dout("calling invalidate_authorizer()\n");
                con->ops->invalidate_authorizer(con);
        }

        if (con->ops->fault)
                con->ops->fault(con);
}



/*
 * create a new messenger instance
 */
struct ceph_messenger *ceph_messenger_create(struct ceph_entity_addr *myaddr,
                                             u32 supported_features,
                                             u32 required_features)
{
        struct ceph_messenger *msgr;

        msgr = kzalloc(sizeof(*msgr), GFP_KERNEL);
        if (msgr == NULL)
                return ERR_PTR(-ENOMEM);

        msgr->supported_features = supported_features;
        msgr->required_features = required_features;

        spin_lock_init(&msgr->global_seq_lock);

        /* the zero page is needed if a request is "canceled" while the message
         * is being written over the socket */
        msgr->zero_page = __page_cache_alloc(GFP_KERNEL | __GFP_ZERO);
        if (!msgr->zero_page) {
                kfree(msgr);
                return ERR_PTR(-ENOMEM);
        }
        kmap(msgr->zero_page);

        if (myaddr)
                msgr->inst.addr = *myaddr;

        /* select a random nonce */
        msgr->inst.addr.type = 0;
        get_random_bytes(&msgr->inst.addr.nonce, sizeof(msgr->inst.addr.nonce));
        encode_my_addr(msgr);

        dout("messenger_create %p\n", msgr);
        return msgr;
}
EXPORT_SYMBOL(ceph_messenger_create);

void ceph_messenger_destroy(struct ceph_messenger *msgr)
{
        dout("destroy %p\n", msgr);
        kunmap(msgr->zero_page);
        __free_page(msgr->zero_page);
        kfree(msgr);
        dout("destroyed messenger %p\n", msgr);
}
EXPORT_SYMBOL(ceph_messenger_destroy);

static void clear_standby(struct ceph_connection *con)
{
        /* come back from STANDBY? */
        if (test_and_clear_bit(STANDBY, &con->state)) {
                mutex_lock(&con->mutex);
                dout("clear_standby %p and ++connect_seq\n", con);
                con->connect_seq++;
                WARN_ON(test_bit(WRITE_PENDING, &con->state));
                WARN_ON(test_bit(KEEPALIVE_PENDING, &con->state));
                mutex_unlock(&con->mutex);
        }
}

/*
 * Queue up an outgoing message on the given connection.
 */
void ceph_con_send(struct ceph_connection *con, struct ceph_msg *msg)
{
        if (test_bit(CLOSED, &con->state)) {
                dout("con_send %p closed, dropping %p\n", con, msg);
                ceph_msg_put(msg);
                return;
        }

        /* set src+dst */
        msg->hdr.src = con->msgr->inst.name;

        BUG_ON(msg->front.iov_len != le32_to_cpu(msg->hdr.front_len));

        msg->needs_out_seq = true;

        /* queue */
        mutex_lock(&con->mutex);
        BUG_ON(!list_empty(&msg->list_head));
        list_add_tail(&msg->list_head, &con->out_queue);
        dout("----- %p to %s%lld %d=%s len %d+%d+%d -----\n", msg,
             ENTITY_NAME(con->peer_name), le16_to_cpu(msg->hdr.type),
             ceph_msg_type_name(le16_to_cpu(msg->hdr.type)),
             le32_to_cpu(msg->hdr.front_len),
             le32_to_cpu(msg->hdr.middle_len),
             le32_to_cpu(msg->hdr.data_len));
        mutex_unlock(&con->mutex);

        /* if there wasn't anything waiting to send before, queue
         * new work */
        clear_standby(con);
        if (test_and_set_bit(WRITE_PENDING, &con->state) == 0)
                queue_con(con);
}
EXPORT_SYMBOL(ceph_con_send);

/*
 * Revoke a message that was previously queued for send
 */
void ceph_con_revoke(struct ceph_connection *con, struct ceph_msg *msg)
{
        mutex_lock(&con->mutex);
        if (!list_empty(&msg->list_head)) {
                dout("con_revoke %p msg %p - was on queue\n", con, msg);
                list_del_init(&msg->list_head);
                ceph_msg_put(msg);
                msg->hdr.seq = 0;
        }
        if (con->out_msg == msg) {
                dout("con_revoke %p msg %p - was sending\n", con, msg);
                con->out_msg = NULL;
                if (con->out_kvec_is_msg) {
                        con->out_skip = con->out_kvec_bytes;
                        con->out_kvec_is_msg = false;
                }
                ceph_msg_put(msg);
                msg->hdr.seq = 0;
        }
        mutex_unlock(&con->mutex);
}

/*
 * Revoke a message that we may be reading data into
 */
void ceph_con_revoke_message(struct ceph_connection *con, struct ceph_msg *msg)
{
        mutex_lock(&con->mutex);
        if (con->in_msg && con->in_msg == msg) {
                unsigned front_len = le32_to_cpu(con->in_hdr.front_len);
                unsigned middle_len = le32_to_cpu(con->in_hdr.middle_len);
                unsigned data_len = le32_to_cpu(con->in_hdr.data_len);

                /* skip rest of message */
                dout("con_revoke_pages %p msg %p revoked\n", con, msg);
                        con->in_base_pos = con->in_base_pos -
                                sizeof(struct ceph_msg_header) -
                                front_len -
                                middle_len -
                                data_len -
                                sizeof(struct ceph_msg_footer);
                ceph_msg_put(con->in_msg);
                con->in_msg = NULL;
                con->in_tag = CEPH_MSGR_TAG_READY;
                con->in_seq++;
        } else {
                dout("con_revoke_pages %p msg %p pages %p no-op\n",
                     con, con->in_msg, msg);
        }
        mutex_unlock(&con->mutex);
}

/*
 * Queue a keepalive byte to ensure the tcp connection is alive.
 */
void ceph_con_keepalive(struct ceph_connection *con)
{
        dout("con_keepalive %p\n", con);
        clear_standby(con);
        if (test_and_set_bit(KEEPALIVE_PENDING, &con->state) == 0 &&
            test_and_set_bit(WRITE_PENDING, &con->state) == 0)
                queue_con(con);
}
EXPORT_SYMBOL(ceph_con_keepalive);


/*
 * construct a new message with given type, size
 * the new msg has a ref count of 1.
 */
struct ceph_msg *ceph_msg_new(int type, int front_len, gfp_t flags,
                              bool can_fail)
{
        struct ceph_msg *m;

        m = kmalloc(sizeof(*m), flags);
        if (m == NULL)
                goto out;
        kref_init(&m->kref);
        INIT_LIST_HEAD(&m->list_head);

        m->hdr.tid = 0;
        m->hdr.type = cpu_to_le16(type);
        m->hdr.priority = cpu_to_le16(CEPH_MSG_PRIO_DEFAULT);
        m->hdr.version = 0;
        m->hdr.front_len = cpu_to_le32(front_len);
        m->hdr.middle_len = 0;
        m->hdr.data_len = 0;
        m->hdr.data_off = 0;
        m->hdr.reserved = 0;
        m->footer.front_crc = 0;
        m->footer.middle_crc = 0;
        m->footer.data_crc = 0;
        m->footer.flags = 0;
        m->front_max = front_len;
        m->front_is_vmalloc = false;
        m->more_to_follow = false;
        m->ack_stamp = 0;
        m->pool = NULL;

        /* middle */
        m->middle = NULL;

        /* data */
        m->nr_pages = 0;
        m->page_alignment = 0;
        m->pages = NULL;
        m->pagelist = NULL;
        m->bio = NULL;
        m->bio_iter = NULL;
        m->bio_seg = 0;
        m->trail = NULL;

        /* front */
        if (front_len) {
                if (front_len > PAGE_CACHE_SIZE) {
                        m->front.iov_base = __vmalloc(front_len, flags,
                                                      PAGE_KERNEL);
                        m->front_is_vmalloc = true;
                } else {
                        m->front.iov_base = kmalloc(front_len, flags);
                }
                if (m->front.iov_base == NULL) {
                        dout("ceph_msg_new can't allocate %d bytes\n",
                             front_len);
                        goto out2;
                }
        } else {
                m->front.iov_base = NULL;
        }
        m->front.iov_len = front_len;

        dout("ceph_msg_new %p front %d\n", m, front_len);
        return m;

out2:
        ceph_msg_put(m);
out:
        if (!can_fail) {
                pr_err("msg_new can't create type %d front %d\n", type,
                       front_len);
                WARN_ON(1);
        } else {
                dout("msg_new can't create type %d front %d\n", type,
                     front_len);
        }
        return NULL;
}
EXPORT_SYMBOL(ceph_msg_new);

/*
 * Allocate "middle" portion of a message, if it is needed and wasn't
 * allocated by alloc_msg.  This allows us to read a small fixed-size
 * per-type header in the front and then gracefully fail (i.e.,
 * propagate the error to the caller based on info in the front) when
 * the middle is too large.
 */
static int ceph_alloc_middle(struct ceph_connection *con, struct ceph_msg *msg)
{
        int type = le16_to_cpu(msg->hdr.type);
        int middle_len = le32_to_cpu(msg->hdr.middle_len);

        dout("alloc_middle %p type %d %s middle_len %d\n", msg, type,
             ceph_msg_type_name(type), middle_len);
        BUG_ON(!middle_len);
        BUG_ON(msg->middle);

        msg->middle = ceph_buffer_new(middle_len, GFP_NOFS);
        if (!msg->middle)
                return -ENOMEM;
        return 0;
}

/*
 * Generic message allocator, for incoming messages.
 */
static struct ceph_msg *ceph_alloc_msg(struct ceph_connection *con,
                                struct ceph_msg_header *hdr,
                                int *skip)
{
        int type = le16_to_cpu(hdr->type);
        int front_len = le32_to_cpu(hdr->front_len);
        int middle_len = le32_to_cpu(hdr->middle_len);
        struct ceph_msg *msg = NULL;
        int ret;

        if (con->ops->alloc_msg) {
                mutex_unlock(&con->mutex);
                msg = con->ops->alloc_msg(con, hdr, skip);
                mutex_lock(&con->mutex);
                if (!msg || *skip)
                        return NULL;
        }
        if (!msg) {
                *skip = 0;
                msg = ceph_msg_new(type, front_len, GFP_NOFS, false);
                if (!msg) {
                        pr_err("unable to allocate msg type %d len %d\n",
                               type, front_len);
                        return NULL;
                }
                msg->page_alignment = le16_to_cpu(hdr->data_off);
        }
        memcpy(&msg->hdr, &con->in_hdr, sizeof(con->in_hdr));

        if (middle_len && !msg->middle) {
                ret = ceph_alloc_middle(con, msg);
                if (ret < 0) {
                        ceph_msg_put(msg);
                        return NULL;
                }
        }

        return msg;
}


/*
 * Free a generically kmalloc'd message.
 */
void ceph_msg_kfree(struct ceph_msg *m)
{
        dout("msg_kfree %p\n", m);
        if (m->front_is_vmalloc)
                vfree(m->front.iov_base);
        else
                kfree(m->front.iov_base);
        kfree(m);
}

/*
 * Drop a msg ref.  Destroy as needed.
 */
void ceph_msg_last_put(struct kref *kref)
{
        struct ceph_msg *m = container_of(kref, struct ceph_msg, kref);

        dout("ceph_msg_put last one on %p\n", m);
        WARN_ON(!list_empty(&m->list_head));

        /* drop middle, data, if any */
        if (m->middle) {
                ceph_buffer_put(m->middle);
                m->middle = NULL;
        }
        m->nr_pages = 0;
        m->pages = NULL;

        if (m->pagelist) {
                ceph_pagelist_release(m->pagelist);
                kfree(m->pagelist);
                m->pagelist = NULL;
        }

        m->trail = NULL;

        if (m->pool)
                ceph_msgpool_put(m->pool, m);
        else
                ceph_msg_kfree(m);
}
EXPORT_SYMBOL(ceph_msg_last_put);

void ceph_msg_dump(struct ceph_msg *msg)
{
        pr_debug("msg_dump %p (front_max %d nr_pages %d)\n", msg,
                 msg->front_max, msg->nr_pages);
        print_hex_dump(KERN_DEBUG, "header: ",
                       DUMP_PREFIX_OFFSET, 16, 1,
                       &msg->hdr, sizeof(msg->hdr), true);
        print_hex_dump(KERN_DEBUG, " front: ",
                       DUMP_PREFIX_OFFSET, 16, 1,
                       msg->front.iov_base, msg->front.iov_len, true);
        if (msg->middle)
                print_hex_dump(KERN_DEBUG, "middle: ",
                               DUMP_PREFIX_OFFSET, 16, 1,
                               msg->middle->vec.iov_base,
                               msg->middle->vec.iov_len, true);
        print_hex_dump(KERN_DEBUG, "footer: ",
                       DUMP_PREFIX_OFFSET, 16, 1,
                       &msg->footer, sizeof(msg->footer), true);
}
EXPORT_SYMBOL(ceph_msg_dump);