mds_client.c

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#include <linux/ceph/ceph_debug.h>

#include <linux/fs.h>
#include <linux/wait.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>

#include "super.h"
#include "mds_client.h"

#include <linux/ceph/ceph_features.h>
#include <linux/ceph/messenger.h>
#include <linux/ceph/decode.h>
#include <linux/ceph/pagelist.h>
#include <linux/ceph/auth.h>
#include <linux/ceph/debugfs.h>

/*
 * A cluster of MDS (metadata server) daemons is responsible for
 * managing the file system namespace (the directory hierarchy and
 * inodes) and for coordinating shared access to storage.  Metadata is
 * partitioning hierarchically across a number of servers, and that
 * partition varies over time as the cluster adjusts the distribution
 * in order to balance load.
 *
 * The MDS client is primarily responsible to managing synchronous
 * metadata requests for operations like open, unlink, and so forth.
 * If there is a MDS failure, we find out about it when we (possibly
 * request and) receive a new MDS map, and can resubmit affected
 * requests.
 *
 * For the most part, though, we take advantage of a lossless
 * communications channel to the MDS, and do not need to worry about
 * timing out or resubmitting requests.
 *
 * We maintain a stateful "session" with each MDS we interact with.
 * Within each session, we sent periodic heartbeat messages to ensure
 * any capabilities or leases we have been issues remain valid.  If
 * the session times out and goes stale, our leases and capabilities
 * are no longer valid.
 */

struct ceph_reconnect_state {
    struct ceph_pagelist *pagelist;
    bool flock;
};

static void __wake_requests(struct ceph_mds_client *mdsc,
                struct list_head *head);

static const struct ceph_connection_operations mds_con_ops;


/*
 * mds reply parsing
 */

/*
 * parse individual inode info
 */
static int parse_reply_info_in(void **p, void *end,
                   struct ceph_mds_reply_info_in *info,
                   int features)
{
    int err = -EIO;

    info->in = *p;
    *p += sizeof(struct ceph_mds_reply_inode) +
        sizeof(*info->in->fragtree.splits) *
        le32_to_cpu(info->in->fragtree.nsplits);

    ceph_decode_32_safe(p, end, info->symlink_len, bad);
    ceph_decode_need(p, end, info->symlink_len, bad);
    info->symlink = *p;
    *p += info->symlink_len;

    if (features & CEPH_FEATURE_DIRLAYOUTHASH)
        ceph_decode_copy_safe(p, end, &info->dir_layout,
                      sizeof(info->dir_layout), bad);
    else
        memset(&info->dir_layout, 0, sizeof(info->dir_layout));

    ceph_decode_32_safe(p, end, info->xattr_len, bad);
    ceph_decode_need(p, end, info->xattr_len, bad);
    info->xattr_data = *p;
    *p += info->xattr_len;
    return 0;
bad:
    return err;
}

/*
 * parse a normal reply, which may contain a (dir+)dentry and/or a
 * target inode.
 */
static int parse_reply_info_trace(void **p, void *end,
                  struct ceph_mds_reply_info_parsed *info,
                  int features)
{
    int err;

    if (info->head->is_dentry) {
        err = parse_reply_info_in(p, end, &info->diri, features);
        if (err < 0)
            goto out_bad;

        if (unlikely(*p + sizeof(*info->dirfrag) > end))
            goto bad;
        info->dirfrag = *p;
        *p += sizeof(*info->dirfrag) +
            sizeof(u32)*le32_to_cpu(info->dirfrag->ndist);
        if (unlikely(*p > end))
            goto bad;

        ceph_decode_32_safe(p, end, info->dname_len, bad);
        ceph_decode_need(p, end, info->dname_len, bad);
        info->dname = *p;
        *p += info->dname_len;
        info->dlease = *p;
        *p += sizeof(*info->dlease);
    }

    if (info->head->is_target) {
        err = parse_reply_info_in(p, end, &info->targeti, features);
        if (err < 0)
            goto out_bad;
    }

    if (unlikely(*p != end))
        goto bad;
    return 0;

bad:
    err = -EIO;
out_bad:
    pr_err("problem parsing mds trace %d\n", err);
    return err;
}

/*
 * parse readdir results
 */
static int parse_reply_info_dir(void **p, void *end,
                struct ceph_mds_reply_info_parsed *info,
                int features)
{
    u32 num, i = 0;
    int err;

    info->dir_dir = *p;
    if (*p + sizeof(*info->dir_dir) > end)
        goto bad;
    *p += sizeof(*info->dir_dir) +
        sizeof(u32)*le32_to_cpu(info->dir_dir->ndist);
    if (*p > end)
        goto bad;

    ceph_decode_need(p, end, sizeof(num) + 2, bad);
    num = ceph_decode_32(p);
    info->dir_end = ceph_decode_8(p);
    info->dir_complete = ceph_decode_8(p);
    if (num == 0)
        goto done;

    /* alloc large array */
    info->dir_nr = num;
    info->dir_in = kcalloc(num, sizeof(*info->dir_in) +
                   sizeof(*info->dir_dname) +
                   sizeof(*info->dir_dname_len) +
                   sizeof(*info->dir_dlease),
                   GFP_NOFS);
    if (info->dir_in == NULL) {
        err = -ENOMEM;
        goto out_bad;
    }
    info->dir_dname = (void *)(info->dir_in + num);
    info->dir_dname_len = (void *)(info->dir_dname + num);
    info->dir_dlease = (void *)(info->dir_dname_len + num);

    while (num) {
        /* dentry */
        ceph_decode_need(p, end, sizeof(u32)*2, bad);
        info->dir_dname_len[i] = ceph_decode_32(p);
        ceph_decode_need(p, end, info->dir_dname_len[i], bad);
        info->dir_dname[i] = *p;
        *p += info->dir_dname_len[i];
        dout("parsed dir dname '%.*s'\n", info->dir_dname_len[i],
             info->dir_dname[i]);
        info->dir_dlease[i] = *p;
        *p += sizeof(struct ceph_mds_reply_lease);

        /* inode */
        err = parse_reply_info_in(p, end, &info->dir_in[i], features);
        if (err < 0)
            goto out_bad;
        i++;
        num--;
    }

done:
    if (*p != end)
        goto bad;
    return 0;

bad:
    err = -EIO;
out_bad:
    pr_err("problem parsing dir contents %d\n", err);
    return err;
}

/*
 * parse fcntl F_GETLK results
 */
static int parse_reply_info_filelock(void **p, void *end,
                     struct ceph_mds_reply_info_parsed *info,
                     int features)
{
    if (*p + sizeof(*info->filelock_reply) > end)
        goto bad;

    info->filelock_reply = *p;
    *p += sizeof(*info->filelock_reply);

    if (unlikely(*p != end))
        goto bad;
    return 0;

bad:
    return -EIO;
}

/*
 * parse extra results
 */
static int parse_reply_info_extra(void **p, void *end,
                  struct ceph_mds_reply_info_parsed *info,
                  int features)
{
    if (info->head->op == CEPH_MDS_OP_GETFILELOCK)
        return parse_reply_info_filelock(p, end, info, features);
    else
        return parse_reply_info_dir(p, end, info, features);
}

/*
 * parse entire mds reply
 */
static int parse_reply_info(struct ceph_msg *msg,
                struct ceph_mds_reply_info_parsed *info,
                int features)
{
    void *p, *end;
    u32 len;
    int err;

    info->head = msg->front.iov_base;
    p = msg->front.iov_base + sizeof(struct ceph_mds_reply_head);
    end = p + msg->front.iov_len - sizeof(struct ceph_mds_reply_head);

    /* trace */
    ceph_decode_32_safe(&p, end, len, bad);
    if (len > 0) {
        ceph_decode_need(&p, end, len, bad);
        err = parse_reply_info_trace(&p, p+len, info, features);
        if (err < 0)
            goto out_bad;
    }

    /* extra */
    ceph_decode_32_safe(&p, end, len, bad);
    if (len > 0) {
        ceph_decode_need(&p, end, len, bad);
        err = parse_reply_info_extra(&p, p+len, info, features);
        if (err < 0)
            goto out_bad;
    }

    /* snap blob */
    ceph_decode_32_safe(&p, end, len, bad);
    info->snapblob_len = len;
    info->snapblob = p;
    p += len;

    if (p != end)
        goto bad;
    return 0;

bad:
    err = -EIO;
out_bad:
    pr_err("mds parse_reply err %d\n", err);
    return err;
}

static void destroy_reply_info(struct ceph_mds_reply_info_parsed *info)
{
    kfree(info->dir_in);
}


/*
 * sessions
 */
static const char *session_state_name(int s)
{
    switch (s) {
    case CEPH_MDS_SESSION_NEW: return "new";
    case CEPH_MDS_SESSION_OPENING: return "opening";
    case CEPH_MDS_SESSION_OPEN: return "open";
    case CEPH_MDS_SESSION_HUNG: return "hung";
    case CEPH_MDS_SESSION_CLOSING: return "closing";
    case CEPH_MDS_SESSION_RESTARTING: return "restarting";
    case CEPH_MDS_SESSION_RECONNECTING: return "reconnecting";
    default: return "???";
    }
}

static struct ceph_mds_session *get_session(struct ceph_mds_session *s)
{
    if (atomic_inc_not_zero(&s->s_ref)) {
        dout("mdsc get_session %p %d -> %d\n", s,
             atomic_read(&s->s_ref)-1, atomic_read(&s->s_ref));
        return s;
    } else {
        dout("mdsc get_session %p 0 -- FAIL", s);
        return NULL;
    }
}

void ceph_put_mds_session(struct ceph_mds_session *s)
{
    dout("mdsc put_session %p %d -> %d\n", s,
         atomic_read(&s->s_ref), atomic_read(&s->s_ref)-1);
    if (atomic_dec_and_test(&s->s_ref)) {
        if (s->s_auth.authorizer)
             s->s_mdsc->fsc->client->monc.auth->ops->destroy_authorizer(
                 s->s_mdsc->fsc->client->monc.auth,
                 s->s_auth.authorizer);
        kfree(s);
    }
}

/*
 * called under mdsc->mutex
 */
struct ceph_mds_session *__ceph_lookup_mds_session(struct ceph_mds_client *mdsc,
                           int mds)
{
    struct ceph_mds_session *session;

    if (mds >= mdsc->max_sessions || mdsc->sessions[mds] == NULL)
        return NULL;
    session = mdsc->sessions[mds];
    dout("lookup_mds_session %p %d\n", session,
         atomic_read(&session->s_ref));
    get_session(session);
    return session;
}

static bool __have_session(struct ceph_mds_client *mdsc, int mds)
{
    if (mds >= mdsc->max_sessions)
        return false;
    return mdsc->sessions[mds];
}

static int __verify_registered_session(struct ceph_mds_client *mdsc,
                       struct ceph_mds_session *s)
{
    if (s->s_mds >= mdsc->max_sessions ||
        mdsc->sessions[s->s_mds] != s)
        return -ENOENT;
    return 0;
}

/*
 * create+register a new session for given mds.
 * called under mdsc->mutex.
 */
static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
                         int mds)
{
    struct ceph_mds_session *s;

    s = kzalloc(sizeof(*s), GFP_NOFS);
    if (!s)
        return ERR_PTR(-ENOMEM);
    s->s_mdsc = mdsc;
    s->s_mds = mds;
    s->s_state = CEPH_MDS_SESSION_NEW;
    s->s_ttl = 0;
    s->s_seq = 0;
    mutex_init(&s->s_mutex);

    ceph_con_init(&s->s_con, s, &mds_con_ops, &mdsc->fsc->client->msgr);

    spin_lock_init(&s->s_gen_ttl_lock);
    s->s_cap_gen = 0;
    s->s_cap_ttl = jiffies - 1;

    spin_lock_init(&s->s_cap_lock);
    s->s_renew_requested = 0;
    s->s_renew_seq = 0;
    INIT_LIST_HEAD(&s->s_caps);
    s->s_nr_caps = 0;
    s->s_trim_caps = 0;
    atomic_set(&s->s_ref, 1);
    INIT_LIST_HEAD(&s->s_waiting);
    INIT_LIST_HEAD(&s->s_unsafe);
    s->s_num_cap_releases = 0;
    s->s_cap_iterator = NULL;
    INIT_LIST_HEAD(&s->s_cap_releases);
    INIT_LIST_HEAD(&s->s_cap_releases_done);
    INIT_LIST_HEAD(&s->s_cap_flushing);
    INIT_LIST_HEAD(&s->s_cap_snaps_flushing);

    dout("register_session mds%d\n", mds);
    if (mds >= mdsc->max_sessions) {
        int newmax = 1 << get_count_order(mds+1);
        struct ceph_mds_session **sa;

        dout("register_session realloc to %d\n", newmax);
        sa = kcalloc(newmax, sizeof(void *), GFP_NOFS);
        if (sa == NULL)
            goto fail_realloc;
        if (mdsc->sessions) {
            memcpy(sa, mdsc->sessions,
                   mdsc->max_sessions * sizeof(void *));
            kfree(mdsc->sessions);
        }
        mdsc->sessions = sa;
        mdsc->max_sessions = newmax;
    }
    mdsc->sessions[mds] = s;
    atomic_inc(&s->s_ref);  /* one ref to sessions[], one to caller */

    ceph_con_open(&s->s_con, CEPH_ENTITY_TYPE_MDS, mds,
              ceph_mdsmap_get_addr(mdsc->mdsmap, mds));

    return s;

fail_realloc:
    kfree(s);
    return ERR_PTR(-ENOMEM);
}

/*
 * called under mdsc->mutex
 */
static void __unregister_session(struct ceph_mds_client *mdsc,
                   struct ceph_mds_session *s)
{
    dout("__unregister_session mds%d %p\n", s->s_mds, s);
    BUG_ON(mdsc->sessions[s->s_mds] != s);
    mdsc->sessions[s->s_mds] = NULL;
    ceph_con_close(&s->s_con);
    ceph_put_mds_session(s);
}

/*
 * drop session refs in request.
 *
 * should be last request ref, or hold mdsc->mutex
 */
static void put_request_session(struct ceph_mds_request *req)
{
    if (req->r_session) {
        ceph_put_mds_session(req->r_session);
        req->r_session = NULL;
    }
}

void ceph_mdsc_release_request(struct kref *kref)
{
    struct ceph_mds_request *req = container_of(kref,
                            struct ceph_mds_request,
                            r_kref);
    if (req->r_request)
        ceph_msg_put(req->r_request);
    if (req->r_reply) {
        ceph_msg_put(req->r_reply);
        destroy_reply_info(&req->r_reply_info);
    }
    if (req->r_inode) {
        ceph_put_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);
        iput(req->r_inode);
    }
    if (req->r_locked_dir)
        ceph_put_cap_refs(ceph_inode(req->r_locked_dir), CEPH_CAP_PIN);
    if (req->r_target_inode)
        iput(req->r_target_inode);
    if (req->r_dentry)
        dput(req->r_dentry);
    if (req->r_old_dentry) {
        /*
         * track (and drop pins for) r_old_dentry_dir
         * separately, since r_old_dentry's d_parent may have
         * changed between the dir mutex being dropped and
         * this request being freed.
         */
        ceph_put_cap_refs(ceph_inode(req->r_old_dentry_dir),
                  CEPH_CAP_PIN);
        dput(req->r_old_dentry);
        iput(req->r_old_dentry_dir);
    }
    kfree(req->r_path1);
    kfree(req->r_path2);
    put_request_session(req);
    ceph_unreserve_caps(req->r_mdsc, &req->r_caps_reservation);
    kfree(req);
}

/*
 * lookup session, bump ref if found.
 *
 * called under mdsc->mutex.
 */
static struct ceph_mds_request *__lookup_request(struct ceph_mds_client *mdsc,
                         u64 tid)
{
    struct ceph_mds_request *req;
    struct rb_node *n = mdsc->request_tree.rb_node;

    while (n) {
        req = rb_entry(n, struct ceph_mds_request, r_node);
        if (tid < req->r_tid)
            n = n->rb_left;
        else if (tid > req->r_tid)
            n = n->rb_right;
        else {
            ceph_mdsc_get_request(req);
            return req;
        }
    }
    return NULL;
}

static void __insert_request(struct ceph_mds_client *mdsc,
                 struct ceph_mds_request *new)
{
    struct rb_node **p = &mdsc->request_tree.rb_node;
    struct rb_node *parent = NULL;
    struct ceph_mds_request *req = NULL;

    while (*p) {
        parent = *p;
        req = rb_entry(parent, struct ceph_mds_request, r_node);
        if (new->r_tid < req->r_tid)
            p = &(*p)->rb_left;
        else if (new->r_tid > req->r_tid)
            p = &(*p)->rb_right;
        else
            BUG();
    }

    rb_link_node(&new->r_node, parent, p);
    rb_insert_color(&new->r_node, &mdsc->request_tree);
}

/*
 * Register an in-flight request, and assign a tid.  Link to directory
 * are modifying (if any).
 *
 * Called under mdsc->mutex.
 */
static void __register_request(struct ceph_mds_client *mdsc,
                   struct ceph_mds_request *req,
                   struct inode *dir)
{
    req->r_tid = ++mdsc->last_tid;
    if (req->r_num_caps)
        ceph_reserve_caps(mdsc, &req->r_caps_reservation,
                  req->r_num_caps);
    dout("__register_request %p tid %lld\n", req, req->r_tid);
    ceph_mdsc_get_request(req);
    __insert_request(mdsc, req);

    req->r_uid = current_fsuid();
    req->r_gid = current_fsgid();

    if (dir) {
        struct ceph_inode_info *ci = ceph_inode(dir);

        ihold(dir);
        spin_lock(&ci->i_unsafe_lock);
        req->r_unsafe_dir = dir;
        list_add_tail(&req->r_unsafe_dir_item, &ci->i_unsafe_dirops);
        spin_unlock(&ci->i_unsafe_lock);
    }
}

static void __unregister_request(struct ceph_mds_client *mdsc,
                 struct ceph_mds_request *req)
{
    dout("__unregister_request %p tid %lld\n", req, req->r_tid);
    rb_erase(&req->r_node, &mdsc->request_tree);
    RB_CLEAR_NODE(&req->r_node);

    if (req->r_unsafe_dir) {
        struct ceph_inode_info *ci = ceph_inode(req->r_unsafe_dir);

        spin_lock(&ci->i_unsafe_lock);
        list_del_init(&req->r_unsafe_dir_item);
        spin_unlock(&ci->i_unsafe_lock);

        iput(req->r_unsafe_dir);
        req->r_unsafe_dir = NULL;
    }

    ceph_mdsc_put_request(req);
}

/*
 * Choose mds to send request to next.  If there is a hint set in the
 * request (e.g., due to a prior forward hint from the mds), use that.
 * Otherwise, consult frag tree and/or caps to identify the
 * appropriate mds.  If all else fails, choose randomly.
 *
 * Called under mdsc->mutex.
 */
static struct dentry *get_nonsnap_parent(struct dentry *dentry)
{
    /*
     * we don't need to worry about protecting the d_parent access
     * here because we never renaming inside the snapped namespace
     * except to resplice to another snapdir, and either the old or new
     * result is a valid result.
     */
    while (!IS_ROOT(dentry) && ceph_snap(dentry->d_inode) != CEPH_NOSNAP)
        dentry = dentry->d_parent;
    return dentry;
}

static int __choose_mds(struct ceph_mds_client *mdsc,
            struct ceph_mds_request *req)
{
    struct inode *inode;
    struct ceph_inode_info *ci;
    struct ceph_cap *cap;
    int mode = req->r_direct_mode;
    int mds = -1;
    u32 hash = req->r_direct_hash;
    bool is_hash = req->r_direct_is_hash;

    /*
     * is there a specific mds we should try?  ignore hint if we have
     * no session and the mds is not up (active or recovering).
     */
    if (req->r_resend_mds >= 0 &&
        (__have_session(mdsc, req->r_resend_mds) ||
         ceph_mdsmap_get_state(mdsc->mdsmap, req->r_resend_mds) > 0)) {
        dout("choose_mds using resend_mds mds%d\n",
             req->r_resend_mds);
        return req->r_resend_mds;
    }

    if (mode == USE_RANDOM_MDS)
        goto random;

    inode = NULL;
    if (req->r_inode) {
        inode = req->r_inode;
    } else if (req->r_dentry) {
        /* ignore race with rename; old or new d_parent is okay */
        struct dentry *parent = req->r_dentry->d_parent;
        struct inode *dir = parent->d_inode;

        if (dir->i_sb != mdsc->fsc->sb) {
            /* not this fs! */
            inode = req->r_dentry->d_inode;
        } else if (ceph_snap(dir) != CEPH_NOSNAP) {
            /* direct snapped/virtual snapdir requests
             * based on parent dir inode */
            struct dentry *dn = get_nonsnap_parent(parent);
            inode = dn->d_inode;
            dout("__choose_mds using nonsnap parent %p\n", inode);
        } else if (req->r_dentry->d_inode) {
            /* dentry target */
            inode = req->r_dentry->d_inode;
        } else {
            /* dir + name */
            inode = dir;
            hash = ceph_dentry_hash(dir, req->r_dentry);
            is_hash = true;
        }
    }

    dout("__choose_mds %p is_hash=%d (%d) mode %d\n", inode, (int)is_hash,
         (int)hash, mode);
    if (!inode)
        goto random;
    ci = ceph_inode(inode);

    if (is_hash && S_ISDIR(inode->i_mode)) {
        struct ceph_inode_frag frag;
        int found;

        ceph_choose_frag(ci, hash, &frag, &found);
        if (found) {
            if (mode == USE_ANY_MDS && frag.ndist > 0) {
                u8 r;

                /* choose a random replica */
                get_random_bytes(&r, 1);
                r %= frag.ndist;
                mds = frag.dist[r];
                dout("choose_mds %p %llx.%llx "
                     "frag %u mds%d (%d/%d)\n",
                     inode, ceph_vinop(inode),
                     frag.frag, mds,
                     (int)r, frag.ndist);
                if (ceph_mdsmap_get_state(mdsc->mdsmap, mds) >=
                    CEPH_MDS_STATE_ACTIVE)
                    return mds;
            }

            /* since this file/dir wasn't known to be
             * replicated, then we want to look for the
             * authoritative mds. */
            mode = USE_AUTH_MDS;
            if (frag.mds >= 0) {
                /* choose auth mds */
                mds = frag.mds;
                dout("choose_mds %p %llx.%llx "
                     "frag %u mds%d (auth)\n",
                     inode, ceph_vinop(inode), frag.frag, mds);
                if (ceph_mdsmap_get_state(mdsc->mdsmap, mds) >=
                    CEPH_MDS_STATE_ACTIVE)
                    return mds;
            }
        }
    }

    spin_lock(&ci->i_ceph_lock);
    cap = NULL;
    if (mode == USE_AUTH_MDS)
        cap = ci->i_auth_cap;
    if (!cap && !RB_EMPTY_ROOT(&ci->i_caps))
        cap = rb_entry(rb_first(&ci->i_caps), struct ceph_cap, ci_node);
    if (!cap) {
        spin_unlock(&ci->i_ceph_lock);
        goto random;
    }
    mds = cap->session->s_mds;
    dout("choose_mds %p %llx.%llx mds%d (%scap %p)\n",
         inode, ceph_vinop(inode), mds,
         cap == ci->i_auth_cap ? "auth " : "", cap);
    spin_unlock(&ci->i_ceph_lock);
    return mds;

random:
    mds = ceph_mdsmap_get_random_mds(mdsc->mdsmap);
    dout("choose_mds chose random mds%d\n", mds);
    return mds;
}


/*
 * session messages
 */
static struct ceph_msg *create_session_msg(u32 op, u64 seq)
{
    struct ceph_msg *msg;
    struct ceph_mds_session_head *h;

    msg = ceph_msg_new(CEPH_MSG_CLIENT_SESSION, sizeof(*h), GFP_NOFS,
               false);
    if (!msg) {
        pr_err("create_session_msg ENOMEM creating msg\n");
        return NULL;
    }
    h = msg->front.iov_base;
    h->op = cpu_to_le32(op);
    h->seq = cpu_to_le64(seq);
    return msg;
}

/*
 * send session open request.
 *
 * called under mdsc->mutex
 */
static int __open_session(struct ceph_mds_client *mdsc,
              struct ceph_mds_session *session)
{
    struct ceph_msg *msg;
    int mstate;
    int mds = session->s_mds;

    /* wait for mds to go active? */
    mstate = ceph_mdsmap_get_state(mdsc->mdsmap, mds);
    dout("open_session to mds%d (%s)\n", mds,
         ceph_mds_state_name(mstate));
    session->s_state = CEPH_MDS_SESSION_OPENING;
    session->s_renew_requested = jiffies;

    /* send connect message */
    msg = create_session_msg(CEPH_SESSION_REQUEST_OPEN, session->s_seq);
    if (!msg)
        return -ENOMEM;
    ceph_con_send(&session->s_con, msg);
    return 0;
}

/*
 * open sessions for any export targets for the given mds
 *
 * called under mdsc->mutex
 */
static void __open_export_target_sessions(struct ceph_mds_client *mdsc,
                      struct ceph_mds_session *session)
{
    struct ceph_mds_info *mi;
    struct ceph_mds_session *ts;
    int i, mds = session->s_mds;
    int target;

    if (mds >= mdsc->mdsmap->m_max_mds)
        return;
    mi = &mdsc->mdsmap->m_info[mds];
    dout("open_export_target_sessions for mds%d (%d targets)\n",
         session->s_mds, mi->num_export_targets);

    for (i = 0; i < mi->num_export_targets; i++) {
        target = mi->export_targets[i];
        ts = __ceph_lookup_mds_session(mdsc, target);
        if (!ts) {
            ts = register_session(mdsc, target);
            if (IS_ERR(ts))
                return;
        }
        if (session->s_state == CEPH_MDS_SESSION_NEW ||
            session->s_state == CEPH_MDS_SESSION_CLOSING)
            __open_session(mdsc, session);
        else
            dout(" mds%d target mds%d %p is %s\n", session->s_mds,
                 i, ts, session_state_name(ts->s_state));
        ceph_put_mds_session(ts);
    }
}

void ceph_mdsc_open_export_target_sessions(struct ceph_mds_client *mdsc,
                       struct ceph_mds_session *session)
{
    mutex_lock(&mdsc->mutex);
    __open_export_target_sessions(mdsc, session);
    mutex_unlock(&mdsc->mutex);
}

/*
 * session caps
 */

/*
 * Free preallocated cap messages assigned to this session
 */
static void cleanup_cap_releases(struct ceph_mds_session *session)
{
    struct ceph_msg *msg;

    spin_lock(&session->s_cap_lock);
    while (!list_empty(&session->s_cap_releases)) {
        msg = list_first_entry(&session->s_cap_releases,
                       struct ceph_msg, list_head);
        list_del_init(&msg->list_head);
        ceph_msg_put(msg);
    }
    while (!list_empty(&session->s_cap_releases_done)) {
        msg = list_first_entry(&session->s_cap_releases_done,
                       struct ceph_msg, list_head);
        list_del_init(&msg->list_head);
        ceph_msg_put(msg);
    }
    spin_unlock(&session->s_cap_lock);
}

/*
 * Helper to safely iterate over all caps associated with a session, with
 * special care taken to handle a racing __ceph_remove_cap().
 *
 * Caller must hold session s_mutex.
 */
static int iterate_session_caps(struct ceph_mds_session *session,
                 int (*cb)(struct inode *, struct ceph_cap *,
                        void *), void *arg)
{
    struct list_head *p;
    struct ceph_cap *cap;
    struct inode *inode, *last_inode = NULL;
    struct ceph_cap *old_cap = NULL;
    int ret;

    dout("iterate_session_caps %p mds%d\n", session, session->s_mds);
    spin_lock(&session->s_cap_lock);
    p = session->s_caps.next;
    while (p != &session->s_caps) {
        cap = list_entry(p, struct ceph_cap, session_caps);
        inode = igrab(&cap->ci->vfs_inode);
        if (!inode) {
            p = p->next;
            continue;
        }
        session->s_cap_iterator = cap;
        spin_unlock(&session->s_cap_lock);

        if (last_inode) {
            iput(last_inode);
            last_inode = NULL;
        }
        if (old_cap) {
            ceph_put_cap(session->s_mdsc, old_cap);
            old_cap = NULL;
        }

        ret = cb(inode, cap, arg);
        last_inode = inode;

        spin_lock(&session->s_cap_lock);
        p = p->next;
        if (cap->ci == NULL) {
            dout("iterate_session_caps  finishing cap %p removal\n",
                 cap);
            BUG_ON(cap->session != session);
            list_del_init(&cap->session_caps);
            session->s_nr_caps--;
            cap->session = NULL;
            old_cap = cap;  /* put_cap it w/o locks held */
        }
        if (ret < 0)
            goto out;
    }
    ret = 0;
out:
    session->s_cap_iterator = NULL;
    spin_unlock(&session->s_cap_lock);

    if (last_inode)
        iput(last_inode);
    if (old_cap)
        ceph_put_cap(session->s_mdsc, old_cap);

    return ret;
}

static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
                  void *arg)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    int drop = 0;

    dout("removing cap %p, ci is %p, inode is %p\n",
         cap, ci, &ci->vfs_inode);
    spin_lock(&ci->i_ceph_lock);
    __ceph_remove_cap(cap);
    if (!__ceph_is_any_real_caps(ci)) {
        struct ceph_mds_client *mdsc =
            ceph_sb_to_client(inode->i_sb)->mdsc;

        spin_lock(&mdsc->cap_dirty_lock);
        if (!list_empty(&ci->i_dirty_item)) {
            pr_info(" dropping dirty %s state for %p %lld\n",
                ceph_cap_string(ci->i_dirty_caps),
                inode, ceph_ino(inode));
            ci->i_dirty_caps = 0;
            list_del_init(&ci->i_dirty_item);
            drop = 1;
        }
        if (!list_empty(&ci->i_flushing_item)) {
            pr_info(" dropping dirty+flushing %s state for %p %lld\n",
                ceph_cap_string(ci->i_flushing_caps),
                inode, ceph_ino(inode));
            ci->i_flushing_caps = 0;
            list_del_init(&ci->i_flushing_item);
            mdsc->num_cap_flushing--;
            drop = 1;
        }
        if (drop && ci->i_wrbuffer_ref) {
            pr_info(" dropping dirty data for %p %lld\n",
                inode, ceph_ino(inode));
            ci->i_wrbuffer_ref = 0;
            ci->i_wrbuffer_ref_head = 0;
            drop++;
        }
        spin_unlock(&mdsc->cap_dirty_lock);
    }
    spin_unlock(&ci->i_ceph_lock);
    while (drop--)
        iput(inode);
    return 0;
}

/*
 * caller must hold session s_mutex
 */
static void remove_session_caps(struct ceph_mds_session *session)
{
    dout("remove_session_caps on %p\n", session);
    iterate_session_caps(session, remove_session_caps_cb, NULL);
    BUG_ON(session->s_nr_caps > 0);
    BUG_ON(!list_empty(&session->s_cap_flushing));
    cleanup_cap_releases(session);
}

/*
 * wake up any threads waiting on this session's caps.  if the cap is
 * old (didn't get renewed on the client reconnect), remove it now.
 *
 * caller must hold s_mutex.
 */
static int wake_up_session_cb(struct inode *inode, struct ceph_cap *cap,
                  void *arg)
{
    struct ceph_inode_info *ci = ceph_inode(inode);

    wake_up_all(&ci->i_cap_wq);
    if (arg) {
        spin_lock(&ci->i_ceph_lock);
        ci->i_wanted_max_size = 0;
        ci->i_requested_max_size = 0;
        spin_unlock(&ci->i_ceph_lock);
    }
    return 0;
}

static void wake_up_session_caps(struct ceph_mds_session *session,
                 int reconnect)
{
    dout("wake_up_session_caps %p mds%d\n", session, session->s_mds);
    iterate_session_caps(session, wake_up_session_cb,
                 (void *)(unsigned long)reconnect);
}

/*
 * Send periodic message to MDS renewing all currently held caps.  The
 * ack will reset the expiration for all caps from this session.
 *
 * caller holds s_mutex
 */
static int send_renew_caps(struct ceph_mds_client *mdsc,
               struct ceph_mds_session *session)
{
    struct ceph_msg *msg;
    int state;

    if (time_after_eq(jiffies, session->s_cap_ttl) &&
        time_after_eq(session->s_cap_ttl, session->s_renew_requested))
        pr_info("mds%d caps stale\n", session->s_mds);
    session->s_renew_requested = jiffies;

    /* do not try to renew caps until a recovering mds has reconnected
     * with its clients. */
    state = ceph_mdsmap_get_state(mdsc->mdsmap, session->s_mds);
    if (state < CEPH_MDS_STATE_RECONNECT) {
        dout("send_renew_caps ignoring mds%d (%s)\n",
             session->s_mds, ceph_mds_state_name(state));
        return 0;
    }

    dout("send_renew_caps to mds%d (%s)\n", session->s_mds,
        ceph_mds_state_name(state));
    msg = create_session_msg(CEPH_SESSION_REQUEST_RENEWCAPS,
                 ++session->s_renew_seq);
    if (!msg)
        return -ENOMEM;
    ceph_con_send(&session->s_con, msg);
    return 0;
}

/*
 * Note new cap ttl, and any transition from stale -> not stale (fresh?).
 *
 * Called under session->s_mutex
 */
static void renewed_caps(struct ceph_mds_client *mdsc,
             struct ceph_mds_session *session, int is_renew)
{
    int was_stale;
    int wake = 0;

    spin_lock(&session->s_cap_lock);
    was_stale = is_renew && time_after_eq(jiffies, session->s_cap_ttl);

    session->s_cap_ttl = session->s_renew_requested +
        mdsc->mdsmap->m_session_timeout*HZ;

    if (was_stale) {
        if (time_before(jiffies, session->s_cap_ttl)) {
            pr_info("mds%d caps renewed\n", session->s_mds);
            wake = 1;
        } else {
            pr_info("mds%d caps still stale\n", session->s_mds);
        }
    }
    dout("renewed_caps mds%d ttl now %lu, was %s, now %s\n",
         session->s_mds, session->s_cap_ttl, was_stale ? "stale" : "fresh",
         time_before(jiffies, session->s_cap_ttl) ? "stale" : "fresh");
    spin_unlock(&session->s_cap_lock);

    if (wake)
        wake_up_session_caps(session, 0);
}

/*
 * send a session close request
 */
static int request_close_session(struct ceph_mds_client *mdsc,
                 struct ceph_mds_session *session)
{
    struct ceph_msg *msg;

    dout("request_close_session mds%d state %s seq %lld\n",
         session->s_mds, session_state_name(session->s_state),
         session->s_seq);
    msg = create_session_msg(CEPH_SESSION_REQUEST_CLOSE, session->s_seq);
    if (!msg)
        return -ENOMEM;
    ceph_con_send(&session->s_con, msg);
    return 0;
}

/*
 * Called with s_mutex held.
 */
static int __close_session(struct ceph_mds_client *mdsc,
             struct ceph_mds_session *session)
{
    if (session->s_state >= CEPH_MDS_SESSION_CLOSING)
        return 0;
    session->s_state = CEPH_MDS_SESSION_CLOSING;
    return request_close_session(mdsc, session);
}

/*
 * Trim old(er) caps.
 *
 * Because we can't cache an inode without one or more caps, we do
 * this indirectly: if a cap is unused, we prune its aliases, at which
 * point the inode will hopefully get dropped to.
 *
 * Yes, this is a bit sloppy.  Our only real goal here is to respond to
 * memory pressure from the MDS, though, so it needn't be perfect.
 */
static int trim_caps_cb(struct inode *inode, struct ceph_cap *cap, void *arg)
{
    struct ceph_mds_session *session = arg;
    struct ceph_inode_info *ci = ceph_inode(inode);
    int used, oissued, mine;

    if (session->s_trim_caps <= 0)
        return -1;

    spin_lock(&ci->i_ceph_lock);
    mine = cap->issued | cap->implemented;
    used = __ceph_caps_used(ci);
    oissued = __ceph_caps_issued_other(ci, cap);

    dout("trim_caps_cb %p cap %p mine %s oissued %s used %s\n",
         inode, cap, ceph_cap_string(mine), ceph_cap_string(oissued),
         ceph_cap_string(used));
    if (ci->i_dirty_caps)
        goto out;   /* dirty caps */
    if ((used & ~oissued) & mine)
        goto out;   /* we need these caps */

    session->s_trim_caps--;
    if (oissued) {
        /* we aren't the only cap.. just remove us */
        __ceph_remove_cap(cap);
    } else {
        /* try to drop referring dentries */
        spin_unlock(&ci->i_ceph_lock);
        d_prune_aliases(inode);
        dout("trim_caps_cb %p cap %p  pruned, count now %d\n",
             inode, cap, atomic_read(&inode->i_count));
        return 0;
    }

out:
    spin_unlock(&ci->i_ceph_lock);
    return 0;
}

/*
 * Trim session cap count down to some max number.
 */
static int trim_caps(struct ceph_mds_client *mdsc,
             struct ceph_mds_session *session,
             int max_caps)
{
    int trim_caps = session->s_nr_caps - max_caps;

    dout("trim_caps mds%d start: %d / %d, trim %d\n",
         session->s_mds, session->s_nr_caps, max_caps, trim_caps);
    if (trim_caps > 0) {
        session->s_trim_caps = trim_caps;
        iterate_session_caps(session, trim_caps_cb, session);
        dout("trim_caps mds%d done: %d / %d, trimmed %d\n",
             session->s_mds, session->s_nr_caps, max_caps,
            trim_caps - session->s_trim_caps);
        session->s_trim_caps = 0;
    }
    return 0;
}

/*
 * Allocate cap_release messages.  If there is a partially full message
 * in the queue, try to allocate enough to cover it's remainder, so that
 * we can send it immediately.
 *
 * Called under s_mutex.
 */
int ceph_add_cap_releases(struct ceph_mds_client *mdsc,
              struct ceph_mds_session *session)
{
    struct ceph_msg *msg, *partial = NULL;
    struct ceph_mds_cap_release *head;
    int err = -ENOMEM;
    int extra = mdsc->fsc->mount_options->cap_release_safety;
    int num;

    dout("add_cap_releases %p mds%d extra %d\n", session, session->s_mds,
         extra);

    spin_lock(&session->s_cap_lock);

    if (!list_empty(&session->s_cap_releases)) {
        msg = list_first_entry(&session->s_cap_releases,
                       struct ceph_msg,
                 list_head);
        head = msg->front.iov_base;
        num = le32_to_cpu(head->num);
        if (num) {
            dout(" partial %p with (%d/%d)\n", msg, num,
                 (int)CEPH_CAPS_PER_RELEASE);
            extra += CEPH_CAPS_PER_RELEASE - num;
            partial = msg;
        }
    }
    while (session->s_num_cap_releases < session->s_nr_caps + extra) {
        spin_unlock(&session->s_cap_lock);
        msg = ceph_msg_new(CEPH_MSG_CLIENT_CAPRELEASE, PAGE_CACHE_SIZE,
                   GFP_NOFS, false);
        if (!msg)
            goto out_unlocked;
        dout("add_cap_releases %p msg %p now %d\n", session, msg,
             (int)msg->front.iov_len);
        head = msg->front.iov_base;
        head->num = cpu_to_le32(0);
        msg->front.iov_len = sizeof(*head);
        spin_lock(&session->s_cap_lock);
        list_add(&msg->list_head, &session->s_cap_releases);
        session->s_num_cap_releases += CEPH_CAPS_PER_RELEASE;
    }

    if (partial) {
        head = partial->front.iov_base;
        num = le32_to_cpu(head->num);
        dout(" queueing partial %p with %d/%d\n", partial, num,
             (int)CEPH_CAPS_PER_RELEASE);
        list_move_tail(&partial->list_head,
                   &session->s_cap_releases_done);
        session->s_num_cap_releases -= CEPH_CAPS_PER_RELEASE - num;
    }
    err = 0;
    spin_unlock(&session->s_cap_lock);
out_unlocked:
    return err;
}

/*
 * flush all dirty inode data to disk.
 *
 * returns true if we've flushed through want_flush_seq
 */
static int check_cap_flush(struct ceph_mds_client *mdsc, u64 want_flush_seq)
{
    int mds, ret = 1;

    dout("check_cap_flush want %lld\n", want_flush_seq);
    mutex_lock(&mdsc->mutex);
    for (mds = 0; ret && mds < mdsc->max_sessions; mds++) {
        struct ceph_mds_session *session = mdsc->sessions[mds];

        if (!session)
            continue;
        get_session(session);
        mutex_unlock(&mdsc->mutex);

        mutex_lock(&session->s_mutex);
        if (!list_empty(&session->s_cap_flushing)) {
            struct ceph_inode_info *ci =
                list_entry(session->s_cap_flushing.next,
                       struct ceph_inode_info,
                       i_flushing_item);
            struct inode *inode = &ci->vfs_inode;

            spin_lock(&ci->i_ceph_lock);
            if (ci->i_cap_flush_seq <= want_flush_seq) {
                dout("check_cap_flush still flushing %p "
                     "seq %lld <= %lld to mds%d\n", inode,
                     ci->i_cap_flush_seq, want_flush_seq,
                     session->s_mds);
                ret = 0;
            }
            spin_unlock(&ci->i_ceph_lock);
        }
        mutex_unlock(&session->s_mutex);
        ceph_put_mds_session(session);

        if (!ret)
            return ret;
        mutex_lock(&mdsc->mutex);
    }

    mutex_unlock(&mdsc->mutex);
    dout("check_cap_flush ok, flushed thru %lld\n", want_flush_seq);
    return ret;
}

/*
 * called under s_mutex
 */
void ceph_send_cap_releases(struct ceph_mds_client *mdsc,
                struct ceph_mds_session *session)
{
    struct ceph_msg *msg;

    dout("send_cap_releases mds%d\n", session->s_mds);
    spin_lock(&session->s_cap_lock);
    while (!list_empty(&session->s_cap_releases_done)) {
        msg = list_first_entry(&session->s_cap_releases_done,
                 struct ceph_msg, list_head);
        list_del_init(&msg->list_head);
        spin_unlock(&session->s_cap_lock);
        msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
        dout("send_cap_releases mds%d %p\n", session->s_mds, msg);
        ceph_con_send(&session->s_con, msg);
        spin_lock(&session->s_cap_lock);
    }
    spin_unlock(&session->s_cap_lock);
}

static void discard_cap_releases(struct ceph_mds_client *mdsc,
                 struct ceph_mds_session *session)
{
    struct ceph_msg *msg;
    struct ceph_mds_cap_release *head;
    unsigned num;

    dout("discard_cap_releases mds%d\n", session->s_mds);
    spin_lock(&session->s_cap_lock);

    /* zero out the in-progress message */
    msg = list_first_entry(&session->s_cap_releases,
                   struct ceph_msg, list_head);
    head = msg->front.iov_base;
    num = le32_to_cpu(head->num);
    dout("discard_cap_releases mds%d %p %u\n", session->s_mds, msg, num);
    head->num = cpu_to_le32(0);
    session->s_num_cap_releases += num;

    /* requeue completed messages */
    while (!list_empty(&session->s_cap_releases_done)) {
        msg = list_first_entry(&session->s_cap_releases_done,
                 struct ceph_msg, list_head);
        list_del_init(&msg->list_head);

        head = msg->front.iov_base;
        num = le32_to_cpu(head->num);
        dout("discard_cap_releases mds%d %p %u\n", session->s_mds, msg,
             num);
        session->s_num_cap_releases += num;
        head->num = cpu_to_le32(0);
        msg->front.iov_len = sizeof(*head);
        list_add(&msg->list_head, &session->s_cap_releases);
    }

    spin_unlock(&session->s_cap_lock);
}

/*
 * requests
 */

/*
 * Create an mds request.
 */
struct ceph_mds_request *
ceph_mdsc_create_request(struct ceph_mds_client *mdsc, int op, int mode)
{
    struct ceph_mds_request *req = kzalloc(sizeof(*req), GFP_NOFS);

    if (!req)
        return ERR_PTR(-ENOMEM);

    mutex_init(&req->r_fill_mutex);
    req->r_mdsc = mdsc;
    req->r_started = jiffies;
    req->r_resend_mds = -1;
    INIT_LIST_HEAD(&req->r_unsafe_dir_item);
    req->r_fmode = -1;
    kref_init(&req->r_kref);
    INIT_LIST_HEAD(&req->r_wait);
    init_completion(&req->r_completion);
    init_completion(&req->r_safe_completion);
    INIT_LIST_HEAD(&req->r_unsafe_item);

    req->r_op = op;
    req->r_direct_mode = mode;
    return req;
}

/*
 * return oldest (lowest) request, tid in request tree, 0 if none.
 *
 * called under mdsc->mutex.
 */
static struct ceph_mds_request *__get_oldest_req(struct ceph_mds_client *mdsc)
{
    if (RB_EMPTY_ROOT(&mdsc->request_tree))
        return NULL;
    return rb_entry(rb_first(&mdsc->request_tree),
            struct ceph_mds_request, r_node);
}

static u64 __get_oldest_tid(struct ceph_mds_client *mdsc)
{
    struct ceph_mds_request *req = __get_oldest_req(mdsc);

    if (req)
        return req->r_tid;
    return 0;
}

/*
 * Build a dentry's path.  Allocate on heap; caller must kfree.  Based
 * on build_path_from_dentry in fs/cifs/dir.c.
 *
 * If @stop_on_nosnap, generate path relative to the first non-snapped
 * inode.
 *
 * Encode hidden .snap dirs as a double /, i.e.
 *   foo/.snap/bar -> foo//bar
 */
char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *base,
               int stop_on_nosnap)
{
    struct dentry *temp;
    char *path;
    int len, pos;
    unsigned seq;

    if (dentry == NULL)
        return ERR_PTR(-EINVAL);

retry:
    len = 0;
    seq = read_seqbegin(&rename_lock);
    rcu_read_lock();
    for (temp = dentry; !IS_ROOT(temp);) {
        struct inode *inode = temp->d_inode;
        if (inode && ceph_snap(inode) == CEPH_SNAPDIR)
            len++;  /* slash only */
        else if (stop_on_nosnap && inode &&
             ceph_snap(inode) == CEPH_NOSNAP)
            break;
        else
            len += 1 + temp->d_name.len;
        temp = temp->d_parent;
    }
    rcu_read_unlock();
    if (len)
        len--;  /* no leading '/' */

    path = kmalloc(len+1, GFP_NOFS);
    if (path == NULL)
        return ERR_PTR(-ENOMEM);
    pos = len;
    path[pos] = 0;  /* trailing null */
    rcu_read_lock();
    for (temp = dentry; !IS_ROOT(temp) && pos != 0; ) {
        struct inode *inode;

        spin_lock(&temp->d_lock);
        inode = temp->d_inode;
        if (inode && ceph_snap(inode) == CEPH_SNAPDIR) {
            dout("build_path path+%d: %p SNAPDIR\n",
                 pos, temp);
        } else if (stop_on_nosnap && inode &&
               ceph_snap(inode) == CEPH_NOSNAP) {
            spin_unlock(&temp->d_lock);
            break;
        } else {
            pos -= temp->d_name.len;
            if (pos < 0) {
                spin_unlock(&temp->d_lock);
                break;
            }
            strncpy(path + pos, temp->d_name.name,
                temp->d_name.len);
        }
        spin_unlock(&temp->d_lock);
        if (pos)
            path[--pos] = '/';
        temp = temp->d_parent;
    }
    rcu_read_unlock();
    if (pos != 0 || read_seqretry(&rename_lock, seq)) {
        pr_err("build_path did not end path lookup where "
               "expected, namelen is %d, pos is %d\n", len, pos);
        /* presumably this is only possible if racing with a
           rename of one of the parent directories (we can not
           lock the dentries above us to prevent this, but
           retrying should be harmless) */
        kfree(path);
        goto retry;
    }

    *base = ceph_ino(temp->d_inode);
    *plen = len;
    dout("build_path on %p %d built %llx '%.*s'\n",
         dentry, dentry->d_count, *base, len, path);
    return path;
}

static int build_dentry_path(struct dentry *dentry,
                 const char **ppath, int *ppathlen, u64 *pino,
                 int *pfreepath)
{
    char *path;

    if (ceph_snap(dentry->d_parent->d_inode) == CEPH_NOSNAP) {
        *pino = ceph_ino(dentry->d_parent->d_inode);
        *ppath = dentry->d_name.name;
        *ppathlen = dentry->d_name.len;
        return 0;
    }
    path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1);
    if (IS_ERR(path))
        return PTR_ERR(path);
    *ppath = path;
    *pfreepath = 1;
    return 0;
}

static int build_inode_path(struct inode *inode,
                const char **ppath, int *ppathlen, u64 *pino,
                int *pfreepath)
{
    struct dentry *dentry;
    char *path;

    if (ceph_snap(inode) == CEPH_NOSNAP) {
        *pino = ceph_ino(inode);
        *ppathlen = 0;
        return 0;
    }
    dentry = d_find_alias(inode);
    path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1);
    dput(dentry);
    if (IS_ERR(path))
        return PTR_ERR(path);
    *ppath = path;
    *pfreepath = 1;
    return 0;
}

/*
 * request arguments may be specified via an inode *, a dentry *, or
 * an explicit ino+path.
 */
static int set_request_path_attr(struct inode *rinode, struct dentry *rdentry,
                  const char *rpath, u64 rino,
                  const char **ppath, int *pathlen,
                  u64 *ino, int *freepath)
{
    int r = 0;

    if (rinode) {
        r = build_inode_path(rinode, ppath, pathlen, ino, freepath);
        dout(" inode %p %llx.%llx\n", rinode, ceph_ino(rinode),
             ceph_snap(rinode));
    } else if (rdentry) {
        r = build_dentry_path(rdentry, ppath, pathlen, ino, freepath);
        dout(" dentry %p %llx/%.*s\n", rdentry, *ino, *pathlen,
             *ppath);
    } else if (rpath || rino) {
        *ino = rino;
        *ppath = rpath;
        *pathlen = strlen(rpath);
        dout(" path %.*s\n", *pathlen, rpath);
    }

    return r;
}

/*
 * called under mdsc->mutex
 */
static struct ceph_msg *create_request_message(struct ceph_mds_client *mdsc,
                           struct ceph_mds_request *req,
                           int mds)
{
    struct ceph_msg *msg;
    struct ceph_mds_request_head *head;
    const char *path1 = NULL;
    const char *path2 = NULL;
    u64 ino1 = 0, ino2 = 0;
    int pathlen1 = 0, pathlen2 = 0;
    int freepath1 = 0, freepath2 = 0;
    int len;
    u16 releases;
    void *p, *end;
    int ret;

    ret = set_request_path_attr(req->r_inode, req->r_dentry,
                  req->r_path1, req->r_ino1.ino,
                  &path1, &pathlen1, &ino1, &freepath1);
    if (ret < 0) {
        msg = ERR_PTR(ret);
        goto out;
    }

    ret = set_request_path_attr(NULL, req->r_old_dentry,
                  req->r_path2, req->r_ino2.ino,
                  &path2, &pathlen2, &ino2, &freepath2);
    if (ret < 0) {
        msg = ERR_PTR(ret);
        goto out_free1;
    }

    len = sizeof(*head) +
        pathlen1 + pathlen2 + 2*(1 + sizeof(u32) + sizeof(u64));

    /* calculate (max) length for cap releases */
    len += sizeof(struct ceph_mds_request_release) *
        (!!req->r_inode_drop + !!req->r_dentry_drop +
         !!req->r_old_inode_drop + !!req->r_old_dentry_drop);
    if (req->r_dentry_drop)
        len += req->r_dentry->d_name.len;
    if (req->r_old_dentry_drop)
        len += req->r_old_dentry->d_name.len;

    msg = ceph_msg_new(CEPH_MSG_CLIENT_REQUEST, len, GFP_NOFS, false);
    if (!msg) {
        msg = ERR_PTR(-ENOMEM);
        goto out_free2;
    }

    msg->hdr.tid = cpu_to_le64(req->r_tid);

    head = msg->front.iov_base;
    p = msg->front.iov_base + sizeof(*head);
    end = msg->front.iov_base + msg->front.iov_len;

    head->mdsmap_epoch = cpu_to_le32(mdsc->mdsmap->m_epoch);
    head->op = cpu_to_le32(req->r_op);
    head->caller_uid = cpu_to_le32(req->r_uid);
    head->caller_gid = cpu_to_le32(req->r_gid);
    head->args = req->r_args;

    ceph_encode_filepath(&p, end, ino1, path1);
    ceph_encode_filepath(&p, end, ino2, path2);

    /* make note of release offset, in case we need to replay */
    req->r_request_release_offset = p - msg->front.iov_base;

    /* cap releases */
    releases = 0;
    if (req->r_inode_drop)
        releases += ceph_encode_inode_release(&p,
              req->r_inode ? req->r_inode : req->r_dentry->d_inode,
              mds, req->r_inode_drop, req->r_inode_unless, 0);
    if (req->r_dentry_drop)
        releases += ceph_encode_dentry_release(&p, req->r_dentry,
               mds, req->r_dentry_drop, req->r_dentry_unless);
    if (req->r_old_dentry_drop)
        releases += ceph_encode_dentry_release(&p, req->r_old_dentry,
               mds, req->r_old_dentry_drop, req->r_old_dentry_unless);
    if (req->r_old_inode_drop)
        releases += ceph_encode_inode_release(&p,
              req->r_old_dentry->d_inode,
              mds, req->r_old_inode_drop, req->r_old_inode_unless, 0);
    head->num_releases = cpu_to_le16(releases);

    BUG_ON(p > end);
    msg->front.iov_len = p - msg->front.iov_base;
    msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);

    msg->pages = req->r_pages;
    msg->nr_pages = req->r_num_pages;
    msg->hdr.data_len = cpu_to_le32(req->r_data_len);
    msg->hdr.data_off = cpu_to_le16(0);

out_free2:
    if (freepath2)
        kfree((char *)path2);
out_free1:
    if (freepath1)
        kfree((char *)path1);
out:
    return msg;
}

/*
 * called under mdsc->mutex if error, under no mutex if
 * success.
 */
static void complete_request(struct ceph_mds_client *mdsc,
                 struct ceph_mds_request *req)
{
    if (req->r_callback)
        req->r_callback(mdsc, req);
    else
        complete_all(&req->r_completion);
}

/*
 * called under mdsc->mutex
 */
static int __prepare_send_request(struct ceph_mds_client *mdsc,
                  struct ceph_mds_request *req,
                  int mds)
{
    struct ceph_mds_request_head *rhead;
    struct ceph_msg *msg;
    int flags = 0;

    req->r_attempts++;
    if (req->r_inode) {
        struct ceph_cap *cap =
            ceph_get_cap_for_mds(ceph_inode(req->r_inode), mds);

        if (cap)
            req->r_sent_on_mseq = cap->mseq;
        else
            req->r_sent_on_mseq = -1;
    }
    dout("prepare_send_request %p tid %lld %s (attempt %d)\n", req,
         req->r_tid, ceph_mds_op_name(req->r_op), req->r_attempts);

    if (req->r_got_unsafe) {
        /*
         * Replay.  Do not regenerate message (and rebuild
         * paths, etc.); just use the original message.
         * Rebuilding paths will break for renames because
         * d_move mangles the src name.
         */
        msg = req->r_request;
        rhead = msg->front.iov_base;

        flags = le32_to_cpu(rhead->flags);
        flags |= CEPH_MDS_FLAG_REPLAY;
        rhead->flags = cpu_to_le32(flags);

        if (req->r_target_inode)
            rhead->ino = cpu_to_le64(ceph_ino(req->r_target_inode));

        rhead->num_retry = req->r_attempts - 1;

        /* remove cap/dentry releases from message */
        rhead->num_releases = 0;
        msg->hdr.front_len = cpu_to_le32(req->r_request_release_offset);
        msg->front.iov_len = req->r_request_release_offset;
        return 0;
    }

    if (req->r_request) {
        ceph_msg_put(req->r_request);
        req->r_request = NULL;
    }
    msg = create_request_message(mdsc, req, mds);
    if (IS_ERR(msg)) {
        req->r_err = PTR_ERR(msg);
        complete_request(mdsc, req);
        return PTR_ERR(msg);
    }
    req->r_request = msg;

    rhead = msg->front.iov_base;
    rhead->oldest_client_tid = cpu_to_le64(__get_oldest_tid(mdsc));
    if (req->r_got_unsafe)
        flags |= CEPH_MDS_FLAG_REPLAY;
    if (req->r_locked_dir)
        flags |= CEPH_MDS_FLAG_WANT_DENTRY;
    rhead->flags = cpu_to_le32(flags);
    rhead->num_fwd = req->r_num_fwd;
    rhead->num_retry = req->r_attempts - 1;
    rhead->ino = 0;

    dout(" r_locked_dir = %p\n", req->r_locked_dir);
    return 0;
}

/*
 * send request, or put it on the appropriate wait list.
 */
static int __do_request(struct ceph_mds_client *mdsc,
            struct ceph_mds_request *req)
{
    struct ceph_mds_session *session = NULL;
    int mds = -1;
    int err = -EAGAIN;

    if (req->r_err || req->r_got_result)
        goto out;

    if (req->r_timeout &&
        time_after_eq(jiffies, req->r_started + req->r_timeout)) {
        dout("do_request timed out\n");
        err = -EIO;
        goto finish;
    }

    put_request_session(req);

    mds = __choose_mds(mdsc, req);
    if (mds < 0 ||
        ceph_mdsmap_get_state(mdsc->mdsmap, mds) < CEPH_MDS_STATE_ACTIVE) {
        dout("do_request no mds or not active, waiting for map\n");
        list_add(&req->r_wait, &mdsc->waiting_for_map);
        goto out;
    }

    /* get, open session */
    session = __ceph_lookup_mds_session(mdsc, mds);
    if (!session) {
        session = register_session(mdsc, mds);
        if (IS_ERR(session)) {
            err = PTR_ERR(session);
            goto finish;
        }
    }
    req->r_session = get_session(session);

    dout("do_request mds%d session %p state %s\n", mds, session,
         session_state_name(session->s_state));
    if (session->s_state != CEPH_MDS_SESSION_OPEN &&
        session->s_state != CEPH_MDS_SESSION_HUNG) {
        if (session->s_state == CEPH_MDS_SESSION_NEW ||
            session->s_state == CEPH_MDS_SESSION_CLOSING)
            __open_session(mdsc, session);
        list_add(&req->r_wait, &session->s_waiting);
        goto out_session;
    }

    /* send request */
    req->r_resend_mds = -1;   /* forget any previous mds hint */

    if (req->r_request_started == 0)   /* note request start time */
        req->r_request_started = jiffies;

    err = __prepare_send_request(mdsc, req, mds);
    if (!err) {
        ceph_msg_get(req->r_request);
        ceph_con_send(&session->s_con, req->r_request);
    }

out_session:
    ceph_put_mds_session(session);
out:
    return err;

finish:
    req->r_err = err;
    complete_request(mdsc, req);
    goto out;
}

/*
 * called under mdsc->mutex
 */
static void __wake_requests(struct ceph_mds_client *mdsc,
                struct list_head *head)
{
    struct ceph_mds_request *req, *nreq;

    list_for_each_entry_safe(req, nreq, head, r_wait) {
        list_del_init(&req->r_wait);
        __do_request(mdsc, req);
    }
}

/*
 * Wake up threads with requests pending for @mds, so that they can
 * resubmit their requests to a possibly different mds.
 */
static void kick_requests(struct ceph_mds_client *mdsc, int mds)
{
    struct ceph_mds_request *req;
    struct rb_node *p;

    dout("kick_requests mds%d\n", mds);
    for (p = rb_first(&mdsc->request_tree); p; p = rb_next(p)) {
        req = rb_entry(p, struct ceph_mds_request, r_node);
        if (req->r_got_unsafe)
            continue;
        if (req->r_session &&
            req->r_session->s_mds == mds) {
            dout(" kicking tid %llu\n", req->r_tid);
            __do_request(mdsc, req);
        }
    }
}

void ceph_mdsc_submit_request(struct ceph_mds_client *mdsc,
                  struct ceph_mds_request *req)
{
    dout("submit_request on %p\n", req);
    mutex_lock(&mdsc->mutex);
    __register_request(mdsc, req, NULL);
    __do_request(mdsc, req);
    mutex_unlock(&mdsc->mutex);
}

/*
 * Synchrously perform an mds request.  Take care of all of the
 * session setup, forwarding, retry details.
 */
int ceph_mdsc_do_request(struct ceph_mds_client *mdsc,
             struct inode *dir,
             struct ceph_mds_request *req)
{
    int err;

    dout("do_request on %p\n", req);

    /* take CAP_PIN refs for r_inode, r_locked_dir, r_old_dentry */
    if (req->r_inode)
        ceph_get_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);
    if (req->r_locked_dir)
        ceph_get_cap_refs(ceph_inode(req->r_locked_dir), CEPH_CAP_PIN);
    if (req->r_old_dentry)
        ceph_get_cap_refs(ceph_inode(req->r_old_dentry_dir),
                  CEPH_CAP_PIN);

    /* issue */
    mutex_lock(&mdsc->mutex);
    __register_request(mdsc, req, dir);
    __do_request(mdsc, req);

    if (req->r_err) {
        err = req->r_err;
        __unregister_request(mdsc, req);
        dout("do_request early error %d\n", err);
        goto out;
    }

    /* wait */
    mutex_unlock(&mdsc->mutex);
    dout("do_request waiting\n");
    if (req->r_timeout) {
        err = (long)wait_for_completion_killable_timeout(
            &req->r_completion, req->r_timeout);
        if (err == 0)
            err = -EIO;
    } else {
        err = wait_for_completion_killable(&req->r_completion);
    }
    dout("do_request waited, got %d\n", err);
    mutex_lock(&mdsc->mutex);

    /* only abort if we didn't race with a real reply */
    if (req->r_got_result) {
        err = le32_to_cpu(req->r_reply_info.head->result);
    } else if (err < 0) {
        dout("aborted request %lld with %d\n", req->r_tid, err);

        /*
         * ensure we aren't running concurrently with
         * ceph_fill_trace or ceph_readdir_prepopulate, which
         * rely on locks (dir mutex) held by our caller.
         */
        mutex_lock(&req->r_fill_mutex);
        req->r_err = err;
        req->r_aborted = true;
        mutex_unlock(&req->r_fill_mutex);

        if (req->r_locked_dir &&
            (req->r_op & CEPH_MDS_OP_WRITE))
            ceph_invalidate_dir_request(req);
    } else {
        err = req->r_err;
    }

out:
    mutex_unlock(&mdsc->mutex);
    dout("do_request %p done, result %d\n", req, err);
    return err;
}

/*
 * Invalidate dir D_COMPLETE, dentry lease state on an aborted MDS
 * namespace request.
 */
void ceph_invalidate_dir_request(struct ceph_mds_request *req)
{
    struct inode *inode = req->r_locked_dir;
    struct ceph_inode_info *ci = ceph_inode(inode);

    dout("invalidate_dir_request %p (D_COMPLETE, lease(s))\n", inode);
    spin_lock(&ci->i_ceph_lock);
    ceph_dir_clear_complete(inode);
    ci->i_release_count++;
    spin_unlock(&ci->i_ceph_lock);

    if (req->r_dentry)
        ceph_invalidate_dentry_lease(req->r_dentry);
    if (req->r_old_dentry)
        ceph_invalidate_dentry_lease(req->r_old_dentry);
}

/*
 * Handle mds reply.
 *
 * We take the session mutex and parse and process the reply immediately.
 * This preserves the logical ordering of replies, capabilities, etc., sent
 * by the MDS as they are applied to our local cache.
 */
static void handle_reply(struct ceph_mds_session *session, struct ceph_msg *msg)
{
    struct ceph_mds_client *mdsc = session->s_mdsc;
    struct ceph_mds_request *req;
    struct ceph_mds_reply_head *head = msg->front.iov_base;
    struct ceph_mds_reply_info_parsed *rinfo;  /* parsed reply info */
    u64 tid;
    int err, result;
    int mds = session->s_mds;

    if (msg->front.iov_len < sizeof(*head)) {
        pr_err("mdsc_handle_reply got corrupt (short) reply\n");
        ceph_msg_dump(msg);
        return;
    }

    /* get request, session */
    tid = le64_to_cpu(msg->hdr.tid);
    mutex_lock(&mdsc->mutex);
    req = __lookup_request(mdsc, tid);
    if (!req) {
        dout("handle_reply on unknown tid %llu\n", tid);
        mutex_unlock(&mdsc->mutex);
        return;
    }
    dout("handle_reply %p\n", req);

    /* correct session? */
    if (req->r_session != session) {
        pr_err("mdsc_handle_reply got %llu on session mds%d"
               " not mds%d\n", tid, session->s_mds,
               req->r_session ? req->r_session->s_mds : -1);
        mutex_unlock(&mdsc->mutex);
        goto out;
    }

    /* dup? */
    if ((req->r_got_unsafe && !head->safe) ||
        (req->r_got_safe && head->safe)) {
        pr_warning("got a dup %s reply on %llu from mds%d\n",
               head->safe ? "safe" : "unsafe", tid, mds);
        mutex_unlock(&mdsc->mutex);
        goto out;
    }
    if (req->r_got_safe && !head->safe) {
        pr_warning("got unsafe after safe on %llu from mds%d\n",
               tid, mds);
        mutex_unlock(&mdsc->mutex);
        goto out;
    }

    result = le32_to_cpu(head->result);

    /*
     * Handle an ESTALE
     * if we're not talking to the authority, send to them
     * if the authority has changed while we weren't looking,
     * send to new authority
     * Otherwise we just have to return an ESTALE
     */
    if (result == -ESTALE) {
        dout("got ESTALE on request %llu", req->r_tid);
        if (!req->r_inode) {
            /* do nothing; not an authority problem */
        } else if (req->r_direct_mode != USE_AUTH_MDS) {
            dout("not using auth, setting for that now");
            req->r_direct_mode = USE_AUTH_MDS;
            __do_request(mdsc, req);
            mutex_unlock(&mdsc->mutex);
            goto out;
        } else  {
            struct ceph_inode_info *ci = ceph_inode(req->r_inode);
            struct ceph_cap *cap = NULL;

            if (req->r_session)
                cap = ceph_get_cap_for_mds(ci,
                           req->r_session->s_mds);

            dout("already using auth");
            if ((!cap || cap != ci->i_auth_cap) ||
                (cap->mseq != req->r_sent_on_mseq)) {
                dout("but cap changed, so resending");
                __do_request(mdsc, req);
                mutex_unlock(&mdsc->mutex);
                goto out;
            }
        }
        dout("have to return ESTALE on request %llu", req->r_tid);
    }


    if (head->safe) {
        req->r_got_safe = true;
        __unregister_request(mdsc, req);
        complete_all(&req->r_safe_completion);

        if (req->r_got_unsafe) {
            /*
             * We already handled the unsafe response, now do the
             * cleanup.  No need to examine the response; the MDS
             * doesn't include any result info in the safe
             * response.  And even if it did, there is nothing
             * useful we could do with a revised return value.
             */
            dout("got safe reply %llu, mds%d\n", tid, mds);
            list_del_init(&req->r_unsafe_item);

            /* last unsafe request during umount? */
            if (mdsc->stopping && !__get_oldest_req(mdsc))
                complete_all(&mdsc->safe_umount_waiters);
            mutex_unlock(&mdsc->mutex);
            goto out;
        }
    } else {
        req->r_got_unsafe = true;
        list_add_tail(&req->r_unsafe_item, &req->r_session->s_unsafe);
    }

    dout("handle_reply tid %lld result %d\n", tid, result);
    rinfo = &req->r_reply_info;
    err = parse_reply_info(msg, rinfo, session->s_con.peer_features);
    mutex_unlock(&mdsc->mutex);

    mutex_lock(&session->s_mutex);
    if (err < 0) {
        pr_err("mdsc_handle_reply got corrupt reply mds%d(tid:%lld)\n", mds, tid);
        ceph_msg_dump(msg);
        goto out_err;
    }

    /* snap trace */
    if (rinfo->snapblob_len) {
        down_write(&mdsc->snap_rwsem);
        ceph_update_snap_trace(mdsc, rinfo->snapblob,
                   rinfo->snapblob + rinfo->snapblob_len,
                   le32_to_cpu(head->op) == CEPH_MDS_OP_RMSNAP);
        downgrade_write(&mdsc->snap_rwsem);
    } else {
        down_read(&mdsc->snap_rwsem);
    }

    /* insert trace into our cache */
    mutex_lock(&req->r_fill_mutex);
    err = ceph_fill_trace(mdsc->fsc->sb, req, req->r_session);
    if (err == 0) {
        if (result == 0 && req->r_op != CEPH_MDS_OP_GETFILELOCK &&
            rinfo->dir_nr)
            ceph_readdir_prepopulate(req, req->r_session);
        ceph_unreserve_caps(mdsc, &req->r_caps_reservation);
    }
    mutex_unlock(&req->r_fill_mutex);

    up_read(&mdsc->snap_rwsem);
out_err:
    mutex_lock(&mdsc->mutex);
    if (!req->r_aborted) {
        if (err) {
            req->r_err = err;
        } else {
            req->r_reply = msg;
            ceph_msg_get(msg);
            req->r_got_result = true;
        }
    } else {
        dout("reply arrived after request %lld was aborted\n", tid);
    }
    mutex_unlock(&mdsc->mutex);

    ceph_add_cap_releases(mdsc, req->r_session);
    mutex_unlock(&session->s_mutex);

    /* kick calling process */
    complete_request(mdsc, req);
out:
    ceph_mdsc_put_request(req);
    return;
}



/*
 * handle mds notification that our request has been forwarded.
 */
static void handle_forward(struct ceph_mds_client *mdsc,
               struct ceph_mds_session *session,
               struct ceph_msg *msg)
{
    struct ceph_mds_request *req;
    u64 tid = le64_to_cpu(msg->hdr.tid);
    u32 next_mds;
    u32 fwd_seq;
    int err = -EINVAL;
    void *p = msg->front.iov_base;
    void *end = p + msg->front.iov_len;

    ceph_decode_need(&p, end, 2*sizeof(u32), bad);
    next_mds = ceph_decode_32(&p);
    fwd_seq = ceph_decode_32(&p);

    mutex_lock(&mdsc->mutex);
    req = __lookup_request(mdsc, tid);
    if (!req) {
        dout("forward tid %llu to mds%d - req dne\n", tid, next_mds);
        goto out;  /* dup reply? */
    }

    if (req->r_aborted) {
        dout("forward tid %llu aborted, unregistering\n", tid);
        __unregister_request(mdsc, req);
    } else if (fwd_seq <= req->r_num_fwd) {
        dout("forward tid %llu to mds%d - old seq %d <= %d\n",
             tid, next_mds, req->r_num_fwd, fwd_seq);
    } else {
        /* resend. forward race not possible; mds would drop */
        dout("forward tid %llu to mds%d (we resend)\n", tid, next_mds);
        BUG_ON(req->r_err);
        BUG_ON(req->r_got_result);
        req->r_num_fwd = fwd_seq;
        req->r_resend_mds = next_mds;
        put_request_session(req);
        __do_request(mdsc, req);
    }
    ceph_mdsc_put_request(req);
out:
    mutex_unlock(&mdsc->mutex);
    return;

bad:
    pr_err("mdsc_handle_forward decode error err=%d\n", err);
}

/*
 * handle a mds session control message
 */
static void handle_session(struct ceph_mds_session *session,
               struct ceph_msg *msg)
{
    struct ceph_mds_client *mdsc = session->s_mdsc;
    u32 op;
    u64 seq;
    int mds = session->s_mds;
    struct ceph_mds_session_head *h = msg->front.iov_base;
    int wake = 0;

    /* decode */
    if (msg->front.iov_len != sizeof(*h))
        goto bad;
    op = le32_to_cpu(h->op);
    seq = le64_to_cpu(h->seq);

    mutex_lock(&mdsc->mutex);
    if (op == CEPH_SESSION_CLOSE)
        __unregister_session(mdsc, session);
    /* FIXME: this ttl calculation is generous */
    session->s_ttl = jiffies + HZ*mdsc->mdsmap->m_session_autoclose;
    mutex_unlock(&mdsc->mutex);

    mutex_lock(&session->s_mutex);

    dout("handle_session mds%d %s %p state %s seq %llu\n",
         mds, ceph_session_op_name(op), session,
         session_state_name(session->s_state), seq);

    if (session->s_state == CEPH_MDS_SESSION_HUNG) {
        session->s_state = CEPH_MDS_SESSION_OPEN;
        pr_info("mds%d came back\n", session->s_mds);
    }

    switch (op) {
    case CEPH_SESSION_OPEN:
        if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
            pr_info("mds%d reconnect success\n", session->s_mds);
        session->s_state = CEPH_MDS_SESSION_OPEN;
        renewed_caps(mdsc, session, 0);
        wake = 1;
        if (mdsc->stopping)
            __close_session(mdsc, session);
        break;

    case CEPH_SESSION_RENEWCAPS:
        if (session->s_renew_seq == seq)
            renewed_caps(mdsc, session, 1);
        break;

    case CEPH_SESSION_CLOSE:
        if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
            pr_info("mds%d reconnect denied\n", session->s_mds);
        remove_session_caps(session);
        wake = 1; /* for good measure */
        wake_up_all(&mdsc->session_close_wq);
        kick_requests(mdsc, mds);
        break;

    case CEPH_SESSION_STALE:
        pr_info("mds%d caps went stale, renewing\n",
            session->s_mds);
        spin_lock(&session->s_gen_ttl_lock);
        session->s_cap_gen++;
        session->s_cap_ttl = jiffies - 1;
        spin_unlock(&session->s_gen_ttl_lock);
        send_renew_caps(mdsc, session);
        break;

    case CEPH_SESSION_RECALL_STATE:
        trim_caps(mdsc, session, le32_to_cpu(h->max_caps));
        break;

    default:
        pr_err("mdsc_handle_session bad op %d mds%d\n", op, mds);
        WARN_ON(1);
    }

    mutex_unlock(&session->s_mutex);
    if (wake) {
        mutex_lock(&mdsc->mutex);
        __wake_requests(mdsc, &session->s_waiting);
        mutex_unlock(&mdsc->mutex);
    }
    return;

bad:
    pr_err("mdsc_handle_session corrupt message mds%d len %d\n", mds,
           (int)msg->front.iov_len);
    ceph_msg_dump(msg);
    return;
}


/*
 * called under session->mutex.
 */
static void replay_unsafe_requests(struct ceph_mds_client *mdsc,
                   struct ceph_mds_session *session)
{
    struct ceph_mds_request *req, *nreq;
    int err;

    dout("replay_unsafe_requests mds%d\n", session->s_mds);

    mutex_lock(&mdsc->mutex);
    list_for_each_entry_safe(req, nreq, &session->s_unsafe, r_unsafe_item) {
        err = __prepare_send_request(mdsc, req, session->s_mds);
        if (!err) {
            ceph_msg_get(req->r_request);
            ceph_con_send(&session->s_con, req->r_request);
        }
    }
    mutex_unlock(&mdsc->mutex);
}

/*
 * Encode information about a cap for a reconnect with the MDS.
 */
static int encode_caps_cb(struct inode *inode, struct ceph_cap *cap,
              void *arg)
{
    union {
        struct ceph_mds_cap_reconnect v2;
        struct ceph_mds_cap_reconnect_v1 v1;
    } rec;
    size_t reclen;
    struct ceph_inode_info *ci;
    struct ceph_reconnect_state *recon_state = arg;
    struct ceph_pagelist *pagelist = recon_state->pagelist;
    char *path;
    int pathlen, err;
    u64 pathbase;
    struct dentry *dentry;

    ci = cap->ci;

    dout(" adding %p ino %llx.%llx cap %p %lld %s\n",
         inode, ceph_vinop(inode), cap, cap->cap_id,
         ceph_cap_string(cap->issued));
    err = ceph_pagelist_encode_64(pagelist, ceph_ino(inode));
    if (err)
        return err;

    dentry = d_find_alias(inode);
    if (dentry) {
        path = ceph_mdsc_build_path(dentry, &pathlen, &pathbase, 0);
        if (IS_ERR(path)) {
            err = PTR_ERR(path);
            goto out_dput;
        }
    } else {
        path = NULL;
        pathlen = 0;
    }
    err = ceph_pagelist_encode_string(pagelist, path, pathlen);
    if (err)
        goto out_free;

    spin_lock(&ci->i_ceph_lock);
    cap->seq = 0;        /* reset cap seq */
    cap->issue_seq = 0;  /* and issue_seq */

    if (recon_state->flock) {
        rec.v2.cap_id = cpu_to_le64(cap->cap_id);
        rec.v2.wanted = cpu_to_le32(__ceph_caps_wanted(ci));
        rec.v2.issued = cpu_to_le32(cap->issued);
        rec.v2.snaprealm = cpu_to_le64(ci->i_snap_realm->ino);
        rec.v2.pathbase = cpu_to_le64(pathbase);
        rec.v2.flock_len = 0;
        reclen = sizeof(rec.v2);
    } else {
        rec.v1.cap_id = cpu_to_le64(cap->cap_id);
        rec.v1.wanted = cpu_to_le32(__ceph_caps_wanted(ci));
        rec.v1.issued = cpu_to_le32(cap->issued);
        rec.v1.size = cpu_to_le64(inode->i_size);
        ceph_encode_timespec(&rec.v1.mtime, &inode->i_mtime);
        ceph_encode_timespec(&rec.v1.atime, &inode->i_atime);
        rec.v1.snaprealm = cpu_to_le64(ci->i_snap_realm->ino);
        rec.v1.pathbase = cpu_to_le64(pathbase);
        reclen = sizeof(rec.v1);
    }
    spin_unlock(&ci->i_ceph_lock);

    if (recon_state->flock) {
        int num_fcntl_locks, num_flock_locks;
        struct ceph_pagelist_cursor trunc_point;

        ceph_pagelist_set_cursor(pagelist, &trunc_point);
        do {
            lock_flocks();
            ceph_count_locks(inode, &num_fcntl_locks,
                     &num_flock_locks);
            rec.v2.flock_len = (2*sizeof(u32) +
                        (num_fcntl_locks+num_flock_locks) *
                        sizeof(struct ceph_filelock));
            unlock_flocks();

            /* pre-alloc pagelist */
            ceph_pagelist_truncate(pagelist, &trunc_point);
            err = ceph_pagelist_append(pagelist, &rec, reclen);
            if (!err)
                err = ceph_pagelist_reserve(pagelist,
                                rec.v2.flock_len);

            /* encode locks */
            if (!err) {
                lock_flocks();
                err = ceph_encode_locks(inode,
                            pagelist,
                            num_fcntl_locks,
                            num_flock_locks);
                unlock_flocks();
            }
        } while (err == -ENOSPC);
    } else {
        err = ceph_pagelist_append(pagelist, &rec, reclen);
    }

out_free:
    kfree(path);
out_dput:
    dput(dentry);
    return err;
}


/*
 * If an MDS fails and recovers, clients need to reconnect in order to
 * reestablish shared state.  This includes all caps issued through
 * this session _and_ the snap_realm hierarchy.  Because it's not
 * clear which snap realms the mds cares about, we send everything we
 * know about.. that ensures we'll then get any new info the
 * recovering MDS might have.
 *
 * This is a relatively heavyweight operation, but it's rare.
 *
 * called with mdsc->mutex held.
 */
static void send_mds_reconnect(struct ceph_mds_client *mdsc,
                   struct ceph_mds_session *session)
{
    struct ceph_msg *reply;
    struct rb_node *p;
    int mds = session->s_mds;
    int err = -ENOMEM;
    struct ceph_pagelist *pagelist;
    struct ceph_reconnect_state recon_state;

    pr_info("mds%d reconnect start\n", mds);

    pagelist = kmalloc(sizeof(*pagelist), GFP_NOFS);
    if (!pagelist)
        goto fail_nopagelist;
    ceph_pagelist_init(pagelist);

    reply = ceph_msg_new(CEPH_MSG_CLIENT_RECONNECT, 0, GFP_NOFS, false);
    if (!reply)
        goto fail_nomsg;

    mutex_lock(&session->s_mutex);
    session->s_state = CEPH_MDS_SESSION_RECONNECTING;
    session->s_seq = 0;

    ceph_con_close(&session->s_con);
    ceph_con_open(&session->s_con,
              CEPH_ENTITY_TYPE_MDS, mds,
              ceph_mdsmap_get_addr(mdsc->mdsmap, mds));

    /* replay unsafe requests */
    replay_unsafe_requests(mdsc, session);

    down_read(&mdsc->snap_rwsem);

    dout("session %p state %s\n", session,
         session_state_name(session->s_state));

    /* drop old cap expires; we're about to reestablish that state */
    discard_cap_releases(mdsc, session);

    /* traverse this session's caps */
    err = ceph_pagelist_encode_32(pagelist, session->s_nr_caps);
    if (err)
        goto fail;

    recon_state.pagelist = pagelist;
    recon_state.flock = session->s_con.peer_features & CEPH_FEATURE_FLOCK;
    err = iterate_session_caps(session, encode_caps_cb, &recon_state);
    if (err < 0)
        goto fail;

    /*
     * snaprealms.  we provide mds with the ino, seq (version), and
     * parent for all of our realms.  If the mds has any newer info,
     * it will tell us.
     */
    for (p = rb_first(&mdsc->snap_realms); p; p = rb_next(p)) {
        struct ceph_snap_realm *realm =
            rb_entry(p, struct ceph_snap_realm, node);
        struct ceph_mds_snaprealm_reconnect sr_rec;

        dout(" adding snap realm %llx seq %lld parent %llx\n",
             realm->ino, realm->seq, realm->parent_ino);
        sr_rec.ino = cpu_to_le64(realm->ino);
        sr_rec.seq = cpu_to_le64(realm->seq);
        sr_rec.parent = cpu_to_le64(realm->parent_ino);
        err = ceph_pagelist_append(pagelist, &sr_rec, sizeof(sr_rec));
        if (err)
            goto fail;
    }

    reply->pagelist = pagelist;
    if (recon_state.flock)
        reply->hdr.version = cpu_to_le16(2);
    reply->hdr.data_len = cpu_to_le32(pagelist->length);
    reply->nr_pages = calc_pages_for(0, pagelist->length);
    ceph_con_send(&session->s_con, reply);

    mutex_unlock(&session->s_mutex);

    mutex_lock(&mdsc->mutex);
    __wake_requests(mdsc, &session->s_waiting);
    mutex_unlock(&mdsc->mutex);

    up_read(&mdsc->snap_rwsem);
    return;

fail:
    ceph_msg_put(reply);
    up_read(&mdsc->snap_rwsem);
    mutex_unlock(&session->s_mutex);
fail_nomsg:
    ceph_pagelist_release(pagelist);
    kfree(pagelist);
fail_nopagelist:
    pr_err("error %d preparing reconnect for mds%d\n", err, mds);
    return;
}


/*
 * compare old and new mdsmaps, kicking requests
 * and closing out old connections as necessary
 *
 * called under mdsc->mutex.
 */
static void check_new_map(struct ceph_mds_client *mdsc,
              struct ceph_mdsmap *newmap,
              struct ceph_mdsmap *oldmap)
{
    int i;
    int oldstate, newstate;
    struct ceph_mds_session *s;

    dout("check_new_map new %u old %u\n",
         newmap->m_epoch, oldmap->m_epoch);

    for (i = 0; i < oldmap->m_max_mds && i < mdsc->max_sessions; i++) {
        if (mdsc->sessions[i] == NULL)
            continue;
        s = mdsc->sessions[i];
        oldstate = ceph_mdsmap_get_state(oldmap, i);
        newstate = ceph_mdsmap_get_state(newmap, i);

        dout("check_new_map mds%d state %s%s -> %s%s (session %s)\n",
             i, ceph_mds_state_name(oldstate),
             ceph_mdsmap_is_laggy(oldmap, i) ? " (laggy)" : "",
             ceph_mds_state_name(newstate),
             ceph_mdsmap_is_laggy(newmap, i) ? " (laggy)" : "",
             session_state_name(s->s_state));

        if (i >= newmap->m_max_mds ||
            memcmp(ceph_mdsmap_get_addr(oldmap, i),
               ceph_mdsmap_get_addr(newmap, i),
               sizeof(struct ceph_entity_addr))) {
            if (s->s_state == CEPH_MDS_SESSION_OPENING) {
                /* the session never opened, just close it
                 * out now */
                __wake_requests(mdsc, &s->s_waiting);
                __unregister_session(mdsc, s);
            } else {
                /* just close it */
                mutex_unlock(&mdsc->mutex);
                mutex_lock(&s->s_mutex);
                mutex_lock(&mdsc->mutex);
                ceph_con_close(&s->s_con);
                mutex_unlock(&s->s_mutex);
                s->s_state = CEPH_MDS_SESSION_RESTARTING;
            }

            /* kick any requests waiting on the recovering mds */
            kick_requests(mdsc, i);
        } else if (oldstate == newstate) {
            continue;  /* nothing new with this mds */
        }

        /*
         * send reconnect?
         */
        if (s->s_state == CEPH_MDS_SESSION_RESTARTING &&
            newstate >= CEPH_MDS_STATE_RECONNECT) {
            mutex_unlock(&mdsc->mutex);
            send_mds_reconnect(mdsc, s);
            mutex_lock(&mdsc->mutex);
        }

        /*
         * kick request on any mds that has gone active.
         */
        if (oldstate < CEPH_MDS_STATE_ACTIVE &&
            newstate >= CEPH_MDS_STATE_ACTIVE) {
            if (oldstate != CEPH_MDS_STATE_CREATING &&
                oldstate != CEPH_MDS_STATE_STARTING)
                pr_info("mds%d recovery completed\n", s->s_mds);
            kick_requests(mdsc, i);
            ceph_kick_flushing_caps(mdsc, s);
            wake_up_session_caps(s, 1);
        }
    }

    for (i = 0; i < newmap->m_max_mds && i < mdsc->max_sessions; i++) {
        s = mdsc->sessions[i];
        if (!s)
            continue;
        if (!ceph_mdsmap_is_laggy(newmap, i))
            continue;
        if (s->s_state == CEPH_MDS_SESSION_OPEN ||
            s->s_state == CEPH_MDS_SESSION_HUNG ||
            s->s_state == CEPH_MDS_SESSION_CLOSING) {
            dout(" connecting to export targets of laggy mds%d\n",
                 i);
            __open_export_target_sessions(mdsc, s);
        }
    }
}



/*
 * leases
 */

/*
 * caller must hold session s_mutex, dentry->d_lock
 */
void __ceph_mdsc_drop_dentry_lease(struct dentry *dentry)
{
    struct ceph_dentry_info *di = ceph_dentry(dentry);

    ceph_put_mds_session(di->lease_session);
    di->lease_session = NULL;
}

static void handle_lease(struct ceph_mds_client *mdsc,
             struct ceph_mds_session *session,
             struct ceph_msg *msg)
{
    struct super_block *sb = mdsc->fsc->sb;
    struct inode *inode;
    struct dentry *parent, *dentry;
    struct ceph_dentry_info *di;
    int mds = session->s_mds;
    struct ceph_mds_lease *h = msg->front.iov_base;
    u32 seq;
    struct ceph_vino vino;
    struct qstr dname;
    int release = 0;

    dout("handle_lease from mds%d\n", mds);

    /* decode */
    if (msg->front.iov_len < sizeof(*h) + sizeof(u32))
        goto bad;
    vino.ino = le64_to_cpu(h->ino);
    vino.snap = CEPH_NOSNAP;
    seq = le32_to_cpu(h->seq);
    dname.name = (void *)h + sizeof(*h) + sizeof(u32);
    dname.len = msg->front.iov_len - sizeof(*h) - sizeof(u32);
    if (dname.len != get_unaligned_le32(h+1))
        goto bad;

    mutex_lock(&session->s_mutex);
    session->s_seq++;

    /* lookup inode */
    inode = ceph_find_inode(sb, vino);
    dout("handle_lease %s, ino %llx %p %.*s\n",
         ceph_lease_op_name(h->action), vino.ino, inode,
         dname.len, dname.name);
    if (inode == NULL) {
        dout("handle_lease no inode %llx\n", vino.ino);
        goto release;
    }

    /* dentry */
    parent = d_find_alias(inode);
    if (!parent) {
        dout("no parent dentry on inode %p\n", inode);
        WARN_ON(1);
        goto release;  /* hrm... */
    }
    dname.hash = full_name_hash(dname.name, dname.len);
    dentry = d_lookup(parent, &dname);
    dput(parent);
    if (!dentry)
        goto release;

    spin_lock(&dentry->d_lock);
    di = ceph_dentry(dentry);
    switch (h->action) {
    case CEPH_MDS_LEASE_REVOKE:
        if (di->lease_session == session) {
            if (ceph_seq_cmp(di->lease_seq, seq) > 0)
                h->seq = cpu_to_le32(di->lease_seq);
            __ceph_mdsc_drop_dentry_lease(dentry);
        }
        release = 1;
        break;

    case CEPH_MDS_LEASE_RENEW:
        if (di->lease_session == session &&
            di->lease_gen == session->s_cap_gen &&
            di->lease_renew_from &&
            di->lease_renew_after == 0) {
            unsigned long duration =
                le32_to_cpu(h->duration_ms) * HZ / 1000;

            di->lease_seq = seq;
            dentry->d_time = di->lease_renew_from + duration;
            di->lease_renew_after = di->lease_renew_from +
                (duration >> 1);
            di->lease_renew_from = 0;
        }
        break;
    }
    spin_unlock(&dentry->d_lock);
    dput(dentry);

    if (!release)
        goto out;

release:
    /* let's just reuse the same message */
    h->action = CEPH_MDS_LEASE_REVOKE_ACK;
    ceph_msg_get(msg);
    ceph_con_send(&session->s_con, msg);

out:
    iput(inode);
    mutex_unlock(&session->s_mutex);
    return;

bad:
    pr_err("corrupt lease message\n");
    ceph_msg_dump(msg);
}

void ceph_mdsc_lease_send_msg(struct ceph_mds_session *session,
                  struct inode *inode,
                  struct dentry *dentry, char action,
                  u32 seq)
{
    struct ceph_msg *msg;
    struct ceph_mds_lease *lease;
    int len = sizeof(*lease) + sizeof(u32);
    int dnamelen = 0;

    dout("lease_send_msg inode %p dentry %p %s to mds%d\n",
         inode, dentry, ceph_lease_op_name(action), session->s_mds);
    dnamelen = dentry->d_name.len;
    len += dnamelen;

    msg = ceph_msg_new(CEPH_MSG_CLIENT_LEASE, len, GFP_NOFS, false);
    if (!msg)
        return;
    lease = msg->front.iov_base;
    lease->action = action;
    lease->ino = cpu_to_le64(ceph_vino(inode).ino);
    lease->first = lease->last = cpu_to_le64(ceph_vino(inode).snap);
    lease->seq = cpu_to_le32(seq);
    put_unaligned_le32(dnamelen, lease + 1);
    memcpy((void *)(lease + 1) + 4, dentry->d_name.name, dnamelen);

    /*
     * if this is a preemptive lease RELEASE, no need to
     * flush request stream, since the actual request will
     * soon follow.
     */
    msg->more_to_follow = (action == CEPH_MDS_LEASE_RELEASE);

    ceph_con_send(&session->s_con, msg);
}

/*
 * Preemptively release a lease we expect to invalidate anyway.
 * Pass @inode always, @dentry is optional.
 */
void ceph_mdsc_lease_release(struct ceph_mds_client *mdsc, struct inode *inode,
                 struct dentry *dentry)
{
    struct ceph_dentry_info *di;
    struct ceph_mds_session *session;
    u32 seq;

    BUG_ON(inode == NULL);
    BUG_ON(dentry == NULL);

    /* is dentry lease valid? */
    spin_lock(&dentry->d_lock);
    di = ceph_dentry(dentry);
    if (!di || !di->lease_session ||
        di->lease_session->s_mds < 0 ||
        di->lease_gen != di->lease_session->s_cap_gen ||
        !time_before(jiffies, dentry->d_time)) {
        dout("lease_release inode %p dentry %p -- "
             "no lease\n",
             inode, dentry);
        spin_unlock(&dentry->d_lock);
        return;
    }

    /* we do have a lease on this dentry; note mds and seq */
    session = ceph_get_mds_session(di->lease_session);
    seq = di->lease_seq;
    __ceph_mdsc_drop_dentry_lease(dentry);
    spin_unlock(&dentry->d_lock);

    dout("lease_release inode %p dentry %p to mds%d\n",
         inode, dentry, session->s_mds);
    ceph_mdsc_lease_send_msg(session, inode, dentry,
                 CEPH_MDS_LEASE_RELEASE, seq);
    ceph_put_mds_session(session);
}

/*
 * drop all leases (and dentry refs) in preparation for umount
 */
static void drop_leases(struct ceph_mds_client *mdsc)
{
    int i;

    dout("drop_leases\n");
    mutex_lock(&mdsc->mutex);
    for (i = 0; i < mdsc->max_sessions; i++) {
        struct ceph_mds_session *s = __ceph_lookup_mds_session(mdsc, i);
        if (!s)
            continue;
        mutex_unlock(&mdsc->mutex);
        mutex_lock(&s->s_mutex);
        mutex_unlock(&s->s_mutex);
        ceph_put_mds_session(s);
        mutex_lock(&mdsc->mutex);
    }
    mutex_unlock(&mdsc->mutex);
}



/*
 * delayed work -- periodically trim expired leases, renew caps with mds
 */
static void schedule_delayed(struct ceph_mds_client *mdsc)
{
    int delay = 5;
    unsigned hz = round_jiffies_relative(HZ * delay);
    schedule_delayed_work(&mdsc->delayed_work, hz);
}

static void delayed_work(struct work_struct *work)
{
    int i;
    struct ceph_mds_client *mdsc =
        container_of(work, struct ceph_mds_client, delayed_work.work);
    int renew_interval;
    int renew_caps;

    dout("mdsc delayed_work\n");
    ceph_check_delayed_caps(mdsc);

    mutex_lock(&mdsc->mutex);
    renew_interval = mdsc->mdsmap->m_session_timeout >> 2;
    renew_caps = time_after_eq(jiffies, HZ*renew_interval +
                   mdsc->last_renew_caps);
    if (renew_caps)
        mdsc->last_renew_caps = jiffies;

    for (i = 0; i < mdsc->max_sessions; i++) {
        struct ceph_mds_session *s = __ceph_lookup_mds_session(mdsc, i);
        if (s == NULL)
            continue;
        if (s->s_state == CEPH_MDS_SESSION_CLOSING) {
            dout("resending session close request for mds%d\n",
                 s->s_mds);
            request_close_session(mdsc, s);
            ceph_put_mds_session(s);
            continue;
        }
        if (s->s_ttl && time_after(jiffies, s->s_ttl)) {
            if (s->s_state == CEPH_MDS_SESSION_OPEN) {
                s->s_state = CEPH_MDS_SESSION_HUNG;
                pr_info("mds%d hung\n", s->s_mds);
            }
        }
        if (s->s_state < CEPH_MDS_SESSION_OPEN) {
            /* this mds is failed or recovering, just wait */
            ceph_put_mds_session(s);
            continue;
        }
        mutex_unlock(&mdsc->mutex);

        mutex_lock(&s->s_mutex);
        if (renew_caps)
            send_renew_caps(mdsc, s);
        else
            ceph_con_keepalive(&s->s_con);
        ceph_add_cap_releases(mdsc, s);
        if (s->s_state == CEPH_MDS_SESSION_OPEN ||
            s->s_state == CEPH_MDS_SESSION_HUNG)
            ceph_send_cap_releases(mdsc, s);
        mutex_unlock(&s->s_mutex);
        ceph_put_mds_session(s);

        mutex_lock(&mdsc->mutex);
    }
    mutex_unlock(&mdsc->mutex);

    schedule_delayed(mdsc);
}

int ceph_mdsc_init(struct ceph_fs_client *fsc)

{
    struct ceph_mds_client *mdsc;

    mdsc = kzalloc(sizeof(struct ceph_mds_client), GFP_NOFS);
    if (!mdsc)
        return -ENOMEM;
    mdsc->fsc = fsc;
    fsc->mdsc = mdsc;
    mutex_init(&mdsc->mutex);
    mdsc->mdsmap = kzalloc(sizeof(*mdsc->mdsmap), GFP_NOFS);
    if (mdsc->mdsmap == NULL)
        return -ENOMEM;

    init_completion(&mdsc->safe_umount_waiters);
    init_waitqueue_head(&mdsc->session_close_wq);
    INIT_LIST_HEAD(&mdsc->waiting_for_map);
    mdsc->sessions = NULL;
    mdsc->max_sessions = 0;
    mdsc->stopping = 0;
    init_rwsem(&mdsc->snap_rwsem);
    mdsc->snap_realms = RB_ROOT;
    INIT_LIST_HEAD(&mdsc->snap_empty);
    spin_lock_init(&mdsc->snap_empty_lock);
    mdsc->last_tid = 0;
    mdsc->request_tree = RB_ROOT;
    INIT_DELAYED_WORK(&mdsc->delayed_work, delayed_work);
    mdsc->last_renew_caps = jiffies;
    INIT_LIST_HEAD(&mdsc->cap_delay_list);
    spin_lock_init(&mdsc->cap_delay_lock);
    INIT_LIST_HEAD(&mdsc->snap_flush_list);
    spin_lock_init(&mdsc->snap_flush_lock);
    mdsc->cap_flush_seq = 0;
    INIT_LIST_HEAD(&mdsc->cap_dirty);
    INIT_LIST_HEAD(&mdsc->cap_dirty_migrating);
    mdsc->num_cap_flushing = 0;
    spin_lock_init(&mdsc->cap_dirty_lock);
    init_waitqueue_head(&mdsc->cap_flushing_wq);
    spin_lock_init(&mdsc->dentry_lru_lock);
    INIT_LIST_HEAD(&mdsc->dentry_lru);

    ceph_caps_init(mdsc);
    ceph_adjust_min_caps(mdsc, fsc->min_caps);

    return 0;
}

/*
 * Wait for safe replies on open mds requests.  If we time out, drop
 * all requests from the tree to avoid dangling dentry refs.
 */
static void wait_requests(struct ceph_mds_client *mdsc)
{
    struct ceph_mds_request *req;
    struct ceph_fs_client *fsc = mdsc->fsc;

    mutex_lock(&mdsc->mutex);
    if (__get_oldest_req(mdsc)) {
        mutex_unlock(&mdsc->mutex);

        dout("wait_requests waiting for requests\n");
        wait_for_completion_timeout(&mdsc->safe_umount_waiters,
                    fsc->client->options->mount_timeout * HZ);

        /* tear down remaining requests */
        mutex_lock(&mdsc->mutex);
        while ((req = __get_oldest_req(mdsc))) {
            dout("wait_requests timed out on tid %llu\n",
                 req->r_tid);
            __unregister_request(mdsc, req);
        }
    }
    mutex_unlock(&mdsc->mutex);
    dout("wait_requests done\n");
}

/*
 * called before mount is ro, and before dentries are torn down.
 * (hmm, does this still race with new lookups?)
 */
void ceph_mdsc_pre_umount(struct ceph_mds_client *mdsc)
{
    dout("pre_umount\n");
    mdsc->stopping = 1;

    drop_leases(mdsc);
    ceph_flush_dirty_caps(mdsc);
    wait_requests(mdsc);

    /*
     * wait for reply handlers to drop their request refs and
     * their inode/dcache refs
     */
    ceph_msgr_flush();
}

/*
 * wait for all write mds requests to flush.
 */
static void wait_unsafe_requests(struct ceph_mds_client *mdsc, u64 want_tid)
{
    struct ceph_mds_request *req = NULL, *nextreq;
    struct rb_node *n;

    mutex_lock(&mdsc->mutex);
    dout("wait_unsafe_requests want %lld\n", want_tid);
restart:
    req = __get_oldest_req(mdsc);
    while (req && req->r_tid <= want_tid) {
        /* find next request */
        n = rb_next(&req->r_node);
        if (n)
            nextreq = rb_entry(n, struct ceph_mds_request, r_node);
        else
            nextreq = NULL;
        if ((req->r_op & CEPH_MDS_OP_WRITE)) {
            /* write op */
            ceph_mdsc_get_request(req);
            if (nextreq)
                ceph_mdsc_get_request(nextreq);
            mutex_unlock(&mdsc->mutex);
            dout("wait_unsafe_requests  wait on %llu (want %llu)\n",
                 req->r_tid, want_tid);
            wait_for_completion(&req->r_safe_completion);
            mutex_lock(&mdsc->mutex);
            ceph_mdsc_put_request(req);
            if (!nextreq)
                break;  /* next dne before, so we're done! */
            if (RB_EMPTY_NODE(&nextreq->r_node)) {
                /* next request was removed from tree */
                ceph_mdsc_put_request(nextreq);
                goto restart;
            }
            ceph_mdsc_put_request(nextreq);  /* won't go away */
        }
        req = nextreq;
    }
    mutex_unlock(&mdsc->mutex);
    dout("wait_unsafe_requests done\n");
}

void ceph_mdsc_sync(struct ceph_mds_client *mdsc)
{
    u64 want_tid, want_flush;

    if (mdsc->fsc->mount_state == CEPH_MOUNT_SHUTDOWN)
        return;

    dout("sync\n");
    mutex_lock(&mdsc->mutex);
    want_tid = mdsc->last_tid;
    want_flush = mdsc->cap_flush_seq;
    mutex_unlock(&mdsc->mutex);
    dout("sync want tid %lld flush_seq %lld\n", want_tid, want_flush);

    ceph_flush_dirty_caps(mdsc);

    wait_unsafe_requests(mdsc, want_tid);
    wait_event(mdsc->cap_flushing_wq, check_cap_flush(mdsc, want_flush));
}

/*
 * true if all sessions are closed, or we force unmount
 */
static bool done_closing_sessions(struct ceph_mds_client *mdsc)
{
    int i, n = 0;

    if (mdsc->fsc->mount_state == CEPH_MOUNT_SHUTDOWN)
        return true;

    mutex_lock(&mdsc->mutex);
    for (i = 0; i < mdsc->max_sessions; i++)
        if (mdsc->sessions[i])
            n++;
    mutex_unlock(&mdsc->mutex);
    return n == 0;
}

/*
 * called after sb is ro.
 */
void ceph_mdsc_close_sessions(struct ceph_mds_client *mdsc)
{
    struct ceph_mds_session *session;
    int i;
    struct ceph_fs_client *fsc = mdsc->fsc;
    unsigned long timeout = fsc->client->options->mount_timeout * HZ;

    dout("close_sessions\n");

    /* close sessions */
    mutex_lock(&mdsc->mutex);
    for (i = 0; i < mdsc->max_sessions; i++) {
        session = __ceph_lookup_mds_session(mdsc, i);
        if (!session)
            continue;
        mutex_unlock(&mdsc->mutex);
        mutex_lock(&session->s_mutex);
        __close_session(mdsc, session);
        mutex_unlock(&session->s_mutex);
        ceph_put_mds_session(session);
        mutex_lock(&mdsc->mutex);
    }
    mutex_unlock(&mdsc->mutex);

    dout("waiting for sessions to close\n");
    wait_event_timeout(mdsc->session_close_wq, done_closing_sessions(mdsc),
               timeout);

    /* tear down remaining sessions */
    mutex_lock(&mdsc->mutex);
    for (i = 0; i < mdsc->max_sessions; i++) {
        if (mdsc->sessions[i]) {
            session = get_session(mdsc->sessions[i]);
            __unregister_session(mdsc, session);
            mutex_unlock(&mdsc->mutex);
            mutex_lock(&session->s_mutex);
            remove_session_caps(session);
            mutex_unlock(&session->s_mutex);
            ceph_put_mds_session(session);
            mutex_lock(&mdsc->mutex);
        }
    }
    WARN_ON(!list_empty(&mdsc->cap_delay_list));
    mutex_unlock(&mdsc->mutex);

    ceph_cleanup_empty_realms(mdsc);

    cancel_delayed_work_sync(&mdsc->delayed_work); /* cancel timer */

    dout("stopped\n");
}

static void ceph_mdsc_stop(struct ceph_mds_client *mdsc)
{
    dout("stop\n");
    cancel_delayed_work_sync(&mdsc->delayed_work); /* cancel timer */
    if (mdsc->mdsmap)
        ceph_mdsmap_destroy(mdsc->mdsmap);
    kfree(mdsc->sessions);
    ceph_caps_finalize(mdsc);
}

void ceph_mdsc_destroy(struct ceph_fs_client *fsc)
{
    struct ceph_mds_client *mdsc = fsc->mdsc;

    dout("mdsc_destroy %p\n", mdsc);
    ceph_mdsc_stop(mdsc);

    /* flush out any connection work with references to us */
    ceph_msgr_flush();

    fsc->mdsc = NULL;
    kfree(mdsc);
    dout("mdsc_destroy %p done\n", mdsc);
}


/*
 * handle mds map update.
 */
void ceph_mdsc_handle_map(struct ceph_mds_client *mdsc, struct ceph_msg *msg)
{
    u32 epoch;
    u32 maplen;
    void *p = msg->front.iov_base;
    void *end = p + msg->front.iov_len;
    struct ceph_mdsmap *newmap, *oldmap;
    struct ceph_fsid fsid;
    int err = -EINVAL;

    ceph_decode_need(&p, end, sizeof(fsid)+2*sizeof(u32), bad);
    ceph_decode_copy(&p, &fsid, sizeof(fsid));
    if (ceph_check_fsid(mdsc->fsc->client, &fsid) < 0)
        return;
    epoch = ceph_decode_32(&p);
    maplen = ceph_decode_32(&p);
    dout("handle_map epoch %u len %d\n", epoch, (int)maplen);

    /* do we need it? */
    ceph_monc_got_mdsmap(&mdsc->fsc->client->monc, epoch);
    mutex_lock(&mdsc->mutex);
    if (mdsc->mdsmap && epoch <= mdsc->mdsmap->m_epoch) {
        dout("handle_map epoch %u <= our %u\n",
             epoch, mdsc->mdsmap->m_epoch);
        mutex_unlock(&mdsc->mutex);
        return;
    }

    newmap = ceph_mdsmap_decode(&p, end);
    if (IS_ERR(newmap)) {
        err = PTR_ERR(newmap);
        goto bad_unlock;
    }

    /* swap into place */
    if (mdsc->mdsmap) {
        oldmap = mdsc->mdsmap;
        mdsc->mdsmap = newmap;
        check_new_map(mdsc, newmap, oldmap);
        ceph_mdsmap_destroy(oldmap);
    } else {
        mdsc->mdsmap = newmap;  /* first mds map */
    }
    mdsc->fsc->sb->s_maxbytes = mdsc->mdsmap->m_max_file_size;

    __wake_requests(mdsc, &mdsc->waiting_for_map);

    mutex_unlock(&mdsc->mutex);
    schedule_delayed(mdsc);
    return;

bad_unlock:
    mutex_unlock(&mdsc->mutex);
bad:
    pr_err("error decoding mdsmap %d\n", err);
    return;
}

static struct ceph_connection *con_get(struct ceph_connection *con)
{
    struct ceph_mds_session *s = con->private;

    if (get_session(s)) {
        dout("mdsc con_get %p ok (%d)\n", s, atomic_read(&s->s_ref));
        return con;
    }
    dout("mdsc con_get %p FAIL\n", s);
    return NULL;
}

static void con_put(struct ceph_connection *con)
{
    struct ceph_mds_session *s = con->private;

    dout("mdsc con_put %p (%d)\n", s, atomic_read(&s->s_ref) - 1);
    ceph_put_mds_session(s);
}

/*
 * if the client is unresponsive for long enough, the mds will kill
 * the session entirely.
 */
static void peer_reset(struct ceph_connection *con)
{
    struct ceph_mds_session *s = con->private;
    struct ceph_mds_client *mdsc = s->s_mdsc;

    pr_warning("mds%d closed our session\n", s->s_mds);
    send_mds_reconnect(mdsc, s);
}

static void dispatch(struct ceph_connection *con, struct ceph_msg *msg)
{
    struct ceph_mds_session *s = con->private;
    struct ceph_mds_client *mdsc = s->s_mdsc;
    int type = le16_to_cpu(msg->hdr.type);

    mutex_lock(&mdsc->mutex);
    if (__verify_registered_session(mdsc, s) < 0) {
        mutex_unlock(&mdsc->mutex);
        goto out;
    }
    mutex_unlock(&mdsc->mutex);

    switch (type) {
    case CEPH_MSG_MDS_MAP:
        ceph_mdsc_handle_map(mdsc, msg);
        break;
    case CEPH_MSG_CLIENT_SESSION:
        handle_session(s, msg);
        break;
    case CEPH_MSG_CLIENT_REPLY:
        handle_reply(s, msg);
        break;
    case CEPH_MSG_CLIENT_REQUEST_FORWARD:
        handle_forward(mdsc, s, msg);
        break;
    case CEPH_MSG_CLIENT_CAPS:
        ceph_handle_caps(s, msg);
        break;
    case CEPH_MSG_CLIENT_SNAP:
        ceph_handle_snap(mdsc, s, msg);
        break;
    case CEPH_MSG_CLIENT_LEASE:
        handle_lease(mdsc, s, msg);
        break;

    default:
        pr_err("received unknown message type %d %s\n", type,
               ceph_msg_type_name(type));
    }
out:
    ceph_msg_put(msg);
}

/*
 * authentication
 */

/*
 * Note: returned pointer is the address of a structure that's
 * managed separately.  Caller must *not* attempt to free it.
 */
static struct ceph_auth_handshake *get_authorizer(struct ceph_connection *con,
                    int *proto, int force_new)
{
    struct ceph_mds_session *s = con->private;
    struct ceph_mds_client *mdsc = s->s_mdsc;
    struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;
    struct ceph_auth_handshake *auth = &s->s_auth;

    if (force_new && auth->authorizer) {
        if (ac->ops && ac->ops->destroy_authorizer)
            ac->ops->destroy_authorizer(ac, auth->authorizer);
        auth->authorizer = NULL;
    }
    if (!auth->authorizer && ac->ops && ac->ops->create_authorizer) {
        int ret = ac->ops->create_authorizer(ac, CEPH_ENTITY_TYPE_MDS,
                            auth);
        if (ret)
            return ERR_PTR(ret);
    }
    *proto = ac->protocol;

    return auth;
}


static int verify_authorizer_reply(struct ceph_connection *con, int len)
{
    struct ceph_mds_session *s = con->private;
    struct ceph_mds_client *mdsc = s->s_mdsc;
    struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;

    return ac->ops->verify_authorizer_reply(ac, s->s_auth.authorizer, len);
}

static int invalidate_authorizer(struct ceph_connection *con)
{
    struct ceph_mds_session *s = con->private;
    struct ceph_mds_client *mdsc = s->s_mdsc;
    struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;

    if (ac->ops->invalidate_authorizer)
        ac->ops->invalidate_authorizer(ac, CEPH_ENTITY_TYPE_MDS);

    return ceph_monc_validate_auth(&mdsc->fsc->client->monc);
}

static const struct ceph_connection_operations mds_con_ops = {
    .get = con_get,
    .put = con_put,
    .dispatch = dispatch,
    .get_authorizer = get_authorizer,
    .verify_authorizer_reply = verify_authorizer_reply,
    .invalidate_authorizer = invalidate_authorizer,
    .peer_reset = peer_reset,
};

/* eof */