caps.c

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#include <linux/ceph/ceph_debug.h>

#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/wait.h>
#include <linux/writeback.h>

#include "super.h"
#include "mds_client.h"
#include <linux/ceph/decode.h>
#include <linux/ceph/messenger.h>

/*
 * Capability management
 *
 * The Ceph metadata servers control client access to inode metadata
 * and file data by issuing capabilities, granting clients permission
 * to read and/or write both inode field and file data to OSDs
 * (storage nodes).  Each capability consists of a set of bits
 * indicating which operations are allowed.
 *
 * If the client holds a *_SHARED cap, the client has a coherent value
 * that can be safely read from the cached inode.
 *
 * In the case of a *_EXCL (exclusive) or FILE_WR capabilities, the
 * client is allowed to change inode attributes (e.g., file size,
 * mtime), note its dirty state in the ceph_cap, and asynchronously
 * flush that metadata change to the MDS.
 *
 * In the event of a conflicting operation (perhaps by another
 * client), the MDS will revoke the conflicting client capabilities.
 *
 * In order for a client to cache an inode, it must hold a capability
 * with at least one MDS server.  When inodes are released, release
 * notifications are batched and periodically sent en masse to the MDS
 * cluster to release server state.
 */


/*
 * Generate readable cap strings for debugging output.
 */
#define MAX_CAP_STR 20
static char cap_str[MAX_CAP_STR][40];
static DEFINE_SPINLOCK(cap_str_lock);
static int last_cap_str;

static char *gcap_string(char *s, int c)
{
    if (c & CEPH_CAP_GSHARED)
        *s++ = 's';
    if (c & CEPH_CAP_GEXCL)
        *s++ = 'x';
    if (c & CEPH_CAP_GCACHE)
        *s++ = 'c';
    if (c & CEPH_CAP_GRD)
        *s++ = 'r';
    if (c & CEPH_CAP_GWR)
        *s++ = 'w';
    if (c & CEPH_CAP_GBUFFER)
        *s++ = 'b';
    if (c & CEPH_CAP_GLAZYIO)
        *s++ = 'l';
    return s;
}

const char *ceph_cap_string(int caps)
{
    int i;
    char *s;
    int c;

    spin_lock(&cap_str_lock);
    i = last_cap_str++;
    if (last_cap_str == MAX_CAP_STR)
        last_cap_str = 0;
    spin_unlock(&cap_str_lock);

    s = cap_str[i];

    if (caps & CEPH_CAP_PIN)
        *s++ = 'p';

    c = (caps >> CEPH_CAP_SAUTH) & 3;
    if (c) {
        *s++ = 'A';
        s = gcap_string(s, c);
    }

    c = (caps >> CEPH_CAP_SLINK) & 3;
    if (c) {
        *s++ = 'L';
        s = gcap_string(s, c);
    }

    c = (caps >> CEPH_CAP_SXATTR) & 3;
    if (c) {
        *s++ = 'X';
        s = gcap_string(s, c);
    }

    c = caps >> CEPH_CAP_SFILE;
    if (c) {
        *s++ = 'F';
        s = gcap_string(s, c);
    }

    if (s == cap_str[i])
        *s++ = '-';
    *s = 0;
    return cap_str[i];
}

void ceph_caps_init(struct ceph_mds_client *mdsc)
{
    INIT_LIST_HEAD(&mdsc->caps_list);
    spin_lock_init(&mdsc->caps_list_lock);
}

void ceph_caps_finalize(struct ceph_mds_client *mdsc)
{
    struct ceph_cap *cap;

    spin_lock(&mdsc->caps_list_lock);
    while (!list_empty(&mdsc->caps_list)) {
        cap = list_first_entry(&mdsc->caps_list,
                       struct ceph_cap, caps_item);
        list_del(&cap->caps_item);
        kmem_cache_free(ceph_cap_cachep, cap);
    }
    mdsc->caps_total_count = 0;
    mdsc->caps_avail_count = 0;
    mdsc->caps_use_count = 0;
    mdsc->caps_reserve_count = 0;
    mdsc->caps_min_count = 0;
    spin_unlock(&mdsc->caps_list_lock);
}

void ceph_adjust_min_caps(struct ceph_mds_client *mdsc, int delta)
{
    spin_lock(&mdsc->caps_list_lock);
    mdsc->caps_min_count += delta;
    BUG_ON(mdsc->caps_min_count < 0);
    spin_unlock(&mdsc->caps_list_lock);
}

int ceph_reserve_caps(struct ceph_mds_client *mdsc,
              struct ceph_cap_reservation *ctx, int need)
{
    int i;
    struct ceph_cap *cap;
    int have;
    int alloc = 0;
    LIST_HEAD(newcaps);
    int ret = 0;

    dout("reserve caps ctx=%p need=%d\n", ctx, need);

    /* first reserve any caps that are already allocated */
    spin_lock(&mdsc->caps_list_lock);
    if (mdsc->caps_avail_count >= need)
        have = need;
    else
        have = mdsc->caps_avail_count;
    mdsc->caps_avail_count -= have;
    mdsc->caps_reserve_count += have;
    BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
                     mdsc->caps_reserve_count +
                     mdsc->caps_avail_count);
    spin_unlock(&mdsc->caps_list_lock);

    for (i = have; i < need; i++) {
        cap = kmem_cache_alloc(ceph_cap_cachep, GFP_NOFS);
        if (!cap) {
            ret = -ENOMEM;
            goto out_alloc_count;
        }
        list_add(&cap->caps_item, &newcaps);
        alloc++;
    }
    BUG_ON(have + alloc != need);

    spin_lock(&mdsc->caps_list_lock);
    mdsc->caps_total_count += alloc;
    mdsc->caps_reserve_count += alloc;
    list_splice(&newcaps, &mdsc->caps_list);

    BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
                     mdsc->caps_reserve_count +
                     mdsc->caps_avail_count);
    spin_unlock(&mdsc->caps_list_lock);

    ctx->count = need;
    dout("reserve caps ctx=%p %d = %d used + %d resv + %d avail\n",
         ctx, mdsc->caps_total_count, mdsc->caps_use_count,
         mdsc->caps_reserve_count, mdsc->caps_avail_count);
    return 0;

out_alloc_count:
    /* we didn't manage to reserve as much as we needed */
    pr_warning("reserve caps ctx=%p ENOMEM need=%d got=%d\n",
           ctx, need, have);
    return ret;
}

int ceph_unreserve_caps(struct ceph_mds_client *mdsc,
            struct ceph_cap_reservation *ctx)
{
    dout("unreserve caps ctx=%p count=%d\n", ctx, ctx->count);
    if (ctx->count) {
        spin_lock(&mdsc->caps_list_lock);
        BUG_ON(mdsc->caps_reserve_count < ctx->count);
        mdsc->caps_reserve_count -= ctx->count;
        mdsc->caps_avail_count += ctx->count;
        ctx->count = 0;
        dout("unreserve caps %d = %d used + %d resv + %d avail\n",
             mdsc->caps_total_count, mdsc->caps_use_count,
             mdsc->caps_reserve_count, mdsc->caps_avail_count);
        BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
                         mdsc->caps_reserve_count +
                         mdsc->caps_avail_count);
        spin_unlock(&mdsc->caps_list_lock);
    }
    return 0;
}

static struct ceph_cap *get_cap(struct ceph_mds_client *mdsc,
                struct ceph_cap_reservation *ctx)
{
    struct ceph_cap *cap = NULL;

    /* temporary, until we do something about cap import/export */
    if (!ctx) {
        cap = kmem_cache_alloc(ceph_cap_cachep, GFP_NOFS);
        if (cap) {
            mdsc->caps_use_count++;
            mdsc->caps_total_count++;
        }
        return cap;
    }

    spin_lock(&mdsc->caps_list_lock);
    dout("get_cap ctx=%p (%d) %d = %d used + %d resv + %d avail\n",
         ctx, ctx->count, mdsc->caps_total_count, mdsc->caps_use_count,
         mdsc->caps_reserve_count, mdsc->caps_avail_count);
    BUG_ON(!ctx->count);
    BUG_ON(ctx->count > mdsc->caps_reserve_count);
    BUG_ON(list_empty(&mdsc->caps_list));

    ctx->count--;
    mdsc->caps_reserve_count--;
    mdsc->caps_use_count++;

    cap = list_first_entry(&mdsc->caps_list, struct ceph_cap, caps_item);
    list_del(&cap->caps_item);

    BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
           mdsc->caps_reserve_count + mdsc->caps_avail_count);
    spin_unlock(&mdsc->caps_list_lock);
    return cap;
}

void ceph_put_cap(struct ceph_mds_client *mdsc, struct ceph_cap *cap)
{
    spin_lock(&mdsc->caps_list_lock);
    dout("put_cap %p %d = %d used + %d resv + %d avail\n",
         cap, mdsc->caps_total_count, mdsc->caps_use_count,
         mdsc->caps_reserve_count, mdsc->caps_avail_count);
    mdsc->caps_use_count--;
    /*
     * Keep some preallocated caps around (ceph_min_count), to
     * avoid lots of free/alloc churn.
     */
    if (mdsc->caps_avail_count >= mdsc->caps_reserve_count +
                      mdsc->caps_min_count) {
        mdsc->caps_total_count--;
        kmem_cache_free(ceph_cap_cachep, cap);
    } else {
        mdsc->caps_avail_count++;
        list_add(&cap->caps_item, &mdsc->caps_list);
    }

    BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
           mdsc->caps_reserve_count + mdsc->caps_avail_count);
    spin_unlock(&mdsc->caps_list_lock);
}

void ceph_reservation_status(struct ceph_fs_client *fsc,
                 int *total, int *avail, int *used, int *reserved,
                 int *min)
{
    struct ceph_mds_client *mdsc = fsc->mdsc;

    if (total)
        *total = mdsc->caps_total_count;
    if (avail)
        *avail = mdsc->caps_avail_count;
    if (used)
        *used = mdsc->caps_use_count;
    if (reserved)
        *reserved = mdsc->caps_reserve_count;
    if (min)
        *min = mdsc->caps_min_count;
}

/*
 * Find ceph_cap for given mds, if any.
 *
 * Called with i_ceph_lock held.
 */
static struct ceph_cap *__get_cap_for_mds(struct ceph_inode_info *ci, int mds)
{
    struct ceph_cap *cap;
    struct rb_node *n = ci->i_caps.rb_node;

    while (n) {
        cap = rb_entry(n, struct ceph_cap, ci_node);
        if (mds < cap->mds)
            n = n->rb_left;
        else if (mds > cap->mds)
            n = n->rb_right;
        else
            return cap;
    }
    return NULL;
}

struct ceph_cap *ceph_get_cap_for_mds(struct ceph_inode_info *ci, int mds)
{
    struct ceph_cap *cap;

    spin_lock(&ci->i_ceph_lock);
    cap = __get_cap_for_mds(ci, mds);
    spin_unlock(&ci->i_ceph_lock);
    return cap;
}

/*
 * Return id of any MDS with a cap, preferably FILE_WR|BUFFER|EXCL, else -1.
 */
static int __ceph_get_cap_mds(struct ceph_inode_info *ci)
{
    struct ceph_cap *cap;
    int mds = -1;
    struct rb_node *p;

    /* prefer mds with WR|BUFFER|EXCL caps */
    for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
        cap = rb_entry(p, struct ceph_cap, ci_node);
        mds = cap->mds;
        if (cap->issued & (CEPH_CAP_FILE_WR |
                   CEPH_CAP_FILE_BUFFER |
                   CEPH_CAP_FILE_EXCL))
            break;
    }
    return mds;
}

int ceph_get_cap_mds(struct inode *inode)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    int mds;
    spin_lock(&ci->i_ceph_lock);
    mds = __ceph_get_cap_mds(ceph_inode(inode));
    spin_unlock(&ci->i_ceph_lock);
    return mds;
}

/*
 * Called under i_ceph_lock.
 */
static void __insert_cap_node(struct ceph_inode_info *ci,
                  struct ceph_cap *new)
{
    struct rb_node **p = &ci->i_caps.rb_node;
    struct rb_node *parent = NULL;
    struct ceph_cap *cap = NULL;

    while (*p) {
        parent = *p;
        cap = rb_entry(parent, struct ceph_cap, ci_node);
        if (new->mds < cap->mds)
            p = &(*p)->rb_left;
        else if (new->mds > cap->mds)
            p = &(*p)->rb_right;
        else
            BUG();
    }

    rb_link_node(&new->ci_node, parent, p);
    rb_insert_color(&new->ci_node, &ci->i_caps);
}

/*
 * (re)set cap hold timeouts, which control the delayed release
 * of unused caps back to the MDS.  Should be called on cap use.
 */
static void __cap_set_timeouts(struct ceph_mds_client *mdsc,
                   struct ceph_inode_info *ci)
{
    struct ceph_mount_options *ma = mdsc->fsc->mount_options;

    ci->i_hold_caps_min = round_jiffies(jiffies +
                        ma->caps_wanted_delay_min * HZ);
    ci->i_hold_caps_max = round_jiffies(jiffies +
                        ma->caps_wanted_delay_max * HZ);
    dout("__cap_set_timeouts %p min %lu max %lu\n", &ci->vfs_inode,
         ci->i_hold_caps_min - jiffies, ci->i_hold_caps_max - jiffies);
}

/*
 * (Re)queue cap at the end of the delayed cap release list.
 *
 * If I_FLUSH is set, leave the inode at the front of the list.
 *
 * Caller holds i_ceph_lock
 *    -> we take mdsc->cap_delay_lock
 */
static void __cap_delay_requeue(struct ceph_mds_client *mdsc,
                struct ceph_inode_info *ci)
{
    __cap_set_timeouts(mdsc, ci);
    dout("__cap_delay_requeue %p flags %d at %lu\n", &ci->vfs_inode,
         ci->i_ceph_flags, ci->i_hold_caps_max);
    if (!mdsc->stopping) {
        spin_lock(&mdsc->cap_delay_lock);
        if (!list_empty(&ci->i_cap_delay_list)) {
            if (ci->i_ceph_flags & CEPH_I_FLUSH)
                goto no_change;
            list_del_init(&ci->i_cap_delay_list);
        }
        list_add_tail(&ci->i_cap_delay_list, &mdsc->cap_delay_list);
no_change:
        spin_unlock(&mdsc->cap_delay_lock);
    }
}

/*
 * Queue an inode for immediate writeback.  Mark inode with I_FLUSH,
 * indicating we should send a cap message to flush dirty metadata
 * asap, and move to the front of the delayed cap list.
 */
static void __cap_delay_requeue_front(struct ceph_mds_client *mdsc,
                      struct ceph_inode_info *ci)
{
    dout("__cap_delay_requeue_front %p\n", &ci->vfs_inode);
    spin_lock(&mdsc->cap_delay_lock);
    ci->i_ceph_flags |= CEPH_I_FLUSH;
    if (!list_empty(&ci->i_cap_delay_list))
        list_del_init(&ci->i_cap_delay_list);
    list_add(&ci->i_cap_delay_list, &mdsc->cap_delay_list);
    spin_unlock(&mdsc->cap_delay_lock);
}

/*
 * Cancel delayed work on cap.
 *
 * Caller must hold i_ceph_lock.
 */
static void __cap_delay_cancel(struct ceph_mds_client *mdsc,
                   struct ceph_inode_info *ci)
{
    dout("__cap_delay_cancel %p\n", &ci->vfs_inode);
    if (list_empty(&ci->i_cap_delay_list))
        return;
    spin_lock(&mdsc->cap_delay_lock);
    list_del_init(&ci->i_cap_delay_list);
    spin_unlock(&mdsc->cap_delay_lock);
}

/*
 * Common issue checks for add_cap, handle_cap_grant.
 */
static void __check_cap_issue(struct ceph_inode_info *ci, struct ceph_cap *cap,
                  unsigned issued)
{
    unsigned had = __ceph_caps_issued(ci, NULL);

    /*
     * Each time we receive FILE_CACHE anew, we increment
     * i_rdcache_gen.
     */
    if ((issued & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)) &&
        (had & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)) == 0)
        ci->i_rdcache_gen++;

    /*
     * if we are newly issued FILE_SHARED, clear D_COMPLETE; we
     * don't know what happened to this directory while we didn't
     * have the cap.
     */
    if ((issued & CEPH_CAP_FILE_SHARED) &&
        (had & CEPH_CAP_FILE_SHARED) == 0) {
        ci->i_shared_gen++;
        if (S_ISDIR(ci->vfs_inode.i_mode))
            ceph_dir_clear_complete(&ci->vfs_inode);
    }
}

/*
 * Add a capability under the given MDS session.
 *
 * Caller should hold session snap_rwsem (read) and s_mutex.
 *
 * @fmode is the open file mode, if we are opening a file, otherwise
 * it is < 0.  (This is so we can atomically add the cap and add an
 * open file reference to it.)
 */
int ceph_add_cap(struct inode *inode,
         struct ceph_mds_session *session, u64 cap_id,
         int fmode, unsigned issued, unsigned wanted,
         unsigned seq, unsigned mseq, u64 realmino, int flags,
         struct ceph_cap_reservation *caps_reservation)
{
    struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
    struct ceph_inode_info *ci = ceph_inode(inode);
    struct ceph_cap *new_cap = NULL;
    struct ceph_cap *cap;
    int mds = session->s_mds;
    int actual_wanted;

    dout("add_cap %p mds%d cap %llx %s seq %d\n", inode,
         session->s_mds, cap_id, ceph_cap_string(issued), seq);

    /*
     * If we are opening the file, include file mode wanted bits
     * in wanted.
     */
    if (fmode >= 0)
        wanted |= ceph_caps_for_mode(fmode);

retry:
    spin_lock(&ci->i_ceph_lock);
    cap = __get_cap_for_mds(ci, mds);
    if (!cap) {
        if (new_cap) {
            cap = new_cap;
            new_cap = NULL;
        } else {
            spin_unlock(&ci->i_ceph_lock);
            new_cap = get_cap(mdsc, caps_reservation);
            if (new_cap == NULL)
                return -ENOMEM;
            goto retry;
        }

        cap->issued = 0;
        cap->implemented = 0;
        cap->mds = mds;
        cap->mds_wanted = 0;

        cap->ci = ci;
        __insert_cap_node(ci, cap);

        /* clear out old exporting info?  (i.e. on cap import) */
        if (ci->i_cap_exporting_mds == mds) {
            ci->i_cap_exporting_issued = 0;
            ci->i_cap_exporting_mseq = 0;
            ci->i_cap_exporting_mds = -1;
        }

        /* add to session cap list */
        cap->session = session;
        spin_lock(&session->s_cap_lock);
        list_add_tail(&cap->session_caps, &session->s_caps);
        session->s_nr_caps++;
        spin_unlock(&session->s_cap_lock);
    } else if (new_cap)
        ceph_put_cap(mdsc, new_cap);

    if (!ci->i_snap_realm) {
        /*
         * add this inode to the appropriate snap realm
         */
        struct ceph_snap_realm *realm = ceph_lookup_snap_realm(mdsc,
                                   realmino);
        if (realm) {
            ceph_get_snap_realm(mdsc, realm);
            spin_lock(&realm->inodes_with_caps_lock);
            ci->i_snap_realm = realm;
            list_add(&ci->i_snap_realm_item,
                 &realm->inodes_with_caps);
            spin_unlock(&realm->inodes_with_caps_lock);
        } else {
            pr_err("ceph_add_cap: couldn't find snap realm %llx\n",
                   realmino);
            WARN_ON(!realm);
        }
    }

    __check_cap_issue(ci, cap, issued);

    /*
     * If we are issued caps we don't want, or the mds' wanted
     * value appears to be off, queue a check so we'll release
     * later and/or update the mds wanted value.
     */
    actual_wanted = __ceph_caps_wanted(ci);
    if ((wanted & ~actual_wanted) ||
        (issued & ~actual_wanted & CEPH_CAP_ANY_WR)) {
        dout(" issued %s, mds wanted %s, actual %s, queueing\n",
             ceph_cap_string(issued), ceph_cap_string(wanted),
             ceph_cap_string(actual_wanted));
        __cap_delay_requeue(mdsc, ci);
    }

    if (flags & CEPH_CAP_FLAG_AUTH)
        ci->i_auth_cap = cap;
    else if (ci->i_auth_cap == cap)
        ci->i_auth_cap = NULL;

    dout("add_cap inode %p (%llx.%llx) cap %p %s now %s seq %d mds%d\n",
         inode, ceph_vinop(inode), cap, ceph_cap_string(issued),
         ceph_cap_string(issued|cap->issued), seq, mds);
    cap->cap_id = cap_id;
    cap->issued = issued;
    cap->implemented |= issued;
    cap->mds_wanted |= wanted;
    cap->seq = seq;
    cap->issue_seq = seq;
    cap->mseq = mseq;
    cap->cap_gen = session->s_cap_gen;

    if (fmode >= 0)
        __ceph_get_fmode(ci, fmode);
    spin_unlock(&ci->i_ceph_lock);
    wake_up_all(&ci->i_cap_wq);
    return 0;
}

/*
 * Return true if cap has not timed out and belongs to the current
 * generation of the MDS session (i.e. has not gone 'stale' due to
 * us losing touch with the mds).
 */
static int __cap_is_valid(struct ceph_cap *cap)
{
    unsigned long ttl;
    u32 gen;

    spin_lock(&cap->session->s_gen_ttl_lock);
    gen = cap->session->s_cap_gen;
    ttl = cap->session->s_cap_ttl;
    spin_unlock(&cap->session->s_gen_ttl_lock);

    if (cap->cap_gen < gen || time_after_eq(jiffies, ttl)) {
        dout("__cap_is_valid %p cap %p issued %s "
             "but STALE (gen %u vs %u)\n", &cap->ci->vfs_inode,
             cap, ceph_cap_string(cap->issued), cap->cap_gen, gen);
        return 0;
    }

    return 1;
}

/*
 * Return set of valid cap bits issued to us.  Note that caps time
 * out, and may be invalidated in bulk if the client session times out
 * and session->s_cap_gen is bumped.
 */
int __ceph_caps_issued(struct ceph_inode_info *ci, int *implemented)
{
    int have = ci->i_snap_caps | ci->i_cap_exporting_issued;
    struct ceph_cap *cap;
    struct rb_node *p;

    if (implemented)
        *implemented = 0;
    for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
        cap = rb_entry(p, struct ceph_cap, ci_node);
        if (!__cap_is_valid(cap))
            continue;
        dout("__ceph_caps_issued %p cap %p issued %s\n",
             &ci->vfs_inode, cap, ceph_cap_string(cap->issued));
        have |= cap->issued;
        if (implemented)
            *implemented |= cap->implemented;
    }
    return have;
}

/*
 * Get cap bits issued by caps other than @ocap
 */
int __ceph_caps_issued_other(struct ceph_inode_info *ci, struct ceph_cap *ocap)
{
    int have = ci->i_snap_caps;
    struct ceph_cap *cap;
    struct rb_node *p;

    for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
        cap = rb_entry(p, struct ceph_cap, ci_node);
        if (cap == ocap)
            continue;
        if (!__cap_is_valid(cap))
            continue;
        have |= cap->issued;
    }
    return have;
}

/*
 * Move a cap to the end of the LRU (oldest caps at list head, newest
 * at list tail).
 */
static void __touch_cap(struct ceph_cap *cap)
{
    struct ceph_mds_session *s = cap->session;

    spin_lock(&s->s_cap_lock);
    if (s->s_cap_iterator == NULL) {
        dout("__touch_cap %p cap %p mds%d\n", &cap->ci->vfs_inode, cap,
             s->s_mds);
        list_move_tail(&cap->session_caps, &s->s_caps);
    } else {
        dout("__touch_cap %p cap %p mds%d NOP, iterating over caps\n",
             &cap->ci->vfs_inode, cap, s->s_mds);
    }
    spin_unlock(&s->s_cap_lock);
}

/*
 * Check if we hold the given mask.  If so, move the cap(s) to the
 * front of their respective LRUs.  (This is the preferred way for
 * callers to check for caps they want.)
 */
int __ceph_caps_issued_mask(struct ceph_inode_info *ci, int mask, int touch)
{
    struct ceph_cap *cap;
    struct rb_node *p;
    int have = ci->i_snap_caps;

    if ((have & mask) == mask) {
        dout("__ceph_caps_issued_mask %p snap issued %s"
             " (mask %s)\n", &ci->vfs_inode,
             ceph_cap_string(have),
             ceph_cap_string(mask));
        return 1;
    }

    for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
        cap = rb_entry(p, struct ceph_cap, ci_node);
        if (!__cap_is_valid(cap))
            continue;
        if ((cap->issued & mask) == mask) {
            dout("__ceph_caps_issued_mask %p cap %p issued %s"
                 " (mask %s)\n", &ci->vfs_inode, cap,
                 ceph_cap_string(cap->issued),
                 ceph_cap_string(mask));
            if (touch)
                __touch_cap(cap);
            return 1;
        }

        /* does a combination of caps satisfy mask? */
        have |= cap->issued;
        if ((have & mask) == mask) {
            dout("__ceph_caps_issued_mask %p combo issued %s"
                 " (mask %s)\n", &ci->vfs_inode,
                 ceph_cap_string(cap->issued),
                 ceph_cap_string(mask));
            if (touch) {
                struct rb_node *q;

                /* touch this + preceding caps */
                __touch_cap(cap);
                for (q = rb_first(&ci->i_caps); q != p;
                     q = rb_next(q)) {
                    cap = rb_entry(q, struct ceph_cap,
                               ci_node);
                    if (!__cap_is_valid(cap))
                        continue;
                    __touch_cap(cap);
                }
            }
            return 1;
        }
    }

    return 0;
}

/*
 * Return true if mask caps are currently being revoked by an MDS.
 */
int ceph_caps_revoking(struct ceph_inode_info *ci, int mask)
{
    struct inode *inode = &ci->vfs_inode;
    struct ceph_cap *cap;
    struct rb_node *p;
    int ret = 0;

    spin_lock(&ci->i_ceph_lock);
    for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
        cap = rb_entry(p, struct ceph_cap, ci_node);
        if (__cap_is_valid(cap) &&
            (cap->implemented & ~cap->issued & mask)) {
            ret = 1;
            break;
        }
    }
    spin_unlock(&ci->i_ceph_lock);
    dout("ceph_caps_revoking %p %s = %d\n", inode,
         ceph_cap_string(mask), ret);
    return ret;
}

int __ceph_caps_used(struct ceph_inode_info *ci)
{
    int used = 0;
    if (ci->i_pin_ref)
        used |= CEPH_CAP_PIN;
    if (ci->i_rd_ref)
        used |= CEPH_CAP_FILE_RD;
    if (ci->i_rdcache_ref || ci->vfs_inode.i_data.nrpages)
        used |= CEPH_CAP_FILE_CACHE;
    if (ci->i_wr_ref)
        used |= CEPH_CAP_FILE_WR;
    if (ci->i_wb_ref || ci->i_wrbuffer_ref)
        used |= CEPH_CAP_FILE_BUFFER;
    return used;
}

/*
 * wanted, by virtue of open file modes
 */
int __ceph_caps_file_wanted(struct ceph_inode_info *ci)
{
    int want = 0;
    int mode;
    for (mode = 0; mode < CEPH_FILE_MODE_NUM; mode++)
        if (ci->i_nr_by_mode[mode])
            want |= ceph_caps_for_mode(mode);
    return want;
}

/*
 * Return caps we have registered with the MDS(s) as 'wanted'.
 */
int __ceph_caps_mds_wanted(struct ceph_inode_info *ci)
{
    struct ceph_cap *cap;
    struct rb_node *p;
    int mds_wanted = 0;

    for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
        cap = rb_entry(p, struct ceph_cap, ci_node);
        if (!__cap_is_valid(cap))
            continue;
        mds_wanted |= cap->mds_wanted;
    }
    return mds_wanted;
}

/*
 * called under i_ceph_lock
 */
static int __ceph_is_any_caps(struct ceph_inode_info *ci)
{
    return !RB_EMPTY_ROOT(&ci->i_caps) || ci->i_cap_exporting_mds >= 0;
}

/*
 * Remove a cap.  Take steps to deal with a racing iterate_session_caps.
 *
 * caller should hold i_ceph_lock.
 * caller will not hold session s_mutex if called from destroy_inode.
 */
void __ceph_remove_cap(struct ceph_cap *cap)
{
    struct ceph_mds_session *session = cap->session;
    struct ceph_inode_info *ci = cap->ci;
    struct ceph_mds_client *mdsc =
        ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc;
    int removed = 0;

    dout("__ceph_remove_cap %p from %p\n", cap, &ci->vfs_inode);

    /* remove from session list */
    spin_lock(&session->s_cap_lock);
    if (session->s_cap_iterator == cap) {
        /* not yet, we are iterating over this very cap */
        dout("__ceph_remove_cap  delaying %p removal from session %p\n",
             cap, cap->session);
    } else {
        list_del_init(&cap->session_caps);
        session->s_nr_caps--;
        cap->session = NULL;
        removed = 1;
    }
    /* protect backpointer with s_cap_lock: see iterate_session_caps */
    cap->ci = NULL;
    spin_unlock(&session->s_cap_lock);

    /* remove from inode list */
    rb_erase(&cap->ci_node, &ci->i_caps);
    if (ci->i_auth_cap == cap)
        ci->i_auth_cap = NULL;

    if (removed)
        ceph_put_cap(mdsc, cap);

    if (!__ceph_is_any_caps(ci) && ci->i_snap_realm) {
        struct ceph_snap_realm *realm = ci->i_snap_realm;
        spin_lock(&realm->inodes_with_caps_lock);
        list_del_init(&ci->i_snap_realm_item);
        ci->i_snap_realm_counter++;
        ci->i_snap_realm = NULL;
        spin_unlock(&realm->inodes_with_caps_lock);
        ceph_put_snap_realm(mdsc, realm);
    }
    if (!__ceph_is_any_real_caps(ci))
        __cap_delay_cancel(mdsc, ci);
}

/*
 * Build and send a cap message to the given MDS.
 *
 * Caller should be holding s_mutex.
 */
static int send_cap_msg(struct ceph_mds_session *session,
            u64 ino, u64 cid, int op,
            int caps, int wanted, int dirty,
            u32 seq, u64 flush_tid, u32 issue_seq, u32 mseq,
            u64 size, u64 max_size,
            struct timespec *mtime, struct timespec *atime,
            u64 time_warp_seq,
            uid_t uid, gid_t gid, umode_t mode,
            u64 xattr_version,
            struct ceph_buffer *xattrs_buf,
            u64 follows)
{
    struct ceph_mds_caps *fc;
    struct ceph_msg *msg;

    dout("send_cap_msg %s %llx %llx caps %s wanted %s dirty %s"
         " seq %u/%u mseq %u follows %lld size %llu/%llu"
         " xattr_ver %llu xattr_len %d\n", ceph_cap_op_name(op),
         cid, ino, ceph_cap_string(caps), ceph_cap_string(wanted),
         ceph_cap_string(dirty),
         seq, issue_seq, mseq, follows, size, max_size,
         xattr_version, xattrs_buf ? (int)xattrs_buf->vec.iov_len : 0);

    msg = ceph_msg_new(CEPH_MSG_CLIENT_CAPS, sizeof(*fc), GFP_NOFS, false);
    if (!msg)
        return -ENOMEM;

    msg->hdr.tid = cpu_to_le64(flush_tid);

    fc = msg->front.iov_base;
    memset(fc, 0, sizeof(*fc));

    fc->cap_id = cpu_to_le64(cid);
    fc->op = cpu_to_le32(op);
    fc->seq = cpu_to_le32(seq);
    fc->issue_seq = cpu_to_le32(issue_seq);
    fc->migrate_seq = cpu_to_le32(mseq);
    fc->caps = cpu_to_le32(caps);
    fc->wanted = cpu_to_le32(wanted);
    fc->dirty = cpu_to_le32(dirty);
    fc->ino = cpu_to_le64(ino);
    fc->snap_follows = cpu_to_le64(follows);

    fc->size = cpu_to_le64(size);
    fc->max_size = cpu_to_le64(max_size);
    if (mtime)
        ceph_encode_timespec(&fc->mtime, mtime);
    if (atime)
        ceph_encode_timespec(&fc->atime, atime);
    fc->time_warp_seq = cpu_to_le32(time_warp_seq);

    fc->uid = cpu_to_le32(uid);
    fc->gid = cpu_to_le32(gid);
    fc->mode = cpu_to_le32(mode);

    fc->xattr_version = cpu_to_le64(xattr_version);
    if (xattrs_buf) {
        msg->middle = ceph_buffer_get(xattrs_buf);
        fc->xattr_len = cpu_to_le32(xattrs_buf->vec.iov_len);
        msg->hdr.middle_len = cpu_to_le32(xattrs_buf->vec.iov_len);
    }

    ceph_con_send(&session->s_con, msg);
    return 0;
}

static void __queue_cap_release(struct ceph_mds_session *session,
                u64 ino, u64 cap_id, u32 migrate_seq,
                u32 issue_seq)
{
    struct ceph_msg *msg;
    struct ceph_mds_cap_release *head;
    struct ceph_mds_cap_item *item;

    spin_lock(&session->s_cap_lock);
    BUG_ON(!session->s_num_cap_releases);
    msg = list_first_entry(&session->s_cap_releases,
                   struct ceph_msg, list_head);

    dout(" adding %llx release to mds%d msg %p (%d left)\n",
         ino, session->s_mds, msg, session->s_num_cap_releases);

    BUG_ON(msg->front.iov_len + sizeof(*item) > PAGE_CACHE_SIZE);
    head = msg->front.iov_base;
    le32_add_cpu(&head->num, 1);
    item = msg->front.iov_base + msg->front.iov_len;
    item->ino = cpu_to_le64(ino);
    item->cap_id = cpu_to_le64(cap_id);
    item->migrate_seq = cpu_to_le32(migrate_seq);
    item->seq = cpu_to_le32(issue_seq);

    session->s_num_cap_releases--;

    msg->front.iov_len += sizeof(*item);
    if (le32_to_cpu(head->num) == CEPH_CAPS_PER_RELEASE) {
        dout(" release msg %p full\n", msg);
        list_move_tail(&msg->list_head, &session->s_cap_releases_done);
    } else {
        dout(" release msg %p at %d/%d (%d)\n", msg,
             (int)le32_to_cpu(head->num),
             (int)CEPH_CAPS_PER_RELEASE,
             (int)msg->front.iov_len);
    }
    spin_unlock(&session->s_cap_lock);
}

/*
 * Queue cap releases when an inode is dropped from our cache.  Since
 * inode is about to be destroyed, there is no need for i_ceph_lock.
 */
void ceph_queue_caps_release(struct inode *inode)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    struct rb_node *p;

    p = rb_first(&ci->i_caps);
    while (p) {
        struct ceph_cap *cap = rb_entry(p, struct ceph_cap, ci_node);
        struct ceph_mds_session *session = cap->session;

        __queue_cap_release(session, ceph_ino(inode), cap->cap_id,
                    cap->mseq, cap->issue_seq);
        p = rb_next(p);
        __ceph_remove_cap(cap);
    }
}

/*
 * Send a cap msg on the given inode.  Update our caps state, then
 * drop i_ceph_lock and send the message.
 *
 * Make note of max_size reported/requested from mds, revoked caps
 * that have now been implemented.
 *
 * Make half-hearted attempt ot to invalidate page cache if we are
 * dropping RDCACHE.  Note that this will leave behind locked pages
 * that we'll then need to deal with elsewhere.
 *
 * Return non-zero if delayed release, or we experienced an error
 * such that the caller should requeue + retry later.
 *
 * called with i_ceph_lock, then drops it.
 * caller should hold snap_rwsem (read), s_mutex.
 */
static int __send_cap(struct ceph_mds_client *mdsc, struct ceph_cap *cap,
              int op, int used, int want, int retain, int flushing,
              unsigned *pflush_tid)
    __releases(cap->ci->i_ceph_lock)
{
    struct ceph_inode_info *ci = cap->ci;
    struct inode *inode = &ci->vfs_inode;
    u64 cap_id = cap->cap_id;
    int held, revoking, dropping, keep;
    u64 seq, issue_seq, mseq, time_warp_seq, follows;
    u64 size, max_size;
    struct timespec mtime, atime;
    int wake = 0;
    umode_t mode;
    uid_t uid;
    gid_t gid;
    struct ceph_mds_session *session;
    u64 xattr_version = 0;
    struct ceph_buffer *xattr_blob = NULL;
    int delayed = 0;
    u64 flush_tid = 0;
    int i;
    int ret;

    held = cap->issued | cap->implemented;
    revoking = cap->implemented & ~cap->issued;
    retain &= ~revoking;
    dropping = cap->issued & ~retain;

    dout("__send_cap %p cap %p session %p %s -> %s (revoking %s)\n",
         inode, cap, cap->session,
         ceph_cap_string(held), ceph_cap_string(held & retain),
         ceph_cap_string(revoking));
    BUG_ON((retain & CEPH_CAP_PIN) == 0);

    session = cap->session;

    /* don't release wanted unless we've waited a bit. */
    if ((ci->i_ceph_flags & CEPH_I_NODELAY) == 0 &&
        time_before(jiffies, ci->i_hold_caps_min)) {
        dout(" delaying issued %s -> %s, wanted %s -> %s on send\n",
             ceph_cap_string(cap->issued),
             ceph_cap_string(cap->issued & retain),
             ceph_cap_string(cap->mds_wanted),
             ceph_cap_string(want));
        want |= cap->mds_wanted;
        retain |= cap->issued;
        delayed = 1;
    }
    ci->i_ceph_flags &= ~(CEPH_I_NODELAY | CEPH_I_FLUSH);

    cap->issued &= retain;  /* drop bits we don't want */
    if (cap->implemented & ~cap->issued) {
        /*
         * Wake up any waiters on wanted -> needed transition.
         * This is due to the weird transition from buffered
         * to sync IO... we need to flush dirty pages _before_
         * allowing sync writes to avoid reordering.
         */
        wake = 1;
    }
    cap->implemented &= cap->issued | used;
    cap->mds_wanted = want;

    if (flushing) {
        /*
         * assign a tid for flush operations so we can avoid
         * flush1 -> dirty1 -> flush2 -> flushack1 -> mark
         * clean type races.  track latest tid for every bit
         * so we can handle flush AxFw, flush Fw, and have the
         * first ack clean Ax.
         */
        flush_tid = ++ci->i_cap_flush_last_tid;
        if (pflush_tid)
            *pflush_tid = flush_tid;
        dout(" cap_flush_tid %d\n", (int)flush_tid);
        for (i = 0; i < CEPH_CAP_BITS; i++)
            if (flushing & (1 << i))
                ci->i_cap_flush_tid[i] = flush_tid;

        follows = ci->i_head_snapc->seq;
    } else {
        follows = 0;
    }

    keep = cap->implemented;
    seq = cap->seq;
    issue_seq = cap->issue_seq;
    mseq = cap->mseq;
    size = inode->i_size;
    ci->i_reported_size = size;
    max_size = ci->i_wanted_max_size;
    ci->i_requested_max_size = max_size;
    mtime = inode->i_mtime;
    atime = inode->i_atime;
    time_warp_seq = ci->i_time_warp_seq;
    uid = inode->i_uid;
    gid = inode->i_gid;
    mode = inode->i_mode;

    if (flushing & CEPH_CAP_XATTR_EXCL) {
        __ceph_build_xattrs_blob(ci);
        xattr_blob = ci->i_xattrs.blob;
        xattr_version = ci->i_xattrs.version;
    }

    spin_unlock(&ci->i_ceph_lock);

    ret = send_cap_msg(session, ceph_vino(inode).ino, cap_id,
        op, keep, want, flushing, seq, flush_tid, issue_seq, mseq,
        size, max_size, &mtime, &atime, time_warp_seq,
        uid, gid, mode, xattr_version, xattr_blob,
        follows);
    if (ret < 0) {
        dout("error sending cap msg, must requeue %p\n", inode);
        delayed = 1;
    }

    if (wake)
        wake_up_all(&ci->i_cap_wq);

    return delayed;
}

/*
 * When a snapshot is taken, clients accumulate dirty metadata on
 * inodes with capabilities in ceph_cap_snaps to describe the file
 * state at the time the snapshot was taken.  This must be flushed
 * asynchronously back to the MDS once sync writes complete and dirty
 * data is written out.
 *
 * Unless @again is true, skip cap_snaps that were already sent to
 * the MDS (i.e., during this session).
 *
 * Called under i_ceph_lock.  Takes s_mutex as needed.
 */
void __ceph_flush_snaps(struct ceph_inode_info *ci,
            struct ceph_mds_session **psession,
            int again)
        __releases(ci->i_ceph_lock)
        __acquires(ci->i_ceph_lock)
{
    struct inode *inode = &ci->vfs_inode;
    int mds;
    struct ceph_cap_snap *capsnap;
    u32 mseq;
    struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
    struct ceph_mds_session *session = NULL; /* if session != NULL, we hold
                            session->s_mutex */
    u64 next_follows = 0;  /* keep track of how far we've gotten through the
                 i_cap_snaps list, and skip these entries next time
                 around to avoid an infinite loop */

    if (psession)
        session = *psession;

    dout("__flush_snaps %p\n", inode);
retry:
    list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
        /* avoid an infiniute loop after retry */
        if (capsnap->follows < next_follows)
            continue;
        /*
         * we need to wait for sync writes to complete and for dirty
         * pages to be written out.
         */
        if (capsnap->dirty_pages || capsnap->writing)
            break;

        /*
         * if cap writeback already occurred, we should have dropped
         * the capsnap in ceph_put_wrbuffer_cap_refs.
         */
        BUG_ON(capsnap->dirty == 0);

        /* pick mds, take s_mutex */
        if (ci->i_auth_cap == NULL) {
            dout("no auth cap (migrating?), doing nothing\n");
            goto out;
        }

        /* only flush each capsnap once */
        if (!again && !list_empty(&capsnap->flushing_item)) {
            dout("already flushed %p, skipping\n", capsnap);
            continue;
        }

        mds = ci->i_auth_cap->session->s_mds;
        mseq = ci->i_auth_cap->mseq;

        if (session && session->s_mds != mds) {
            dout("oops, wrong session %p mutex\n", session);
            mutex_unlock(&session->s_mutex);
            ceph_put_mds_session(session);
            session = NULL;
        }
        if (!session) {
            spin_unlock(&ci->i_ceph_lock);
            mutex_lock(&mdsc->mutex);
            session = __ceph_lookup_mds_session(mdsc, mds);
            mutex_unlock(&mdsc->mutex);
            if (session) {
                dout("inverting session/ino locks on %p\n",
                     session);
                mutex_lock(&session->s_mutex);
            }
            /*
             * if session == NULL, we raced against a cap
             * deletion or migration.  retry, and we'll
             * get a better @mds value next time.
             */
            spin_lock(&ci->i_ceph_lock);
            goto retry;
        }

        capsnap->flush_tid = ++ci->i_cap_flush_last_tid;
        atomic_inc(&capsnap->nref);
        if (!list_empty(&capsnap->flushing_item))
            list_del_init(&capsnap->flushing_item);
        list_add_tail(&capsnap->flushing_item,
                  &session->s_cap_snaps_flushing);
        spin_unlock(&ci->i_ceph_lock);

        dout("flush_snaps %p cap_snap %p follows %lld tid %llu\n",
             inode, capsnap, capsnap->follows, capsnap->flush_tid);
        send_cap_msg(session, ceph_vino(inode).ino, 0,
                 CEPH_CAP_OP_FLUSHSNAP, capsnap->issued, 0,
                 capsnap->dirty, 0, capsnap->flush_tid, 0, mseq,
                 capsnap->size, 0,
                 &capsnap->mtime, &capsnap->atime,
                 capsnap->time_warp_seq,
                 capsnap->uid, capsnap->gid, capsnap->mode,
                 capsnap->xattr_version, capsnap->xattr_blob,
                 capsnap->follows);

        next_follows = capsnap->follows + 1;
        ceph_put_cap_snap(capsnap);

        spin_lock(&ci->i_ceph_lock);
        goto retry;
    }

    /* we flushed them all; remove this inode from the queue */
    spin_lock(&mdsc->snap_flush_lock);
    list_del_init(&ci->i_snap_flush_item);
    spin_unlock(&mdsc->snap_flush_lock);

out:
    if (psession)
        *psession = session;
    else if (session) {
        mutex_unlock(&session->s_mutex);
        ceph_put_mds_session(session);
    }
}

static void ceph_flush_snaps(struct ceph_inode_info *ci)
{
    spin_lock(&ci->i_ceph_lock);
    __ceph_flush_snaps(ci, NULL, 0);
    spin_unlock(&ci->i_ceph_lock);
}

/*
 * Mark caps dirty.  If inode is newly dirty, return the dirty flags.
 * Caller is then responsible for calling __mark_inode_dirty with the
 * returned flags value.
 */
int __ceph_mark_dirty_caps(struct ceph_inode_info *ci, int mask)
{
    struct ceph_mds_client *mdsc =
        ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc;
    struct inode *inode = &ci->vfs_inode;
    int was = ci->i_dirty_caps;
    int dirty = 0;

    dout("__mark_dirty_caps %p %s dirty %s -> %s\n", &ci->vfs_inode,
         ceph_cap_string(mask), ceph_cap_string(was),
         ceph_cap_string(was | mask));
    ci->i_dirty_caps |= mask;
    if (was == 0) {
        if (!ci->i_head_snapc)
            ci->i_head_snapc = ceph_get_snap_context(
                ci->i_snap_realm->cached_context);
        dout(" inode %p now dirty snapc %p\n", &ci->vfs_inode,
            ci->i_head_snapc);
        BUG_ON(!list_empty(&ci->i_dirty_item));
        spin_lock(&mdsc->cap_dirty_lock);
        list_add(&ci->i_dirty_item, &mdsc->cap_dirty);
        spin_unlock(&mdsc->cap_dirty_lock);
        if (ci->i_flushing_caps == 0) {
            ihold(inode);
            dirty |= I_DIRTY_SYNC;
        }
    }
    BUG_ON(list_empty(&ci->i_dirty_item));
    if (((was | ci->i_flushing_caps) & CEPH_CAP_FILE_BUFFER) &&
        (mask & CEPH_CAP_FILE_BUFFER))
        dirty |= I_DIRTY_DATASYNC;
    __cap_delay_requeue(mdsc, ci);
    return dirty;
}

/*
 * Add dirty inode to the flushing list.  Assigned a seq number so we
 * can wait for caps to flush without starving.
 *
 * Called under i_ceph_lock.
 */
static int __mark_caps_flushing(struct inode *inode,
                 struct ceph_mds_session *session)
{
    struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
    struct ceph_inode_info *ci = ceph_inode(inode);
    int flushing;

    BUG_ON(ci->i_dirty_caps == 0);
    BUG_ON(list_empty(&ci->i_dirty_item));

    flushing = ci->i_dirty_caps;
    dout("__mark_caps_flushing flushing %s, flushing_caps %s -> %s\n",
         ceph_cap_string(flushing),
         ceph_cap_string(ci->i_flushing_caps),
         ceph_cap_string(ci->i_flushing_caps | flushing));
    ci->i_flushing_caps |= flushing;
    ci->i_dirty_caps = 0;
    dout(" inode %p now !dirty\n", inode);

    spin_lock(&mdsc->cap_dirty_lock);
    list_del_init(&ci->i_dirty_item);

    ci->i_cap_flush_seq = ++mdsc->cap_flush_seq;
    if (list_empty(&ci->i_flushing_item)) {
        list_add_tail(&ci->i_flushing_item, &session->s_cap_flushing);
        mdsc->num_cap_flushing++;
        dout(" inode %p now flushing seq %lld\n", inode,
             ci->i_cap_flush_seq);
    } else {
        list_move_tail(&ci->i_flushing_item, &session->s_cap_flushing);
        dout(" inode %p now flushing (more) seq %lld\n", inode,
             ci->i_cap_flush_seq);
    }
    spin_unlock(&mdsc->cap_dirty_lock);

    return flushing;
}

/*
 * try to invalidate mapping pages without blocking.
 */
static int try_nonblocking_invalidate(struct inode *inode)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    u32 invalidating_gen = ci->i_rdcache_gen;

    spin_unlock(&ci->i_ceph_lock);
    invalidate_mapping_pages(&inode->i_data, 0, -1);
    spin_lock(&ci->i_ceph_lock);

    if (inode->i_data.nrpages == 0 &&
        invalidating_gen == ci->i_rdcache_gen) {
        /* success. */
        dout("try_nonblocking_invalidate %p success\n", inode);
        /* save any racing async invalidate some trouble */
        ci->i_rdcache_revoking = ci->i_rdcache_gen - 1;
        return 0;
    }
    dout("try_nonblocking_invalidate %p failed\n", inode);
    return -1;
}

/*
 * Swiss army knife function to examine currently used and wanted
 * versus held caps.  Release, flush, ack revoked caps to mds as
 * appropriate.
 *
 *  CHECK_CAPS_NODELAY - caller is delayed work and we should not delay
 *    cap release further.
 *  CHECK_CAPS_AUTHONLY - we should only check the auth cap
 *  CHECK_CAPS_FLUSH - we should flush any dirty caps immediately, without
 *    further delay.
 */
void ceph_check_caps(struct ceph_inode_info *ci, int flags,
             struct ceph_mds_session *session)
{
    struct ceph_fs_client *fsc = ceph_inode_to_client(&ci->vfs_inode);
    struct ceph_mds_client *mdsc = fsc->mdsc;
    struct inode *inode = &ci->vfs_inode;
    struct ceph_cap *cap;
    int file_wanted, used;
    int took_snap_rwsem = 0;             /* true if mdsc->snap_rwsem held */
    int issued, implemented, want, retain, revoking, flushing = 0;
    int mds = -1;   /* keep track of how far we've gone through i_caps list
               to avoid an infinite loop on retry */
    struct rb_node *p;
    int tried_invalidate = 0;
    int delayed = 0, sent = 0, force_requeue = 0, num;
    int queue_invalidate = 0;
    int is_delayed = flags & CHECK_CAPS_NODELAY;

    /* if we are unmounting, flush any unused caps immediately. */
    if (mdsc->stopping)
        is_delayed = 1;

    spin_lock(&ci->i_ceph_lock);

    if (ci->i_ceph_flags & CEPH_I_FLUSH)
        flags |= CHECK_CAPS_FLUSH;

    /* flush snaps first time around only */
    if (!list_empty(&ci->i_cap_snaps))
        __ceph_flush_snaps(ci, &session, 0);
    goto retry_locked;
retry:
    spin_lock(&ci->i_ceph_lock);
retry_locked:
    file_wanted = __ceph_caps_file_wanted(ci);
    used = __ceph_caps_used(ci);
    want = file_wanted | used;
    issued = __ceph_caps_issued(ci, &implemented);
    revoking = implemented & ~issued;

    retain = want | CEPH_CAP_PIN;
    if (!mdsc->stopping && inode->i_nlink > 0) {
        if (want) {
            retain |= CEPH_CAP_ANY;       /* be greedy */
        } else {
            retain |= CEPH_CAP_ANY_SHARED;
            /*
             * keep RD only if we didn't have the file open RW,
             * because then the mds would revoke it anyway to
             * journal max_size=0.
             */
            if (ci->i_max_size == 0)
                retain |= CEPH_CAP_ANY_RD;
        }
    }

    dout("check_caps %p file_want %s used %s dirty %s flushing %s"
         " issued %s revoking %s retain %s %s%s%s\n", inode,
         ceph_cap_string(file_wanted),
         ceph_cap_string(used), ceph_cap_string(ci->i_dirty_caps),
         ceph_cap_string(ci->i_flushing_caps),
         ceph_cap_string(issued), ceph_cap_string(revoking),
         ceph_cap_string(retain),
         (flags & CHECK_CAPS_AUTHONLY) ? " AUTHONLY" : "",
         (flags & CHECK_CAPS_NODELAY) ? " NODELAY" : "",
         (flags & CHECK_CAPS_FLUSH) ? " FLUSH" : "");

    /*
     * If we no longer need to hold onto old our caps, and we may
     * have cached pages, but don't want them, then try to invalidate.
     * If we fail, it's because pages are locked.... try again later.
     */
    if ((!is_delayed || mdsc->stopping) &&
        ci->i_wrbuffer_ref == 0 &&               /* no dirty pages... */
        inode->i_data.nrpages &&                 /* have cached pages */
        (file_wanted == 0 ||                     /* no open files */
         (revoking & (CEPH_CAP_FILE_CACHE|
              CEPH_CAP_FILE_LAZYIO))) && /*  or revoking cache */
        !tried_invalidate) {
        dout("check_caps trying to invalidate on %p\n", inode);
        if (try_nonblocking_invalidate(inode) < 0) {
            if (revoking & (CEPH_CAP_FILE_CACHE|
                    CEPH_CAP_FILE_LAZYIO)) {
                dout("check_caps queuing invalidate\n");
                queue_invalidate = 1;
                ci->i_rdcache_revoking = ci->i_rdcache_gen;
            } else {
                dout("check_caps failed to invalidate pages\n");
                /* we failed to invalidate pages.  check these
                   caps again later. */
                force_requeue = 1;
                __cap_set_timeouts(mdsc, ci);
            }
        }
        tried_invalidate = 1;
        goto retry_locked;
    }

    num = 0;
    for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
        cap = rb_entry(p, struct ceph_cap, ci_node);
        num++;

        /* avoid looping forever */
        if (mds >= cap->mds ||
            ((flags & CHECK_CAPS_AUTHONLY) && cap != ci->i_auth_cap))
            continue;

        /* NOTE: no side-effects allowed, until we take s_mutex */

        revoking = cap->implemented & ~cap->issued;
        dout(" mds%d cap %p issued %s implemented %s revoking %s\n",
             cap->mds, cap, ceph_cap_string(cap->issued),
             ceph_cap_string(cap->implemented),
             ceph_cap_string(revoking));

        if (cap == ci->i_auth_cap &&
            (cap->issued & CEPH_CAP_FILE_WR)) {
            /* request larger max_size from MDS? */
            if (ci->i_wanted_max_size > ci->i_max_size &&
                ci->i_wanted_max_size > ci->i_requested_max_size) {
                dout("requesting new max_size\n");
                goto ack;
            }

            /* approaching file_max? */
            if ((inode->i_size << 1) >= ci->i_max_size &&
                (ci->i_reported_size << 1) < ci->i_max_size) {
                dout("i_size approaching max_size\n");
                goto ack;
            }
        }
        /* flush anything dirty? */
        if (cap == ci->i_auth_cap && (flags & CHECK_CAPS_FLUSH) &&
            ci->i_dirty_caps) {
            dout("flushing dirty caps\n");
            goto ack;
        }

        /* completed revocation? going down and there are no caps? */
        if (revoking && (revoking & used) == 0) {
            dout("completed revocation of %s\n",
                 ceph_cap_string(cap->implemented & ~cap->issued));
            goto ack;
        }

        /* want more caps from mds? */
        if (want & ~(cap->mds_wanted | cap->issued))
            goto ack;

        /* things we might delay */
        if ((cap->issued & ~retain) == 0 &&
            cap->mds_wanted == want)
            continue;     /* nope, all good */

        if (is_delayed)
            goto ack;

        /* delay? */
        if ((ci->i_ceph_flags & CEPH_I_NODELAY) == 0 &&
            time_before(jiffies, ci->i_hold_caps_max)) {
            dout(" delaying issued %s -> %s, wanted %s -> %s\n",
                 ceph_cap_string(cap->issued),
                 ceph_cap_string(cap->issued & retain),
                 ceph_cap_string(cap->mds_wanted),
                 ceph_cap_string(want));
            delayed++;
            continue;
        }

ack:
        if (ci->i_ceph_flags & CEPH_I_NOFLUSH) {
            dout(" skipping %p I_NOFLUSH set\n", inode);
            continue;
        }

        if (session && session != cap->session) {
            dout("oops, wrong session %p mutex\n", session);
            mutex_unlock(&session->s_mutex);
            session = NULL;
        }
        if (!session) {
            session = cap->session;
            if (mutex_trylock(&session->s_mutex) == 0) {
                dout("inverting session/ino locks on %p\n",
                     session);
                spin_unlock(&ci->i_ceph_lock);
                if (took_snap_rwsem) {
                    up_read(&mdsc->snap_rwsem);
                    took_snap_rwsem = 0;
                }
                mutex_lock(&session->s_mutex);
                goto retry;
            }
        }
        /* take snap_rwsem after session mutex */
        if (!took_snap_rwsem) {
            if (down_read_trylock(&mdsc->snap_rwsem) == 0) {
                dout("inverting snap/in locks on %p\n",
                     inode);
                spin_unlock(&ci->i_ceph_lock);
                down_read(&mdsc->snap_rwsem);
                took_snap_rwsem = 1;
                goto retry;
            }
            took_snap_rwsem = 1;
        }

        if (cap == ci->i_auth_cap && ci->i_dirty_caps)
            flushing = __mark_caps_flushing(inode, session);
        else
            flushing = 0;

        mds = cap->mds;  /* remember mds, so we don't repeat */
        sent++;

        /* __send_cap drops i_ceph_lock */
        delayed += __send_cap(mdsc, cap, CEPH_CAP_OP_UPDATE, used, want,
                      retain, flushing, NULL);
        goto retry; /* retake i_ceph_lock and restart our cap scan. */
    }

    /*
     * Reschedule delayed caps release if we delayed anything,
     * otherwise cancel.
     */
    if (delayed && is_delayed)
        force_requeue = 1;   /* __send_cap delayed release; requeue */
    if (!delayed && !is_delayed)
        __cap_delay_cancel(mdsc, ci);
    else if (!is_delayed || force_requeue)
        __cap_delay_requeue(mdsc, ci);

    spin_unlock(&ci->i_ceph_lock);

    if (queue_invalidate)
        ceph_queue_invalidate(inode);

    if (session)
        mutex_unlock(&session->s_mutex);
    if (took_snap_rwsem)
        up_read(&mdsc->snap_rwsem);
}

/*
 * Try to flush dirty caps back to the auth mds.
 */
static int try_flush_caps(struct inode *inode, struct ceph_mds_session *session,
              unsigned *flush_tid)
{
    struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
    struct ceph_inode_info *ci = ceph_inode(inode);
    int unlock_session = session ? 0 : 1;
    int flushing = 0;

retry:
    spin_lock(&ci->i_ceph_lock);
    if (ci->i_ceph_flags & CEPH_I_NOFLUSH) {
        dout("try_flush_caps skipping %p I_NOFLUSH set\n", inode);
        goto out;
    }
    if (ci->i_dirty_caps && ci->i_auth_cap) {
        struct ceph_cap *cap = ci->i_auth_cap;
        int used = __ceph_caps_used(ci);
        int want = __ceph_caps_wanted(ci);
        int delayed;

        if (!session) {
            spin_unlock(&ci->i_ceph_lock);
            session = cap->session;
            mutex_lock(&session->s_mutex);
            goto retry;
        }
        BUG_ON(session != cap->session);
        if (cap->session->s_state < CEPH_MDS_SESSION_OPEN)
            goto out;

        flushing = __mark_caps_flushing(inode, session);

        /* __send_cap drops i_ceph_lock */
        delayed = __send_cap(mdsc, cap, CEPH_CAP_OP_FLUSH, used, want,
                     cap->issued | cap->implemented, flushing,
                     flush_tid);
        if (!delayed)
            goto out_unlocked;

        spin_lock(&ci->i_ceph_lock);
        __cap_delay_requeue(mdsc, ci);
    }
out:
    spin_unlock(&ci->i_ceph_lock);
out_unlocked:
    if (session && unlock_session)
        mutex_unlock(&session->s_mutex);
    return flushing;
}

/*
 * Return true if we've flushed caps through the given flush_tid.
 */
static int caps_are_flushed(struct inode *inode, unsigned tid)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    int i, ret = 1;

    spin_lock(&ci->i_ceph_lock);
    for (i = 0; i < CEPH_CAP_BITS; i++)
        if ((ci->i_flushing_caps & (1 << i)) &&
            ci->i_cap_flush_tid[i] <= tid) {
            /* still flushing this bit */
            ret = 0;
            break;
        }
    spin_unlock(&ci->i_ceph_lock);
    return ret;
}

/*
 * Wait on any unsafe replies for the given inode.  First wait on the
 * newest request, and make that the upper bound.  Then, if there are
 * more requests, keep waiting on the oldest as long as it is still older
 * than the original request.
 */
static void sync_write_wait(struct inode *inode)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    struct list_head *head = &ci->i_unsafe_writes;
    struct ceph_osd_request *req;
    u64 last_tid;

    spin_lock(&ci->i_unsafe_lock);
    if (list_empty(head))
        goto out;

    /* set upper bound as _last_ entry in chain */
    req = list_entry(head->prev, struct ceph_osd_request,
             r_unsafe_item);
    last_tid = req->r_tid;

    do {
        ceph_osdc_get_request(req);
        spin_unlock(&ci->i_unsafe_lock);
        dout("sync_write_wait on tid %llu (until %llu)\n",
             req->r_tid, last_tid);
        wait_for_completion(&req->r_safe_completion);
        spin_lock(&ci->i_unsafe_lock);
        ceph_osdc_put_request(req);

        /*
         * from here on look at first entry in chain, since we
         * only want to wait for anything older than last_tid
         */
        if (list_empty(head))
            break;
        req = list_entry(head->next, struct ceph_osd_request,
                 r_unsafe_item);
    } while (req->r_tid < last_tid);
out:
    spin_unlock(&ci->i_unsafe_lock);
}

int ceph_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
    struct inode *inode = file->f_mapping->host;
    struct ceph_inode_info *ci = ceph_inode(inode);
    unsigned flush_tid;
    int ret;
    int dirty;

    dout("fsync %p%s\n", inode, datasync ? " datasync" : "");
    sync_write_wait(inode);

    ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
    if (ret < 0)
        return ret;
    mutex_lock(&inode->i_mutex);

    dirty = try_flush_caps(inode, NULL, &flush_tid);
    dout("fsync dirty caps are %s\n", ceph_cap_string(dirty));

    /*
     * only wait on non-file metadata writeback (the mds
     * can recover size and mtime, so we don't need to
     * wait for that)
     */
    if (!datasync && (dirty & ~CEPH_CAP_ANY_FILE_WR)) {
        dout("fsync waiting for flush_tid %u\n", flush_tid);
        ret = wait_event_interruptible(ci->i_cap_wq,
                       caps_are_flushed(inode, flush_tid));
    }

    dout("fsync %p%s done\n", inode, datasync ? " datasync" : "");
    mutex_unlock(&inode->i_mutex);
    return ret;
}

/*
 * Flush any dirty caps back to the mds.  If we aren't asked to wait,
 * queue inode for flush but don't do so immediately, because we can
 * get by with fewer MDS messages if we wait for data writeback to
 * complete first.
 */
int ceph_write_inode(struct inode *inode, struct writeback_control *wbc)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    unsigned flush_tid;
    int err = 0;
    int dirty;
    int wait = wbc->sync_mode == WB_SYNC_ALL;

    dout("write_inode %p wait=%d\n", inode, wait);
    if (wait) {
        dirty = try_flush_caps(inode, NULL, &flush_tid);
        if (dirty)
            err = wait_event_interruptible(ci->i_cap_wq,
                       caps_are_flushed(inode, flush_tid));
    } else {
        struct ceph_mds_client *mdsc =
            ceph_sb_to_client(inode->i_sb)->mdsc;

        spin_lock(&ci->i_ceph_lock);
        if (__ceph_caps_dirty(ci))
            __cap_delay_requeue_front(mdsc, ci);
        spin_unlock(&ci->i_ceph_lock);
    }
    return err;
}

/*
 * After a recovering MDS goes active, we need to resend any caps
 * we were flushing.
 *
 * Caller holds session->s_mutex.
 */
static void kick_flushing_capsnaps(struct ceph_mds_client *mdsc,
                   struct ceph_mds_session *session)
{
    struct ceph_cap_snap *capsnap;

    dout("kick_flushing_capsnaps mds%d\n", session->s_mds);
    list_for_each_entry(capsnap, &session->s_cap_snaps_flushing,
                flushing_item) {
        struct ceph_inode_info *ci = capsnap->ci;
        struct inode *inode = &ci->vfs_inode;
        struct ceph_cap *cap;

        spin_lock(&ci->i_ceph_lock);
        cap = ci->i_auth_cap;
        if (cap && cap->session == session) {
            dout("kick_flushing_caps %p cap %p capsnap %p\n", inode,
                 cap, capsnap);
            __ceph_flush_snaps(ci, &session, 1);
        } else {
            pr_err("%p auth cap %p not mds%d ???\n", inode,
                   cap, session->s_mds);
        }
        spin_unlock(&ci->i_ceph_lock);
    }
}

void ceph_kick_flushing_caps(struct ceph_mds_client *mdsc,
                 struct ceph_mds_session *session)
{
    struct ceph_inode_info *ci;

    kick_flushing_capsnaps(mdsc, session);

    dout("kick_flushing_caps mds%d\n", session->s_mds);
    list_for_each_entry(ci, &session->s_cap_flushing, i_flushing_item) {
        struct inode *inode = &ci->vfs_inode;
        struct ceph_cap *cap;
        int delayed = 0;

        spin_lock(&ci->i_ceph_lock);
        cap = ci->i_auth_cap;
        if (cap && cap->session == session) {
            dout("kick_flushing_caps %p cap %p %s\n", inode,
                 cap, ceph_cap_string(ci->i_flushing_caps));
            delayed = __send_cap(mdsc, cap, CEPH_CAP_OP_FLUSH,
                         __ceph_caps_used(ci),
                         __ceph_caps_wanted(ci),
                         cap->issued | cap->implemented,
                         ci->i_flushing_caps, NULL);
            if (delayed) {
                spin_lock(&ci->i_ceph_lock);
                __cap_delay_requeue(mdsc, ci);
                spin_unlock(&ci->i_ceph_lock);
            }
        } else {
            pr_err("%p auth cap %p not mds%d ???\n", inode,
                   cap, session->s_mds);
            spin_unlock(&ci->i_ceph_lock);
        }
    }
}

static void kick_flushing_inode_caps(struct ceph_mds_client *mdsc,
                     struct ceph_mds_session *session,
                     struct inode *inode)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    struct ceph_cap *cap;
    int delayed = 0;

    spin_lock(&ci->i_ceph_lock);
    cap = ci->i_auth_cap;
    dout("kick_flushing_inode_caps %p flushing %s flush_seq %lld\n", inode,
         ceph_cap_string(ci->i_flushing_caps), ci->i_cap_flush_seq);
    __ceph_flush_snaps(ci, &session, 1);
    if (ci->i_flushing_caps) {
        delayed = __send_cap(mdsc, cap, CEPH_CAP_OP_FLUSH,
                     __ceph_caps_used(ci),
                     __ceph_caps_wanted(ci),
                     cap->issued | cap->implemented,
                     ci->i_flushing_caps, NULL);
        if (delayed) {
            spin_lock(&ci->i_ceph_lock);
            __cap_delay_requeue(mdsc, ci);
            spin_unlock(&ci->i_ceph_lock);
        }
    } else {
        spin_unlock(&ci->i_ceph_lock);
    }
}


/*
 * Take references to capabilities we hold, so that we don't release
 * them to the MDS prematurely.
 *
 * Protected by i_ceph_lock.
 */
static void __take_cap_refs(struct ceph_inode_info *ci, int got)
{
    if (got & CEPH_CAP_PIN)
        ci->i_pin_ref++;
    if (got & CEPH_CAP_FILE_RD)
        ci->i_rd_ref++;
    if (got & CEPH_CAP_FILE_CACHE)
        ci->i_rdcache_ref++;
    if (got & CEPH_CAP_FILE_WR)
        ci->i_wr_ref++;
    if (got & CEPH_CAP_FILE_BUFFER) {
        if (ci->i_wb_ref == 0)
            ihold(&ci->vfs_inode);
        ci->i_wb_ref++;
        dout("__take_cap_refs %p wb %d -> %d (?)\n",
             &ci->vfs_inode, ci->i_wb_ref-1, ci->i_wb_ref);
    }
}

/*
 * Try to grab cap references.  Specify those refs we @want, and the
 * minimal set we @need.  Also include the larger offset we are writing
 * to (when applicable), and check against max_size here as well.
 * Note that caller is responsible for ensuring max_size increases are
 * requested from the MDS.
 */
static int try_get_cap_refs(struct ceph_inode_info *ci, int need, int want,
                int *got, loff_t endoff, int *check_max, int *err)
{
    struct inode *inode = &ci->vfs_inode;
    int ret = 0;
    int have, implemented;
    int file_wanted;

    dout("get_cap_refs %p need %s want %s\n", inode,
         ceph_cap_string(need), ceph_cap_string(want));
    spin_lock(&ci->i_ceph_lock);

    /* make sure file is actually open */
    file_wanted = __ceph_caps_file_wanted(ci);
    if ((file_wanted & need) == 0) {
        dout("try_get_cap_refs need %s file_wanted %s, EBADF\n",
             ceph_cap_string(need), ceph_cap_string(file_wanted));
        *err = -EBADF;
        ret = 1;
        goto out;
    }

    if (need & CEPH_CAP_FILE_WR) {
        if (endoff >= 0 && endoff > (loff_t)ci->i_max_size) {
            dout("get_cap_refs %p endoff %llu > maxsize %llu\n",
                 inode, endoff, ci->i_max_size);
            if (endoff > ci->i_wanted_max_size) {
                *check_max = 1;
                ret = 1;
            }
            goto out;
        }
        /*
         * If a sync write is in progress, we must wait, so that we
         * can get a final snapshot value for size+mtime.
         */
        if (__ceph_have_pending_cap_snap(ci)) {
            dout("get_cap_refs %p cap_snap_pending\n", inode);
            goto out;
        }
    }
    have = __ceph_caps_issued(ci, &implemented);

    /*
     * disallow writes while a truncate is pending
     */
    if (ci->i_truncate_pending)
        have &= ~CEPH_CAP_FILE_WR;

    if ((have & need) == need) {
        /*
         * Look at (implemented & ~have & not) so that we keep waiting
         * on transition from wanted -> needed caps.  This is needed
         * for WRBUFFER|WR -> WR to avoid a new WR sync write from
         * going before a prior buffered writeback happens.
         */
        int not = want & ~(have & need);
        int revoking = implemented & ~have;
        dout("get_cap_refs %p have %s but not %s (revoking %s)\n",
             inode, ceph_cap_string(have), ceph_cap_string(not),
             ceph_cap_string(revoking));
        if ((revoking & not) == 0) {
            *got = need | (have & want);
            __take_cap_refs(ci, *got);
            ret = 1;
        }
    } else {
        dout("get_cap_refs %p have %s needed %s\n", inode,
             ceph_cap_string(have), ceph_cap_string(need));
    }
out:
    spin_unlock(&ci->i_ceph_lock);
    dout("get_cap_refs %p ret %d got %s\n", inode,
         ret, ceph_cap_string(*got));
    return ret;
}

/*
 * Check the offset we are writing up to against our current
 * max_size.  If necessary, tell the MDS we want to write to
 * a larger offset.
 */
static void check_max_size(struct inode *inode, loff_t endoff)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    int check = 0;

    /* do we need to explicitly request a larger max_size? */
    spin_lock(&ci->i_ceph_lock);
    if ((endoff >= ci->i_max_size ||
         endoff > (inode->i_size << 1)) &&
        endoff > ci->i_wanted_max_size) {
        dout("write %p at large endoff %llu, req max_size\n",
             inode, endoff);
        ci->i_wanted_max_size = endoff;
        check = 1;
    }
    spin_unlock(&ci->i_ceph_lock);
    if (check)
        ceph_check_caps(ci, CHECK_CAPS_AUTHONLY, NULL);
}

/*
 * Wait for caps, and take cap references.  If we can't get a WR cap
 * due to a small max_size, make sure we check_max_size (and possibly
 * ask the mds) so we don't get hung up indefinitely.
 */
int ceph_get_caps(struct ceph_inode_info *ci, int need, int want, int *got,
          loff_t endoff)
{
    int check_max, ret, err;

retry:
    if (endoff > 0)
        check_max_size(&ci->vfs_inode, endoff);
    check_max = 0;
    err = 0;
    ret = wait_event_interruptible(ci->i_cap_wq,
                       try_get_cap_refs(ci, need, want,
                            got, endoff,
                            &check_max, &err));
    if (err)
        ret = err;
    if (check_max)
        goto retry;
    return ret;
}

/*
 * Take cap refs.  Caller must already know we hold at least one ref
 * on the caps in question or we don't know this is safe.
 */
void ceph_get_cap_refs(struct ceph_inode_info *ci, int caps)
{
    spin_lock(&ci->i_ceph_lock);
    __take_cap_refs(ci, caps);
    spin_unlock(&ci->i_ceph_lock);
}

/*
 * Release cap refs.
 *
 * If we released the last ref on any given cap, call ceph_check_caps
 * to release (or schedule a release).
 *
 * If we are releasing a WR cap (from a sync write), finalize any affected
 * cap_snap, and wake up any waiters.
 */
void ceph_put_cap_refs(struct ceph_inode_info *ci, int had)
{
    struct inode *inode = &ci->vfs_inode;
    int last = 0, put = 0, flushsnaps = 0, wake = 0;
    struct ceph_cap_snap *capsnap;

    spin_lock(&ci->i_ceph_lock);
    if (had & CEPH_CAP_PIN)
        --ci->i_pin_ref;
    if (had & CEPH_CAP_FILE_RD)
        if (--ci->i_rd_ref == 0)
            last++;
    if (had & CEPH_CAP_FILE_CACHE)
        if (--ci->i_rdcache_ref == 0)
            last++;
    if (had & CEPH_CAP_FILE_BUFFER) {
        if (--ci->i_wb_ref == 0) {
            last++;
            put++;
        }
        dout("put_cap_refs %p wb %d -> %d (?)\n",
             inode, ci->i_wb_ref+1, ci->i_wb_ref);
    }
    if (had & CEPH_CAP_FILE_WR)
        if (--ci->i_wr_ref == 0) {
            last++;
            if (!list_empty(&ci->i_cap_snaps)) {
                capsnap = list_first_entry(&ci->i_cap_snaps,
                             struct ceph_cap_snap,
                             ci_item);
                if (capsnap->writing) {
                    capsnap->writing = 0;
                    flushsnaps =
                        __ceph_finish_cap_snap(ci,
                                       capsnap);
                    wake = 1;
                }
            }
        }
    spin_unlock(&ci->i_ceph_lock);

    dout("put_cap_refs %p had %s%s%s\n", inode, ceph_cap_string(had),
         last ? " last" : "", put ? " put" : "");

    if (last && !flushsnaps)
        ceph_check_caps(ci, 0, NULL);
    else if (flushsnaps)
        ceph_flush_snaps(ci);
    if (wake)
        wake_up_all(&ci->i_cap_wq);
    if (put)
        iput(inode);
}

/*
 * Release @nr WRBUFFER refs on dirty pages for the given @snapc snap
 * context.  Adjust per-snap dirty page accounting as appropriate.
 * Once all dirty data for a cap_snap is flushed, flush snapped file
 * metadata back to the MDS.  If we dropped the last ref, call
 * ceph_check_caps.
 */
void ceph_put_wrbuffer_cap_refs(struct ceph_inode_info *ci, int nr,
                struct ceph_snap_context *snapc)
{
    struct inode *inode = &ci->vfs_inode;
    int last = 0;
    int complete_capsnap = 0;
    int drop_capsnap = 0;
    int found = 0;
    struct ceph_cap_snap *capsnap = NULL;

    spin_lock(&ci->i_ceph_lock);
    ci->i_wrbuffer_ref -= nr;
    last = !ci->i_wrbuffer_ref;

    if (ci->i_head_snapc == snapc) {
        ci->i_wrbuffer_ref_head -= nr;
        if (ci->i_wrbuffer_ref_head == 0 &&
            ci->i_dirty_caps == 0 && ci->i_flushing_caps == 0) {
            BUG_ON(!ci->i_head_snapc);
            ceph_put_snap_context(ci->i_head_snapc);
            ci->i_head_snapc = NULL;
        }
        dout("put_wrbuffer_cap_refs on %p head %d/%d -> %d/%d %s\n",
             inode,
             ci->i_wrbuffer_ref+nr, ci->i_wrbuffer_ref_head+nr,
             ci->i_wrbuffer_ref, ci->i_wrbuffer_ref_head,
             last ? " LAST" : "");
    } else {
        list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
            if (capsnap->context == snapc) {
                found = 1;
                break;
            }
        }
        BUG_ON(!found);
        capsnap->dirty_pages -= nr;
        if (capsnap->dirty_pages == 0) {
            complete_capsnap = 1;
            if (capsnap->dirty == 0)
                /* cap writeback completed before we created
                 * the cap_snap; no FLUSHSNAP is needed */
                drop_capsnap = 1;
        }
        dout("put_wrbuffer_cap_refs on %p cap_snap %p "
             " snap %lld %d/%d -> %d/%d %s%s%s\n",
             inode, capsnap, capsnap->context->seq,
             ci->i_wrbuffer_ref+nr, capsnap->dirty_pages + nr,
             ci->i_wrbuffer_ref, capsnap->dirty_pages,
             last ? " (wrbuffer last)" : "",
             complete_capsnap ? " (complete capsnap)" : "",
             drop_capsnap ? " (drop capsnap)" : "");
        if (drop_capsnap) {
            ceph_put_snap_context(capsnap->context);
            list_del(&capsnap->ci_item);
            list_del(&capsnap->flushing_item);
            ceph_put_cap_snap(capsnap);
        }
    }

    spin_unlock(&ci->i_ceph_lock);

    if (last) {
        ceph_check_caps(ci, CHECK_CAPS_AUTHONLY, NULL);
        iput(inode);
    } else if (complete_capsnap) {
        ceph_flush_snaps(ci);
        wake_up_all(&ci->i_cap_wq);
    }
    if (drop_capsnap)
        iput(inode);
}

/*
 * Handle a cap GRANT message from the MDS.  (Note that a GRANT may
 * actually be a revocation if it specifies a smaller cap set.)
 *
 * caller holds s_mutex and i_ceph_lock, we drop both.
 *
 * return value:
 *  0 - ok
 *  1 - check_caps on auth cap only (writeback)
 *  2 - check_caps (ack revoke)
 */
static void handle_cap_grant(struct inode *inode, struct ceph_mds_caps *grant,
                 struct ceph_mds_session *session,
                 struct ceph_cap *cap,
                 struct ceph_buffer *xattr_buf)
        __releases(ci->i_ceph_lock)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    int mds = session->s_mds;
    int seq = le32_to_cpu(grant->seq);
    int newcaps = le32_to_cpu(grant->caps);
    int issued, implemented, used, wanted, dirty;
    u64 size = le64_to_cpu(grant->size);
    u64 max_size = le64_to_cpu(grant->max_size);
    struct timespec mtime, atime, ctime;
    int check_caps = 0;
    int wake = 0;
    int writeback = 0;
    int revoked_rdcache = 0;
    int queue_invalidate = 0;

    dout("handle_cap_grant inode %p cap %p mds%d seq %d %s\n",
         inode, cap, mds, seq, ceph_cap_string(newcaps));
    dout(" size %llu max_size %llu, i_size %llu\n", size, max_size,
        inode->i_size);

    /*
     * If CACHE is being revoked, and we have no dirty buffers,
     * try to invalidate (once).  (If there are dirty buffers, we
     * will invalidate _after_ writeback.)
     */
    if (((cap->issued & ~newcaps) & CEPH_CAP_FILE_CACHE) &&
        (newcaps & CEPH_CAP_FILE_LAZYIO) == 0 &&
        !ci->i_wrbuffer_ref) {
        if (try_nonblocking_invalidate(inode) == 0) {
            revoked_rdcache = 1;
        } else {
            /* there were locked pages.. invalidate later
               in a separate thread. */
            if (ci->i_rdcache_revoking != ci->i_rdcache_gen) {
                queue_invalidate = 1;
                ci->i_rdcache_revoking = ci->i_rdcache_gen;
            }
        }
    }

    /* side effects now are allowed */

    issued = __ceph_caps_issued(ci, &implemented);
    issued |= implemented | __ceph_caps_dirty(ci);

    cap->cap_gen = session->s_cap_gen;

    __check_cap_issue(ci, cap, newcaps);

    if ((issued & CEPH_CAP_AUTH_EXCL) == 0) {
        inode->i_mode = le32_to_cpu(grant->mode);
        inode->i_uid = le32_to_cpu(grant->uid);
        inode->i_gid = le32_to_cpu(grant->gid);
        dout("%p mode 0%o uid.gid %d.%d\n", inode, inode->i_mode,
             inode->i_uid, inode->i_gid);
    }

    if ((issued & CEPH_CAP_LINK_EXCL) == 0)
        set_nlink(inode, le32_to_cpu(grant->nlink));

    if ((issued & CEPH_CAP_XATTR_EXCL) == 0 && grant->xattr_len) {
        int len = le32_to_cpu(grant->xattr_len);
        u64 version = le64_to_cpu(grant->xattr_version);

        if (version > ci->i_xattrs.version) {
            dout(" got new xattrs v%llu on %p len %d\n",
                 version, inode, len);
            if (ci->i_xattrs.blob)
                ceph_buffer_put(ci->i_xattrs.blob);
            ci->i_xattrs.blob = ceph_buffer_get(xattr_buf);
            ci->i_xattrs.version = version;
        }
    }

    /* size/ctime/mtime/atime? */
    ceph_fill_file_size(inode, issued,
                le32_to_cpu(grant->truncate_seq),
                le64_to_cpu(grant->truncate_size), size);
    ceph_decode_timespec(&mtime, &grant->mtime);
    ceph_decode_timespec(&atime, &grant->atime);
    ceph_decode_timespec(&ctime, &grant->ctime);
    ceph_fill_file_time(inode, issued,
                le32_to_cpu(grant->time_warp_seq), &ctime, &mtime,
                &atime);

    /* max size increase? */
    if (max_size != ci->i_max_size) {
        dout("max_size %lld -> %llu\n", ci->i_max_size, max_size);
        ci->i_max_size = max_size;
        if (max_size >= ci->i_wanted_max_size) {
            ci->i_wanted_max_size = 0;  /* reset */
            ci->i_requested_max_size = 0;
        }
        wake = 1;
    }

    /* check cap bits */
    wanted = __ceph_caps_wanted(ci);
    used = __ceph_caps_used(ci);
    dirty = __ceph_caps_dirty(ci);
    dout(" my wanted = %s, used = %s, dirty %s\n",
         ceph_cap_string(wanted),
         ceph_cap_string(used),
         ceph_cap_string(dirty));
    if (wanted != le32_to_cpu(grant->wanted)) {
        dout("mds wanted %s -> %s\n",
             ceph_cap_string(le32_to_cpu(grant->wanted)),
             ceph_cap_string(wanted));
        grant->wanted = cpu_to_le32(wanted);
    }

    cap->seq = seq;

    /* file layout may have changed */
    ci->i_layout = grant->layout;

    /* revocation, grant, or no-op? */
    if (cap->issued & ~newcaps) {
        int revoking = cap->issued & ~newcaps;

        dout("revocation: %s -> %s (revoking %s)\n",
             ceph_cap_string(cap->issued),
             ceph_cap_string(newcaps),
             ceph_cap_string(revoking));
        if (revoking & used & CEPH_CAP_FILE_BUFFER)
            writeback = 1;  /* initiate writeback; will delay ack */
        else if (revoking == CEPH_CAP_FILE_CACHE &&
             (newcaps & CEPH_CAP_FILE_LAZYIO) == 0 &&
             queue_invalidate)
            ; /* do nothing yet, invalidation will be queued */
        else if (cap == ci->i_auth_cap)
            check_caps = 1; /* check auth cap only */
        else
            check_caps = 2; /* check all caps */
        cap->issued = newcaps;
        cap->implemented |= newcaps;
    } else if (cap->issued == newcaps) {
        dout("caps unchanged: %s -> %s\n",
             ceph_cap_string(cap->issued), ceph_cap_string(newcaps));
    } else {
        dout("grant: %s -> %s\n", ceph_cap_string(cap->issued),
             ceph_cap_string(newcaps));
        cap->issued = newcaps;
        cap->implemented |= newcaps; /* add bits only, to
                          * avoid stepping on a
                          * pending revocation */
        wake = 1;
    }
    BUG_ON(cap->issued & ~cap->implemented);

    spin_unlock(&ci->i_ceph_lock);
    if (writeback)
        /*
         * queue inode for writeback: we can't actually call
         * filemap_write_and_wait, etc. from message handler
         * context.
         */
        ceph_queue_writeback(inode);
    if (queue_invalidate)
        ceph_queue_invalidate(inode);
    if (wake)
        wake_up_all(&ci->i_cap_wq);

    if (check_caps == 1)
        ceph_check_caps(ci, CHECK_CAPS_NODELAY|CHECK_CAPS_AUTHONLY,
                session);
    else if (check_caps == 2)
        ceph_check_caps(ci, CHECK_CAPS_NODELAY, session);
    else
        mutex_unlock(&session->s_mutex);
}

/*
 * Handle FLUSH_ACK from MDS, indicating that metadata we sent to the
 * MDS has been safely committed.
 */
static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,
                 struct ceph_mds_caps *m,
                 struct ceph_mds_session *session,
                 struct ceph_cap *cap)
    __releases(ci->i_ceph_lock)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
    unsigned seq = le32_to_cpu(m->seq);
    int dirty = le32_to_cpu(m->dirty);
    int cleaned = 0;
    int drop = 0;
    int i;

    for (i = 0; i < CEPH_CAP_BITS; i++)
        if ((dirty & (1 << i)) &&
            flush_tid == ci->i_cap_flush_tid[i])
            cleaned |= 1 << i;

    dout("handle_cap_flush_ack inode %p mds%d seq %d on %s cleaned %s,"
         " flushing %s -> %s\n",
         inode, session->s_mds, seq, ceph_cap_string(dirty),
         ceph_cap_string(cleaned), ceph_cap_string(ci->i_flushing_caps),
         ceph_cap_string(ci->i_flushing_caps & ~cleaned));

    if (ci->i_flushing_caps == (ci->i_flushing_caps & ~cleaned))
        goto out;

    ci->i_flushing_caps &= ~cleaned;

    spin_lock(&mdsc->cap_dirty_lock);
    if (ci->i_flushing_caps == 0) {
        list_del_init(&ci->i_flushing_item);
        if (!list_empty(&session->s_cap_flushing))
            dout(" mds%d still flushing cap on %p\n",
                 session->s_mds,
                 &list_entry(session->s_cap_flushing.next,
                     struct ceph_inode_info,
                     i_flushing_item)->vfs_inode);
        mdsc->num_cap_flushing--;
        wake_up_all(&mdsc->cap_flushing_wq);
        dout(" inode %p now !flushing\n", inode);

        if (ci->i_dirty_caps == 0) {
            dout(" inode %p now clean\n", inode);
            BUG_ON(!list_empty(&ci->i_dirty_item));
            drop = 1;
            if (ci->i_wrbuffer_ref_head == 0) {
                BUG_ON(!ci->i_head_snapc);
                ceph_put_snap_context(ci->i_head_snapc);
                ci->i_head_snapc = NULL;
            }
        } else {
            BUG_ON(list_empty(&ci->i_dirty_item));
        }
    }
    spin_unlock(&mdsc->cap_dirty_lock);
    wake_up_all(&ci->i_cap_wq);

out:
    spin_unlock(&ci->i_ceph_lock);
    if (drop)
        iput(inode);
}

/*
 * Handle FLUSHSNAP_ACK.  MDS has flushed snap data to disk and we can
 * throw away our cap_snap.
 *
 * Caller hold s_mutex.
 */
static void handle_cap_flushsnap_ack(struct inode *inode, u64 flush_tid,
                     struct ceph_mds_caps *m,
                     struct ceph_mds_session *session)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    u64 follows = le64_to_cpu(m->snap_follows);
    struct ceph_cap_snap *capsnap;
    int drop = 0;

    dout("handle_cap_flushsnap_ack inode %p ci %p mds%d follows %lld\n",
         inode, ci, session->s_mds, follows);

    spin_lock(&ci->i_ceph_lock);
    list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
        if (capsnap->follows == follows) {
            if (capsnap->flush_tid != flush_tid) {
                dout(" cap_snap %p follows %lld tid %lld !="
                     " %lld\n", capsnap, follows,
                     flush_tid, capsnap->flush_tid);
                break;
            }
            WARN_ON(capsnap->dirty_pages || capsnap->writing);
            dout(" removing %p cap_snap %p follows %lld\n",
                 inode, capsnap, follows);
            ceph_put_snap_context(capsnap->context);
            list_del(&capsnap->ci_item);
            list_del(&capsnap->flushing_item);
            ceph_put_cap_snap(capsnap);
            drop = 1;
            break;
        } else {
            dout(" skipping cap_snap %p follows %lld\n",
                 capsnap, capsnap->follows);
        }
    }
    spin_unlock(&ci->i_ceph_lock);
    if (drop)
        iput(inode);
}

/*
 * Handle TRUNC from MDS, indicating file truncation.
 *
 * caller hold s_mutex.
 */
static void handle_cap_trunc(struct inode *inode,
                 struct ceph_mds_caps *trunc,
                 struct ceph_mds_session *session)
    __releases(ci->i_ceph_lock)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    int mds = session->s_mds;
    int seq = le32_to_cpu(trunc->seq);
    u32 truncate_seq = le32_to_cpu(trunc->truncate_seq);
    u64 truncate_size = le64_to_cpu(trunc->truncate_size);
    u64 size = le64_to_cpu(trunc->size);
    int implemented = 0;
    int dirty = __ceph_caps_dirty(ci);
    int issued = __ceph_caps_issued(ceph_inode(inode), &implemented);
    int queue_trunc = 0;

    issued |= implemented | dirty;

    dout("handle_cap_trunc inode %p mds%d seq %d to %lld seq %d\n",
         inode, mds, seq, truncate_size, truncate_seq);
    queue_trunc = ceph_fill_file_size(inode, issued,
                      truncate_seq, truncate_size, size);
    spin_unlock(&ci->i_ceph_lock);

    if (queue_trunc)
        ceph_queue_vmtruncate(inode);
}

/*
 * Handle EXPORT from MDS.  Cap is being migrated _from_ this mds to a
 * different one.  If we are the most recent migration we've seen (as
 * indicated by mseq), make note of the migrating cap bits for the
 * duration (until we see the corresponding IMPORT).
 *
 * caller holds s_mutex
 */
static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex,
                  struct ceph_mds_session *session,
                  int *open_target_sessions)
{
    struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
    struct ceph_inode_info *ci = ceph_inode(inode);
    int mds = session->s_mds;
    unsigned mseq = le32_to_cpu(ex->migrate_seq);
    struct ceph_cap *cap = NULL, *t;
    struct rb_node *p;
    int remember = 1;

    dout("handle_cap_export inode %p ci %p mds%d mseq %d\n",
         inode, ci, mds, mseq);

    spin_lock(&ci->i_ceph_lock);

    /* make sure we haven't seen a higher mseq */
    for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
        t = rb_entry(p, struct ceph_cap, ci_node);
        if (ceph_seq_cmp(t->mseq, mseq) > 0) {
            dout(" higher mseq on cap from mds%d\n",
                 t->session->s_mds);
            remember = 0;
        }
        if (t->session->s_mds == mds)
            cap = t;
    }

    if (cap) {
        if (remember) {
            /* make note */
            ci->i_cap_exporting_mds = mds;
            ci->i_cap_exporting_mseq = mseq;
            ci->i_cap_exporting_issued = cap->issued;

            /*
             * make sure we have open sessions with all possible
             * export targets, so that we get the matching IMPORT
             */
            *open_target_sessions = 1;

            /*
             * we can't flush dirty caps that we've seen the
             * EXPORT but no IMPORT for
             */
            spin_lock(&mdsc->cap_dirty_lock);
            if (!list_empty(&ci->i_dirty_item)) {
                dout(" moving %p to cap_dirty_migrating\n",
                     inode);
                list_move(&ci->i_dirty_item,
                      &mdsc->cap_dirty_migrating);
            }
            spin_unlock(&mdsc->cap_dirty_lock);
        }
        __ceph_remove_cap(cap);
    }
    /* else, we already released it */

    spin_unlock(&ci->i_ceph_lock);
}

/*
 * Handle cap IMPORT.  If there are temp bits from an older EXPORT,
 * clean them up.
 *
 * caller holds s_mutex.
 */
static void handle_cap_import(struct ceph_mds_client *mdsc,
                  struct inode *inode, struct ceph_mds_caps *im,
                  struct ceph_mds_session *session,
                  void *snaptrace, int snaptrace_len)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    int mds = session->s_mds;
    unsigned issued = le32_to_cpu(im->caps);
    unsigned wanted = le32_to_cpu(im->wanted);
    unsigned seq = le32_to_cpu(im->seq);
    unsigned mseq = le32_to_cpu(im->migrate_seq);
    u64 realmino = le64_to_cpu(im->realm);
    u64 cap_id = le64_to_cpu(im->cap_id);

    if (ci->i_cap_exporting_mds >= 0 &&
        ceph_seq_cmp(ci->i_cap_exporting_mseq, mseq) < 0) {
        dout("handle_cap_import inode %p ci %p mds%d mseq %d"
             " - cleared exporting from mds%d\n",
             inode, ci, mds, mseq,
             ci->i_cap_exporting_mds);
        ci->i_cap_exporting_issued = 0;
        ci->i_cap_exporting_mseq = 0;
        ci->i_cap_exporting_mds = -1;

        spin_lock(&mdsc->cap_dirty_lock);
        if (!list_empty(&ci->i_dirty_item)) {
            dout(" moving %p back to cap_dirty\n", inode);
            list_move(&ci->i_dirty_item, &mdsc->cap_dirty);
        }
        spin_unlock(&mdsc->cap_dirty_lock);
    } else {
        dout("handle_cap_import inode %p ci %p mds%d mseq %d\n",
             inode, ci, mds, mseq);
    }

    down_write(&mdsc->snap_rwsem);
    ceph_update_snap_trace(mdsc, snaptrace, snaptrace+snaptrace_len,
                   false);
    downgrade_write(&mdsc->snap_rwsem);
    ceph_add_cap(inode, session, cap_id, -1,
             issued, wanted, seq, mseq, realmino, CEPH_CAP_FLAG_AUTH,
             NULL /* no caps context */);
    kick_flushing_inode_caps(mdsc, session, inode);
    up_read(&mdsc->snap_rwsem);

    /* make sure we re-request max_size, if necessary */
    spin_lock(&ci->i_ceph_lock);
    ci->i_requested_max_size = 0;
    spin_unlock(&ci->i_ceph_lock);
}

/*
 * Handle a caps message from the MDS.
 *
 * Identify the appropriate session, inode, and call the right handler
 * based on the cap op.
 */
void ceph_handle_caps(struct ceph_mds_session *session,
              struct ceph_msg *msg)
{
    struct ceph_mds_client *mdsc = session->s_mdsc;
    struct super_block *sb = mdsc->fsc->sb;
    struct inode *inode;
    struct ceph_inode_info *ci;
    struct ceph_cap *cap;
    struct ceph_mds_caps *h;
    int mds = session->s_mds;
    int op;
    u32 seq, mseq;
    struct ceph_vino vino;
    u64 cap_id;
    u64 size, max_size;
    u64 tid;
    void *snaptrace;
    size_t snaptrace_len;
    void *flock;
    u32 flock_len;
    int open_target_sessions = 0;

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

    /* decode */
    tid = le64_to_cpu(msg->hdr.tid);
    if (msg->front.iov_len < sizeof(*h))
        goto bad;
    h = msg->front.iov_base;
    op = le32_to_cpu(h->op);
    vino.ino = le64_to_cpu(h->ino);
    vino.snap = CEPH_NOSNAP;
    cap_id = le64_to_cpu(h->cap_id);
    seq = le32_to_cpu(h->seq);
    mseq = le32_to_cpu(h->migrate_seq);
    size = le64_to_cpu(h->size);
    max_size = le64_to_cpu(h->max_size);

    snaptrace = h + 1;
    snaptrace_len = le32_to_cpu(h->snap_trace_len);

    if (le16_to_cpu(msg->hdr.version) >= 2) {
        void *p, *end;

        p = snaptrace + snaptrace_len;
        end = msg->front.iov_base + msg->front.iov_len;
        ceph_decode_32_safe(&p, end, flock_len, bad);
        flock = p;
    } else {
        flock = NULL;
        flock_len = 0;
    }

    mutex_lock(&session->s_mutex);
    session->s_seq++;
    dout(" mds%d seq %lld cap seq %u\n", session->s_mds, session->s_seq,
         (unsigned)seq);

    /* lookup ino */
    inode = ceph_find_inode(sb, vino);
    ci = ceph_inode(inode);
    dout(" op %s ino %llx.%llx inode %p\n", ceph_cap_op_name(op), vino.ino,
         vino.snap, inode);
    if (!inode) {
        dout(" i don't have ino %llx\n", vino.ino);

        if (op == CEPH_CAP_OP_IMPORT)
            __queue_cap_release(session, vino.ino, cap_id,
                        mseq, seq);
        goto flush_cap_releases;
    }

    /* these will work even if we don't have a cap yet */
    switch (op) {
    case CEPH_CAP_OP_FLUSHSNAP_ACK:
        handle_cap_flushsnap_ack(inode, tid, h, session);
        goto done;

    case CEPH_CAP_OP_EXPORT:
        handle_cap_export(inode, h, session, &open_target_sessions);
        goto done;

    case CEPH_CAP_OP_IMPORT:
        handle_cap_import(mdsc, inode, h, session,
                  snaptrace, snaptrace_len);
        ceph_check_caps(ceph_inode(inode), 0, session);
        goto done_unlocked;
    }

    /* the rest require a cap */
    spin_lock(&ci->i_ceph_lock);
    cap = __get_cap_for_mds(ceph_inode(inode), mds);
    if (!cap) {
        dout(" no cap on %p ino %llx.%llx from mds%d\n",
             inode, ceph_ino(inode), ceph_snap(inode), mds);
        spin_unlock(&ci->i_ceph_lock);
        goto flush_cap_releases;
    }

    /* note that each of these drops i_ceph_lock for us */
    switch (op) {
    case CEPH_CAP_OP_REVOKE:
    case CEPH_CAP_OP_GRANT:
        handle_cap_grant(inode, h, session, cap, msg->middle);
        goto done_unlocked;

    case CEPH_CAP_OP_FLUSH_ACK:
        handle_cap_flush_ack(inode, tid, h, session, cap);
        break;

    case CEPH_CAP_OP_TRUNC:
        handle_cap_trunc(inode, h, session);
        break;

    default:
        spin_unlock(&ci->i_ceph_lock);
        pr_err("ceph_handle_caps: unknown cap op %d %s\n", op,
               ceph_cap_op_name(op));
    }

    goto done;

flush_cap_releases:
    /*
     * send any full release message to try to move things
     * along for the mds (who clearly thinks we still have this
     * cap).
     */
    ceph_add_cap_releases(mdsc, session);
    ceph_send_cap_releases(mdsc, session);

done:
    mutex_unlock(&session->s_mutex);
done_unlocked:
    if (inode)
        iput(inode);
    if (open_target_sessions)
        ceph_mdsc_open_export_target_sessions(mdsc, session);
    return;

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

/*
 * Delayed work handler to process end of delayed cap release LRU list.
 */
void ceph_check_delayed_caps(struct ceph_mds_client *mdsc)
{
    struct ceph_inode_info *ci;
    int flags = CHECK_CAPS_NODELAY;

    dout("check_delayed_caps\n");
    while (1) {
        spin_lock(&mdsc->cap_delay_lock);
        if (list_empty(&mdsc->cap_delay_list))
            break;
        ci = list_first_entry(&mdsc->cap_delay_list,
                      struct ceph_inode_info,
                      i_cap_delay_list);
        if ((ci->i_ceph_flags & CEPH_I_FLUSH) == 0 &&
            time_before(jiffies, ci->i_hold_caps_max))
            break;
        list_del_init(&ci->i_cap_delay_list);
        spin_unlock(&mdsc->cap_delay_lock);
        dout("check_delayed_caps on %p\n", &ci->vfs_inode);
        ceph_check_caps(ci, flags, NULL);
    }
    spin_unlock(&mdsc->cap_delay_lock);
}

/*
 * Flush all dirty caps to the mds
 */
void ceph_flush_dirty_caps(struct ceph_mds_client *mdsc)
{
    struct ceph_inode_info *ci;
    struct inode *inode;

    dout("flush_dirty_caps\n");
    spin_lock(&mdsc->cap_dirty_lock);
    while (!list_empty(&mdsc->cap_dirty)) {
        ci = list_first_entry(&mdsc->cap_dirty, struct ceph_inode_info,
                      i_dirty_item);
        inode = &ci->vfs_inode;
        ihold(inode);
        dout("flush_dirty_caps %p\n", inode);
        spin_unlock(&mdsc->cap_dirty_lock);
        ceph_check_caps(ci, CHECK_CAPS_NODELAY|CHECK_CAPS_FLUSH, NULL);
        iput(inode);
        spin_lock(&mdsc->cap_dirty_lock);
    }
    spin_unlock(&mdsc->cap_dirty_lock);
    dout("flush_dirty_caps done\n");
}

/*
 * Drop open file reference.  If we were the last open file,
 * we may need to release capabilities to the MDS (or schedule
 * their delayed release).
 */
void ceph_put_fmode(struct ceph_inode_info *ci, int fmode)
{
    struct inode *inode = &ci->vfs_inode;
    int last = 0;

    spin_lock(&ci->i_ceph_lock);
    dout("put_fmode %p fmode %d %d -> %d\n", inode, fmode,
         ci->i_nr_by_mode[fmode], ci->i_nr_by_mode[fmode]-1);
    BUG_ON(ci->i_nr_by_mode[fmode] == 0);
    if (--ci->i_nr_by_mode[fmode] == 0)
        last++;
    spin_unlock(&ci->i_ceph_lock);

    if (last && ci->i_vino.snap == CEPH_NOSNAP)
        ceph_check_caps(ci, 0, NULL);
}

/*
 * Helpers for embedding cap and dentry lease releases into mds
 * requests.
 *
 * @force is used by dentry_release (below) to force inclusion of a
 * record for the directory inode, even when there aren't any caps to
 * drop.
 */
int ceph_encode_inode_release(void **p, struct inode *inode,
                  int mds, int drop, int unless, int force)
{
    struct ceph_inode_info *ci = ceph_inode(inode);
    struct ceph_cap *cap;
    struct ceph_mds_request_release *rel = *p;
    int used, dirty;
    int ret = 0;

    spin_lock(&ci->i_ceph_lock);
    used = __ceph_caps_used(ci);
    dirty = __ceph_caps_dirty(ci);

    dout("encode_inode_release %p mds%d used|dirty %s drop %s unless %s\n",
         inode, mds, ceph_cap_string(used|dirty), ceph_cap_string(drop),
         ceph_cap_string(unless));

    /* only drop unused, clean caps */
    drop &= ~(used | dirty);

    cap = __get_cap_for_mds(ci, mds);
    if (cap && __cap_is_valid(cap)) {
        if (force ||
            ((cap->issued & drop) &&
             (cap->issued & unless) == 0)) {
            if ((cap->issued & drop) &&
                (cap->issued & unless) == 0) {
                dout("encode_inode_release %p cap %p %s -> "
                     "%s\n", inode, cap,
                     ceph_cap_string(cap->issued),
                     ceph_cap_string(cap->issued & ~drop));
                cap->issued &= ~drop;
                cap->implemented &= ~drop;
                if (ci->i_ceph_flags & CEPH_I_NODELAY) {
                    int wanted = __ceph_caps_wanted(ci);
                    dout("  wanted %s -> %s (act %s)\n",
                         ceph_cap_string(cap->mds_wanted),
                         ceph_cap_string(cap->mds_wanted &
                                 ~wanted),
                         ceph_cap_string(wanted));
                    cap->mds_wanted &= wanted;
                }
            } else {
                dout("encode_inode_release %p cap %p %s"
                     " (force)\n", inode, cap,
                     ceph_cap_string(cap->issued));
            }

            rel->ino = cpu_to_le64(ceph_ino(inode));
            rel->cap_id = cpu_to_le64(cap->cap_id);
            rel->seq = cpu_to_le32(cap->seq);
            rel->issue_seq = cpu_to_le32(cap->issue_seq),
            rel->mseq = cpu_to_le32(cap->mseq);
            rel->caps = cpu_to_le32(cap->issued);
            rel->wanted = cpu_to_le32(cap->mds_wanted);
            rel->dname_len = 0;
            rel->dname_seq = 0;
            *p += sizeof(*rel);
            ret = 1;
        } else {
            dout("encode_inode_release %p cap %p %s\n",
                 inode, cap, ceph_cap_string(cap->issued));
        }
    }
    spin_unlock(&ci->i_ceph_lock);
    return ret;
}

int ceph_encode_dentry_release(void **p, struct dentry *dentry,
                   int mds, int drop, int unless)
{
    struct inode *dir = dentry->d_parent->d_inode;
    struct ceph_mds_request_release *rel = *p;
    struct ceph_dentry_info *di = ceph_dentry(dentry);
    int force = 0;
    int ret;

    /*
     * force an record for the directory caps if we have a dentry lease.
     * this is racy (can't take i_ceph_lock and d_lock together), but it
     * doesn't have to be perfect; the mds will revoke anything we don't
     * release.
     */
    spin_lock(&dentry->d_lock);
    if (di->lease_session && di->lease_session->s_mds == mds)
        force = 1;
    spin_unlock(&dentry->d_lock);

    ret = ceph_encode_inode_release(p, dir, mds, drop, unless, force);

    spin_lock(&dentry->d_lock);
    if (ret && di->lease_session && di->lease_session->s_mds == mds) {
        dout("encode_dentry_release %p mds%d seq %d\n",
             dentry, mds, (int)di->lease_seq);
        rel->dname_len = cpu_to_le32(dentry->d_name.len);
        memcpy(*p, dentry->d_name.name, dentry->d_name.len);
        *p += dentry->d_name.len;
        rel->dname_seq = cpu_to_le32(di->lease_seq);
        __ceph_mdsc_drop_dentry_lease(dentry);
    }
    spin_unlock(&dentry->d_lock);
    return ret;
}