static ngx_int_t
ngx_http_file_cache_exists(ngx_http_file_cache_t *cache, ngx_http_cache_t *c)
{
    ngx_int_t                    rc;
    ngx_http_file_cache_node_t  *fcn;

    ngx_shmtx_lock(&cache->shpool->mutex);

    fcn = c->node;

    if (fcn == NULL) {
        fcn = ngx_http_file_cache_lookup(cache, c->key);
    }

    if (fcn) {
        ngx_queue_remove(&fcn->queue);

        if (c->node == NULL) {
            fcn->uses++;
            fcn->count++;
        }

        if (fcn->error) {

            if (fcn->valid_sec < ngx_time()) {
                goto renew;
            }

            rc = NGX_OK;

            goto done;
        }

        if (fcn->exists || fcn->uses >= c->min_uses) {

            c->exists = fcn->exists;
            if (fcn->body_start) {
                c->body_start = fcn->body_start;
            }

            rc = NGX_OK;

            goto done;
        }

        rc = NGX_AGAIN;

        goto done;
    }

    fcn = ngx_slab_calloc_locked(cache->shpool,
                                 sizeof(ngx_http_file_cache_node_t));
    if (fcn == NULL) {
        ngx_shmtx_unlock(&cache->shpool->mutex);

        (void) ngx_http_file_cache_forced_expire(cache);

        ngx_shmtx_lock(&cache->shpool->mutex);

        fcn = ngx_slab_calloc_locked(cache->shpool,
                                     sizeof(ngx_http_file_cache_node_t));
        if (fcn == NULL) {
            ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, 0,
                          "could not allocate node%s", cache->shpool->log_ctx);
            rc = NGX_ERROR;
            goto failed;
        }
    }

    ngx_memcpy((u_char *) &fcn->node.key, c->key, sizeof(ngx_rbtree_key_t));

    ngx_memcpy(fcn->key, &c->key[sizeof(ngx_rbtree_key_t)],
               NGX_HTTP_CACHE_KEY_LEN - sizeof(ngx_rbtree_key_t));

    ngx_rbtree_insert(&cache->sh->rbtree, &fcn->node);

    fcn->uses = 1;
    fcn->count = 1;

renew:

    rc = NGX_DECLINED;

    fcn->valid_msec = 0;
    fcn->error = 0;
    fcn->exists = 0;
    fcn->valid_sec = 0;
    fcn->uniq = 0;
    fcn->body_start = 0;
    fcn->fs_size = 0;

done:

    fcn->expire = ngx_time() + cache->inactive;

    ngx_queue_insert_head(&cache->sh->queue, &fcn->queue);

    c->uniq = fcn->uniq;
    c->error = fcn->error;
    c->node = fcn;

failed:

    ngx_shmtx_unlock(&cache->shpool->mutex);

    return rc;
}