ngx_async_open_file_cache.c

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_event.h>

#if (NGX_THREADS)

#include "ngx_async_open_file_cache.h"

/*
 * open file cache caches
 *    open file handles with stat() info;
 *    directories stat() info;
 *    files and directories errors: not found, access denied, etc.
 */


#define NGX_MIN_READ_AHEAD  (128 * 1024)


#if (NGX_HAVE_OPENAT)
static ngx_fd_t ngx_openat_file_owner(ngx_fd_t at_fd, const u_char *name,
    ngx_int_t mode, ngx_int_t create, ngx_int_t access, ngx_log_t *log);
#if (NGX_HAVE_O_PATH)
static ngx_int_t ngx_file_o_path_info(ngx_fd_t fd, ngx_file_info_t *fi,
    ngx_log_t *log);
#endif
#endif
static ngx_fd_t ngx_open_file_wrapper(ngx_str_t *name,
    ngx_open_file_info_t *of, ngx_int_t mode, ngx_int_t create,
    ngx_int_t access, ngx_log_t *log);
static ngx_int_t ngx_file_info_wrapper(ngx_str_t *name,
    ngx_open_file_info_t *of, ngx_file_info_t *fi, ngx_log_t *log);
static ngx_int_t ngx_open_and_stat_file(ngx_str_t *name,
    ngx_open_file_info_t *of, ngx_log_t *log);
static void ngx_open_file_add_event(ngx_open_file_cache_t *cache,
    ngx_cached_open_file_t *file, ngx_open_file_info_t *of, ngx_log_t *log);
static void ngx_open_file_cleanup(void *data);
static void ngx_close_cached_file(ngx_open_file_cache_t *cache,
    ngx_cached_open_file_t *file, ngx_uint_t min_uses, ngx_log_t *log);
static void ngx_open_file_del_event(ngx_cached_open_file_t *file);
static void ngx_expire_old_cached_files(ngx_open_file_cache_t *cache,
    ngx_uint_t n, ngx_log_t *log);
static ngx_cached_open_file_t *
    ngx_open_file_lookup(ngx_open_file_cache_t *cache, ngx_str_t *name,
    uint32_t hash);
static void ngx_open_file_cache_remove(ngx_event_t *ev);


static ngx_int_t
ngx_save_open_file_to_cache(ngx_open_file_cache_t *cache, ngx_cached_open_file_t *file, ngx_str_t *name, uint32_t hash,
    ngx_open_file_info_t *of, ngx_log_t *log, ngx_pool_cleanup_t *cln, ngx_int_t open_rc)
{
    time_t                          now;
    ngx_open_file_cache_cleanup_t  *ofcln;

    now = ngx_time();

    if (file) {

        file->count--;

        if (open_rc != NGX_OK && (of->err == 0 || !of->errors)) {

            ngx_open_file_del_event(file);

            if (file->close) {

                /* file was already removed from rbtree and cache->current was decremented,
                    cleaning it up here instead of going to failed since that will make it happen again */

                if (file->count == 0) {

                    if (ngx_close_file(file->fd) == NGX_FILE_ERROR) {
                        ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                            ngx_close_file_n " \"%s\" failed",
                            file->name);
                    }

                    ngx_free(file->name);
                    ngx_free(file);
                }

                file = NULL;

            } else {

                ngx_queue_remove(&file->queue);
            }

            goto failed;
        }

        if (!of->is_dir && of->err == 0 && of->uniq == file->uniq) {

            file->uses++;

            if (!file->close) {
                ngx_queue_remove(&file->queue);
            }

            if (file->event) {
                file->use_event = 1;
            }

            of->is_directio = file->is_directio;

            goto update;
        }

        if (file->close) {

            ngx_close_cached_file(cache, file, 0, log);

            file = ngx_open_file_lookup(cache, name, hash);
        }

    } else {

        file = ngx_open_file_lookup(cache, name, hash);
    }

    if (file) {

        file->uses++;

        ngx_queue_remove(&file->queue);

        if (file->fd == NGX_INVALID_FILE && file->err == 0 && !file->is_dir) {

            /* file was not used often enough to keep open */
            if (open_rc != NGX_OK && (of->err == 0 || !of->errors)) {
                goto failed;
            }

            goto add_event;
        }

        if (file->use_event
            || (file->event == NULL
                && (of->uniq == 0 || of->uniq == file->uniq)
                && now - file->created < of->valid
#if (NGX_HAVE_OPENAT)
                && of->disable_symlinks == file->disable_symlinks
                && of->disable_symlinks_from == file->disable_symlinks_from
#endif
            ))
        {
            /* initially had a cache miss, but now that the open completed, there's a cache hit
                closing the file handle and using the cached handle instead */
            if (of->fd != NGX_INVALID_FILE) {

                ngx_log_debug1(NGX_LOG_DEBUG_ALLOC, log, 0, "file cleanup: fd:%d",
                               of->fd);

                if (ngx_close_file(of->fd) == NGX_FILE_ERROR) {
                    ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                                  ngx_close_file_n " \"%s\" failed", name->data);
                }
                of->fd = NGX_INVALID_FILE;
            }
            
            if (file->err == 0) {
                of->err = 0;
                of->failed = NULL;

                of->fd = file->fd;
                of->uniq = file->uniq;
                of->mtime = file->mtime;
                of->size = file->size;

                of->is_dir = file->is_dir;
                of->is_file = file->is_file;
                of->is_link = file->is_link;
                of->is_exec = file->is_exec;
                of->is_directio = file->is_directio;

                if (!file->is_dir) {
                    file->count++;
                    ngx_open_file_add_event(cache, file, of, log);
                }

            } else {
                of->err = file->err;
#if (NGX_HAVE_OPENAT)
                of->failed = file->disable_symlinks ? ngx_openat_file_n
                                                    : ngx_open_file_n;
#else
                of->failed = ngx_open_file_n;
#endif
            }

            goto found;
        }

        if (open_rc != NGX_OK && (of->err == 0 || !of->errors)) {
            goto failed;
        }
        
        if (of->is_dir) {

            if (file->is_dir || file->err) {
                goto update;
            }

            /* file became directory */

        } else if (of->err == 0) {  /* file */

            if (file->is_dir || file->err) {
                goto add_event;
            }

            /* file was changed */

        } else { /* error to cache */

            if (file->err || file->is_dir) {
                goto update;
            }

            /* file was removed, etc. */
        }

        if (file->count == 0) {

            ngx_open_file_del_event(file);

            if (ngx_close_file(file->fd) == NGX_FILE_ERROR) {
                ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                              ngx_close_file_n " \"%V\" failed", name);
            }

            goto add_event;
        }

        ngx_rbtree_delete(&cache->rbtree, &file->node);

        cache->current--;

        file->close = 1;

        goto create;
    }

    /* not found */
    
    if (open_rc != NGX_OK && (of->err == 0 || !of->errors)) {
        goto failed;
    }

create:

    if (cache->current >= cache->max) {
        ngx_expire_old_cached_files(cache, 0, log);
    }

    file = ngx_alloc(sizeof(ngx_cached_open_file_t), log);

    if (file == NULL) {
        goto failed;
    }

    file->name = ngx_alloc(name->len + 1, log);

    if (file->name == NULL) {
        ngx_free(file);
        file = NULL;
        goto failed;
    }

    ngx_cpystrn(file->name, name->data, name->len + 1);

    file->node.key = hash;

    ngx_rbtree_insert(&cache->rbtree, &file->node);

    cache->current++;

    file->uses = 1;
    file->count = 0;
    file->use_event = 0;
    file->event = NULL;
    file->close = 0;

add_event:

    ngx_open_file_add_event(cache, file, of, log);

update:

    file->fd = of->fd;
    file->err = of->err;
#if (NGX_HAVE_OPENAT)
    file->disable_symlinks = of->disable_symlinks;
    file->disable_symlinks_from = of->disable_symlinks_from;
#endif

    if (of->err == 0) {
        file->uniq = of->uniq;
        file->mtime = of->mtime;
        file->size = of->size;

        file->is_dir = of->is_dir;
        file->is_file = of->is_file;
        file->is_link = of->is_link;
        file->is_exec = of->is_exec;
        file->is_directio = of->is_directio;

        if (!of->is_dir) {
            file->count++;
        }
    }

    file->created = now;

found:

    file->accessed = now;

    if (!file->close)
    {
        ngx_queue_insert_head(&cache->expire_queue, &file->queue);
    }

    ngx_log_debug5(NGX_LOG_DEBUG_CORE, log, 0,
                   "cached open file: %s, fd:%d, c:%d, e:%d, u:%d",
                   file->name, file->fd, file->count, file->err, file->uses);

    if (of->err == 0) {

        if (!of->is_dir) {
            cln->handler = ngx_open_file_cleanup;
            ofcln = cln->data;

            ofcln->cache = cache;
            ofcln->file = file;
            ofcln->min_uses = of->min_uses;
            ofcln->log = log;
        }

        return NGX_OK;
    }

    return NGX_ERROR;

failed:

    if (file) {
        ngx_rbtree_delete(&cache->rbtree, &file->node);

        cache->current--;

        if (file->count == 0) {

            if (file->fd != NGX_INVALID_FILE) {
                if (ngx_close_file(file->fd) == NGX_FILE_ERROR) {
                    ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                                  ngx_close_file_n " \"%s\" failed",
                                  file->name);
                }
            }

            ngx_free(file->name);
            ngx_free(file);

        } else {
            file->close = 1;
        }
    }

    if (of->fd != NGX_INVALID_FILE) {
        if (ngx_close_file(of->fd) == NGX_FILE_ERROR) {
            ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                          ngx_close_file_n " \"%V\" failed", name);
        }
    }

    return NGX_ERROR;
}


#if (NGX_HAVE_OPENAT)

static ngx_fd_t
ngx_openat_file_owner(ngx_fd_t at_fd, const u_char *name,
    ngx_int_t mode, ngx_int_t create, ngx_int_t access, ngx_log_t *log)
{
    ngx_fd_t         fd;
    ngx_err_t        err;
    ngx_file_info_t  fi, atfi;

    /*
     * To allow symlinks with the same owner, use openat() (followed
     * by fstat()) and fstatat(AT_SYMLINK_NOFOLLOW), and then compare
     * uids between fstat() and fstatat().
     *
     * As there is a race between openat() and fstatat() we don't
     * know if openat() in fact opened symlink or not.  Therefore,
     * we have to compare uids even if fstatat() reports the opened
     * component isn't a symlink (as we don't know whether it was
     * symlink during openat() or not).
     */

    fd = ngx_openat_file(at_fd, name, mode, create, access);

    if (fd == NGX_INVALID_FILE) {
        return NGX_INVALID_FILE;
    }

    if (ngx_file_at_info(at_fd, name, &atfi, AT_SYMLINK_NOFOLLOW)
        == NGX_FILE_ERROR)
    {
        err = ngx_errno;
        goto failed;
    }

#if (NGX_HAVE_O_PATH)
    if (ngx_file_o_path_info(fd, &fi, log) == NGX_ERROR) {
        err = ngx_errno;
        goto failed;
    }
#else
    if (ngx_fd_info(fd, &fi) == NGX_FILE_ERROR) {
        err = ngx_errno;
        goto failed;
    }
#endif

    if (fi.st_uid != atfi.st_uid) {
        err = NGX_ELOOP;
        goto failed;
    }

    return fd;

failed:

    if (ngx_close_file(fd) == NGX_FILE_ERROR) {
        ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                      ngx_close_file_n " \"%V\" failed", name);
    }

    ngx_set_errno(err);

    return NGX_INVALID_FILE;
}


#if (NGX_HAVE_O_PATH)

static ngx_int_t
ngx_file_o_path_info(ngx_fd_t fd, ngx_file_info_t *fi, ngx_log_t *log)
{
    static ngx_uint_t  use_fstat = 1;

    /*
     * In Linux 2.6.39 the O_PATH flag was introduced that allows to obtain
     * a descriptor without actually opening file or directory.  It requires
     * less permissions for path components, but till Linux 3.6 fstat() returns
     * EBADF on such descriptors, and fstatat() with the AT_EMPTY_PATH flag
     * should be used instead.
     *
     * Three scenarios are handled in this function:
     *
     * 1) The kernel is newer than 3.6 or fstat() with O_PATH support was
     *    backported by vendor.  Then fstat() is used.
     *
     * 2) The kernel is newer than 2.6.39 but older than 3.6.  In this case
     *    the first call of fstat() returns EBADF and we fallback to fstatat()
     *    with AT_EMPTY_PATH which was introduced at the same time as O_PATH.
     *
     * 3) The kernel is older than 2.6.39 but nginx was build with O_PATH
     *    support.  Since descriptors are opened with O_PATH|O_RDONLY flags
     *    and O_PATH is ignored by the kernel then the O_RDONLY flag is
     *    actually used.  In this case fstat() just works.
     */

    if (use_fstat) {
        if (ngx_fd_info(fd, fi) != NGX_FILE_ERROR) {
            return NGX_OK;
        }

        if (ngx_errno != NGX_EBADF) {
            return NGX_ERROR;
        }

        ngx_log_error(NGX_LOG_NOTICE, log, 0,
                      "fstat(O_PATH) failed with EBADF, "
                      "switching to fstatat(AT_EMPTY_PATH)");

        use_fstat = 0;
    }

    if (ngx_file_at_info(fd, "", fi, AT_EMPTY_PATH) != NGX_FILE_ERROR) {
        return NGX_OK;
    }

    return NGX_ERROR;
}

#endif

#endif /* NGX_HAVE_OPENAT */


static ngx_fd_t
ngx_open_file_wrapper(ngx_str_t *name, ngx_open_file_info_t *of,
    ngx_int_t mode, ngx_int_t create, ngx_int_t access, ngx_log_t *log)
{
    ngx_fd_t  fd;

#if !(NGX_HAVE_OPENAT)

    fd = ngx_open_file(name->data, mode, create, access);

    if (fd == NGX_INVALID_FILE) {
        of->err = ngx_errno;
        of->failed = ngx_open_file_n;
        return NGX_INVALID_FILE;
    }

    return fd;

#else

    u_char           *p, *cp, *end;
    ngx_fd_t          at_fd;
    ngx_str_t         at_name;

    if (of->disable_symlinks == NGX_DISABLE_SYMLINKS_OFF) {
        fd = ngx_open_file(name->data, mode, create, access);

        if (fd == NGX_INVALID_FILE) {
            of->err = ngx_errno;
            of->failed = ngx_open_file_n;
            return NGX_INVALID_FILE;
        }

        return fd;
    }

    p = name->data;
    end = p + name->len;

    at_name = *name;

    if (of->disable_symlinks_from) {

        cp = p + of->disable_symlinks_from;

        *cp = '\0';

        at_fd = ngx_open_file(p, NGX_FILE_SEARCH|NGX_FILE_NONBLOCK,
                              NGX_FILE_OPEN, 0);

        *cp = '/';

        if (at_fd == NGX_INVALID_FILE) {
            of->err = ngx_errno;
            of->failed = ngx_open_file_n;
            return NGX_INVALID_FILE;
        }

        at_name.len = of->disable_symlinks_from;
        p = cp + 1;

    } else if (*p == '/') {

        at_fd = ngx_open_file("/",
                              NGX_FILE_SEARCH|NGX_FILE_NONBLOCK,
                              NGX_FILE_OPEN, 0);

        if (at_fd == NGX_INVALID_FILE) {
            of->err = ngx_errno;
            of->failed = ngx_openat_file_n;
            return NGX_INVALID_FILE;
        }

        at_name.len = 1;
        p++;

    } else {
        at_fd = NGX_AT_FDCWD;
    }

    for ( ;; ) {
        cp = ngx_strlchr(p, end, '/');
        if (cp == NULL) {
            break;
        }

        if (cp == p) {
            p++;
            continue;
        }

        *cp = '\0';

        if (of->disable_symlinks == NGX_DISABLE_SYMLINKS_NOTOWNER) {
            fd = ngx_openat_file_owner(at_fd, p,
                                       NGX_FILE_SEARCH|NGX_FILE_NONBLOCK,
                                       NGX_FILE_OPEN, 0, log);

        } else {
            fd = ngx_openat_file(at_fd, p,
                           NGX_FILE_SEARCH|NGX_FILE_NONBLOCK|NGX_FILE_NOFOLLOW,
                           NGX_FILE_OPEN, 0);
        }

        *cp = '/';

        if (fd == NGX_INVALID_FILE) {
            of->err = ngx_errno;
            of->failed = ngx_openat_file_n;
            goto failed;
        }

        if (at_fd != NGX_AT_FDCWD && ngx_close_file(at_fd) == NGX_FILE_ERROR) {
            ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                          ngx_close_file_n " \"%V\" failed", &at_name);
        }

        p = cp + 1;
        at_fd = fd;
        at_name.len = cp - at_name.data;
    }

    if (p == end) {

        /*
         * If pathname ends with a trailing slash, assume the last path
         * component is a directory and reopen it with requested flags;
         * if not, fail with ENOTDIR as per POSIX.
         *
         * We cannot rely on O_DIRECTORY in the loop above to check
         * that the last path component is a directory because
         * O_DIRECTORY doesn't work on FreeBSD 8.  Fortunately, by
         * reopening a directory, we don't depend on it at all.
         */

        fd = ngx_openat_file(at_fd, ".", mode, create, access);
        goto done;
    }

    if (of->disable_symlinks == NGX_DISABLE_SYMLINKS_NOTOWNER
        && !(create & (NGX_FILE_CREATE_OR_OPEN|NGX_FILE_TRUNCATE)))
    {
        fd = ngx_openat_file_owner(at_fd, p, mode, create, access, log);

    } else {
        fd = ngx_openat_file(at_fd, p, mode|NGX_FILE_NOFOLLOW, create, access);
    }

done:

    if (fd == NGX_INVALID_FILE) {
        of->err = ngx_errno;
        of->failed = ngx_openat_file_n;
    }

failed:

    if (at_fd != NGX_AT_FDCWD && ngx_close_file(at_fd) == NGX_FILE_ERROR) {
        ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                      ngx_close_file_n " \"%V\" failed", &at_name);
    }

    return fd;
#endif
}


static ngx_int_t
ngx_file_info_wrapper(ngx_str_t *name, ngx_open_file_info_t *of,
    ngx_file_info_t *fi, ngx_log_t *log)
{
    ngx_int_t  rc;

#if !(NGX_HAVE_OPENAT)

    rc = ngx_file_info(name->data, fi);

    if (rc == NGX_FILE_ERROR) {
        of->err = ngx_errno;
        of->failed = ngx_file_info_n;
        return NGX_FILE_ERROR;
    }

    return rc;

#else

    ngx_fd_t  fd;

    if (of->disable_symlinks == NGX_DISABLE_SYMLINKS_OFF) {

        rc = ngx_file_info(name->data, fi);

        if (rc == NGX_FILE_ERROR) {
            of->err = ngx_errno;
            of->failed = ngx_file_info_n;
            return NGX_FILE_ERROR;
        }

        return rc;
    }

    fd = ngx_open_file_wrapper(name, of, NGX_FILE_RDONLY|NGX_FILE_NONBLOCK,
                               NGX_FILE_OPEN, 0, log);

    if (fd == NGX_INVALID_FILE) {
        return NGX_FILE_ERROR;
    }

    rc = ngx_fd_info(fd, fi);

    if (rc == NGX_FILE_ERROR) {
        of->err = ngx_errno;
        of->failed = ngx_fd_info_n;
    }

    if (ngx_close_file(fd) == NGX_FILE_ERROR) {
        ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                      ngx_close_file_n " \"%V\" failed", name);
    }

    return rc;
#endif
}


static ngx_int_t
ngx_open_and_stat_file(ngx_str_t *name, ngx_open_file_info_t *of,
    ngx_log_t *log)
{
    ngx_fd_t         fd;
    ngx_file_info_t  fi;

    if (of->fd != NGX_INVALID_FILE) {

        if (ngx_file_info_wrapper(name, of, &fi, log) == NGX_FILE_ERROR) {
            of->fd = NGX_INVALID_FILE;
            return NGX_ERROR;
        }

        if (of->uniq == ngx_file_uniq(&fi)) {
            goto done;
        }

    } else if (of->test_dir) {

        if (ngx_file_info_wrapper(name, of, &fi, log) == NGX_FILE_ERROR) {
            of->fd = NGX_INVALID_FILE;
            return NGX_ERROR;
        }

        if (ngx_is_dir(&fi)) {
            goto done;
        }
    }

    if (!of->log) {

        /*
         * Use non-blocking open() not to hang on FIFO files, etc.
         * This flag has no effect on a regular files.
         */

        fd = ngx_open_file_wrapper(name, of, NGX_FILE_RDONLY|NGX_FILE_NONBLOCK,
                                   NGX_FILE_OPEN, 0, log);

    } else {
        fd = ngx_open_file_wrapper(name, of, NGX_FILE_APPEND,
                                   NGX_FILE_CREATE_OR_OPEN,
                                   NGX_FILE_DEFAULT_ACCESS, log);
    }

    if (fd == NGX_INVALID_FILE) {
        of->fd = NGX_INVALID_FILE;
        return NGX_ERROR;
    }

    if (ngx_fd_info(fd, &fi) == NGX_FILE_ERROR) {
        ngx_log_error(NGX_LOG_CRIT, log, ngx_errno,
                      ngx_fd_info_n " \"%V\" failed", name);

        if (ngx_close_file(fd) == NGX_FILE_ERROR) {
            ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                          ngx_close_file_n " \"%V\" failed", name);
        }

        of->fd = NGX_INVALID_FILE;

        return NGX_ERROR;
    }

    if (ngx_is_dir(&fi)) {
        if (ngx_close_file(fd) == NGX_FILE_ERROR) {
            ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                          ngx_close_file_n " \"%V\" failed", name);
        }

        of->fd = NGX_INVALID_FILE;

    } else {
        of->fd = fd;

        if (of->read_ahead && ngx_file_size(&fi) > NGX_MIN_READ_AHEAD) {
            if (ngx_read_ahead(fd, of->read_ahead) == NGX_ERROR) {
                ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                              ngx_read_ahead_n " \"%V\" failed", name);
            }
        }

        if (of->directio <= ngx_file_size(&fi)) {
            if (ngx_directio_on(fd) == NGX_FILE_ERROR) {
                ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                              ngx_directio_on_n " \"%V\" failed", name);

            } else {
                of->is_directio = 1;
            }
        }
    }

done:

    of->uniq = ngx_file_uniq(&fi);
    of->mtime = ngx_file_mtime(&fi);
    of->size = ngx_file_size(&fi);
    of->fs_size = ngx_file_fs_size(&fi);
    of->is_dir = ngx_is_dir(&fi);
    of->is_file = ngx_is_file(&fi);
    of->is_link = ngx_is_link(&fi);
    of->is_exec = ngx_is_exec(&fi);

    return NGX_OK;
}


/*
 * we ignore any possible event setting error and
 * fallback to usual periodic file retests
 */

static void
ngx_open_file_add_event(ngx_open_file_cache_t *cache,
    ngx_cached_open_file_t *file, ngx_open_file_info_t *of, ngx_log_t *log)
{
    ngx_open_file_cache_event_t  *fev;

    if (!(ngx_event_flags & NGX_USE_VNODE_EVENT)
        || !of->events
        || file->event
        || of->fd == NGX_INVALID_FILE
        || file->uses < of->min_uses)
    {
        return;
    }

    file->use_event = 0;

    file->event = ngx_calloc(sizeof(ngx_event_t), log);
    if (file->event== NULL) {
        return;
    }

    fev = ngx_alloc(sizeof(ngx_open_file_cache_event_t), log);
    if (fev == NULL) {
        ngx_free(file->event);
        file->event = NULL;
        return;
    }

    fev->fd = of->fd;
    fev->file = file;
    fev->cache = cache;

    file->event->handler = ngx_open_file_cache_remove;
    file->event->data = fev;

    /*
     * although vnode event may be called while ngx_cycle->poll
     * destruction, however, cleanup procedures are run before any
     * memory freeing and events will be canceled.
     */

    file->event->log = ngx_cycle->log;

    if (ngx_add_event(file->event, NGX_VNODE_EVENT, NGX_ONESHOT_EVENT)
        != NGX_OK)
    {
        ngx_free(file->event->data);
        ngx_free(file->event);
        file->event = NULL;
        return;
    }

    /*
     * we do not set file->use_event here because there may be a race
     * condition: a file may be deleted between opening the file and
     * adding event, so we rely upon event notification only after
     * one file revalidation on next file access
     */

    return;
}


static void
ngx_open_file_cleanup(void *data)
{
    ngx_open_file_cache_cleanup_t  *c = data;

    c->file->count--;

    ngx_close_cached_file(c->cache, c->file, c->min_uses, c->log);

    /* drop one or two expired open files */
    ngx_expire_old_cached_files(c->cache, 1, c->log);
}


static void
ngx_close_cached_file(ngx_open_file_cache_t *cache,
    ngx_cached_open_file_t *file, ngx_uint_t min_uses, ngx_log_t *log)
{
    ngx_log_debug5(NGX_LOG_DEBUG_CORE, log, 0,
                   "close cached open file: %s, fd:%d, c:%d, u:%d, %d",
                   file->name, file->fd, file->count, file->uses, file->close);

    if (!file->close) {

        file->accessed = ngx_time();

        ngx_queue_remove(&file->queue);

        ngx_queue_insert_head(&cache->expire_queue, &file->queue);

        if (file->uses >= min_uses || file->count) {
            return;
        }
    }

    ngx_open_file_del_event(file);

    if (file->count) {
        return;
    }

    if (file->fd != NGX_INVALID_FILE) {

        if (ngx_close_file(file->fd) == NGX_FILE_ERROR) {
            ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
                          ngx_close_file_n " \"%s\" failed", file->name);
        }

        file->fd = NGX_INVALID_FILE;
    }

    if (!file->close) {
        return;
    }

    ngx_free(file->name);
    ngx_free(file);
}


static void
ngx_open_file_del_event(ngx_cached_open_file_t *file)
{
    if (file->event == NULL) {
        return;
    }

    (void) ngx_del_event(file->event, NGX_VNODE_EVENT,
                         file->count ? NGX_FLUSH_EVENT : NGX_CLOSE_EVENT);

    ngx_free(file->event->data);
    ngx_free(file->event);
    file->event = NULL;
    file->use_event = 0;
}


static void
ngx_expire_old_cached_files(ngx_open_file_cache_t *cache, ngx_uint_t n,
    ngx_log_t *log)
{
    time_t                   now;
    ngx_queue_t             *q;
    ngx_cached_open_file_t  *file;

    now = ngx_time();

    /*
     * n == 1 deletes one or two inactive files
     * n == 0 deletes least recently used file by force
     *        and one or two inactive files
     */

    while (n < 3) {

        if (ngx_queue_empty(&cache->expire_queue)) {
            return;
        }

        q = ngx_queue_last(&cache->expire_queue);

        file = ngx_queue_data(q, ngx_cached_open_file_t, queue);

        if (n++ != 0 && now - file->accessed <= cache->inactive) {
            return;
        }

        ngx_queue_remove(q);

        ngx_rbtree_delete(&cache->rbtree, &file->node);

        cache->current--;

        ngx_log_debug1(NGX_LOG_DEBUG_CORE, log, 0,
                       "expire cached open file: %s", file->name);

        if (!file->err && !file->is_dir) {
            file->close = 1;
            ngx_close_cached_file(cache, file, 0, log);

        } else {
            ngx_free(file->name);
            ngx_free(file);
        }
    }
}


static ngx_cached_open_file_t *
ngx_open_file_lookup(ngx_open_file_cache_t *cache, ngx_str_t *name,
    uint32_t hash)
{
    ngx_int_t                rc;
    ngx_rbtree_node_t       *node, *sentinel;
    ngx_cached_open_file_t  *file;

    node = cache->rbtree.root;
    sentinel = cache->rbtree.sentinel;

    while (node != sentinel) {

        if (hash < node->key) {
            node = node->left;
            continue;
        }

        if (hash > node->key) {
            node = node->right;
            continue;
        }

        /* hash == node->key */

        file = (ngx_cached_open_file_t *) node;

        rc = ngx_strcmp(name->data, file->name);

        if (rc == 0) {
            return file;
        }

        node = (rc < 0) ? node->left : node->right;
    }

    return NULL;
}


static void
ngx_open_file_cache_remove(ngx_event_t *ev)
{
    ngx_cached_open_file_t       *file;
    ngx_open_file_cache_event_t  *fev;

    fev = ev->data;
    file = fev->file;

    ngx_queue_remove(&file->queue);

    ngx_rbtree_delete(&fev->cache->rbtree, &file->node);

    fev->cache->current--;

    /* NGX_ONESHOT_EVENT was already deleted */
    file->event = NULL;
    file->use_event = 0;

    file->close = 1;

    ngx_close_cached_file(fev->cache, file, 0, ev->log);

    /* free memory only when fev->cache and fev->file are already not needed */

    ngx_free(ev->data);
    ngx_free(ev);
}


/* Note: returns NGX_DONE on cache miss */
static ngx_int_t
ngx_get_open_file_from_cache(ngx_open_file_cache_t *cache, ngx_str_t *name,
uint32_t hash, ngx_open_file_info_t *of, ngx_log_t *log, ngx_pool_cleanup_t *cln, ngx_cached_open_file_t **out_file)
{
    time_t                          now;
    ngx_cached_open_file_t         *file;
    ngx_open_file_cache_cleanup_t  *ofcln;

    now = ngx_time();

    file = ngx_open_file_lookup(cache, name, hash);

    if (!file) {
        return NGX_DONE;
    }

    if (file->fd == NGX_INVALID_FILE && file->err == 0 && !file->is_dir) {

        /* file was not used often enough to keep open */

        return NGX_DONE;
    }

    if (!file->use_event
        && (file->event != NULL
            || (of->uniq != 0 && of->uniq != file->uniq)
            || now - file->created >= of->valid
#if (NGX_HAVE_OPENAT)
            || of->disable_symlinks != file->disable_symlinks
            || of->disable_symlinks_from != file->disable_symlinks_from
#endif
        ))
    {
        ngx_log_debug4(NGX_LOG_DEBUG_CORE, log, 0,
                       "retest open file: %s, fd:%d, c:%d, e:%d",
                       file->name, file->fd, file->count, file->err);

        if (file->is_dir) {

            /*
             * chances that directory became file are very small
             * so test_dir flag allows to use a single syscall
             * in ngx_file_info() instead of three syscalls
             */

            of->test_dir = 1;
        }
        else if (!file->err)
        {
            /* increment the count to prevent the handle from getting closed by some other request */
            file->count++;

            *out_file = file;
        }

        of->fd = file->fd;
        of->uniq = file->uniq;

        return NGX_DONE;
    }
    
    if (file->err == 0) {

        of->fd = file->fd;
        of->uniq = file->uniq;
        of->mtime = file->mtime;
        of->size = file->size;

        of->is_dir = file->is_dir;
        of->is_file = file->is_file;
        of->is_link = file->is_link;
        of->is_exec = file->is_exec;
        of->is_directio = file->is_directio;

        if (!file->is_dir) {
            file->count++;
            ngx_open_file_add_event(cache, file, of, log);
        }

    } else {
        of->err = file->err;
#if (NGX_HAVE_OPENAT)
        of->failed = file->disable_symlinks ? ngx_openat_file_n
                                            : ngx_open_file_n;
#else
        of->failed = ngx_open_file_n;
#endif
    }

    file->uses++;

    file->accessed = now;

    ngx_queue_remove(&file->queue);

    ngx_queue_insert_head(&cache->expire_queue, &file->queue);

    ngx_log_debug5(NGX_LOG_DEBUG_CORE, log, 0,
                   "cached open file: %s, fd:%d, c:%d, e:%d, u:%d",
                   file->name, file->fd, file->count, file->err, file->uses);

    if (of->err == 0) {

        if (!of->is_dir) {
            cln->handler = ngx_open_file_cleanup;
            ofcln = cln->data;

            ofcln->cache = cache;
            ofcln->file = file;
            ofcln->min_uses = of->min_uses;
            ofcln->log = log;
        }

        return NGX_OK;
    }

    return NGX_ERROR;
}

typedef struct {
	ngx_open_file_cache_t *cache;
	ngx_str_t name;
	uint32_t hash;
	ngx_open_file_info_t *of;
	ngx_cached_open_file_t *file;
	ngx_async_open_file_callback_t callback;
	void* context;
	ngx_log_t* log;
	ngx_pool_cleanup_t *cln;
	ngx_int_t err;
} ngx_async_open_file_ctx_t;

static void
ngx_thread_open_handler(void *data, ngx_log_t *log)
{
	ngx_async_open_file_ctx_t* ctx = data;
	
	ctx->err = ngx_open_and_stat_file(&ctx->name, ctx->of, log);
}

static void
ngx_async_open_thread_event_handler(ngx_event_t *ev)
{
	ngx_pool_cleanup_file_t *clnf;
	ngx_async_open_file_ctx_t* ctx;
	ngx_int_t rc;

	ctx = ev->data;

	if (ctx->cache != NULL)
	{
		rc = ngx_save_open_file_to_cache(ctx->cache, ctx->file, &ctx->name, ctx->hash, ctx->of, ctx->log, ctx->cln, ctx->err);
	}
	else
	{
		rc = ctx->err;

		// set up the cleanup of the file
		if (ctx->err == NGX_OK && !ctx->of->is_dir) {
			ctx->cln->handler = ngx_pool_cleanup_file;
			clnf = ctx->cln->data;

			clnf->fd = ctx->of->fd;
			clnf->name = ctx->name.data;
			clnf->log = ctx->log;
		}
	}

	// notify the caller
	ctx->callback(ctx->context, rc);
}

ngx_int_t
ngx_async_open_cached_file(
	ngx_open_file_cache_t *cache, 
	ngx_str_t *name,
	ngx_open_file_info_t *of, 
	ngx_pool_t *pool, 
	ngx_thread_pool_t *tp, 
	ngx_thread_task_t **taskp, 
	ngx_async_open_file_callback_t callback, 
	void* context)
{
	ngx_async_open_file_ctx_t* ctx;
	ngx_cached_open_file_t *file = NULL;
	ngx_pool_cleanup_t *cln;
	ngx_thread_task_t *task;
	ngx_int_t rc;
	uint32_t hash = 0;

	of->fd = NGX_INVALID_FILE;
	of->err = 0;

	if (cache != NULL)
	{
		cln = ngx_pool_cleanup_add(pool, sizeof(ngx_open_file_cache_cleanup_t));
		if (cln == NULL) 
		{
			return NGX_ERROR;
		}

		hash = ngx_crc32_long(name->data, name->len);

		// try to fetch from cache
		rc = ngx_get_open_file_from_cache(cache, name, hash, of, pool->log, cln, &file);
		if (rc != NGX_DONE)
		{
			return rc;
		}
	}
	else
	{
		cln = ngx_pool_cleanup_add(pool, sizeof(ngx_pool_cleanup_file_t));
		if (cln == NULL) 
		{
			ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pool->log, 0,
				"ngx_async_open_cached_file: ngx_pool_cleanup_add failed");
			return NGX_ERROR;
		}
	}

	// allocate the task if needed
	task = *taskp;

	if (task == NULL) {
		task = ngx_thread_task_alloc(pool, sizeof(ngx_async_open_file_ctx_t));
		if (task == NULL) 
		{
			ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pool->log, 0,
				"ngx_async_open_cached_file: ngx_thread_task_alloc failed");
			goto failed;
		}

		task->handler = ngx_thread_open_handler;

		*taskp = task;
	}

	// initialize the context
	ctx = task->ctx;
	ctx->cache = cache;
	ctx->name = *name;
	ctx->hash = hash;
	ctx->of = of;
	ctx->file = file;
	ctx->callback = callback;
	ctx->context = context;
	ctx->log = pool->log;
	ctx->cln = cln;

	// post the task
	task->event.data = ctx;
	task->event.handler = ngx_async_open_thread_event_handler;

	if (ngx_thread_task_post(tp, task) != NGX_OK) 
	{
		ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pool->log, 0,
			"ngx_async_open_cached_file: ngx_thread_task_post failed");
		goto failed;
	}

	return NGX_AGAIN;

failed:

	if (file != NULL)
	{
		file->count--;
		ngx_close_cached_file(cache, file, of->min_uses, pool->log);
	}

	return NGX_ERROR;
}

#endif // NGX_THREADS