/*
 * Copyright (C) 2012-2020 all contributors <cmogstored-public@yhbt.net>
 * License: GPL-3.0+ <https://www.gnu.org/licenses/gpl-3.0.txt>
 */

#define _GNU_SOURCE 1 /* needed for _ATFILE_SOURCE on glibc 2.5 - 2.9 */
#include <dirent.h> /* needed for FreeBSD */
#include "cmogstored.h"

/* same default as MogileFS upstream */
static pthread_mutex_t svc_lock = PTHREAD_MUTEX_INITIALIZER;
static Hash_table *by_docroot; /* enforce one mog_svc per docroot: */
static mode_t mog_umask;

/*
 * maintain an internal queue of requests for the "server aio_threads = N"
 * command in the side channel.  The worker handling the client request must
 * tell the main thread do change thread counts asynchronously (because
 * the worker thread handling the request may die from a thread count
 * reduction, so we have a worker thread make a fire-and-forget request
 * to the notify thread.
 */
static pthread_mutex_t aio_threads_lock = PTHREAD_MUTEX_INITIALIZER;
static SIMPLEQ_HEAD(sq, mog_svc) aio_threads_qhead =
				SIMPLEQ_HEAD_INITIALIZER(aio_threads_qhead);

static void svc_free(void *ptr)
{
	struct mog_svc *svc = ptr;

	if (closedir(svc->dir) < 0)
		syslog(LOG_ERR, "closedir(%s) failed with: %m", svc->docroot);
	CHECK(int, 0, pthread_mutex_destroy(&svc->devstats_lock));
	mog_free(svc->docroot);
	if (svc->by_st_dev)
		hash_free(svc->by_st_dev);
	if (svc->by_mog_devid)
		hash_free(svc->by_mog_devid);
	free(svc);
}

static size_t svc_hash(const void *x, size_t tablesize)
{
	const struct mog_svc *svc = x;

	return hash_string(svc->docroot, tablesize);
}

static bool svc_cmp(const void *a, const void *b)
{
	const struct mog_svc *svc_a = a;
	const struct mog_svc *svc_b = b;

	return strcmp(svc_a->docroot, svc_b->docroot) == 0;
}

static void svc_atexit(void) /* called atexit */
{
	hash_free(by_docroot);
}

static void svc_once(void)
{
	by_docroot = hash_initialize(7, NULL, svc_hash, svc_cmp, svc_free);
	mog_oom_if_null(by_docroot);

	mog_umask = umask(0);
	umask(mog_umask);
	atexit(svc_atexit);
}

bool mog_svc_atfork_child(void *svc_ptr, void *parent)
{
	struct mog_svc *svc = svc_ptr;
	pid_t ppid = *((pid_t *)parent);
	const char *failfn;

	if (closedir(svc->dir) < 0) {
		failfn = "closedir";
		goto err;
	}

	svc->dir = opendir(svc->docroot);
	if (svc->dir == NULL) {
		failfn = "opendir";
		goto err;
	}

	svc->docroot_fd = dirfd(svc->dir);
	if (svc->docroot_fd < 0) {
		failfn = "dirfd";
		goto err;
	}
	return true;
err:
	syslog(LOG_ERR, "%s(%s) failed with: %m", failfn, svc->docroot);
	kill(ppid, SIGTERM);
	return false;
}

struct mog_svc * mog_svc_new(const char *docroot)
{
	struct mog_svc *svc;
	DIR *dir;
	int fd;

	if (!docroot) docroot = MOG_DEFAULT_DOCROOT;

	docroot = mog_canonpath_die(docroot, CAN_EXISTING);

	dir = opendir(docroot);
	if (dir == NULL) {
		syslog(LOG_ERR, "opendir(%s) failed with: %m", docroot);
		mog_free(docroot);
		return NULL;
	}

	fd = dirfd(dir);
	if (fd < 0) {
		syslog(LOG_ERR, "dirfd(%s) failed with: %m", docroot);
		mog_free(docroot);
		return NULL;
	}

	CHECK(int, 0, pthread_mutex_lock(&svc_lock));

	if (!by_docroot)
		svc_once();

	svc = xzalloc(sizeof(struct mog_svc));
	svc->persist_client = 1;
	svc->docroot = docroot;
	svc->docroot_fd = fd;
	svc->dir = dir;
	svc->put_perms = (~mog_umask) & 0666;
	svc->mkcol_perms = (~mog_umask) & 0777;
	svc->thr_per_dev = 10;
	svc->idle_timeout = 5;
	CHECK(int, 0, pthread_mutex_init(&svc->devstats_lock, NULL));
	CHECK(int, 0, pthread_mutex_init(&svc->by_mog_devid_lock, NULL));
	svc->by_mog_devid = hash_initialize(7, NULL, mog_dev_hash,
					mog_dev_cmp, mog_dev_free);
	mog_oom_if_null(svc->by_mog_devid);

	switch (hash_insert_if_absent(by_docroot, svc, NULL)) {
	case 0:
		svc_free(svc);
		svc = NULL;
	case 1: break;
	default: mog_oom();
	}

	CHECK(int, 0, pthread_mutex_unlock(&svc_lock));

	return svc;
}

size_t mog_svc_each(Hash_processor processor, void *data)
{
	size_t rv;

	CHECK(int, 0, pthread_mutex_lock(&svc_lock));
	rv = hash_do_for_each(by_docroot, processor, data);
	CHECK(int, 0, pthread_mutex_unlock(&svc_lock));

	return rv;
}

static bool cloexec_disable(struct mog_fd *mfd) /* vfork-safe */
{
	if (mfd)
		CHECK(int, 0, mog_set_cloexec(mfd->fd, false));
	return true;
}

static bool svc_cloexec_off_i(void *svcptr, void *unused) /* vfork-safe */
{
	struct mog_svc *svc = svcptr;

	return (cloexec_disable(svc->mgmt_mfd)
	        && cloexec_disable(svc->http_mfd)
	        && cloexec_disable(svc->httpget_mfd));
}

/*
 * Only call this from a freshly forked upgrade child process.
 * This holds no locks to avoid potential deadlocks in post-fork mutexes
 */
void mog_svc_upgrade_prepare(void) /* vfork-safe */
{
	(void)hash_do_for_each(by_docroot, svc_cloexec_off_i, NULL);
}

/* this is only called by the main (notify) thread */
void mog_svc_thrpool_rescale(struct mog_svc *svc, unsigned ndev_new)
{
	unsigned size = ndev_new * svc->thr_per_dev;
	struct mog_thrpool *tp = &svc->queue->thrpool;

	/* respect user-setting */
	if (svc->user_set_aio_threads) {
		mog_svc_dev_user_rescale(svc, ndev_new);
		if (tp->n_threads >= ndev_new)
			return;

		syslog(LOG_WARNING,
			"server aio_threads=%u is less than devcount=%u",
			tp->n_threads, ndev_new);

		return;
	}

	if (size < svc->thr_per_dev)
		size = svc->thr_per_dev;

	if (svc->nmogdev)
		syslog(LOG_INFO,
		       "devcount(%u->%u), updating server aio_threads=%u",
		       svc->nmogdev, ndev_new, size);
	mog_thrpool_set_size(tp, size);
}

/* Hash iterator function */
bool mog_svc_start_each(void *svc_ptr, void *main_ptr)
{
	struct mog_svc *svc = svc_ptr;
	struct mog_main *mog_main = main_ptr;
	struct mog_accept *ac;
	size_t athr = (size_t)num_processors(NPROC_CURRENT);
	struct mog_queue *q = mog_queue_new();
	size_t nthr = svc->nmogdev * svc->thr_per_dev;

	if (!nthr)
		nthr = svc->thr_per_dev;

	/*
	 * try to distribute accept() callers between workers more evenly
	 * with wake-one accept() behavior by trimming down on acceptors
	 * having too many acceptor threads does not make sense, these
	 * threads are only bounded by lock contention and local bus speeds.
	 * Increasing threads here just leads to lock contention inside the
	 * kernel (accept/accept4/EPOLL_CTL_ADD)
	 */
	athr = mog_main->worker_processes > 1 ? 1 : MIN(2, athr);

	svc->queue = q;
	mog_thrpool_start(&q->thrpool, nthr, mog_queue_loop, q);

	if (svc->mgmt_mfd) {
		mog_main->have_mgmt = true;
		ac = &svc->mgmt_mfd->as.accept;

		/*
		 * mgmt port is rarely used and always persistent, so it
		 * does not need multiple threads for blocking accept()
		 */
		mog_thrpool_start(&ac->thrpool, 1, mog_accept_loop, ac);
	}

	if (svc->http_mfd) {
		ac = &svc->http_mfd->as.accept;
		mog_thrpool_start(&ac->thrpool, athr, mog_accept_loop, ac);
	}

	if (svc->httpget_mfd) {
		ac = &svc->httpget_mfd->as.accept;
		mog_thrpool_start(&ac->thrpool, athr, mog_accept_loop, ac);
	}

	return true;
}

/*
 * Fire and forget, we must run the actual thread count manipulation
 * in the main notify thread because we may end up terminating the
 * thread which invoked this.
 *
 * Called by threads inside the thrpool to wake-up the main/notify thread.
 */
void mog_svc_aio_threads_enqueue(struct mog_svc *svc, unsigned size)
{
	unsigned prev_enq;

	CHECK(int, 0, pthread_mutex_lock(&aio_threads_lock));

	prev_enq = svc->user_req_aio_threads;
	svc->user_req_aio_threads = size;
	if (!prev_enq)
		/* put into the queue so main thread can process it */
		SIMPLEQ_INSERT_TAIL(&aio_threads_qhead, svc, qentry);

	CHECK(int, 0, pthread_mutex_unlock(&aio_threads_lock));

	/* wake up the main thread so it can process the queue */
	mog_notify(MOG_NOTIFY_AIO_THREADS);
}

/* this runs in the main (notify) thread */
void mog_svc_aio_threads_handler(void)
{
	struct mog_svc *svc;

	/* guard against requests bundled in one wakeup by looping here */
	for (;;) {
		unsigned req_size = 0;

		CHECK(int, 0, pthread_mutex_lock(&aio_threads_lock));
		svc = SIMPLEQ_FIRST(&aio_threads_qhead);
		if (svc) {
			SIMPLEQ_REMOVE_HEAD(&aio_threads_qhead, qentry);
			req_size = svc->user_req_aio_threads;
			svc->user_req_aio_threads = 0;
		}
		CHECK(int, 0, pthread_mutex_unlock(&aio_threads_lock));

		/*
		 * spurious wakeup is possible since we loop here
		 * (and we must loop, see above comment)
		 */
		if (svc == NULL || req_size == 0)
			return;

		syslog(LOG_INFO, "server aio_threads=%u", req_size);
		svc->user_set_aio_threads = req_size;
		if (svc->nmogdev)
			mog_svc_dev_user_rescale(svc, svc->nmogdev);
		mog_thrpool_set_size(&svc->queue->thrpool, req_size);
	}
}