/*-
 * Copyright (c) 2013  Peter Grehan <grehan@freebsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>
#include <sys/queue.h>
#include <sys/errno.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/disk.h>

#include <assert.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <pthread_np.h>
#include <signal.h>
#include <unistd.h>
#include <vdsk.h>

#include <machine/atomic.h>

#include "bhyverun.h"
#include "mevent.h"
#include "block_if.h"

#define BLOCKIF_SIG	0xb109b109

#define BLOCKIF_NUMTHR	8
#define BLOCKIF_MAXREQ	(64 + BLOCKIF_NUMTHR)

enum blockop {
	BOP_READ,
	BOP_WRITE,
	BOP_FLUSH,
	BOP_DELETE
};

enum blockstat {
	BST_FREE,
	BST_BLOCK,
	BST_PEND,
	BST_BUSY,
	BST_DONE
};

struct blockif_elem {
	TAILQ_ENTRY(blockif_elem) be_link;
	struct blockif_req  *be_req;
	enum blockop	     be_op;
	enum blockstat	     be_status;
	pthread_t            be_tid;
	off_t		     be_block;
};

struct blockif_ctxt {
	int			bc_magic;
	int			bc_candelete;
	int			bc_rdonly;
	int			bc_closing;
	pthread_t		bc_btid[BLOCKIF_NUMTHR];
        pthread_mutex_t		bc_mtx;
        pthread_cond_t		bc_cond;

	/* Request elements and free/pending/busy queues */
	TAILQ_HEAD(, blockif_elem) bc_freeq;       
	TAILQ_HEAD(, blockif_elem) bc_pendq;
	TAILQ_HEAD(, blockif_elem) bc_busyq;
	struct blockif_elem	bc_reqs[BLOCKIF_MAXREQ];
};

static pthread_once_t blockif_once = PTHREAD_ONCE_INIT;

struct blockif_sig_elem {
	pthread_mutex_t			bse_mtx;
	pthread_cond_t			bse_cond;
	int				bse_pending;
	struct blockif_sig_elem		*bse_next;
};

static struct blockif_sig_elem *blockif_bse_head;

static int
blockif_enqueue(struct blockif_ctxt *bc, struct blockif_req *breq,
		enum blockop op)
{
	struct blockif_elem *be, *tbe;
	off_t off;
	int i;

	be = TAILQ_FIRST(&bc->bc_freeq);
	assert(be != NULL);
	assert(be->be_status == BST_FREE);
	TAILQ_REMOVE(&bc->bc_freeq, be, be_link);
	be->be_req = breq;
	be->be_op = op;
	switch (op) {
	case BOP_READ:
	case BOP_WRITE:
	case BOP_DELETE:
		off = breq->br_offset;
		for (i = 0; i < breq->br_iovcnt; i++)
			off += breq->br_iov[i].iov_len;
		break;
	default:
		off = OFF_MAX;
	}
	be->be_block = off;
	TAILQ_FOREACH(tbe, &bc->bc_pendq, be_link) {
		if (tbe->be_block == breq->br_offset)
			break;
	}
	if (tbe == NULL) {
		TAILQ_FOREACH(tbe, &bc->bc_busyq, be_link) {
			if (tbe->be_block == breq->br_offset)
				break;
		}
	}
	if (tbe == NULL)
		be->be_status = BST_PEND;
	else
		be->be_status = BST_BLOCK;
	TAILQ_INSERT_TAIL(&bc->bc_pendq, be, be_link);
	return (be->be_status == BST_PEND);
}

static int
blockif_dequeue(struct blockif_ctxt *bc, pthread_t t, struct blockif_elem **bep)
{
	struct blockif_elem *be;

	TAILQ_FOREACH(be, &bc->bc_pendq, be_link) {
		if (be->be_status == BST_PEND)
			break;
		assert(be->be_status == BST_BLOCK);
	}
	if (be == NULL)
		return (0);
	TAILQ_REMOVE(&bc->bc_pendq, be, be_link);
	be->be_status = BST_BUSY;
	be->be_tid = t;
	TAILQ_INSERT_TAIL(&bc->bc_busyq, be, be_link);
	*bep = be;
	return (1);
}

static void
blockif_complete(struct blockif_ctxt *bc, struct blockif_elem *be)
{
	struct blockif_elem *tbe;

	if (be->be_status == BST_DONE || be->be_status == BST_BUSY)
		TAILQ_REMOVE(&bc->bc_busyq, be, be_link);
	else
		TAILQ_REMOVE(&bc->bc_pendq, be, be_link);
	TAILQ_FOREACH(tbe, &bc->bc_pendq, be_link) {
		if (tbe->be_req->br_offset == be->be_block)
			tbe->be_status = BST_PEND;
	}
	be->be_tid = 0;
	be->be_status = BST_FREE;
	be->be_req = NULL;
	TAILQ_INSERT_TAIL(&bc->bc_freeq, be, be_link);
}

static void
blockif_proc(struct blockif_ctxt *bc, struct blockif_elem *be, uint8_t *buf)
{
	struct blockif_req *br;
	int err;

	br = be->be_req;
	if (br->br_iovcnt <= 1)
		buf = NULL;
	err = 0;
	switch (be->be_op) {
	case BOP_READ:
		err = vdsk_read(bc, br->br_offset, br->br_iov, br->br_iovcnt);
		break;
	case BOP_WRITE:
		err = vdsk_write(bc, br->br_offset, br->br_iov, br->br_iovcnt);
		break;
	case BOP_FLUSH:
		err = vdsk_flush(bc);
		break;
	case BOP_DELETE:
		err = vdsk_trim(bc, br->br_offset, br->br_resid);
		break;
	default:
		err = EINVAL;
		break;
	}

	be->be_status = BST_DONE;

	(*br->br_callback)(br, err);
}

static void *
blockif_thr(void *arg)
{
	struct blockif_ctxt *bc;
	struct blockif_elem *be;
	pthread_t t;

	bc = arg;
	t = pthread_self();

	pthread_mutex_lock(&bc->bc_mtx);
	for (;;) {
		while (blockif_dequeue(bc, t, &be)) {
			pthread_mutex_unlock(&bc->bc_mtx);
			blockif_proc(bc, be, NULL);
			pthread_mutex_lock(&bc->bc_mtx);
			blockif_complete(bc, be);
		}
		/* Check ctxt status here to see if exit requested */
		if (bc->bc_closing)
			break;
		pthread_cond_wait(&bc->bc_cond, &bc->bc_mtx);
	}
	pthread_mutex_unlock(&bc->bc_mtx);

	pthread_exit(NULL);
	return (NULL);
}

static void
blockif_sigcont_handler(int signal, enum ev_type type, void *arg)
{
	struct blockif_sig_elem *bse;

	for (;;) {
		/*
		 * Process the entire list even if not intended for
		 * this thread.
		 */
		do {
			bse = blockif_bse_head;
			if (bse == NULL)
				return;
		} while (!atomic_cmpset_ptr((uintptr_t *)&blockif_bse_head,
					    (uintptr_t)bse,
					    (uintptr_t)bse->bse_next));

		pthread_mutex_lock(&bse->bse_mtx);
		bse->bse_pending = 0;
		pthread_cond_signal(&bse->bse_cond);
		pthread_mutex_unlock(&bse->bse_mtx);
	}
}

static void
blockif_init(void)
{
	mevent_add(SIGCONT, EVF_SIGNAL, blockif_sigcont_handler, NULL);
	(void) signal(SIGCONT, SIG_IGN);
}

struct blockif_ctxt *
blockif_open(const char *optstr, const char *ident)
{
	char tname[MAXCOMLEN + 1];
	char *nopt, *xopts, *cp;
	struct blockif_ctxt *bc;
	int extra, i;
	int nocache, sync, ro, candelete, ssopt, pssopt;

	pthread_once(&blockif_once, blockif_init);

	ssopt = 0;
	nocache = 0;
	sync = 0;
	ro = 0;

	/*
	 * The first element in the optstring is always a pathname.
	 * Optional elements follow
	 */
	nopt = xopts = strdup(optstr);
	while (xopts != NULL) {
		cp = strsep(&xopts, ",");
		if (cp == nopt)		/* file or device pathname */
			continue;
		else if (!strcmp(cp, "nocache"))
			nocache = 1;
		else if (!strcmp(cp, "sync") || !strcmp(cp, "direct"))
			sync = 1;
		else if (!strcmp(cp, "ro"))
			ro = 1;
		else if (sscanf(cp, "sectorsize=%d/%d", &ssopt, &pssopt) == 2)
			;
		else if (sscanf(cp, "sectorsize=%d", &ssopt) == 1)
			pssopt = ssopt;
		else {
			fprintf(stderr, "Invalid device option \"%s\"\n", cp);
			return (NULL);
		}
	}

	extra = 0;
	if (nocache)
		extra |= O_DIRECT;
	if (sync)
		extra |= O_SYNC;

	bc = vdsk_open(nopt, (ro ? O_RDONLY : O_RDWR) | extra, sizeof(*bc));
	if (bc == NULL && !ro) {
		/* Attempt a r/w fail with a r/o open */
		bc = vdsk_open(nopt, O_RDONLY | extra, sizeof(*bc));
		ro = 1;
	}

	if (bc == NULL) {
		perror("Could not open backing file");
		return (NULL);
	}

	bc->bc_magic = BLOCKIF_SIG;
	bc->bc_candelete = candelete;
	bc->bc_rdonly = ro;
	pthread_mutex_init(&bc->bc_mtx, NULL);
	pthread_cond_init(&bc->bc_cond, NULL);
	TAILQ_INIT(&bc->bc_freeq);
	TAILQ_INIT(&bc->bc_pendq);
	TAILQ_INIT(&bc->bc_busyq);
	for (i = 0; i < BLOCKIF_MAXREQ; i++) {
		bc->bc_reqs[i].be_status = BST_FREE;
		TAILQ_INSERT_HEAD(&bc->bc_freeq, &bc->bc_reqs[i], be_link);
	}

	for (i = 0; i < BLOCKIF_NUMTHR; i++) {
		pthread_create(&bc->bc_btid[i], NULL, blockif_thr, bc);
		snprintf(tname, sizeof(tname), "blk-%s-%d", ident, i);
		pthread_set_name_np(bc->bc_btid[i], tname);
	}

	return (bc);
}

static int
blockif_request(struct blockif_ctxt *bc, struct blockif_req *breq,
		enum blockop op)
{
	int err;

	err = 0;

	pthread_mutex_lock(&bc->bc_mtx);
	if (!TAILQ_EMPTY(&bc->bc_freeq)) {
		/*
		 * Enqueue and inform the block i/o thread
		 * that there is work available
		 */
		if (blockif_enqueue(bc, breq, op))
			pthread_cond_signal(&bc->bc_cond);
	} else {
		/*
		 * Callers are not allowed to enqueue more than
		 * the specified blockif queue limit. Return an
		 * error to indicate that the queue length has been
		 * exceeded.
		 */
		err = E2BIG;
	}
	pthread_mutex_unlock(&bc->bc_mtx);

	return (err);
}

int
blockif_read(struct blockif_ctxt *bc, struct blockif_req *breq)
{

	assert(bc->bc_magic == BLOCKIF_SIG);
	return (blockif_request(bc, breq, BOP_READ));
}

int
blockif_write(struct blockif_ctxt *bc, struct blockif_req *breq)
{

	assert(bc->bc_magic == BLOCKIF_SIG);
	return (blockif_request(bc, breq, BOP_WRITE));
}

int
blockif_flush(struct blockif_ctxt *bc, struct blockif_req *breq)
{

	assert(bc->bc_magic == BLOCKIF_SIG);
	return (blockif_request(bc, breq, BOP_FLUSH));
}

int
blockif_delete(struct blockif_ctxt *bc, struct blockif_req *breq)
{

	assert(bc->bc_magic == BLOCKIF_SIG);
	return (blockif_request(bc, breq, BOP_DELETE));
}

int
blockif_cancel(struct blockif_ctxt *bc, struct blockif_req *breq)
{
	struct blockif_elem *be;

	assert(bc->bc_magic == BLOCKIF_SIG);

	pthread_mutex_lock(&bc->bc_mtx);
	/*
	 * Check pending requests.
	 */
	TAILQ_FOREACH(be, &bc->bc_pendq, be_link) {
		if (be->be_req == breq)
			break;
	}
	if (be != NULL) {
		/*
		 * Found it.
		 */
		blockif_complete(bc, be);
		pthread_mutex_unlock(&bc->bc_mtx);

		return (0);
	}

	/*
	 * Check in-flight requests.
	 */
	TAILQ_FOREACH(be, &bc->bc_busyq, be_link) {
		if (be->be_req == breq)
			break;
	}
	if (be == NULL) {
		/*
		 * Didn't find it.
		 */
		pthread_mutex_unlock(&bc->bc_mtx);
		return (EINVAL);
	}

	/*
	 * Interrupt the processing thread to force it return
	 * prematurely via it's normal callback path.
	 */
	while (be->be_status == BST_BUSY) {
		struct blockif_sig_elem bse, *old_head;

		pthread_mutex_init(&bse.bse_mtx, NULL);
		pthread_cond_init(&bse.bse_cond, NULL);

		bse.bse_pending = 1;

		do {
			old_head = blockif_bse_head;
			bse.bse_next = old_head;
		} while (!atomic_cmpset_ptr((uintptr_t *)&blockif_bse_head,
					    (uintptr_t)old_head,
					    (uintptr_t)&bse));

		pthread_kill(be->be_tid, SIGCONT);

		pthread_mutex_lock(&bse.bse_mtx);
		while (bse.bse_pending)
			pthread_cond_wait(&bse.bse_cond, &bse.bse_mtx);
		pthread_mutex_unlock(&bse.bse_mtx);
	}

	pthread_mutex_unlock(&bc->bc_mtx);

	/*
	 * The processing thread has been interrupted.  Since it's not
	 * clear if the callback has been invoked yet, return EBUSY.
	 */
	return (EBUSY);
}

int
blockif_close(struct blockif_ctxt *bc)
{
	void *jval;
	int err, i;

	err = 0;

	assert(bc->bc_magic == BLOCKIF_SIG);

	/*
	 * Stop the block i/o thread
	 */
	pthread_mutex_lock(&bc->bc_mtx);
	bc->bc_closing = 1;
	pthread_mutex_unlock(&bc->bc_mtx);
	pthread_cond_broadcast(&bc->bc_cond);
	for (i = 0; i < BLOCKIF_NUMTHR; i++)
		pthread_join(bc->bc_btid[i], &jval);

	/* XXX Cancel queued i/o's ??? */

	/*
	 * Release resources
	 */
	bc->bc_magic = 0;
	vdsk_close(bc);

	return (0);
}

/*
 * Return virtual C/H/S values for a given block. Use the algorithm
 * outlined in the VHD specification to calculate values.
 */
void
blockif_chs(struct blockif_ctxt *bc, uint16_t *c, uint8_t *h, uint8_t *s)
{
	off_t sectors;		/* total sectors of the block dev */
	off_t hcyl;		/* cylinders times heads */
	uint16_t secpt;		/* sectors per track */
	uint8_t heads;

	assert(bc->bc_magic == BLOCKIF_SIG);

	sectors = vdsk_capacity(bc) / vdsk_sectorsize(bc);

	/* Clamp the size to the largest possible with CHS */
	if (sectors > 65535UL*16*255)
		sectors = 65535UL*16*255;

	if (sectors >= 65536UL*16*63) {
		secpt = 255;
		heads = 16;
		hcyl = sectors / secpt;
	} else {
		secpt = 17;
		hcyl = sectors / secpt;
		heads = (hcyl + 1023) / 1024;

		if (heads < 4)
			heads = 4;

		if (hcyl >= (heads * 1024) || heads > 16) {
			secpt = 31;
			heads = 16;
			hcyl = sectors / secpt;
		}
		if (hcyl >= (heads * 1024)) {
			secpt = 63;
			heads = 16;
			hcyl = sectors / secpt;
		}
	}

	*c = hcyl / heads;
	*h = heads;
	*s = secpt;
}

/*
 * Accessors
 */
off_t
blockif_size(struct blockif_ctxt *bc)
{

	assert(bc->bc_magic == BLOCKIF_SIG);
	return (vdsk_capacity(bc));
}

int
blockif_sectsz(struct blockif_ctxt *bc)
{

	assert(bc->bc_magic == BLOCKIF_SIG);
	return (vdsk_sectorsize(bc));
}

void
blockif_psectsz(struct blockif_ctxt *bc, int *size, int *off)
{

	assert(bc->bc_magic == BLOCKIF_SIG);
	*size = vdsk_sectorsize(bc);
	*off = 0;
}

int
blockif_queuesz(struct blockif_ctxt *bc)
{

	assert(bc->bc_magic == BLOCKIF_SIG);
	return (BLOCKIF_MAXREQ - 1);
}

int
blockif_is_ro(struct blockif_ctxt *bc)
{

	assert(bc->bc_magic == BLOCKIF_SIG);
	return (bc->bc_rdonly);
}

int
blockif_candelete(struct blockif_ctxt *bc)
{

	assert(bc->bc_magic == BLOCKIF_SIG);
	return (bc->bc_candelete);
}