// SPDX-License-Identifier: GPL-2.0+ OR Apache-2.0
/*
 * Copyright (C) 2018-2019 HUAWEI, Inc.
 *             http://www.huawei.com/
 * Created by Miao Xie <miaoxie@huawei.com>
 * with heavy changes by Gao Xiang <xiang@kernel.org>
 */
#include <stdlib.h>
#include <erofs/bitops.h>
#include "erofs/print.h"
#include "liberofs_cache.h"

static int erofs_bh_flush_drop_directly(struct erofs_buffer_head *bh,
					bool abort)
{
	return erofs_bh_flush_generic_end(bh);
}

const struct erofs_bhops erofs_drop_directly_bhops = {
	.flush = erofs_bh_flush_drop_directly,
};

static int erofs_bh_flush_skip_write(struct erofs_buffer_head *bh, bool abort)
{
	return -EBUSY;
}

const struct erofs_bhops erofs_skip_write_bhops = {
	.flush = erofs_bh_flush_skip_write,
};

struct erofs_bufmgr *erofs_buffer_init(struct erofs_sb_info *sbi,
				       erofs_blk_t startblk,
				       struct erofs_vfile *vf)
{
	unsigned int blksiz = erofs_blksiz(sbi);
	struct erofs_bufmgr *bmgr;
	int i, j, k;

	bmgr = malloc(sizeof(struct erofs_bufmgr));
	if (!bmgr)
		return NULL;

	bmgr->sbi = sbi;
	for (i = 0; i < ARRAY_SIZE(bmgr->watermeter); i++) {
		for (j = 0; j < ARRAY_SIZE(bmgr->watermeter[0]); j++) {
			for (k = 0; k < blksiz; k++)
				init_list_head(&bmgr->watermeter[i][j][k]);
			memset(bmgr->bktmap[i][j], 0,
			       (blksiz / BITS_PER_LONG) * sizeof(unsigned long));
		}
	}
	init_list_head(&bmgr->blkh.list);
	bmgr->blkh.blkaddr = EROFS_NULL_ADDR;
	bmgr->tail_blkaddr = startblk;
	bmgr->last_mapped_block = &bmgr->blkh;
	bmgr->metablkcnt = 0;
	bmgr->dsunit = 0;
	bmgr->vf = vf ?: &sbi->bdev;
	return bmgr;
}

static void erofs_clear_bbktmap(struct erofs_bufmgr *bmgr, int type,
				bool mapped, int nr)
{
	int bit = erofs_blksiz(bmgr->sbi) - (nr + 1);

	DBG_BUGON(bit < 0);
	__erofs_clear_bit(bit, bmgr->bktmap[type][mapped]);
}

static void erofs_set_bbktmap(struct erofs_bufmgr *bmgr, int type,
			      bool mapped, int nr)
{
	int bit = erofs_blksiz(bmgr->sbi) - (nr + 1);

	DBG_BUGON(bit < 0);
	__erofs_set_bit(bit, bmgr->bktmap[type][mapped]);
}

static void erofs_update_bwatermeter(struct erofs_buffer_block *bb, bool free)
{
	struct erofs_bufmgr *bmgr = bb->buffers.fsprivate;
	struct erofs_sb_info *sbi = bmgr->sbi;
	unsigned int blksiz = erofs_blksiz(sbi);
	bool mapped = bb->blkaddr != EROFS_NULL_ADDR;
	struct list_head *h = bmgr->watermeter[bb->type][mapped];
	unsigned int nr;

	if (bb->sibling.next == bb->sibling.prev) {
		if ((uintptr_t)(bb->sibling.next - h) < blksiz) {
			nr = bb->sibling.next - h;
			erofs_clear_bbktmap(bmgr, bb->type, mapped, nr);
		} else if (bb->sibling.next != &bb->sibling) {
			nr = bb->sibling.next -
				bmgr->watermeter[bb->type][!mapped];
			erofs_clear_bbktmap(bmgr, bb->type, !mapped, nr);
		}
	}
	list_del(&bb->sibling);
	if (free)
		return;
	nr = bb->buffers.off & (blksiz - 1);
	list_add_tail(&bb->sibling, h + nr);
	erofs_set_bbktmap(bmgr, bb->type, mapped, nr);
}

/* return occupied bytes in specific buffer block if succeed */
static int __erofs_battach(struct erofs_buffer_block *bb,
			   struct erofs_buffer_head *bh,
			   erofs_off_t incr,
			   unsigned int alignsize,
			   unsigned int inline_ext,
			   bool dryrun)
{
	struct erofs_bufmgr *bmgr = bb->buffers.fsprivate;
	struct erofs_sb_info *sbi = bmgr->sbi;
	const unsigned int blkmask = erofs_blksiz(sbi) - 1;
	erofs_off_t boff = bb->buffers.off;
	const erofs_off_t alignedoffset = round_up(boff, alignsize);
	bool tailupdate = false;
	erofs_blk_t blkaddr;
	int oob;

	DBG_BUGON(alignsize & (alignsize - 1));
	/* inline data must never span block boundaries */
	if (erofs_blkoff(sbi, alignedoffset + incr + blkmask)
			+ inline_ext > blkmask)
		return -ENOSPC;

	oob = cmpsgn(alignedoffset + incr + inline_ext,
		     bb->buffers.nblocks << sbi->blkszbits);
	if (oob >= 0) {
		/* the next buffer block should be EROFS_NULL_ADDR all the time */
		if (oob && list_next_entry(bb, list)->blkaddr != EROFS_NULL_ADDR)
			return -EINVAL;

		blkaddr = bb->blkaddr;
		if (blkaddr != EROFS_NULL_ADDR) {
			tailupdate = (bmgr->tail_blkaddr == blkaddr +
				      bb->buffers.nblocks);
			if (oob && !tailupdate)
				return -EINVAL;
		}
	}

	if (!dryrun) {
		if (bh) {
			bh->off = alignedoffset;
			bh->block = bb;
			list_add_tail(&bh->list, &bb->buffers.list);
		}
		boff = alignedoffset + incr;
		bb->buffers.off = boff;
		bb->buffers.nblocks = max_t(erofs_blk_t, bb->buffers.nblocks,
					    BLK_ROUND_UP(sbi, boff));
		/* need to update the tail_blkaddr */
		if (tailupdate)
			bmgr->tail_blkaddr = blkaddr + bb->buffers.nblocks;
		erofs_update_bwatermeter(bb, false);
	}
	return ((alignedoffset + incr + blkmask) & blkmask) + 1;
}

int erofs_bh_balloon(struct erofs_buffer_head *bh, erofs_off_t incr)
{
	struct erofs_buffer_block *const bb = bh->block;

	/* should be the tail bh in the corresponding buffer block */
	if (bh->list.next != &bb->buffers.list)
		return -EINVAL;

	return __erofs_battach(bb, NULL, incr, 1, 0, false);
}

static bool __find_next_bucket(struct erofs_bufmgr *bmgr, int type, bool mapped,
			       unsigned int *index, unsigned int end)
{
	const unsigned int blksiz = erofs_blksiz(bmgr->sbi);
	const unsigned int blkmask = blksiz - 1;
	unsigned int l = *index, r;

	if (l <= end) {
		DBG_BUGON(l < end);
		return false;
	}

	l = blkmask - (l & blkmask);
	r = blkmask - (end & blkmask);
	if (l >= r) {
		l = erofs_find_next_bit(bmgr->bktmap[type][mapped], blksiz, l);
		if (l < blksiz) {
			*index = round_down(*index, blksiz) + blkmask - l;
			return true;
		}
		l = 0;
		*index -= blksiz;
	}
	l = erofs_find_next_bit(bmgr->bktmap[type][mapped], r, l);
	if (l >= r)
		return false;
	*index = round_down(*index, blksiz) + blkmask - l;
	return true;
}

static int erofs_bfind_for_attach(struct erofs_bufmgr *bmgr,
				  int type, erofs_off_t size,
				  unsigned int inline_ext,
				  unsigned int alignsize,
				  struct erofs_buffer_block **bbp)
{
	const unsigned int blksiz = erofs_blksiz(bmgr->sbi);
	const unsigned int blkmask = blksiz - 1;
	struct erofs_buffer_block *cur, *bb;
	unsigned int index, used0, end, mapped;
	unsigned int usedmax, used;
	int ret;

	if (alignsize == blksiz) {
		*bbp = NULL;
		return 0;
	}
	usedmax = 0;
	bb = NULL;

	mapped = ARRAY_SIZE(bmgr->watermeter);
	used0 = rounddown(blksiz - ((size + inline_ext) & blkmask), alignsize);
	if (__erofs_unlikely(bmgr->dsunit > 1)) {
		end = used0 + alignsize - 1;
	} else {
		end = blksiz;
		if (size + inline_ext >= blksiz)
			--mapped;
	}
	index = used0 + blksiz;

	while (mapped) {
		--mapped;
		for (; __find_next_bucket(bmgr, type, mapped, &index, end);
		     --index) {
			struct list_head *bt;

			used = index & blkmask;
			bt = bmgr->watermeter[type][mapped] + used;
			DBG_BUGON(list_empty(bt));
			cur = list_first_entry(bt, struct erofs_buffer_block,
					       sibling);

			/* skip the last mapped block */
			if (mapped &&
			    list_next_entry(cur, list)->blkaddr == EROFS_NULL_ADDR) {
				DBG_BUGON(cur != bmgr->last_mapped_block);
				cur = list_next_entry(cur, sibling);
				if (&cur->sibling == bt)
					continue;
			}

			DBG_BUGON(cur->type != type);
			DBG_BUGON((cur->blkaddr != EROFS_NULL_ADDR) ^ mapped);
			DBG_BUGON(used != (cur->buffers.off & blkmask));

			ret = __erofs_battach(cur, NULL, size, alignsize,
					      inline_ext, true);
			if (ret < 0) {
				DBG_BUGON(mapped && !(bmgr->dsunit > 1));
				continue;
			}

			used = ret + inline_ext;

			/* should contain all data in the current block */
			DBG_BUGON(used > blksiz);
			if (used > usedmax) {
				usedmax = used;
				bb = cur;
			}
			break;
		}
		end = used0 + alignsize - 1;
		index = used0 + blksiz;

		/* try the last mapped block independently */
		cur = bmgr->last_mapped_block;
		if (mapped && cur != &bmgr->blkh && cur->type == type) {
			ret = __erofs_battach(cur, NULL, size,
					      alignsize, inline_ext, true);
			if (ret >= 0) {
				used = ret + inline_ext;
				DBG_BUGON(used > blksiz);
				if (used > usedmax) {
					usedmax = used;
					bb = cur;
				}
			}
		}
	}
	*bbp = bb;
	return 0;
}

struct erofs_buffer_head *erofs_balloc(struct erofs_bufmgr *bmgr,
				       int type, erofs_off_t size,
				       unsigned int inline_ext)
{
	struct erofs_buffer_block *bb;
	struct erofs_buffer_head *bh;
	unsigned int alignsize;
	int ret;

	ret = get_alignsize(bmgr->sbi, type, &type);
	if (ret < 0)
		return ERR_PTR(ret);

	DBG_BUGON(type < 0 || type > META);
	alignsize = ret;

	/* try to find if we could reuse an allocated buffer block */
	ret = erofs_bfind_for_attach(bmgr, type, size, inline_ext,
				     alignsize, &bb);
	if (ret)
		return ERR_PTR(ret);

	if (bb) {
		bh = malloc(sizeof(struct erofs_buffer_head));
		if (!bh)
			return ERR_PTR(-ENOMEM);
	} else {
		/* get a new buffer block instead */
		bb = malloc(sizeof(struct erofs_buffer_block));
		if (!bb)
			return ERR_PTR(-ENOMEM);

		bb->type = type;
		bb->blkaddr = EROFS_NULL_ADDR;
		bb->buffers.off = 0;
		bb->buffers.nblocks = 0;
		bb->buffers.fsprivate = bmgr;
		init_list_head(&bb->buffers.list);
		if (type == DATA)
			list_add(&bb->list,
				 &bmgr->last_mapped_block->list);
		else
			list_add_tail(&bb->list, &bmgr->blkh.list);
		init_list_head(&bb->sibling);

		bh = malloc(sizeof(struct erofs_buffer_head));
		if (!bh) {
			free(bb);
			return ERR_PTR(-ENOMEM);
		}
	}

	ret = __erofs_battach(bb, bh, size, alignsize, inline_ext, false);
	if (ret < 0) {
		free(bh);
		return ERR_PTR(ret);
	}
	return bh;
}

struct erofs_buffer_head *erofs_battach(struct erofs_buffer_head *bh,
					int type, unsigned int size)
{
	struct erofs_buffer_block *const bb = bh->block;
	struct erofs_bufmgr *bmgr = bb->buffers.fsprivate;
	struct erofs_buffer_head *nbh;
	unsigned int alignsize;
	int ret = get_alignsize(bmgr->sbi, type, &type);

	if (ret < 0)
		return ERR_PTR(ret);
	alignsize = ret;

	/* should be the tail bh in the corresponding buffer block */
	if (bh->list.next != &bb->buffers.list)
		return ERR_PTR(-EINVAL);

	nbh = malloc(sizeof(*nbh));
	if (!nbh)
		return ERR_PTR(-ENOMEM);

	ret = __erofs_battach(bb, nbh, size, alignsize, 0, false);
	if (ret < 0) {
		free(nbh);
		return ERR_PTR(ret);
	}
	return nbh;
}

static void __erofs_mapbh(struct erofs_buffer_block *bb)
{
	struct erofs_bufmgr *bmgr = bb->buffers.fsprivate;
	erofs_blk_t blkaddr = bmgr->tail_blkaddr;

	if (bb->blkaddr == EROFS_NULL_ADDR) {
		bb->blkaddr = blkaddr;
		if (__erofs_unlikely(bmgr->dsunit > 1) && bb->type == DATA) {
			struct erofs_buffer_block *pb = list_prev_entry(bb, list);

			bb->blkaddr = roundup(blkaddr, bmgr->dsunit);
			if (pb != &bmgr->blkh &&
			    pb->blkaddr + pb->buffers.nblocks >= blkaddr) {
				DBG_BUGON(pb->blkaddr + pb->buffers.nblocks > blkaddr);
				pb->buffers.nblocks = bb->blkaddr - pb->blkaddr;
			}
		}
		bmgr->last_mapped_block = bb;
		erofs_update_bwatermeter(bb, false);
	}

	blkaddr = bb->blkaddr + bb->buffers.nblocks;
	if (blkaddr > bmgr->tail_blkaddr)
		bmgr->tail_blkaddr = blkaddr;
}

erofs_blk_t erofs_mapbh(struct erofs_bufmgr *bmgr,
			struct erofs_buffer_block *bb)
{
	struct erofs_buffer_block *t;

	if (!bmgr)
		bmgr = bb->buffers.fsprivate;
	t = bmgr->last_mapped_block;

	if (bb && bb->blkaddr != EROFS_NULL_ADDR)
		return bb->blkaddr;
	do {
		t = list_next_entry(t, list);
		if (t == &bmgr->blkh)
			break;

		DBG_BUGON(t->blkaddr != EROFS_NULL_ADDR);
		__erofs_mapbh(t);
	} while (t != bb);
	return bmgr->tail_blkaddr;
}

static void erofs_bfree(struct erofs_buffer_block *bb)
{
	struct erofs_bufmgr *bmgr = bb->buffers.fsprivate;

	DBG_BUGON(!list_empty(&bb->buffers.list));

	if (bb == bmgr->last_mapped_block)
		bmgr->last_mapped_block = list_prev_entry(bb, list);

	erofs_update_bwatermeter(bb, true);
	list_del(&bb->list);
	free(bb);
}

static int __erofs_bflush(struct erofs_bufmgr *bmgr,
			  struct erofs_buffer_block *bb, bool abort)
{
	struct erofs_sb_info *sbi = bmgr->sbi;
	const unsigned int blksiz = erofs_blksiz(sbi);
	struct erofs_buffer_block *p, *n;
	erofs_blk_t blkaddr;

	list_for_each_entry_safe(p, n, &bmgr->blkh.list, list) {
		struct erofs_buffer_head *bh, *nbh;
		unsigned int padding;
		bool skip = false;
		int ret;

		if (p == bb)
			break;

		__erofs_mapbh(p);
		blkaddr = p->blkaddr + BLK_ROUND_UP(sbi, p->buffers.off);

		list_for_each_entry_safe(bh, nbh, &p->buffers.list, list) {
			if (bh->op == &erofs_skip_write_bhops) {
				if (!abort) {
					skip = true;
					continue;
				}
				bh->op = &erofs_drop_directly_bhops;
			}

			/* flush and remove bh */
			ret = bh->op->flush(bh, abort);
			if (__erofs_unlikely(ret == -EBUSY && !abort)) {
				skip = true;
				continue;
			}
			if (ret < 0)
				return ret;
		}

		if (skip)
			continue;

		padding = blksiz - (p->buffers.off & (blksiz - 1));
		if (padding != blksiz) {
			ret = erofs_io_fallocate(bmgr->vf,
					   erofs_pos(sbi, blkaddr) - padding,
					   padding, true);
			if (ret < 0)
				return ret;
		}

		if (p->type != DATA)
			bmgr->metablkcnt += p->buffers.nblocks;
		erofs_dbg("block %llu to %llu flushed", p->blkaddr | 0ULL,
			  (blkaddr - 1) | 0ULL);
		erofs_bfree(p);
	}
	return 0;
}

int erofs_bflush(struct erofs_bufmgr *bmgr, struct erofs_buffer_block *bb)
{
	return __erofs_bflush(bmgr, bb, false);
}

void erofs_bdrop(struct erofs_buffer_head *bh, bool tryrevoke)
{
	struct erofs_buffer_block *const bb = bh->block;
	struct erofs_bufmgr *bmgr = bb->buffers.fsprivate;
	const erofs_blk_t blkaddr = bh->block->blkaddr;
	bool rollback = false;

	/* tail_blkaddr could be rolled back after revoking all bhs */
	if (tryrevoke && blkaddr != EROFS_NULL_ADDR &&
	    bmgr->tail_blkaddr == blkaddr + bb->buffers.nblocks)
		rollback = true;

	bh->op = &erofs_drop_directly_bhops;
	erofs_bh_flush_generic_end(bh);

	if (!list_empty(&bb->buffers.list))
		return;

	if (!rollback && bb->type != DATA)
		bmgr->metablkcnt += bb->buffers.nblocks;
	erofs_bfree(bb);
	if (rollback)
		bmgr->tail_blkaddr = blkaddr;
}

erofs_blk_t erofs_total_metablocks(struct erofs_bufmgr *bmgr)
{
	return bmgr->metablkcnt;
}

void erofs_buffer_exit(struct erofs_bufmgr *bmgr)
{
	DBG_BUGON(__erofs_bflush(bmgr, NULL, true));
	DBG_BUGON(!list_empty(&bmgr->blkh.list));
	free(bmgr);
}