path: root/fs/erofs/zmap.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2018-2019 HUAWEI, Inc.
 *             https://www.huawei.com/
 */
#include "internal.h"
#include <linux/unaligned.h>
#include <trace/events/erofs.h>

struct z_erofs_maprecorder {
	struct inode *inode;
	struct erofs_map_blocks *map;
	u64 lcn;
	/* compression extent information gathered */
	u8  type, headtype;
	u16 clusterofs;
	u16 delta[2];
	erofs_blk_t pblk, compressedblks;
	erofs_off_t nextpackoff;
	bool partialref, in_mbox;
};

static int z_erofs_load_full_lcluster(struct z_erofs_maprecorder *m, u64 lcn)
{
	struct inode *const inode = m->inode;
	struct erofs_inode *const vi = EROFS_I(inode);
	const erofs_off_t pos = Z_EROFS_FULL_INDEX_START(erofs_iloc(inode) +
			vi->inode_isize + vi->xattr_isize) +
			lcn * sizeof(struct z_erofs_lcluster_index);
	struct z_erofs_lcluster_index *di;
	unsigned int advise;

	di = erofs_read_metabuf(&m->map->buf, inode->i_sb, pos, m->in_mbox);
	if (IS_ERR(di))
		return PTR_ERR(di);
	m->lcn = lcn;
	m->nextpackoff = pos + sizeof(struct z_erofs_lcluster_index);

	advise = le16_to_cpu(di->di_advise);
	m->type = advise & Z_EROFS_LI_LCLUSTER_TYPE_MASK;
	if (m->type == Z_EROFS_LCLUSTER_TYPE_NONHEAD) {
		m->clusterofs = 1 << vi->z_lclusterbits;
		m->delta[0] = le16_to_cpu(di->di_u.delta[0]);
		if (m->delta[0] & Z_EROFS_LI_D0_CBLKCNT) {
			if (!(vi->z_advise & (Z_EROFS_ADVISE_BIG_PCLUSTER_1 |
					Z_EROFS_ADVISE_BIG_PCLUSTER_2))) {
				DBG_BUGON(1);
				return -EFSCORRUPTED;
			}
			m->compressedblks = m->delta[0] & ~Z_EROFS_LI_D0_CBLKCNT;
			m->delta[0] = 1;
		}
		m->delta[1] = le16_to_cpu(di->di_u.delta[1]);
	} else {
		m->partialref = !!(advise & Z_EROFS_LI_PARTIAL_REF);
		m->clusterofs = le16_to_cpu(di->di_clusterofs);
		m->pblk = le32_to_cpu(di->di_u.blkaddr);
	}
	return 0;
}

static unsigned int decode_compactedbits(unsigned int lobits,
					 u8 *in, unsigned int pos, u8 *type)
{
	const unsigned int v = get_unaligned_le32(in + pos / 8) >> (pos & 7);
	const unsigned int lo = v & ((1 << lobits) - 1);

	*type = (v >> lobits) & 3;
	return lo;
}

static int get_compacted_la_distance(unsigned int lobits,
				     unsigned int encodebits,
				     unsigned int vcnt, u8 *in, int i)
{
	unsigned int lo, d1 = 0;
	u8 type;

	DBG_BUGON(i >= vcnt);

	do {
		lo = decode_compactedbits(lobits, in, encodebits * i, &type);

		if (type != Z_EROFS_LCLUSTER_TYPE_NONHEAD)
			return d1;
		++d1;
	} while (++i < vcnt);

	/* vcnt - 1 (Z_EROFS_LCLUSTER_TYPE_NONHEAD) item */
	if (!(lo & Z_EROFS_LI_D0_CBLKCNT))
		d1 += lo - 1;
	return d1;
}

static int z_erofs_load_compact_lcluster(struct z_erofs_maprecorder *m,
					 u64 lcn, bool lookahead)
{
	struct inode *const inode = m->inode;
	struct erofs_inode *const vi = EROFS_I(inode);
	const erofs_off_t ebase = Z_EROFS_MAP_HEADER_END(erofs_iloc(inode) +
			vi->inode_isize + vi->xattr_isize);
	const unsigned int lclusterbits = vi->z_lclusterbits;
	const unsigned int totalidx = erofs_iblks(inode);
	unsigned int compacted_4b_initial, compacted_2b, amortizedshift;
	unsigned int vcnt, lo, lobits, encodebits, nblk, bytes;
	bool big_pcluster = vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1;
	erofs_off_t pos;
	u8 *in, type;
	int i;

	if (lcn >= totalidx || lclusterbits > 14)
		return -EINVAL;

	m->lcn = lcn;
	/* used to align to 32-byte (compacted_2b) alignment */
	compacted_4b_initial = ((32 - ebase % 32) / 4) & 7;
	compacted_2b = 0;
	if ((vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B) &&
	    compacted_4b_initial < totalidx)
		compacted_2b = rounddown(totalidx - compacted_4b_initial, 16);

	pos = ebase;
	amortizedshift = 2;	/* compact_4b */
	if (lcn >= compacte