// 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;
        unsigned long 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,
                                      unsigned long 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,
                                         unsigned long 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 >= compacted_4b_initial) {
                pos += compacted_4b_initial * 4;
                lcn -= compacted_4b_initial;
                if (lcn < compacted_2b) {
                        amortizedshift = 1;
                } else {
                        pos += compacted_2b * 2;
                        lcn -= compacted_2b;
                }
        }
        pos += lcn * (1 << amortizedshift);

        /* figure out the lcluster count in this pack */
        if (1 << amortizedshift == 4 && lclusterbits <= 14)
                vcnt = 2;
        else if (1 << amortizedshift == 2 && lclusterbits <= 12)
                vcnt = 16;
        else
                return -EOPNOTSUPP;

        in = erofs_read_metabuf(&m->map->buf, inode->i_sb, pos, m->in_mbox);
        if (IS_ERR(in))
                return PTR_ERR(in);

        /* it doesn't equal to round_up(..) */
        m->nextpackoff = round_down(pos, vcnt << amortizedshift) +
                         (vcnt << amortizedshift);
        lobits = max(lclusterbits, ilog2(Z_EROFS_LI_D0_CBLKCNT) + 1U);
        encodebits = ((vcnt << amortizedshift) - sizeof(__le32)) * 8 / vcnt;
        bytes = pos & ((vcnt << amortizedshift) - 1);
        in -= bytes;
        i = bytes >> amortizedshift;

        lo = decode_compactedbits(lobits, in, encodebits * i, &type);
        m->type = type;
        if (type == Z_EROFS_LCLUSTER_TYPE_NONHEAD) {
                m->clusterofs = 1 << lclusterbits;

                /* figure out lookahead_distance: delta[1] if needed */
                if (lookahead)
                        m->delta[1] = get_compacted_la_distance(lobits,
                                                encodebits, vcnt, in, i);
                if (lo & Z_EROFS_LI_D0_CBLKCNT) {
                        if (!big_pcluster) {
                                DBG_BUGON(1);
                                return -EFSCORRUPTED;
                        }
                        m->compressedblks = lo & ~Z_EROFS_LI_D0_CBLKCNT;
                        m->delta[0] = 1;
                        return 0;
                } else if (i + 1 != (int)vcnt) {
                        m->delta[0] = lo;
                        return 0;
                }
                /*
                 * since the last lcluster in the pack is special,
                 * of which lo saves delta[1] rather than delta[0].
                 * Hence, get delta[0] by the previous lcluster indirectly.
                 */
                lo = decode_compactedbits(lobits, in,
                                          encodebits * (i - 1), &type);
                if (type != Z_EROFS_LCLUSTER_TYPE_NONHEAD)
                        lo = 0;
                else if (lo & Z_EROFS_LI_D0_CBLKCNT)
                        lo = 1;
                m->delta[0] = lo + 1;
                return 0;
        }
        m->clusterofs = lo;
        m->delta[0] = 0;
        /* figout out blkaddr (pblk) for HEAD lclusters */
        if (!big_pcluster) {
                nblk = 1;
                while (i > 0) {
                        --i;
                        lo = decode_compactedbits(lobits, in,
                                                  encodebits * i, &type);
                        if (type == Z_EROFS_LCLUSTER_TYPE_NONHEAD)
                                i -= lo;

                        if (i >= 0)
                                ++nblk;
                }
        } else {
                nblk = 0;
                while (i > 0) {
                        --i;
                        lo = decode_compactedbits(lobits, in,
                                                  encodebits * i, &type);
                        if (type == Z_EROFS_LCLUSTER_TYPE_NONHEAD) {
                                if (lo & Z_EROFS_LI_D0_CBLKCNT) {
                                        --i;
                                        nblk += lo & ~Z_EROFS_LI_D0_CBLKCNT;
                                        continue;
                                }
                                /* bigpcluster shouldn't have plain d0 == 1 */
                                if (lo <= 1) {
                                        DBG_BUGON(1);
                                        return -EFSCORRUPTED;
                                }
                                i -= lo - 2;
                                continue;
                        }
                        ++nblk;
                }
        }
        in += (vcnt << amortizedshift) - sizeof(__le32);
        m->pblk = le32_to_cpu(*(__le32 *)in) + nblk;
        return 0;
}

static int z_erofs_load_lcluster_from_disk(struct z_erofs_maprecorder *m,
                                           unsigned int lcn, bool lookahead)
{
        struct erofs_inode *vi = EROFS_I(m->inode);
        int err;

        if (vi->datalayout == EROFS_INODE_COMPRESSED_COMPACT) {
                err = z_erofs_load_compact_lcluster(m, lcn, lookahead);
        } else {
                DBG_BUGON(vi->datalayout != EROFS_INODE_COMPRESSED_FULL);
                err = z_erofs_load_full_lcluster(m, lcn);
        }
        if (err)
                return err;

        if (m->type >= Z_EROFS_LCLUSTER_TYPE_MAX) {
                erofs_err(m->inode->i_sb, "unknown type %u @ lcn %u of nid %llu",
                          m->type, lcn, EROFS_I(m->inode)->nid);
                DBG_BUGON(1);
                return -EOPNOTSUPP;
        } else if (m->type != Z_EROFS_LCLUSTER_TYPE_NONHEAD &&
                   m->clusterofs >= (1 << vi->z_lclusterbits)) {
                DBG_BUGON(1);
                return -EFSCORRUPTED;
        }
        return 0;
}

static int z_erofs_extent_lookback(struct z_erofs_maprecorder *m,
                                   unsigned int lookback_distance)
{
        struct super_block *sb = m->inode->i_sb;
        struct erofs_inode *const vi = EROFS_I(m->inode);
        const unsigned int lclusterbits = vi->z_lclusterbits;

        while (m->lcn >= lookback_distance) {
                unsigned long lcn = m->lcn - lookback_distance;
                int err;

                if (!lookback_distance)
                        break;

                err = z_erofs_load_lcluster_from_disk(m, lcn, false);
                if (err)
                        return err;
                if (m->type == Z_EROFS_LCLUSTER_TYPE_NONHEAD) {
                        lookback_distance = m->delta[0];
                        continue;
                }
                m->headtype = m->type;
                m->map->m_la = (lcn << lclusterbits) | m->clusterofs;
                return 0;
        }
        erofs_err(sb, "bogus lookback distance %u @ lcn %lu of nid %llu",
                  lookback_distance, m->lcn, vi->nid);
        DBG_BUGON(1);
        return -EFSCORRUPTED;
}

static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m,
                                            unsigned int initial_lcn)
{
        struct inode *inode = m->inode;
        struct super_block *sb = inode->i_sb;
        struct erofs_inode *vi = EROFS_I(inode);
        bool bigpcl1 = vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1;
        bool bigpcl2 = vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_2;
        unsigned long lcn = m->lcn + 1;
        int err;

        DBG_BUGON(m->type == Z_EROFS_LCLUSTER_TYPE_NONHEAD);
        DBG_BUGON(m->type != m->headtype);

        if ((m->headtype == Z_EROFS_LCLUSTER_TYPE_HEAD1 && !bigpcl1) ||
            ((m->headtype == Z_EROFS_LCLUSTER_TYPE_PLAIN ||
              m->headtype == Z_EROFS_LCLUSTER_TYPE_HEAD2) && !bigpcl2) ||
            (lcn << vi->z_lclusterbits) >= inode->i_size)
                m->compressedblks = 1;

        if (m->compressedblks)
                goto out;

        err = z_erofs_load_lcluster_from_disk(m, lcn, false);
        if (err)
                return err;

        /*
         * If the 1st NONHEAD lcluster has already been handled initially w/o
         * valid compressedblks, which means at least it mustn't be CBLKCNT, or
         * an internal implemenatation error is detected.
         *
         * The following code can also handle it properly anyway, but let's
         * BUG_ON in the debugging mode only for developers to notice that.
         */
        DBG_BUGON(lcn == initial_lcn &&
                  m->type == Z_EROFS_LCLUSTER_TYPE_NONHEAD);

        if (m->type == Z_EROFS_LCLUSTER_TYPE_NONHEAD && m->delta[0] != 1) {
                erofs_err(sb, "bogus CBLKCNT @ lcn %lu of nid %llu", lcn, vi->nid);
                DBG_BUGON(1);
                return -EFSCORRUPTED;
        }

        /*
         * if the 1st NONHEAD lcluster is actually PLAIN or HEAD type rather
         * than CBLKCNT, it's a 1 block-sized pcluster.
         */
        if (m->type != Z_EROFS_LCLUSTER_TYPE_NONHEAD || !m->compressedblks)
                m->compressedblks = 1;
out:
        m->map->m_plen = erofs_pos(sb, m->compressedblks);
        return 0;
}

static int z_erofs_get_extent_decompressedlen(struct z_erofs_maprecorder *m)
{
        struct inode *inode = m->inode;
        struct erofs_inode *vi = EROFS_I(inode);
        struct erofs_map_blocks *map = m->map;
        unsigned int lclusterbits = vi->z_lclusterbits;
        u64 lcn = m->lcn, headlcn = map->m_la >> lclusterbits;
        int err;

        while (1) {
                /* handle the last EOF pcluster (no next HEAD lcluster) */
                if ((lcn << lclusterbits) >= inode->i_size) {
                        map->m_llen = inode->i_size - map->m_la;
                        return 0;
                }

                err = z_erofs_load_lcluster_from_disk(m, lcn, true);
                if (err)
                        return err;

                if (m->type == Z_EROFS_LCLUSTER_TYPE_NONHEAD) {
                        /* work around invalid d1 generated by pre-1.0 mkfs */
                        if (unlikely(!m->delta[1])) {
                                m->delta[1] = 1;
                                DBG_BUGON(1);
                        }
                } else if (m->type < Z_EROFS_LCLUSTER_TYPE_MAX) {
                        if (lcn != headlcn)
                                break;  /* ends at the next HEAD lcluster */
                        m->delta[1] = 1;
                }
                lcn += m->delta[1];
        }
        map->m_llen = (lcn << lclusterbits) + m->clusterofs - map->m_la;
        return 0;
}

static int z_erofs_map_blocks_fo(struct inode *inode,
                                 struct erofs_map_blocks *map, int flags)
{
        struct erofs_inode *vi = EROFS_I(inode);
        struct super_block *sb = inode->i_sb;
        bool fragment = vi->z_advise & Z_EROFS_ADVISE_FRAGMENT_PCLUSTER;
        bool ztailpacking = vi->z_idata_size;
        unsigned int lclusterbits = vi->z_lclusterbits;
        struct z_erofs_maprecorder m = {
                .inode = inode,
                .map = map,
                .in_mbox = erofs_inode_in_metabox(inode),
        };
        unsigned int endoff;
        unsigned long initial_lcn;
        unsigned long long ofs, end;
        int err;

        ofs = flags & EROFS_GET_BLOCKS_FINDTAIL ? inode->i_size - 1 : map->m_la;
        if (fragment && !(flags & EROFS_GET_BLOCKS_FINDTAIL) &&
            !vi->z_tailextent_headlcn) {
                map->m_la = 0;
                map->m_llen = inode->i_size;
                map->m_flags = EROFS_MAP_FRAGMENT;
                return 0;
        }
        initial_lcn = ofs >> lclusterbits;
        endoff = ofs & ((1 << lclusterbits) - 1);

        err = z_erofs_load_lcluster_from_disk(&m, initial_lcn, false);
        if (err)
                goto unmap_out;

        if ((flags & EROFS_GET_BLOCKS_FINDTAIL) && ztailpacking)
                vi->z_fragmentoff = m.nextpackoff;
        map->m_flags = EROFS_MAP_MAPPED | EROFS_MAP_ENCODED;
        end = (m.lcn + 1ULL) << lclusterbits;

        if (m.type != Z_EROFS_LCLUSTER_TYPE_NONHEAD && endoff >= m.clusterofs) {
                m.headtype = m.type;
                map->m_la = (m.lcn << lclusterbits) | m.clusterofs;
                /*
                 * For ztailpacking files, in order to inline data more
                 * effectively, special EOF lclusters are now supported
                 * which can have three parts at most.
                 */
                if (ztailpacking && end > inode->i_size)
                        end = inode->i_size;
        } else {
                if (m.type != Z_EROFS_LCLUSTER_TYPE_NONHEAD) {
                        end = (m.lcn << lclusterbits) | m.clusterofs;
                        map->m_flags |= EROFS_MAP_FULL_MAPPED;
                        m.delta[0] = 1;
                }
                /* get the corresponding first chunk */
                err = z_erofs_extent_lookback(&m, m.delta[0]);
                if (err)
                        goto unmap_out;
        }
        if (m.partialref)
                map->m_flags |= EROFS_MAP_PARTIAL_REF;
        map->m_llen = end - map->m_la;

        if (flags & EROFS_GET_BLOCKS_FINDTAIL) {
                vi->z_tailextent_headlcn = m.lcn;
                /* for non-compact indexes, fragmentoff is 64 bits */
                if (fragment && vi->datalayout == EROFS_INODE_COMPRESSED_FULL)
                        vi->z_fragmentoff |= (u64)m.pblk << 32;
        }
        if (ztailpacking && m.lcn == vi->z_tailextent_headlcn) {
                map->m_flags |= EROFS_MAP_META;
                map->m_pa = vi->z_fragmentoff;
                map->m_plen = vi->z_idata_size;
                if (erofs_blkoff(sb, map->m_pa) + map->m_plen > sb->s_blocksize) {
                        erofs_err(sb, "ztailpacking inline data across blocks @ nid %llu",
                                  vi->nid);
                        err = -EFSCORRUPTED;
                        goto unmap_out;
                }
        } else if (fragment && m.lcn == vi->z_tailextent_headlcn) {
                map->m_flags = EROFS_MAP_FRAGMENT;
        } else {
                map->m_pa = erofs_pos(sb, m.pblk);
                err = z_erofs_get_extent_compressedlen(&m, initial_lcn);
                if (err)
                        goto unmap_out;
        }

        if (m.headtype == Z_EROFS_LCLUSTER_TYPE_PLAIN) {
                if (map->m_llen > map->m_plen) {
                        DBG_BUGON(1);
                        err = -EFSCORRUPTED;
                        goto unmap_out;
                }
                if (vi->z_advise & Z_EROFS_ADVISE_INTERLACED_PCLUSTER)
                        map->m_algorithmformat = Z_EROFS_COMPRESSION_INTERLACED;
                else
                        map->m_algorithmformat = Z_EROFS_COMPRESSION_SHIFTED;
        } else if (m.headtype == Z_EROFS_LCLUSTER_TYPE_HEAD2) {
                map->m_algorithmformat = vi->z_algorithmtype[1];
        } else {
                map->m_algorithmformat = vi->z_algorithmtype[0];
        }

        if ((flags & EROFS_GET_BLOCKS_FIEMAP) ||
            ((flags & EROFS_GET_BLOCKS_READMORE) &&
             (map->m_algorithmformat == Z_EROFS_COMPRESSION_LZMA ||
              map->m_algorithmformat == Z_EROFS_COMPRESSION_DEFLATE ||
              map->m_algorithmformat == Z_EROFS_COMPRESSION_ZSTD) &&
              map->m_llen >= i_blocksize(inode))) {
                err = z_erofs_get_extent_decompressedlen(&m);
                if (!err)
                        map->m_flags |= EROFS_MAP_FULL_MAPPED;
        }

unmap_out:
        erofs_unmap_metabuf(&m.map->buf);
        return err;
}

static int z_erofs_map_blocks_ext(struct inode *inode,
                                  struct erofs_map_blocks *map, int flags)
{
        struct erofs_inode *vi = EROFS_I(inode);
        struct super_block *sb = inode->i_sb;
        bool interlaced = vi->z_advise & Z_EROFS_ADVISE_INTERLACED_PCLUSTER;
        unsigned int recsz = z_erofs_extent_recsize(vi->z_advise);
        erofs_off_t pos = round_up(Z_EROFS_MAP_HEADER_END(erofs_iloc(inode) +
                                   vi->inode_isize + vi->xattr_isize), recsz);
        unsigned int bmask = sb->s_blocksize - 1;
        bool in_mbox = erofs_inode_in_metabox(inode);
        erofs_off_t lend = inode->i_size;
        erofs_off_t l, r, mid, pa, la, lstart;
        struct z_erofs_extent *ext;
        unsigned int fmt;
        bool last;

        map->m_flags = 0;
        if (recsz <= offsetof(struct z_erofs_extent, pstart_hi)) {
                if (recsz <= offsetof(struct z_erofs_extent, pstart_lo)) {
                        ext = erofs_read_metabuf(&map->buf, sb, pos, in_mbox);
                        if (IS_ERR(ext))
                                return PTR_ERR(ext);
                        pa = le64_to_cpu(*(__le64 *)ext);
                        pos += sizeof(__le64);
                        lstart = 0;
                } else {
                        lstart = round_down(map->m_la, 1 << vi->z_lclusterbits);
                        pos += (lstart >> vi->z_lclusterbits) * recsz;
                        pa = EROFS_NULL_ADDR;
                }

                for (; lstart <= map->m_la; lstart += 1 << vi->z_lclusterbits) {
                        ext = erofs_read_metabuf(&map->buf, sb, pos, in_mbox);
                        if (IS_ERR(ext))
                                return PTR_ERR(ext);
                        map->m_plen = le32_to_cpu(ext->plen);
                        if (pa != EROFS_NULL_ADDR) {
                                map->m_pa = pa;
                                pa += map->m_plen & Z_EROFS_EXTENT_PLEN_MASK;
                        } else {
                                map->m_pa = le32_to_cpu(ext->pstart_lo);
                        }
                        pos += recsz;
                }
                last = (lstart >= round_up(lend, 1 << vi->z_lclusterbits));
                lend = min(lstart, lend);
                lstart -= 1 << vi->z_lclusterbits;
        } else {
                lstart = lend;
                for (l = 0, r = vi->z_extents; l < r; ) {
                        mid = l + (r - l) / 2;
                        ext = erofs_read_metabuf(&map->buf, sb,
                                                 pos + mid * recsz, in_mbox);
                        if (IS_ERR(ext))
                                return PTR_ERR(ext);

                        la = le32_to_cpu(ext->lstart_lo);
                        pa = le32_to_cpu(ext->pstart_lo) |
                                (u64)le32_to_cpu(ext->pstart_hi) << 32;
                        if (recsz > offsetof(struct z_erofs_extent, lstart_hi))
                                la |= (u64)le32_to_cpu(ext->lstart_hi) << 32;

                        if (la > map->m_la) {
                                r = mid;
                                if (la > lend) {
                                        DBG_BUGON(1);
                                        return -EFSCORRUPTED;
                                }
                                lend = la;
                        } else {
                                l = mid + 1;
                                if (map->m_la == la)
                                        r = min(l + 1, r);
                                lstart = la;
                                map->m_plen = le32_to_cpu(ext->plen);
                                map->m_pa = pa;
                        }
                }
                last = (l >= vi->z_extents);
        }

        if (lstart < lend) {
                map->m_la = lstart;
                if (last && (vi->z_advise & Z_EROFS_ADVISE_FRAGMENT_PCLUSTER)) {
                        map->m_flags = EROFS_MAP_FRAGMENT;
                        vi->z_fragmentoff = map->m_plen;
                        if (recsz > offsetof(struct z_erofs_extent, pstart_lo))
                                vi->z_fragmentoff |= map->m_pa << 32;
                } else if (map->m_plen & Z_EROFS_EXTENT_PLEN_MASK) {
                        map->m_flags |= EROFS_MAP_MAPPED |
                                EROFS_MAP_FULL_MAPPED | EROFS_MAP_ENCODED;
                        fmt = map->m_plen >> Z_EROFS_EXTENT_PLEN_FMT_BIT;
                        if (map->m_plen & Z_EROFS_EXTENT_PLEN_PARTIAL)
                                map->m_flags |= EROFS_MAP_PARTIAL_REF;
                        map->m_plen &= Z_EROFS_EXTENT_PLEN_MASK;
                        if (fmt)
                                map->m_algorithmformat = fmt - 1;
                        else if (interlaced && !((map->m_pa | map->m_plen) & bmask))
                                map->m_algorithmformat =
                                        Z_EROFS_COMPRESSION_INTERLACED;
                        else
                                map->m_algorithmformat =
                                        Z_EROFS_COMPRESSION_SHIFTED;
                }
        }
        map->m_llen = lend - map->m_la;
        return 0;
}

static int z_erofs_fill_inode(struct inode *inode, struct erofs_map_blocks *map)
{
        struct erofs_inode *const vi = EROFS_I(inode);
        struct super_block *const sb = inode->i_sb;
        struct z_erofs_map_header *h;
        erofs_off_t pos;
        int err = 0;

        if (test_bit(EROFS_I_Z_INITED_BIT, &vi->flags)) {
                /*
                 * paired with smp_mb() at the end of the function to ensure
                 * fields will only be observed after the bit is set.
                 */
                smp_mb();
                return 0;
        }

        if (wait_on_bit_lock(&vi->flags, EROFS_I_BL_Z_BIT, TASK_KILLABLE))
                return -ERESTARTSYS;

        if (test_bit(EROFS_I_Z_INITED_BIT, &vi->flags))
                goto out_unlock;

        pos = ALIGN(erofs_iloc(inode) + vi->inode_isize + vi->xattr_isize, 8);
        h = erofs_read_metabuf(&map->buf, sb, pos, erofs_inode_in_metabox(inode));
        if (IS_ERR(h)) {
                err = PTR_ERR(h);
                goto out_unlock;
        }

        /*
         * if the highest bit of the 8-byte map header is set, the whole file
         * is stored in the packed inode. The rest bits keeps z_fragmentoff.
         */
        if (h->h_clusterbits >> Z_EROFS_FRAGMENT_INODE_BIT) {
                vi->z_advise = Z_EROFS_ADVISE_FRAGMENT_PCLUSTER;
                vi->z_fragmentoff = le64_to_cpu(*(__le64 *)h) ^ (1ULL << 63);
                vi->z_tailextent_headlcn = 0;
                goto done;
        }
        vi->z_advise = le16_to_cpu(h->h_advise);
        vi->z_lclusterbits = sb->s_blocksize_bits + (h->h_clusterbits & 15);
        if (vi->datalayout == EROFS_INODE_COMPRESSED_FULL &&
            (vi->z_advise & Z_EROFS_ADVISE_EXTENTS)) {
                vi->z_extents = le32_to_cpu(h->h_extents_lo) |
                        ((u64)le16_to_cpu(h->h_extents_hi) << 32);
                goto done;
        }

        vi->z_algorithmtype[0] = h->h_algorithmtype & 15;
        vi->z_algorithmtype[1] = h->h_algorithmtype >> 4;
        if (vi->z_advise & Z_EROFS_ADVISE_FRAGMENT_PCLUSTER)
                vi->z_fragmentoff = le32_to_cpu(h->h_fragmentoff);
        else if (vi->z_advise & Z_EROFS_ADVISE_INLINE_PCLUSTER)
                vi->z_idata_size = le16_to_cpu(h->h_idata_size);

        if (!erofs_sb_has_big_pcluster(EROFS_SB(sb)) &&
            vi->z_advise & (Z_EROFS_ADVISE_BIG_PCLUSTER_1 |
                            Z_EROFS_ADVISE_BIG_PCLUSTER_2)) {
                erofs_err(sb, "per-inode big pcluster without sb feature for nid %llu",
                          vi->nid);
                err = -EFSCORRUPTED;
                goto out_unlock;
        }
        if (vi->datalayout == EROFS_INODE_COMPRESSED_COMPACT &&
            !(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1) ^
            !(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_2)) {
                erofs_err(sb, "big pcluster head1/2 of compact indexes should be consistent for nid %llu",
                          vi->nid);
                err = -EFSCORRUPTED;
                goto out_unlock;
        }

        if (vi->z_idata_size ||
            (vi->z_advise & Z_EROFS_ADVISE_FRAGMENT_PCLUSTER)) {
                struct erofs_map_blocks tm = {
                        .buf = __EROFS_BUF_INITIALIZER
                };

                err = z_erofs_map_blocks_fo(inode, &tm,
                                            EROFS_GET_BLOCKS_FINDTAIL);
                erofs_put_metabuf(&tm.buf);
                if (err < 0)
                        goto out_unlock;
        }
done:
        /* paired with smp_mb() at the beginning of the function */
        smp_mb();
        set_bit(EROFS_I_Z_INITED_BIT, &vi->flags);
out_unlock:
        clear_and_wake_up_bit(EROFS_I_BL_Z_BIT, &vi->flags);
        return err;
}

static int z_erofs_map_sanity_check(struct inode *inode,
                                    struct erofs_map_blocks *map)
{
        struct erofs_sb_info *sbi = EROFS_I_SB(inode);
        u64 pend;

        if (!(map->m_flags & EROFS_MAP_ENCODED))
                return 0;
        if (unlikely(map->m_algorithmformat >= Z_EROFS_COMPRESSION_RUNTIME_MAX)) {
                erofs_err(inode->i_sb, "unknown algorithm %d @ pos %llu for nid %llu, please upgrade kernel",
                          map->m_algorithmformat, map->m_la, EROFS_I(inode)->nid);
                return -EOPNOTSUPP;
        }
        if (unlikely(map->m_algorithmformat < Z_EROFS_COMPRESSION_MAX &&
                     !(sbi->available_compr_algs & (1 << map->m_algorithmformat)))) {
                erofs_err(inode->i_sb, "inconsistent algorithmtype %u for nid %llu",
                          map->m_algorithmformat, EROFS_I(inode)->nid);
                return -EFSCORRUPTED;
        }
        if (unlikely(map->m_plen > Z_EROFS_PCLUSTER_MAX_SIZE ||
                     map->m_llen > Z_EROFS_PCLUSTER_MAX_DSIZE))
                return -EOPNOTSUPP;
        /* Filesystems beyond 48-bit physical block addresses are invalid */
        if (unlikely(check_add_overflow(map->m_pa, map->m_plen, &pend) ||
                     (pend >> sbi->blkszbits) >= BIT_ULL(48)))
                return -EFSCORRUPTED;
        return 0;
}

int z_erofs_map_blocks_iter(struct inode *inode, struct erofs_map_blocks *map,
                            int flags)
{
        struct erofs_inode *const vi = EROFS_I(inode);
        int err = 0;

        trace_erofs_map_blocks_enter(inode, map, flags);
        if (map->m_la >= inode->i_size) {       /* post-EOF unmapped extent */
                map->m_llen = map->m_la + 1 - inode->i_size;
                map->m_la = inode->i_size;
                map->m_flags = 0;
        } else {
                err = z_erofs_fill_inode(inode, map);
                if (!err) {
                        if (vi->datalayout == EROFS_INODE_COMPRESSED_FULL &&
                            (vi->z_advise & Z_EROFS_ADVISE_EXTENTS))
                                err = z_erofs_map_blocks_ext(inode, map, flags);
                        else
                                err = z_erofs_map_blocks_fo(inode, map, flags);
                }
                if (!err)
                        err = z_erofs_map_sanity_check(inode, map);
                if (err)
                        map->m_llen = 0;
        }
        trace_erofs_map_blocks_exit(inode, map, flags, err);
        return err;
}

static int z_erofs_iomap_begin_report(struct inode *inode, loff_t offset,
                                loff_t length, unsigned int flags,
                                struct iomap *iomap, struct iomap *srcmap)
{
        int ret;
        struct erofs_map_blocks map = { .m_la = offset };

        ret = z_erofs_map_blocks_iter(inode, &map, EROFS_GET_BLOCKS_FIEMAP);
        erofs_put_metabuf(&map.buf);
        if (ret < 0)
                return ret;

        iomap->bdev = inode->i_sb->s_bdev;
        iomap->offset = map.m_la;
        iomap->length = map.m_llen;
        if (map.m_flags & EROFS_MAP_MAPPED) {
                iomap->type = IOMAP_MAPPED;
                iomap->addr = map.m_flags & __EROFS_MAP_FRAGMENT ?
                              IOMAP_NULL_ADDR : map.m_pa;
        } else {
                iomap->type = IOMAP_HOLE;
                iomap->addr = IOMAP_NULL_ADDR;
                /*
                 * No strict rule on how to describe extents for post EOF, yet
                 * we need to do like below. Otherwise, iomap itself will get
                 * into an endless loop on post EOF.
                 *
                 * Calculate the effective offset by subtracting extent start
                 * (map.m_la) from the requested offset, and add it to length.
                 * (NB: offset >= map.m_la always)
                 */
                if (iomap->offset >= inode->i_size)
                        iomap->length = length + offset - map.m_la;
        }
        iomap->flags = 0;
        return 0;
}

const struct iomap_ops z_erofs_iomap_report_ops = {
        .iomap_begin = z_erofs_iomap_begin_report,
};