// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
 */

#include <linux/iversion.h>
#include <linux/namei.h>
#include <linux/slab.h>
#include <linux/buffer_head.h>
#include <linux/nls.h>

#include "exfat_raw.h"
#include "exfat_fs.h"

static inline unsigned long exfat_d_version(struct dentry *dentry)
{
        return (unsigned long) dentry->d_fsdata;
}

static inline void exfat_d_version_set(struct dentry *dentry,
                unsigned long version)
{
        dentry->d_fsdata = (void *) version;
}

/*
 * If new entry was created in the parent, it could create the 8.3 alias (the
 * shortname of logname).  So, the parent may have the negative-dentry which
 * matches the created 8.3 alias.
 *
 * If it happened, the negative dentry isn't actually negative anymore.  So,
 * drop it.
 */
static int exfat_d_revalidate(struct dentry *dentry, unsigned int flags)
{
        int ret;

        if (flags & LOOKUP_RCU)
                return -ECHILD;

        /*
         * This is not negative dentry. Always valid.
         *
         * Note, rename() to existing directory entry will have ->d_inode, and
         * will use existing name which isn't specified name by user.
         *
         * We may be able to drop this positive dentry here. But dropping
         * positive dentry isn't good idea. So it's unsupported like
         * rename("filename", "FILENAME") for now.
         */
        if (d_really_is_positive(dentry))
                return 1;

        /*
         * Drop the negative dentry, in order to make sure to use the case
         * sensitive name which is specified by user if this is for creation.
         */
        if (flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET))
                return 0;

        spin_lock(&dentry->d_lock);
        ret = inode_eq_iversion(d_inode(dentry->d_parent),
                        exfat_d_version(dentry));
        spin_unlock(&dentry->d_lock);
        return ret;
}

/* returns the length of a struct qstr, ignoring trailing dots */
static unsigned int exfat_striptail_len(unsigned int len, const char *name)
{
        while (len && name[len - 1] == '.')
                len--;
        return len;
}

/*
 * Compute the hash for the exfat name corresponding to the dentry.  If the name
 * is invalid, we leave the hash code unchanged so that the existing dentry can
 * be used. The exfat fs routines will return ENOENT or EINVAL as appropriate.
 */
static int exfat_d_hash(const struct dentry *dentry, struct qstr *qstr)
{
        struct super_block *sb = dentry->d_sb;
        struct nls_table *t = EXFAT_SB(sb)->nls_io;
        const unsigned char *name = qstr->name;
        unsigned int len = exfat_striptail_len(qstr->len, qstr->name);
        unsigned long hash = init_name_hash(dentry);
        int i, charlen;
        wchar_t c;

        for (i = 0; i < len; i += charlen) {
                charlen = t->char2uni(&name[i], len - i, &c);
                if (charlen < 0)
                        return charlen;
                hash = partial_name_hash(exfat_toupper(sb, c), hash);
        }

        qstr->hash = end_name_hash(hash);
        return 0;
}

static int exfat_d_cmp(const struct dentry *dentry, unsigned int len,
                const char *str, const struct qstr *name)
{
        struct super_block *sb = dentry->d_sb;
        struct nls_table *t = EXFAT_SB(sb)->nls_io;
        unsigned int alen = exfat_striptail_len(name->len, name->name);
        unsigned int blen = exfat_striptail_len(len, str);
        wchar_t c1, c2;
        int charlen, i;

        if (alen != blen)
                return 1;

        for (i = 0; i < len; i += charlen) {
                charlen = t->char2uni(&name->name[i], alen - i, &c1);
                if (charlen < 0)
                        return 1;
                if (charlen != t->char2uni(&str[i], blen - i, &c2))
                        return 1;

                if (exfat_toupper(sb, c1) != exfat_toupper(sb, c2))
                        return 1;
        }

        return 0;
}

const struct dentry_operations exfat_dentry_ops = {
        .d_revalidate   = exfat_d_revalidate,
        .d_hash         = exfat_d_hash,
        .d_compare      = exfat_d_cmp,
};

static int exfat_utf8_d_hash(const struct dentry *dentry, struct qstr *qstr)
{
        struct super_block *sb = dentry->d_sb;
        const unsigned char *name = qstr->name;
        unsigned int len = exfat_striptail_len(qstr->len, qstr->name);
        unsigned long hash = init_name_hash(dentry);
        int i, charlen;
        unicode_t u;

        for (i = 0; i < len; i += charlen) {
                charlen = utf8_to_utf32(&name[i], len - i, &u);
                if (charlen < 0)
                        return charlen;

                /*
                 * exfat_toupper() works only for code points up to the U+FFFF.
                 */
                hash = partial_name_hash(u <= 0xFFFF ? exfat_toupper(sb, u) : u,
                                         hash);
        }

        qstr->hash = end_name_hash(hash);
        return 0;
}

static int exfat_utf8_d_cmp(const struct dentry *dentry, unsigned int len,
                const char *str, const struct qstr *name)
{
        struct super_block *sb = dentry->d_sb;
        unsigned int alen = exfat_striptail_len(name->len, name->name);
        unsigned int blen = exfat_striptail_len(len, str);
        unicode_t u_a, u_b;
        int charlen, i;

        if (alen != blen)
                return 1;

        for (i = 0; i < alen; i += charlen) {
                charlen = utf8_to_utf32(&name->name[i], alen - i, &u_a);
                if (charlen < 0)
                        return 1;
                if (charlen != utf8_to_utf32(&str[i], blen - i, &u_b))
                        return 1;

                if (u_a <= 0xFFFF && u_b <= 0xFFFF) {
                        if (exfat_toupper(sb, u_a) != exfat_toupper(sb, u_b))
                                return 1;
                } else {
                        if (u_a != u_b)
                                return 1;
                }
        }

        return 0;
}

const struct dentry_operations exfat_utf8_dentry_ops = {
        .d_revalidate   = exfat_d_revalidate,
        .d_hash         = exfat_utf8_d_hash,
        .d_compare      = exfat_utf8_d_cmp,
};

/* used only in search empty_slot() */
#define CNT_UNUSED_NOHIT        (-1)
#define CNT_UNUSED_HIT          (-2)
/* search EMPTY CONTINUOUS "num_entries" entries */
static int exfat_search_empty_slot(struct super_block *sb,
                struct exfat_hint_femp *hint_femp, struct exfat_chain *p_dir,
                int num_entries)
{
        int i, dentry, num_empty = 0;
        int dentries_per_clu;
        unsigned int type;
        struct exfat_chain clu;
        struct exfat_dentry *ep;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        struct buffer_head *bh;

        dentries_per_clu = sbi->dentries_per_clu;

        if (hint_femp->eidx != EXFAT_HINT_NONE) {
                dentry = hint_femp->eidx;
                if (num_entries <= hint_femp->count) {
                        hint_femp->eidx = EXFAT_HINT_NONE;
                        return dentry;
                }

                exfat_chain_dup(&clu, &hint_femp->cur);
        } else {
                exfat_chain_dup(&clu, p_dir);
                dentry = 0;
        }

        while (clu.dir != EXFAT_EOF_CLUSTER) {
                i = dentry & (dentries_per_clu - 1);

                for (; i < dentries_per_clu; i++, dentry++) {
                        ep = exfat_get_dentry(sb, &clu, i, &bh, NULL);
                        if (!ep)
                                return -EIO;
                        type = exfat_get_entry_type(ep);
                        brelse(bh);

                        if (type == TYPE_UNUSED || type == TYPE_DELETED) {
                                num_empty++;
                                if (hint_femp->eidx == EXFAT_HINT_NONE) {
                                        hint_femp->eidx = dentry;
                                        hint_femp->count = CNT_UNUSED_NOHIT;
                                        exfat_chain_set(&hint_femp->cur,
                                                clu.dir, clu.size, clu.flags);
                                }

                                if (type == TYPE_UNUSED &&
                                    hint_femp->count != CNT_UNUSED_HIT)
                                        hint_femp->count = CNT_UNUSED_HIT;
                        } else {
                                if (hint_femp->eidx != EXFAT_HINT_NONE &&
                                    hint_femp->count == CNT_UNUSED_HIT) {
                                        /* unused empty group means
                                         * an empty group which includes
                                         * unused dentry
                                         */
                                        exfat_fs_error(sb,
                                                "found bogus dentry(%d) beyond unused empty group(%d) (start_clu : %u, cur_clu : %u)",
                                                dentry, hint_femp->eidx,
                                                p_dir->dir, clu.dir);
                                        return -EIO;
                                }

                                num_empty = 0;
                                hint_femp->eidx = EXFAT_HINT_NONE;
                        }

                        if (num_empty >= num_entries) {
                                /* found and invalidate hint_femp */
                                hint_femp->eidx = EXFAT_HINT_NONE;
                                return (dentry - (num_entries - 1));
                        }
                }

                if (clu.flags == ALLOC_NO_FAT_CHAIN) {
                        if (--clu.size > 0)
                                clu.dir++;
                        else
                                clu.dir = EXFAT_EOF_CLUSTER;
                } else {
                        if (exfat_get_next_cluster(sb, &clu.dir))
                                return -EIO;
                }
        }

        return -ENOSPC;
}

static int exfat_check_max_dentries(struct inode *inode)
{
        if (EXFAT_B_TO_DEN(i_size_read(inode)) >= MAX_EXFAT_DENTRIES) {
                /*
                 * exFAT spec allows a dir to grow up to 8388608(256MB)
                 * dentries
                 */
                return -ENOSPC;
        }
        return 0;
}

/* find empty directory entry.
 * if there isn't any empty slot, expand cluster chain.
 */
static int exfat_find_empty_entry(struct inode *inode,
                struct exfat_chain *p_dir, int num_entries)
{
        int dentry;
        unsigned int ret, last_clu;
        sector_t sector;
        loff_t size = 0;
        struct exfat_chain clu;
        struct exfat_dentry *ep = NULL;
        struct super_block *sb = inode->i_sb;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        struct exfat_inode_info *ei = EXFAT_I(inode);
        struct exfat_hint_femp hint_femp;

        hint_femp.eidx = EXFAT_HINT_NONE;

        if (ei->hint_femp.eidx != EXFAT_HINT_NONE) {
                hint_femp = ei->hint_femp;
                ei->hint_femp.eidx = EXFAT_HINT_NONE;
        }

        while ((dentry = exfat_search_empty_slot(sb, &hint_femp, p_dir,
                                        num_entries)) < 0) {
                if (dentry == -EIO)
                        break;

                if (exfat_check_max_dentries(inode))
                        return -ENOSPC;

                /* we trust p_dir->size regardless of FAT type */
                if (exfat_find_last_cluster(sb, p_dir, &last_clu))
                        return -EIO;

                /*
                 * Allocate new cluster to this directory
                 */
                exfat_chain_set(&clu, last_clu + 1, 0, p_dir->flags);

                /* allocate a cluster */
                ret = exfat_alloc_cluster(inode, 1, &clu, IS_DIRSYNC(inode));
                if (ret)
                        return ret;

                if (exfat_zeroed_cluster(inode, clu.dir))
                        return -EIO;

                /* append to the FAT chain */
                if (clu.flags != p_dir->flags) {
                        /* no-fat-chain bit is disabled,
                         * so fat-chain should be synced with alloc-bitmap
                         */
                        exfat_chain_cont_cluster(sb, p_dir->dir, p_dir->size);
                        p_dir->flags = ALLOC_FAT_CHAIN;
                        hint_femp.cur.flags = ALLOC_FAT_CHAIN;
                }

                if (clu.flags == ALLOC_FAT_CHAIN)
                        if (exfat_ent_set(sb, last_clu, clu.dir))
                                return -EIO;

                if (hint_femp.eidx == EXFAT_HINT_NONE) {
                        /* the special case that new dentry
                         * should be allocated from the start of new cluster
                         */
                        hint_femp.eidx = EXFAT_B_TO_DEN_IDX(p_dir->size, sbi);
                        hint_femp.count = sbi->dentries_per_clu;

                        exfat_chain_set(&hint_femp.cur, clu.dir, 0, clu.flags);
                }
                hint_femp.cur.size++;
                p_dir->size++;
                size = EXFAT_CLU_TO_B(p_dir->size, sbi);

                /* update the directory entry */
                if (p_dir->dir != sbi->root_dir) {
                        struct buffer_head *bh;

                        ep = exfat_get_dentry(sb,
                                &(ei->dir), ei->entry + 1, &bh, &sector);
                        if (!ep)
                                return -EIO;

                        ep->dentry.stream.valid_size = cpu_to_le64(size);
                        ep->dentry.stream.size = ep->dentry.stream.valid_size;
                        ep->dentry.stream.flags = p_dir->flags;
                        exfat_update_bh(bh, IS_DIRSYNC(inode));
                        brelse(bh);
                        if (exfat_update_dir_chksum(inode, &(ei->dir),
                            ei->entry))
                                return -EIO;
                }

                /* directory inode should be updated in here */
                i_size_write(inode, size);
                EXFAT_I(inode)->i_size_ondisk += sbi->cluster_size;
                EXFAT_I(inode)->i_size_aligned += sbi->cluster_size;
                EXFAT_I(inode)->flags = p_dir->flags;
                inode->i_blocks += 1 << sbi->sect_per_clus_bits;
        }

        return dentry;
}

/*
 * Name Resolution Functions :
 * Zero if it was successful; otherwise nonzero.
 */
static int __exfat_resolve_path(struct inode *inode, const unsigned char *path,
                struct exfat_chain *p_dir, struct exfat_uni_name *p_uniname,
                int lookup)
{
        int namelen;
        int lossy = NLS_NAME_NO_LOSSY;
        struct super_block *sb = inode->i_sb;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        struct exfat_inode_info *ei = EXFAT_I(inode);

        /* strip all trailing periods */
        namelen = exfat_striptail_len(strlen(path), path);
        if (!namelen)
                return -ENOENT;

        if (strlen(path) > (MAX_NAME_LENGTH * MAX_CHARSET_SIZE))
                return -ENAMETOOLONG;

        /*
         * strip all leading spaces :
         * "MS windows 7" supports leading spaces.
         * So we should skip this preprocessing for compatibility.
         */

        /* file name conversion :
         * If lookup case, we allow bad-name for compatibility.
         */
        namelen = exfat_nls_to_utf16(sb, path, namelen, p_uniname,
                        &lossy);
        if (namelen < 0)
                return namelen; /* return error value */

        if ((lossy && !lookup) || !namelen)
                return -EINVAL;

        exfat_chain_set(p_dir, ei->start_clu,
                EXFAT_B_TO_CLU(i_size_read(inode), sbi), ei->flags);

        return 0;
}

static inline int exfat_resolve_path(struct inode *inode,
                const unsigned char *path, struct exfat_chain *dir,
                struct exfat_uni_name *uni)
{
        return __exfat_resolve_path(inode, path, dir, uni, 0);
}

static inline int exfat_resolve_path_for_lookup(struct inode *inode,
                const unsigned char *path, struct exfat_chain *dir,
                struct exfat_uni_name *uni)
{
        return __exfat_resolve_path(inode, path, dir, uni, 1);
}

static inline loff_t exfat_make_i_pos(struct exfat_dir_entry *info)
{
        return ((loff_t) info->dir.dir << 32) | (info->entry & 0xffffffff);
}

static int exfat_add_entry(struct inode *inode, const char *path,
                struct exfat_chain *p_dir, unsigned int type,
                struct exfat_dir_entry *info)
{
        int ret, dentry, num_entries;
        struct super_block *sb = inode->i_sb;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        struct exfat_uni_name uniname;
        struct exfat_chain clu;
        int clu_size = 0;
        unsigned int start_clu = EXFAT_FREE_CLUSTER;

        ret = exfat_resolve_path(inode, path, p_dir, &uniname);
        if (ret)
                goto out;

        num_entries = exfat_calc_num_entries(&uniname);
        if (num_entries < 0) {
                ret = num_entries;
                goto out;
        }

        /* exfat_find_empty_entry must be called before alloc_cluster() */
        dentry = exfat_find_empty_entry(inode, p_dir, num_entries);
        if (dentry < 0) {
                ret = dentry; /* -EIO or -ENOSPC */
                goto out;
        }

        if (type == TYPE_DIR) {
                ret = exfat_alloc_new_dir(inode, &clu);
                if (ret)
                        goto out;
                start_clu = clu.dir;
                clu_size = sbi->cluster_size;
        }

        /* update the directory entry */
        /* fill the dos name directory entry information of the created file.
         * the first cluster is not determined yet. (0)
         */
        ret = exfat_init_dir_entry(inode, p_dir, dentry, type,
                start_clu, clu_size);
        if (ret)
                goto out;

        ret = exfat_init_ext_entry(inode, p_dir, dentry, num_entries, &uniname);
        if (ret)
                goto out;

        info->dir = *p_dir;
        info->entry = dentry;
        info->flags = ALLOC_NO_FAT_CHAIN;
        info->type = type;

        if (type == TYPE_FILE) {
                info->attr = ATTR_ARCHIVE;
                info->start_clu = EXFAT_EOF_CLUSTER;
                info->size = 0;
                info->num_subdirs = 0;
        } else {
                info->attr = ATTR_SUBDIR;
                info->start_clu = start_clu;
                info->size = clu_size;
                info->num_subdirs = EXFAT_MIN_SUBDIR;
        }
        memset(&info->crtime, 0, sizeof(info->crtime));
        memset(&info->mtime, 0, sizeof(info->mtime));
        memset(&info->atime, 0, sizeof(info->atime));
out:
        return ret;
}

static int exfat_create(struct user_namespace *mnt_userns, struct inode *dir,
                        struct dentry *dentry, umode_t mode, bool excl)
{
        struct super_block *sb = dir->i_sb;
        struct inode *inode;
        struct exfat_chain cdir;
        struct exfat_dir_entry info;
        loff_t i_pos;
        int err;

        mutex_lock(&EXFAT_SB(sb)->s_lock);
        exfat_set_volume_dirty(sb);
        err = exfat_add_entry(dir, dentry->d_name.name, &cdir, TYPE_FILE,
                &info);
        exfat_clear_volume_dirty(sb);
        if (err)
                goto unlock;

        inode_inc_iversion(dir);
        dir->i_ctime = dir->i_mtime = current_time(dir);
        if (IS_DIRSYNC(dir))
                exfat_sync_inode(dir);
        else
                mark_inode_dirty(dir);

        i_pos = exfat_make_i_pos(&info);
        inode = exfat_build_inode(sb, &info, i_pos);
        err = PTR_ERR_OR_ZERO(inode);
        if (err)
                goto unlock;

        inode_inc_iversion(inode);
        inode->i_mtime = inode->i_atime = inode->i_ctime =
                EXFAT_I(inode)->i_crtime = current_time(inode);
        exfat_truncate_atime(&inode->i_atime);
        /* timestamp is already written, so mark_inode_dirty() is unneeded. */

        d_instantiate(dentry, inode);
unlock:
        mutex_unlock(&EXFAT_SB(sb)->s_lock);
        return err;
}

/* lookup a file */
static int exfat_find(struct inode *dir, struct qstr *qname,
                struct exfat_dir_entry *info)
{
        int ret, dentry, num_entries, count;
        struct exfat_chain cdir;
        struct exfat_uni_name uni_name;
        struct super_block *sb = dir->i_sb;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        struct exfat_inode_info *ei = EXFAT_I(dir);
        struct exfat_dentry *ep, *ep2;
        struct exfat_entry_set_cache *es;
        /* for optimized dir & entry to prevent long traverse of cluster chain */
        struct exfat_hint hint_opt;

        if (qname->len == 0)
                return -ENOENT;

        /* check the validity of directory name in the given pathname */
        ret = exfat_resolve_path_for_lookup(dir, qname->name, &cdir, &uni_name);
        if (ret)
                return ret;

        num_entries = exfat_calc_num_entries(&uni_name);
        if (num_entries < 0)
                return num_entries;

        /* check the validation of hint_stat and initialize it if required */
        if (ei->version != (inode_peek_iversion_raw(dir) & 0xffffffff)) {
                ei->hint_stat.clu = cdir.dir;
                ei->hint_stat.eidx = 0;
                ei->version = (inode_peek_iversion_raw(dir) & 0xffffffff);
                ei->hint_femp.eidx = EXFAT_HINT_NONE;
        }

        /* search the file name for directories */
        dentry = exfat_find_dir_entry(sb, ei, &cdir, &uni_name,
                        num_entries, TYPE_ALL, &hint_opt);

        if (dentry < 0)
                return dentry; /* -error value */

        info->dir = cdir;
        info->entry = dentry;
        info->num_subdirs = 0;

        /* adjust cdir to the optimized value */
        cdir.dir = hint_opt.clu;
        if (cdir.flags & ALLOC_NO_FAT_CHAIN)
                cdir.size -= dentry / sbi->dentries_per_clu;
        dentry = hint_opt.eidx;
        es = exfat_get_dentry_set(sb, &cdir, dentry, ES_2_ENTRIES);
        if (!es)
                return -EIO;
        ep = exfat_get_dentry_cached(es, 0);
        ep2 = exfat_get_dentry_cached(es, 1);

        info->type = exfat_get_entry_type(ep);
        info->attr = le16_to_cpu(ep->dentry.file.attr);
        info->size = le64_to_cpu(ep2->dentry.stream.valid_size);
        if ((info->type == TYPE_FILE) && (info->size == 0)) {
                info->flags = ALLOC_NO_FAT_CHAIN;
                info->start_clu = EXFAT_EOF_CLUSTER;
        } else {
                info->flags = ep2->dentry.stream.flags;
                info->start_clu =
                        le32_to_cpu(ep2->dentry.stream.start_clu);
        }

        exfat_get_entry_time(sbi, &info->crtime,
                             ep->dentry.file.create_tz,
                             ep->dentry.file.create_time,
                             ep->dentry.file.create_date,
                             ep->dentry.file.create_time_cs);
        exfat_get_entry_time(sbi, &info->mtime,
                             ep->dentry.file.modify_tz,
                             ep->dentry.file.modify_time,
                             ep->dentry.file.modify_date,
                             ep->dentry.file.modify_time_cs);
        exfat_get_entry_time(sbi, &info->atime,
                             ep->dentry.file.access_tz,
                             ep->dentry.file.access_time,
                             ep->dentry.file.access_date,
                             0);
        exfat_free_dentry_set(es, false);

        if (ei->start_clu == EXFAT_FREE_CLUSTER) {
                exfat_fs_error(sb,
                               "non-zero size file starts with zero cluster (size : %llu, p_dir : %u, entry : 0x%08x)",
                               i_size_read(dir), ei->dir.dir, ei->entry);
                return -EIO;
        }

        if (info->type == TYPE_DIR) {
                exfat_chain_set(&cdir, info->start_clu,
                                EXFAT_B_TO_CLU(info->size, sbi), info->flags);
                count = exfat_count_dir_entries(sb, &cdir);
                if (count < 0)
                        return -EIO;

                info->num_subdirs = count + EXFAT_MIN_SUBDIR;
        }
        return 0;
}

static int exfat_d_anon_disconn(struct dentry *dentry)
{
        return IS_ROOT(dentry) && (dentry->d_flags & DCACHE_DISCONNECTED);
}

static struct dentry *exfat_lookup(struct inode *dir, struct dentry *dentry,
                unsigned int flags)
{
        struct super_block *sb = dir->i_sb;
        struct inode *inode;
        struct dentry *alias;
        struct exfat_dir_entry info;
        int err;
        loff_t i_pos;
        mode_t i_mode;

        mutex_lock(&EXFAT_SB(sb)->s_lock);
        err = exfat_find(dir, &dentry->d_name, &info);
        if (err) {
                if (err == -ENOENT) {
                        inode = NULL;
                        goto out;
                }
                goto unlock;
        }

        i_pos = exfat_make_i_pos(&info);
        inode = exfat_build_inode(sb, &info, i_pos);
        err = PTR_ERR_OR_ZERO(inode);
        if (err)
                goto unlock;

        i_mode = inode->i_mode;
        alias = d_find_alias(inode);

        /*
         * Checking "alias->d_parent == dentry->d_parent" to make sure
         * FS is not corrupted (especially double linked dir).
         */
        if (alias && alias->d_parent == dentry->d_parent &&
                        !exfat_d_anon_disconn(alias)) {

                /*
                 * Unhashed alias is able to exist because of revalidate()
                 * called by lookup_fast. You can easily make this status
                 * by calling create and lookup concurrently
                 * In such case, we reuse an alias instead of new dentry
                 */
                if (d_unhashed(alias)) {
                        WARN_ON(alias->d_name.hash_len !=
                                dentry->d_name.hash_len);
                        exfat_info(sb, "rehashed a dentry(%p) in read lookup",
                                   alias);
                        d_drop(dentry);
                        d_rehash(alias);
                } else if (!S_ISDIR(i_mode)) {
                        /*
                         * This inode has non anonymous-DCACHE_DISCONNECTED
                         * dentry. This means, the user did ->lookup() by an
                         * another name (longname vs 8.3 alias of it) in past.
                         *
                         * Switch to new one for reason of locality if possible.
                         */
                        d_move(alias, dentry);
                }
                iput(inode);
                mutex_unlock(&EXFAT_SB(sb)->s_lock);
                return alias;
        }
        dput(alias);
out:
        mutex_unlock(&EXFAT_SB(sb)->s_lock);
        if (!inode)
                exfat_d_version_set(dentry, inode_query_iversion(dir));

        return d_splice_alias(inode, dentry);
unlock:
        mutex_unlock(&EXFAT_SB(sb)->s_lock);
        return ERR_PTR(err);
}

/* remove an entry, BUT don't truncate */
static int exfat_unlink(struct inode *dir, struct dentry *dentry)
{
        struct exfat_chain cdir;
        struct exfat_dentry *ep;
        struct super_block *sb = dir->i_sb;
        struct inode *inode = dentry->d_inode;
        struct exfat_inode_info *ei = EXFAT_I(inode);
        struct buffer_head *bh;
        sector_t sector;
        int num_entries, entry, err = 0;

        mutex_lock(&EXFAT_SB(sb)->s_lock);
        exfat_chain_dup(&cdir, &ei->dir);
        entry = ei->entry;
        if (ei->dir.dir == DIR_DELETED) {
                exfat_err(sb, "abnormal access to deleted dentry");
                err = -ENOENT;
                goto unlock;
        }

        ep = exfat_get_dentry(sb, &cdir, entry, &bh, &sector);
        if (!ep) {
                err = -EIO;
                goto unlock;
        }
        num_entries = exfat_count_ext_entries(sb, &cdir, entry, ep);
        if (num_entries < 0) {
                err = -EIO;
                brelse(bh);
                goto unlock;
        }
        num_entries++;
        brelse(bh);

        exfat_set_volume_dirty(sb);
        /* update the directory entry */
        if (exfat_remove_entries(dir, &cdir, entry, 0, num_entries)) {
                err = -EIO;
                goto unlock;
        }

        /* This doesn't modify ei */
        ei->dir.dir = DIR_DELETED;
        exfat_clear_volume_dirty(sb);

        inode_inc_iversion(dir);
        dir->i_mtime = dir->i_atime = current_time(dir);
        exfat_truncate_atime(&dir->i_atime);
        if (IS_DIRSYNC(dir))
                exfat_sync_inode(dir);
        else
                mark_inode_dirty(dir);

        clear_nlink(inode);
        inode->i_mtime = inode->i_atime = current_time(inode);
        exfat_truncate_atime(&inode->i_atime);
        exfat_unhash_inode(inode);
        exfat_d_version_set(dentry, inode_query_iversion(dir));
unlock:
        mutex_unlock(&EXFAT_SB(sb)->s_lock);
        return err;
}

static int exfat_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
                       struct dentry *dentry, umode_t mode)
{
        struct super_block *sb = dir->i_sb;
        struct inode *inode;
        struct exfat_dir_entry info;
        struct exfat_chain cdir;
        loff_t i_pos;
        int err;

        mutex_lock(&EXFAT_SB(sb)->s_lock);
        exfat_set_volume_dirty(sb);
        err = exfat_add_entry(dir, dentry->d_name.name, &cdir, TYPE_DIR,
                &info);
        exfat_clear_volume_dirty(sb);
        if (err)
                goto unlock;

        inode_inc_iversion(dir);
        dir->i_ctime = dir->i_mtime = current_time(dir);
        if (IS_DIRSYNC(dir))
                exfat_sync_inode(dir);
        else
                mark_inode_dirty(dir);
        inc_nlink(dir);

        i_pos = exfat_make_i_pos(&info);
        inode = exfat_build_inode(sb, &info, i_pos);
        err = PTR_ERR_OR_ZERO(inode);
        if (err)
                goto unlock;

        inode_inc_iversion(inode);
        inode->i_mtime = inode->i_atime = inode->i_ctime =
                EXFAT_I(inode)->i_crtime = current_time(inode);
        exfat_truncate_atime(&inode->i_atime);
        /* timestamp is already written, so mark_inode_dirty() is unneeded. */

        d_instantiate(dentry, inode);

unlock:
        mutex_unlock(&EXFAT_SB(sb)->s_lock);
        return err;
}

static int exfat_check_dir_empty(struct super_block *sb,
                struct exfat_chain *p_dir)
{
        int i, dentries_per_clu;
        unsigned int type;
        struct exfat_chain clu;
        struct exfat_dentry *ep;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        struct buffer_head *bh;

        dentries_per_clu = sbi->dentries_per_clu;

        exfat_chain_dup(&clu, p_dir);

        while (clu.dir != EXFAT_EOF_CLUSTER) {
                for (i = 0; i < dentries_per_clu; i++) {
                        ep = exfat_get_dentry(sb, &clu, i, &bh, NULL);
                        if (!ep)
                                return -EIO;
                        type = exfat_get_entry_type(ep);
                        brelse(bh);
                        if (type == TYPE_UNUSED)
                                return 0;

                        if (type != TYPE_FILE && type != TYPE_DIR)
                                continue;

                        return -ENOTEMPTY;
                }

                if (clu.flags == ALLOC_NO_FAT_CHAIN) {
                        if (--clu.size > 0)
                                clu.dir++;
                        else
                                clu.dir = EXFAT_EOF_CLUSTER;
                } else {
                        if (exfat_get_next_cluster(sb, &(clu.dir)))
                                return -EIO;
                }
        }

        return 0;
}

static int exfat_rmdir(struct inode *dir, struct dentry *dentry)
{
        struct inode *inode = dentry->d_inode;
        struct exfat_dentry *ep;
        struct exfat_chain cdir, clu_to_free;
        struct super_block *sb = inode->i_sb;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        struct exfat_inode_info *ei = EXFAT_I(inode);
        struct buffer_head *bh;
        sector_t sector;
        int num_entries, entry, err;

        mutex_lock(&EXFAT_SB(inode->i_sb)->s_lock);

        exfat_chain_dup(&cdir, &ei->dir);
        entry = ei->entry;

        if (ei->dir.dir == DIR_DELETED) {
                exfat_err(sb, "abnormal access to deleted dentry");
                err = -ENOENT;
                goto unlock;
        }

        exfat_chain_set(&clu_to_free, ei->start_clu,
                EXFAT_B_TO_CLU_ROUND_UP(i_size_read(inode), sbi), ei->flags);

        err = exfat_check_dir_empty(sb, &clu_to_free);
        if (err) {
                if (err == -EIO)
                        exfat_err(sb, "failed to exfat_check_dir_empty : err(%d)",
                                  err);
                goto unlock;
        }

        ep = exfat_get_dentry(sb, &cdir, entry, &bh, &sector);
        if (!ep) {
                err = -EIO;
                goto unlock;
        }

        num_entries = exfat_count_ext_entries(sb, &cdir, entry, ep);
        if (num_entries < 0) {
                err = -EIO;
                brelse(bh);
                goto unlock;
        }
        num_entries++;
        brelse(bh);

        exfat_set_volume_dirty(sb);
        err = exfat_remove_entries(dir, &cdir, entry, 0, num_entries);
        if (err) {
                exfat_err(sb, "failed to exfat_remove_entries : err(%d)", err);
                goto unlock;
        }
        ei->dir.dir = DIR_DELETED;
        exfat_clear_volume_dirty(sb);

        inode_inc_iversion(dir);
        dir->i_mtime = dir->i_atime = current_time(dir);
        exfat_truncate_atime(&dir->i_atime);
        if (IS_DIRSYNC(dir))
                exfat_sync_inode(dir);
        else
                mark_inode_dirty(dir);
        drop_nlink(dir);

        clear_nlink(inode);
        inode->i_mtime = inode->i_atime = current_time(inode);
        exfat_truncate_atime(&inode->i_atime);
        exfat_unhash_inode(inode);
        exfat_d_version_set(dentry, inode_query_iversion(dir));
unlock:
        mutex_unlock(&EXFAT_SB(inode->i_sb)->s_lock);
        return err;

}

static int exfat_rename_file(struct inode *inode, struct exfat_chain *p_dir,
                int oldentry, struct exfat_uni_name *p_uniname,
                struct exfat_inode_info *ei)
{
        int ret, num_old_entries, num_new_entries;
        sector_t sector_old, sector_new;
        struct exfat_dentry *epold, *epnew;
        struct super_block *sb = inode->i_sb;
        struct buffer_head *new_bh, *old_bh;
        int sync = IS_DIRSYNC(inode);

        epold = exfat_get_dentry(sb, p_dir, oldentry, &old_bh, &sector_old);
        if (!epold)
                return -EIO;

        num_old_entries = exfat_count_ext_entries(sb, p_dir, oldentry, epold);
        if (num_old_entries < 0)
                return -EIO;
        num_old_entries++;

        num_new_entries = exfat_calc_num_entries(p_uniname);
        if (num_new_entries < 0)
                return num_new_entries;

        if (num_old_entries < num_new_entries) {
                int newentry;

                newentry =
                        exfat_find_empty_entry(inode, p_dir, num_new_entries);
                if (newentry < 0)
                        return newentry; /* -EIO or -ENOSPC */

                epnew = exfat_get_dentry(sb, p_dir, newentry, &new_bh,
                        &sector_new);
                if (!epnew)
                        return -EIO;

                *epnew = *epold;
                if (exfat_get_entry_type(epnew) == TYPE_FILE) {
                        epnew->dentry.file.attr |= cpu_to_le16(ATTR_ARCHIVE);
                        ei->attr |= ATTR_ARCHIVE;
                }
                exfat_update_bh(new_bh, sync);
                brelse(old_bh);
                brelse(new_bh);

                epold = exfat_get_dentry(sb, p_dir, oldentry + 1, &old_bh,
                        &sector_old);
                if (!epold)
                        return -EIO;
                epnew = exfat_get_dentry(sb, p_dir, newentry + 1, &new_bh,
                        &sector_new);
                if (!epnew) {
                        brelse(old_bh);
                        return -EIO;
                }

                *epnew = *epold;
                exfat_update_bh(new_bh, sync);
                brelse(old_bh);
                brelse(new_bh);

                ret = exfat_init_ext_entry(inode, p_dir, newentry,
                        num_new_entries, p_uniname);
                if (ret)
                        return ret;

                exfat_remove_entries(inode, p_dir, oldentry, 0,
                        num_old_entries);
                ei->entry = newentry;
        } else {
                if (exfat_get_entry_type(epold) == TYPE_FILE) {
                        epold->dentry.file.attr |= cpu_to_le16(ATTR_ARCHIVE);
                        ei->attr |= ATTR_ARCHIVE;
                }
                exfat_update_bh(old_bh, sync);
                brelse(old_bh);
                ret = exfat_init_ext_entry(inode, p_dir, oldentry,
                        num_new_entries, p_uniname);
                if (ret)
                        return ret;

                exfat_remove_entries(inode, p_dir, oldentry, num_new_entries,
                        num_old_entries);
        }
        return 0;
}

static int exfat_move_file(struct inode *inode, struct exfat_chain *p_olddir,
                int oldentry, struct exfat_chain *p_newdir,
                struct exfat_uni_name *p_uniname, struct exfat_inode_info *ei)
{
        int ret, newentry, num_new_entries, num_old_entries;
        sector_t sector_mov, sector_new;
        struct exfat_dentry *epmov, *epnew;
        struct super_block *sb = inode->i_sb;
        struct buffer_head *mov_bh, *new_bh;

        epmov = exfat_get_dentry(sb, p_olddir, oldentry, &mov_bh, &sector_mov);
        if (!epmov)
                return -EIO;

        num_old_entries = exfat_count_ext_entries(sb, p_olddir, oldentry,
                epmov);
        if (num_old_entries < 0)
                return -EIO;
        num_old_entries++;

        num_new_entries = exfat_calc_num_entries(p_uniname);
        if (num_new_entries < 0)
                return num_new_entries;

        newentry = exfat_find_empty_entry(inode, p_newdir, num_new_entries);
        if (newentry < 0)
                return newentry; /* -EIO or -ENOSPC */

        epnew = exfat_get_dentry(sb, p_newdir, newentry, &new_bh, &sector_new);
        if (!epnew)
                return -EIO;

        *epnew = *epmov;
        if (exfat_get_entry_type(epnew) == TYPE_FILE) {
                epnew->dentry.file.attr |= cpu_to_le16(ATTR_ARCHIVE);
                ei->attr |= ATTR_ARCHIVE;
        }
        exfat_update_bh(new_bh, IS_DIRSYNC(inode));
        brelse(mov_bh);
        brelse(new_bh);

        epmov = exfat_get_dentry(sb, p_olddir, oldentry + 1, &mov_bh,
                &sector_mov);
        if (!epmov)
                return -EIO;
        epnew = exfat_get_dentry(sb, p_newdir, newentry + 1, &new_bh,
                &sector_new);
        if (!epnew) {
                brelse(mov_bh);
                return -EIO;
        }

        *epnew = *epmov;
        exfat_update_bh(new_bh, IS_DIRSYNC(inode));
        brelse(mov_bh);
        brelse(new_bh);

        ret = exfat_init_ext_entry(inode, p_newdir, newentry, num_new_entries,
                p_uniname);
        if (ret)
                return ret;

        exfat_remove_entries(inode, p_olddir, oldentry, 0, num_old_entries);

        exfat_chain_set(&ei->dir, p_newdir->dir, p_newdir->size,
                p_newdir->flags);

        ei->entry = newentry;
        return 0;
}

static void exfat_update_parent_info(struct exfat_inode_info *ei,
                struct inode *parent_inode)
{
        struct exfat_sb_info *sbi = EXFAT_SB(parent_inode->i_sb);
        struct exfat_inode_info *parent_ei = EXFAT_I(parent_inode);
        loff_t parent_isize = i_size_read(parent_inode);

        /*
         * the problem that struct exfat_inode_info caches wrong parent info.
         *
         * because of flag-mismatch of ei->dir,
         * there is abnormal traversing cluster chain.
         */
        if (unlikely(parent_ei->flags != ei->dir.flags ||
                     parent_isize != EXFAT_CLU_TO_B(ei->dir.size, sbi) ||
                     parent_ei->start_clu != ei->dir.dir)) {
                exfat_chain_set(&ei->dir, parent_ei->start_clu,
                        EXFAT_B_TO_CLU_ROUND_UP(parent_isize, sbi),
                        parent_ei->flags);
        }
}

/* rename or move a old file into a new file */
static int __exfat_rename(struct inode *old_parent_inode,
                struct exfat_inode_info *ei, struct inode *new_parent_inode,
                struct dentry *new_dentry)
{
        int ret;
        int dentry;
        struct exfat_chain olddir, newdir;
        struct exfat_chain *p_dir = NULL;
        struct exfat_uni_name uni_name;
        struct exfat_dentry *ep;
        struct super_block *sb = old_parent_inode->i_sb;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        const unsigned char *new_path = new_dentry->d_name.name;
        struct inode *new_inode = new_dentry->d_inode;
        int num_entries;
        struct exfat_inode_info *new_ei = NULL;
        unsigned int new_entry_type = TYPE_UNUSED;
        int new_entry = 0;
        struct buffer_head *old_bh, *new_bh = NULL;

        /* check the validity of pointer parameters */
        if (new_path == NULL || strlen(new_path) == 0)
                return -EINVAL;

        if (ei->dir.dir == DIR_DELETED) {
                exfat_err(sb, "abnormal access to deleted source dentry");
                return -ENOENT;
        }

        exfat_update_parent_info(ei, old_parent_inode);

        exfat_chain_dup(&olddir, &ei->dir);
        dentry = ei->entry;

        ep = exfat_get_dentry(sb, &olddir, dentry, &old_bh, NULL);
        if (!ep) {
                ret = -EIO;
                goto out;
        }
        brelse(old_bh);

        /* check whether new dir is existing directory and empty */
        if (new_inode) {
                ret = -EIO;
                new_ei = EXFAT_I(new_inode);

                if (new_ei->dir.dir == DIR_DELETED) {
                        exfat_err(sb, "abnormal access to deleted target dentry");
                        goto out;
                }

                exfat_update_parent_info(new_ei, new_parent_inode);

                p_dir = &(new_ei->dir);
                new_entry = new_ei->entry;
                ep = exfat_get_dentry(sb, p_dir, new_entry, &new_bh, NULL);
                if (!ep)
                        goto out;

                new_entry_type = exfat_get_entry_type(ep);
                brelse(new_bh);

                /* if new_inode exists, update ei */
                if (new_entry_type == TYPE_DIR) {
                        struct exfat_chain new_clu;

                        new_clu.dir = new_ei->start_clu;
                        new_clu.size =
                                EXFAT_B_TO_CLU_ROUND_UP(i_size_read(new_inode),
                                sbi);
                        new_clu.flags = new_ei->flags;

                        ret = exfat_check_dir_empty(sb, &new_clu);
                        if (ret)
                                goto out;
                }
        }

        /* check the validity of directory name in the given new pathname */
        ret = exfat_resolve_path(new_parent_inode, new_path, &newdir,
                        &uni_name);
        if (ret)
                goto out;

        exfat_set_volume_dirty(sb);

        if (olddir.dir == newdir.dir)
                ret = exfat_rename_file(new_parent_inode, &olddir, dentry,
                                &uni_name, ei);
        else
                ret = exfat_move_file(new_parent_inode, &olddir, dentry,
                                &newdir, &uni_name, ei);

        if (!ret && new_inode) {
                /* delete entries of new_dir */
                ep = exfat_get_dentry(sb, p_dir, new_entry, &new_bh, NULL);
                if (!ep) {
                        ret = -EIO;
                        goto del_out;
                }

                num_entries = exfat_count_ext_entries(sb, p_dir, new_entry, ep);
                if (num_entries < 0) {
                        ret = -EIO;
                        goto del_out;
                }
                brelse(new_bh);

                if (exfat_remove_entries(new_inode, p_dir, new_entry, 0,
                                num_entries + 1)) {
                        ret = -EIO;
                        goto del_out;
                }

                /* Free the clusters if new_inode is a dir(as if exfat_rmdir) */
                if (new_entry_type == TYPE_DIR) {
                        /* new_ei, new_clu_to_free */
                        struct exfat_chain new_clu_to_free;

                        exfat_chain_set(&new_clu_to_free, new_ei->start_clu,
                                EXFAT_B_TO_CLU_ROUND_UP(i_size_read(new_inode),
                                sbi), new_ei->flags);

                        if (exfat_free_cluster(new_inode, &new_clu_to_free)) {
                                /* just set I/O error only */
                                ret = -EIO;
                        }

                        i_size_write(new_inode, 0);
                        new_ei->start_clu = EXFAT_EOF_CLUSTER;
                        new_ei->flags = ALLOC_NO_FAT_CHAIN;
                }
del_out:
                /* Update new_inode ei
                 * Prevent syncing removed new_inode
                 * (new_ei is already initialized above code ("if (new_inode)")
                 */
                new_ei->dir.dir = DIR_DELETED;
        }
        exfat_clear_volume_dirty(sb);
out:
        return ret;
}

static int exfat_rename(struct user_namespace *mnt_userns,
                        struct inode *old_dir, struct dentry *old_dentry,
                        struct inode *new_dir, struct dentry *new_dentry,
                        unsigned int flags)
{
        struct inode *old_inode, *new_inode;
        struct super_block *sb = old_dir->i_sb;
        loff_t i_pos;
        int err;

        /*
         * The VFS already checks for existence, so for local filesystems
         * the RENAME_NOREPLACE implementation is equivalent to plain rename.
         * Don't support any other flags
         */
        if (flags & ~RENAME_NOREPLACE)
                return -EINVAL;

        mutex_lock(&EXFAT_SB(sb)->s_lock);
        old_inode = old_dentry->d_inode;
        new_inode = new_dentry->d_inode;

        err = __exfat_rename(old_dir, EXFAT_I(old_inode), new_dir, new_dentry);
        if (err)
                goto unlock;

        inode_inc_iversion(new_dir);
        new_dir->i_ctime = new_dir->i_mtime = new_dir->i_atime =
                EXFAT_I(new_dir)->i_crtime = current_time(new_dir);
        exfat_truncate_atime(&new_dir->i_atime);
        if (IS_DIRSYNC(new_dir))
                exfat_sync_inode(new_dir);
        else
                mark_inode_dirty(new_dir);

        i_pos = ((loff_t)EXFAT_I(old_inode)->dir.dir << 32) |
                (EXFAT_I(old_inode)->entry & 0xffffffff);
        exfat_unhash_inode(old_inode);
        exfat_hash_inode(old_inode, i_pos);
        if (IS_DIRSYNC(new_dir))
                exfat_sync_inode(old_inode);
        else
                mark_inode_dirty(old_inode);

        if (S_ISDIR(old_inode->i_mode) && old_dir != new_dir) {
                drop_nlink(old_dir);
                if (!new_inode)
                        inc_nlink(new_dir);
        }

        inode_inc_iversion(old_dir);
        old_dir->i_ctime = old_dir->i_mtime = current_time(old_dir);
        if (IS_DIRSYNC(old_dir))
                exfat_sync_inode(old_dir);
        else
                mark_inode_dirty(old_dir);

        if (new_inode) {
                exfat_unhash_inode(new_inode);

                /* skip drop_nlink if new_inode already has been dropped */
                if (new_inode->i_nlink) {
                        drop_nlink(new_inode);
                        if (S_ISDIR(new_inode->i_mode))
                                drop_nlink(new_inode);
                } else {
                        exfat_warn(sb, "abnormal access to an inode dropped");
                        WARN_ON(new_inode->i_nlink == 0);
                }
                new_inode->i_ctime = EXFAT_I(new_inode)->i_crtime =
                        current_time(new_inode);
        }

unlock:
        mutex_unlock(&EXFAT_SB(sb)->s_lock);
        return err;
}

const struct inode_operations exfat_dir_inode_operations = {
        .create         = exfat_create,
        .lookup         = exfat_lookup,
        .unlink         = exfat_unlink,
        .mkdir          = exfat_mkdir,
        .rmdir          = exfat_rmdir,
        .rename         = exfat_rename,
        .setattr        = exfat_setattr,
        .getattr        = exfat_getattr,
};