// SPDX-License-Identifier: GPL-2.0
/*
 * fs/f2fs/dir.c
 *
 * Copyright (c) 2012 Samsung Electronics Co., Ltd.
 *             http://www.samsung.com/
 */
#include <asm/unaligned.h>
#include <linux/fs.h>
#include <linux/f2fs_fs.h>
#include <linux/sched/signal.h>
#include <linux/unicode.h>
#include "f2fs.h"
#include "node.h"
#include "acl.h"
#include "xattr.h"
#include <trace/events/f2fs.h>

#ifdef CONFIG_UNICODE
extern struct kmem_cache *f2fs_cf_name_slab;
#endif

static unsigned long dir_blocks(struct inode *inode)
{
        return ((unsigned long long) (i_size_read(inode) + PAGE_SIZE - 1))
                                                        >> PAGE_SHIFT;
}

static unsigned int dir_buckets(unsigned int level, int dir_level)
{
        if (level + dir_level < MAX_DIR_HASH_DEPTH / 2)
                return 1 << (level + dir_level);
        else
                return MAX_DIR_BUCKETS;
}

static unsigned int bucket_blocks(unsigned int level)
{
        if (level < MAX_DIR_HASH_DEPTH / 2)
                return 2;
        else
                return 4;
}

static unsigned char f2fs_filetype_table[F2FS_FT_MAX] = {
        [F2FS_FT_UNKNOWN]       = DT_UNKNOWN,
        [F2FS_FT_REG_FILE]      = DT_REG,
        [F2FS_FT_DIR]           = DT_DIR,
        [F2FS_FT_CHRDEV]        = DT_CHR,
        [F2FS_FT_BLKDEV]        = DT_BLK,
        [F2FS_FT_FIFO]          = DT_FIFO,
        [F2FS_FT_SOCK]          = DT_SOCK,
        [F2FS_FT_SYMLINK]       = DT_LNK,
};

static unsigned char f2fs_type_by_mode[S_IFMT >> S_SHIFT] = {
        [S_IFREG >> S_SHIFT]    = F2FS_FT_REG_FILE,
        [S_IFDIR >> S_SHIFT]    = F2FS_FT_DIR,
        [S_IFCHR >> S_SHIFT]    = F2FS_FT_CHRDEV,
        [S_IFBLK >> S_SHIFT]    = F2FS_FT_BLKDEV,
        [S_IFIFO >> S_SHIFT]    = F2FS_FT_FIFO,
        [S_IFSOCK >> S_SHIFT]   = F2FS_FT_SOCK,
        [S_IFLNK >> S_SHIFT]    = F2FS_FT_SYMLINK,
};

static void set_de_type(struct f2fs_dir_entry *de, umode_t mode)
{
        de->file_type = f2fs_type_by_mode[(mode & S_IFMT) >> S_SHIFT];
}

unsigned char f2fs_get_de_type(struct f2fs_dir_entry *de)
{
        if (de->file_type < F2FS_FT_MAX)
                return f2fs_filetype_table[de->file_type];
        return DT_UNKNOWN;
}

/* If @dir is casefolded, initialize @fname->cf_name from @fname->usr_fname. */
int f2fs_init_casefolded_name(const struct inode *dir,
                              struct f2fs_filename *fname)
{
#ifdef CONFIG_UNICODE
        struct super_block *sb = dir->i_sb;

        if (IS_CASEFOLDED(dir)) {
                fname->cf_name.name = f2fs_kmem_cache_alloc(f2fs_cf_name_slab,
                                        GFP_NOFS, false, F2FS_SB(sb));
                if (!fname->cf_name.name)
                        return -ENOMEM;
                fname->cf_name.len = utf8_casefold(sb->s_encoding,
                                                   fname->usr_fname,
                                                   fname->cf_name.name,
                                                   F2FS_NAME_LEN);
                if ((int)fname->cf_name.len <= 0) {
                        kmem_cache_free(f2fs_cf_name_slab, fname->cf_name.name);
                        fname->cf_name.name = NULL;
                        if (sb_has_strict_encoding(sb))
                                return -EINVAL;
                        /* fall back to treating name as opaque byte sequence */
                }
        }
#endif
        return 0;
}

static int __f2fs_setup_filename(const struct inode *dir,
                                 const struct fscrypt_name *crypt_name,
                                 struct f2fs_filename *fname)
{
        int err;

        memset(fname, 0, sizeof(*fname));

        fname->usr_fname = crypt_name->usr_fname;
        fname->disk_name = crypt_name->disk_name;
#ifdef CONFIG_FS_ENCRYPTION
        fname->crypto_buf = crypt_name->crypto_buf;
#endif
        if (crypt_name->is_nokey_name) {
                /* hash was decoded from the no-key name */
                fname->hash = cpu_to_le32(crypt_name->hash);
        } else {
                err = f2fs_init_casefolded_name(dir, fname);
                if (err) {
                        f2fs_free_filename(fname);
                        return err;
                }
                f2fs_hash_filename(dir, fname);
        }
        return 0;
}

/*
 * Prepare to search for @iname in @dir.  This is similar to
 * fscrypt_setup_filename(), but this also handles computing the casefolded name
 * and the f2fs dirhash if needed, then packing all the information about this
 * filename up into a 'struct f2fs_filename'.
 */
int f2fs_setup_filename(struct inode *dir, const struct qstr *iname,
                        int lookup, struct f2fs_filename *fname)
{
        struct fscrypt_name crypt_name;
        int err;

        err = fscrypt_setup_filename(dir, iname, lookup, &crypt_name);
        if (err)
                return err;

        return __f2fs_setup_filename(dir, &crypt_name, fname);
}

/*
 * Prepare to look up @dentry in @dir.  This is similar to
 * fscrypt_prepare_lookup(), but this also handles computing the casefolded name
 * and the f2fs dirhash if needed, then packing all the information about this
 * filename up into a 'struct f2fs_filename'.
 */
int f2fs_prepare_lookup(struct inode *dir, struct dentry *dentry,
                        struct f2fs_filename *fname)
{
        struct fscrypt_name crypt_name;
        int err;

        err = fscrypt_prepare_lookup(dir, dentry, &crypt_name);
        if (err)
                return err;

        return __f2fs_setup_filename(dir, &crypt_name, fname);
}

void f2fs_free_filename(struct f2fs_filename *fname)
{
#ifdef CONFIG_FS_ENCRYPTION
        kfree(fname->crypto_buf.name);
        fname->crypto_buf.name = NULL;
#endif
#ifdef CONFIG_UNICODE
        if (fname->cf_name.name) {
                kmem_cache_free(f2fs_cf_name_slab, fname->cf_name.name);
                fname->cf_name.name = NULL;
        }
#endif
}

static unsigned long dir_block_index(unsigned int level,
                                int dir_level, unsigned int idx)
{
        unsigned long i;
        unsigned long bidx = 0;

        for (i = 0; i < level; i++)
                bidx += dir_buckets(i, dir_level) * bucket_blocks(i);
        bidx += idx * bucket_blocks(level);
        return bidx;
}

static struct f2fs_dir_entry *find_in_block(struct inode *dir,
                                struct page *dentry_page,
                                const struct f2fs_filename *fname,
                                int *max_slots)
{
        struct f2fs_dentry_block *dentry_blk;
        struct f2fs_dentry_ptr d;

        dentry_blk = (struct f2fs_dentry_block *)page_address(dentry_page);

        make_dentry_ptr_block(dir, &d, dentry_blk);
        return f2fs_find_target_dentry(&d, fname, max_slots);
}

#ifdef CONFIG_UNICODE
/*
 * Test whether a case-insensitive directory entry matches the filename
 * being searched for.
 *
 * Returns 1 for a match, 0 for no match, and -errno on an error.
 */
static int f2fs_match_ci_name(const struct inode *dir, const struct qstr *name,
                               const u8 *de_name, u32 de_name_len)
{
        const struct super_block *sb = dir->i_sb;
        const struct unicode_map *um = sb->s_encoding;
        struct fscrypt_str decrypted_name = FSTR_INIT(NULL, de_name_len);
        struct qstr entry = QSTR_INIT(de_name, de_name_len);
        int res;

        if (IS_ENCRYPTED(dir)) {
                const struct fscrypt_str encrypted_name =
                        FSTR_INIT((u8 *)de_name, de_name_len);

                if (WARN_ON_ONCE(!fscrypt_has_encryption_key(dir)))
                        return -EINVAL;

                decrypted_name.name = kmalloc(de_name_len, GFP_KERNEL);
                if (!decrypted_name.name)
                        return -ENOMEM;
                res = fscrypt_fname_disk_to_usr(dir, 0, 0, &encrypted_name,
                                                &decrypted_name);
                if (res < 0)
                        goto out;
                entry.name = decrypted_name.name;
                entry.len = decrypted_name.len;
        }

        res = utf8_strncasecmp_folded(um, name, &entry);
        /*
         * In strict mode, ignore invalid names.  In non-strict mode,
         * fall back to treating them as opaque byte sequences.
         */
        if (res < 0 && !sb_has_strict_encoding(sb)) {
                res = name->len == entry.len &&
                                memcmp(name->name, entry.name, name->len) == 0;
        } else {
                /* utf8_strncasecmp_folded returns 0 on match */
                res = (res == 0);
        }
out:
        kfree(decrypted_name.name);
        return res;
}
#endif /* CONFIG_UNICODE */

static inline int f2fs_match_name(const struct inode *dir,
                                   const struct f2fs_filename *fname,
                                   const u8 *de_name, u32 de_name_len)
{
        struct fscrypt_name f;

#ifdef CONFIG_UNICODE
        if (fname->cf_name.name) {
                struct qstr cf = FSTR_TO_QSTR(&fname->cf_name);

                return f2fs_match_ci_name(dir, &cf, de_name, de_name_len);
        }
#endif
        f.usr_fname = fname->usr_fname;
        f.disk_name = fname->disk_name;
#ifdef CONFIG_FS_ENCRYPTION
        f.crypto_buf = fname->crypto_buf;
#endif
        return fscrypt_match_name(&f, de_name, de_name_len);
}

struct f2fs_dir_entry *f2fs_find_target_dentry(const struct f2fs_dentry_ptr *d,
                        const struct f2fs_filename *fname, int *max_slots)
{
        struct f2fs_dir_entry *de;
        unsigned long bit_pos = 0;
        int max_len = 0;
        int res = 0;

        if (max_slots)
                *max_slots = 0;
        while (bit_pos < d->max) {
                if (!test_bit_le(bit_pos, d->bitmap)) {
                        bit_pos++;
                        max_len++;
                        continue;
                }

                de = &d->dentry[bit_pos];

                if (unlikely(!de->name_len)) {
                        bit_pos++;
                        continue;
                }

                if (de->hash_code == fname->hash) {
                        res = f2fs_match_name(d->inode, fname,
                                              d->filename[bit_pos],
                                              le16_to_cpu(de->name_len));
                        if (res < 0)
                                return ERR_PTR(res);
                        if (res)
                                goto found;
                }

                if (max_slots && max_len > *max_slots)
                        *max_slots = max_len;
                max_len = 0;

                bit_pos += GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
        }

        de = NULL;
found:
        if (max_slots && max_len > *max_slots)
                *max_slots = max_len;
        return de;
}

static struct f2fs_dir_entry *find_in_level(struct inode *dir,
                                        unsigned int level,
                                        const struct f2fs_filename *fname,
                                        struct page **res_page)
{
        int s = GET_DENTRY_SLOTS(fname->disk_name.len);
        unsigned int nbucket, nblock;
        unsigned int bidx, end_block;
        struct page *dentry_page;
        struct f2fs_dir_entry *de = NULL;
        bool room = false;
        int max_slots;

        nbucket = dir_buckets(level, F2FS_I(dir)->i_dir_level);
        nblock = bucket_blocks(level);

        bidx = dir_block_index(level, F2FS_I(dir)->i_dir_level,
                               le32_to_cpu(fname->hash) % nbucket);
        end_block = bidx + nblock;

        for (; bidx < end_block; bidx++) {
                /* no need to allocate new dentry pages to all the indices */
                dentry_page = f2fs_find_data_page(dir, bidx);
                if (IS_ERR(dentry_page)) {
                        if (PTR_ERR(dentry_page) == -ENOENT) {
                                room = true;
                                continue;
                        } else {
                                *res_page = dentry_page;
                                break;
                        }
                }

                de = find_in_block(dir, dentry_page, fname, &max_slots);
                if (IS_ERR(de)) {
                        *res_page = ERR_CAST(de);
                        de = NULL;
                        break;
                } else if (de) {
                        *res_page = dentry_page;
                        break;
                }

                if (max_slots >= s)
                        room = true;
                f2fs_put_page(dentry_page, 0);
        }

        if (!de && room && F2FS_I(dir)->chash != fname->hash) {
                F2FS_I(dir)->chash = fname->hash;
                F2FS_I(dir)->clevel = level;
        }

        return de;
}

struct f2fs_dir_entry *__f2fs_find_entry(struct inode *dir,
                                         const struct f2fs_filename *fname,
                                         struct page **res_page)
{
        unsigned long npages = dir_blocks(dir);
        struct f2fs_dir_entry *de = NULL;
        unsigned int max_depth;
        unsigned int level;

        *res_page = NULL;

        if (f2fs_has_inline_dentry(dir)) {
                de = f2fs_find_in_inline_dir(dir, fname, res_page);
                goto out;
        }

        if (npages == 0)
                goto out;

        max_depth = F2FS_I(dir)->i_current_depth;
        if (unlikely(max_depth > MAX_DIR_HASH_DEPTH)) {
                f2fs_warn(F2FS_I_SB(dir), "Corrupted max_depth of %lu: %u",
                          dir->i_ino, max_depth);
                max_depth = MAX_DIR_HASH_DEPTH;
                f2fs_i_depth_write(dir, max_depth);
        }

        for (level = 0; level < max_depth; level++) {
                de = find_in_level(dir, level, fname, res_page);
                if (de || IS_ERR(*res_page))
                        break;
        }
out:
        /* This is to increase the speed of f2fs_create */
        if (!de)
                F2FS_I(dir)->task = current;
        return de;
}

/*
 * Find an entry in the specified directory with the wanted name.
 * It returns the page where the entry was found (as a parameter - res_page),
 * and the entry itself. Page is returned mapped and unlocked.
 * Entry is guaranteed to be valid.
 */
struct f2fs_dir_entry *f2fs_find_entry(struct inode *dir,
                        const struct qstr *child, struct page **res_page)
{
        struct f2fs_dir_entry *de = NULL;
        struct f2fs_filename fname;
        int err;

        err = f2fs_setup_filename(dir, child, 1, &fname);
        if (err) {
                if (err == -ENOENT)
                        *res_page = NULL;
                else
                        *res_page = ERR_PTR(err);
                return NULL;
        }

        de = __f2fs_find_entry(dir, &fname, res_page);

        f2fs_free_filename(&fname);
        return de;
}

struct f2fs_dir_entry *f2fs_parent_dir(struct inode *dir, struct page **p)
{
        return f2fs_find_entry(dir, &dotdot_name, p);
}

ino_t f2fs_inode_by_name(struct inode *dir, const struct qstr *qstr,
                                                        struct page **page)
{
        ino_t res = 0;
        struct f2fs_dir_entry *de;

        de = f2fs_find_entry(dir, qstr, page);
        if (de) {
                res = le32_to_cpu(de->ino);
                f2fs_put_page(*page, 0);
        }

        return res;
}

void f2fs_set_link(struct inode *dir, struct f2fs_dir_entry *de,
                struct page *page, struct inode *inode)
{
        enum page_type type = f2fs_has_inline_dentry(dir) ? NODE : DATA;

        lock_page(page);
        f2fs_wait_on_page_writeback(page, type, true, true);
        de->ino = cpu_to_le32(inode->i_ino);
        set_de_type(de, inode->i_mode);
        set_page_dirty(page);

        dir->i_mtime = dir->i_ctime = current_time(dir);
        f2fs_mark_inode_dirty_sync(dir, false);
        f2fs_put_page(page, 1);
}

static void init_dent_inode(struct inode *dir, struct inode *inode,
                            const struct f2fs_filename *fname,
                            struct page *ipage)
{
        struct f2fs_inode *ri;

        if (!fname) /* tmpfile case? */
                return;

        f2fs_wait_on_page_writeback(ipage, NODE, true, true);

        /* copy name info. to this inode page */
        ri = F2FS_INODE(ipage);
        ri->i_namelen = cpu_to_le32(fname->disk_name.len);
        memcpy(ri->i_name, fname->disk_name.name, fname->disk_name.len);
        if (IS_ENCRYPTED(dir)) {
                file_set_enc_name(inode);
                /*
                 * Roll-forward recovery doesn't have encryption keys available,
                 * so it can't compute the dirhash for encrypted+casefolded
                 * filenames.  Append it to i_name if possible.  Else, disable
                 * roll-forward recovery of the dentry (i.e., make fsync'ing the
                 * file force a checkpoint) by setting LOST_PINO.
                 */
                if (IS_CASEFOLDED(dir)) {
                        if (fname->disk_name.len + sizeof(f2fs_hash_t) <=
                            F2FS_NAME_LEN)
                                put_unaligned(fname->hash, (f2fs_hash_t *)
                                        &ri->i_name[fname->disk_name.len]);
                        else
                                file_lost_pino(inode);
                }
        }
        set_page_dirty(ipage);
}

void f2fs_do_make_empty_dir(struct inode *inode, struct inode *parent,
                                        struct f2fs_dentry_ptr *d)
{
        struct fscrypt_str dot = FSTR_INIT(".", 1);
        struct fscrypt_str dotdot = FSTR_INIT("..", 2);

        /* update dirent of "." */
        f2fs_update_dentry(inode->i_ino, inode->i_mode, d, &dot, 0, 0);

        /* update dirent of ".." */
        f2fs_update_dentry(parent->i_ino, parent->i_mode, d, &dotdot, 0, 1);
}

static int make_empty_dir(struct inode *inode,
                struct inode *parent, struct page *page)
{
        struct page *dentry_page;
        struct f2fs_dentry_block *dentry_blk;
        struct f2fs_dentry_ptr d;

        if (f2fs_has_inline_dentry(inode))
                return f2fs_make_empty_inline_dir(inode, parent, page);

        dentry_page = f2fs_get_new_data_page(inode, page, 0, true);
        if (IS_ERR(dentry_page))
                return PTR_ERR(dentry_page);

        dentry_blk = page_address(dentry_page);

        make_dentry_ptr_block(NULL, &d, dentry_blk);
        f2fs_do_make_empty_dir(inode, parent, &d);

        set_page_dirty(dentry_page);
        f2fs_put_page(dentry_page, 1);
        return 0;
}

struct page *f2fs_init_inode_metadata(struct inode *inode, struct inode *dir,
                        const struct f2fs_filename *fname, struct page *dpage)
{
        struct page *page;
        int err;

        if (is_inode_flag_set(inode, FI_NEW_INODE)) {
                page = f2fs_new_inode_page(inode);
                if (IS_ERR(page))
                        return page;

                if (S_ISDIR(inode->i_mode)) {
                        /* in order to handle error case */
                        get_page(page);
                        err = make_empty_dir(inode, dir, page);
                        if (err) {
                                lock_page(page);
                                goto put_error;
                        }
                        put_page(page);
                }

                err = f2fs_init_acl(inode, dir, page, dpage);
                if (err)
                        goto put_error;

                err = f2fs_init_security(inode, dir,
                                         fname ? fname->usr_fname : NULL, page);
                if (err)
                        goto put_error;

                if (IS_ENCRYPTED(inode)) {
                        err = fscrypt_set_context(inode, page);
                        if (err)
                                goto put_error;
                }
        } else {
                page = f2fs_get_node_page(F2FS_I_SB(dir), inode->i_ino);
                if (IS_ERR(page))
                        return page;
        }

        init_dent_inode(dir, inode, fname, page);

        /*
         * This file should be checkpointed during fsync.
         * We lost i_pino from now on.
         */
        if (is_inode_flag_set(inode, FI_INC_LINK)) {
                if (!S_ISDIR(inode->i_mode))
                        file_lost_pino(inode);
                /*
                 * If link the tmpfile to alias through linkat path,
                 * we should remove this inode from orphan list.
                 */
                if (inode->i_nlink == 0)
                        f2fs_remove_orphan_inode(F2FS_I_SB(dir), inode->i_ino);
                f2fs_i_links_write(inode, true);
        }
        return page;

put_error:
        clear_nlink(inode);
        f2fs_update_inode(inode, page);
        f2fs_put_page(page, 1);
        return ERR_PTR(err);
}

void f2fs_update_parent_metadata(struct inode *dir, struct inode *inode,
                                                unsigned int current_depth)
{
        if (inode && is_inode_flag_set(inode, FI_NEW_INODE)) {
                if (S_ISDIR(inode->i_mode))
                        f2fs_i_links_write(dir, true);
                clear_inode_flag(inode, FI_NEW_INODE);
        }
        dir->i_mtime = dir->i_ctime = current_time(dir);
        f2fs_mark_inode_dirty_sync(dir, false);

        if (F2FS_I(dir)->i_current_depth != current_depth)
                f2fs_i_depth_write(dir, current_depth);

        if (inode && is_inode_flag_set(inode, FI_INC_LINK))
                clear_inode_flag(inode, FI_INC_LINK);
}

int f2fs_room_for_filename(const void *bitmap, int slots, int max_slots)
{
        int bit_start = 0;
        int zero_start, zero_end;
next:
        zero_start = find_next_zero_bit_le(bitmap, max_slots, bit_start);
        if (zero_start >= max_slots)
                return max_slots;

        zero_end = find_next_bit_le(bitmap, max_slots, zero_start);
        if (zero_end - zero_start >= slots)
                return zero_start;

        bit_start = zero_end + 1;

        if (zero_end + 1 >= max_slots)
                return max_slots;
        goto next;
}

bool f2fs_has_enough_room(struct inode *dir, struct page *ipage,
                          const struct f2fs_filename *fname)
{
        struct f2fs_dentry_ptr d;
        unsigned int bit_pos;
        int slots = GET_DENTRY_SLOTS(fname->disk_name.len);

        make_dentry_ptr_inline(dir, &d, inline_data_addr(dir, ipage));

        bit_pos = f2fs_room_for_filename(d.bitmap, slots, d.max);

        return bit_pos < d.max;
}

void f2fs_update_dentry(nid_t ino, umode_t mode, struct f2fs_dentry_ptr *d,
                        const struct fscrypt_str *name, f2fs_hash_t name_hash,
                        unsigned int bit_pos)
{
        struct f2fs_dir_entry *de;
        int slots = GET_DENTRY_SLOTS(name->len);
        int i;

        de = &d->dentry[bit_pos];
        de->hash_code = name_hash;
        de->name_len = cpu_to_le16(name->len);
        memcpy(d->filename[bit_pos], name->name, name->len);
        de->ino = cpu_to_le32(ino);
        set_de_type(de, mode);
        for (i = 0; i < slots; i++) {
                __set_bit_le(bit_pos + i, (void *)d->bitmap);
                /* avoid wrong garbage data for readdir */
                if (i)
                        (de + i)->name_len = 0;
        }
}

int f2fs_add_regular_entry(struct inode *dir, const struct f2fs_filename *fname,
                           struct inode *inode, nid_t ino, umode_t mode)
{
        unsigned int bit_pos;
        unsigned int level;
        unsigned int current_depth;
        unsigned long bidx, block;
        unsigned int nbucket, nblock;
        struct page *dentry_page = NULL;
        struct f2fs_dentry_block *dentry_blk = NULL;
        struct f2fs_dentry_ptr d;
        struct page *page = NULL;
        int slots, err = 0;

        level = 0;
        slots = GET_DENTRY_SLOTS(fname->disk_name.len);

        current_depth = F2FS_I(dir)->i_current_depth;
        if (F2FS_I(dir)->chash == fname->hash) {
                level = F2FS_I(dir)->clevel;
                F2FS_I(dir)->chash = 0;
        }

start:
        if (time_to_inject(F2FS_I_SB(dir), FAULT_DIR_DEPTH)) {
                f2fs_show_injection_info(F2FS_I_SB(dir), FAULT_DIR_DEPTH);
                return -ENOSPC;
        }

        if (unlikely(current_depth == MAX_DIR_HASH_DEPTH))
                return -ENOSPC;

        /* Increase the depth, if required */
        if (level == current_depth)
                ++current_depth;

        nbucket = dir_buckets(level, F2FS_I(dir)->i_dir_level);
        nblock = bucket_blocks(level);

        bidx = dir_block_index(level, F2FS_I(dir)->i_dir_level,
                                (le32_to_cpu(fname->hash) % nbucket));

        for (block = bidx; block <= (bidx + nblock - 1); block++) {
                dentry_page = f2fs_get_new_data_page(dir, NULL, block, true);
                if (IS_ERR(dentry_page))
                        return PTR_ERR(dentry_page);

                dentry_blk = page_address(dentry_page);
                bit_pos = f2fs_room_for_filename(&dentry_blk->dentry_bitmap,
                                                slots, NR_DENTRY_IN_BLOCK);
                if (bit_pos < NR_DENTRY_IN_BLOCK)
                        goto add_dentry;

                f2fs_put_page(dentry_page, 1);
        }

        /* Move to next level to find the empty slot for new dentry */
        ++level;
        goto start;
add_dentry:
        f2fs_wait_on_page_writeback(dentry_page, DATA, true, true);

        if (inode) {
                down_write(&F2FS_I(inode)->i_sem);
                page = f2fs_init_inode_metadata(inode, dir, fname, NULL);
                if (IS_ERR(page)) {
                        err = PTR_ERR(page);
                        goto fail;
                }
        }

        make_dentry_ptr_block(NULL, &d, dentry_blk);
        f2fs_update_dentry(ino, mode, &d, &fname->disk_name, fname->hash,
                           bit_pos);

        set_page_dirty(dentry_page);

        if (inode) {
                f2fs_i_pino_write(inode, dir->i_ino);

                /* synchronize inode page's data from inode cache */
                if (is_inode_flag_set(inode, FI_NEW_INODE))
                        f2fs_update_inode(inode, page);

                f2fs_put_page(page, 1);
        }

        f2fs_update_parent_metadata(dir, inode, current_depth);
fail:
        if (inode)
                up_write(&F2FS_I(inode)->i_sem);

        f2fs_put_page(dentry_page, 1);

        return err;
}

int f2fs_add_dentry(struct inode *dir, const struct f2fs_filename *fname,
                    struct inode *inode, nid_t ino, umode_t mode)
{
        int err = -EAGAIN;

        if (f2fs_has_inline_dentry(dir))
                err = f2fs_add_inline_entry(dir, fname, inode, ino, mode);
        if (err == -EAGAIN)
                err = f2fs_add_regular_entry(dir, fname, inode, ino, mode);

        f2fs_update_time(F2FS_I_SB(dir), REQ_TIME);
        return err;
}

/*
 * Caller should grab and release a rwsem by calling f2fs_lock_op() and
 * f2fs_unlock_op().
 */
int f2fs_do_add_link(struct inode *dir, const struct qstr *name,
                                struct inode *inode, nid_t ino, umode_t mode)
{
        struct f2fs_filename fname;
        struct page *page = NULL;
        struct f2fs_dir_entry *de = NULL;
        int err;

        err = f2fs_setup_filename(dir, name, 0, &fname);
        if (err)
                return err;

        /*
         * An immature stackable filesystem shows a race condition between lookup
         * and create. If we have same task when doing lookup and create, it's
         * definitely fine as expected by VFS normally. Otherwise, let's just
         * verify on-disk dentry one more time, which guarantees filesystem
         * consistency more.
         */
        if (current != F2FS_I(dir)->task) {
                de = __f2fs_find_entry(dir, &fname, &page);
                F2FS_I(dir)->task = NULL;
        }
        if (de) {
                f2fs_put_page(page, 0);
                err = -EEXIST;
        } else if (IS_ERR(page)) {
                err = PTR_ERR(page);
        } else {
                err = f2fs_add_dentry(dir, &fname, inode, ino, mode);
        }
        f2fs_free_filename(&fname);
        return err;
}

int f2fs_do_tmpfile(struct inode *inode, struct inode *dir)
{
        struct page *page;
        int err = 0;

        down_write(&F2FS_I(inode)->i_sem);
        page = f2fs_init_inode_metadata(inode, dir, NULL, NULL);
        if (IS_ERR(page)) {
                err = PTR_ERR(page);
                goto fail;
        }
        f2fs_put_page(page, 1);

        clear_inode_flag(inode, FI_NEW_INODE);
        f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
fail:
        up_write(&F2FS_I(inode)->i_sem);
        return err;
}

void f2fs_drop_nlink(struct inode *dir, struct inode *inode)
{
        struct f2fs_sb_info *sbi = F2FS_I_SB(dir);

        down_write(&F2FS_I(inode)->i_sem);

        if (S_ISDIR(inode->i_mode))
                f2fs_i_links_write(dir, false);
        inode->i_ctime = current_time(inode);

        f2fs_i_links_write(inode, false);
        if (S_ISDIR(inode->i_mode)) {
                f2fs_i_links_write(inode, false);
                f2fs_i_size_write(inode, 0);
        }
        up_write(&F2FS_I(inode)->i_sem);

        if (inode->i_nlink == 0)
                f2fs_add_orphan_inode(inode);
        else
                f2fs_release_orphan_inode(sbi);
}

/*
 * It only removes the dentry from the dentry page, corresponding name
 * entry in name page does not need to be touched during deletion.
 */
void f2fs_delete_entry(struct f2fs_dir_entry *dentry, struct page *page,
                                        struct inode *dir, struct inode *inode)
{
        struct  f2fs_dentry_block *dentry_blk;
        unsigned int bit_pos;
        int slots = GET_DENTRY_SLOTS(le16_to_cpu(dentry->name_len));
        int i;

        f2fs_update_time(F2FS_I_SB(dir), REQ_TIME);

        if (F2FS_OPTION(F2FS_I_SB(dir)).fsync_mode == FSYNC_MODE_STRICT)
                f2fs_add_ino_entry(F2FS_I_SB(dir), dir->i_ino, TRANS_DIR_INO);

        if (f2fs_has_inline_dentry(dir))
                return f2fs_delete_inline_entry(dentry, page, dir, inode);

        lock_page(page);
        f2fs_wait_on_page_writeback(page, DATA, true, true);

        dentry_blk = page_address(page);
        bit_pos = dentry - dentry_blk->dentry;
        for (i = 0; i < slots; i++)
                __clear_bit_le(bit_pos + i, &dentry_blk->dentry_bitmap);

        /* Let's check and deallocate this dentry page */
        bit_pos = find_next_bit_le(&dentry_blk->dentry_bitmap,
                        NR_DENTRY_IN_BLOCK,
                        0);
        set_page_dirty(page);

        if (bit_pos == NR_DENTRY_IN_BLOCK &&
                !f2fs_truncate_hole(dir, page->index, page->index + 1)) {
                f2fs_clear_page_cache_dirty_tag(page);
                clear_page_dirty_for_io(page);
                ClearPageUptodate(page);

                clear_page_private_gcing(page);

                inode_dec_dirty_pages(dir);
                f2fs_remove_dirty_inode(dir);

                detach_page_private(page);
                set_page_private(page, 0);
        }
        f2fs_put_page(page, 1);

        dir->i_ctime = dir->i_mtime = current_time(dir);
        f2fs_mark_inode_dirty_sync(dir, false);

        if (inode)
                f2fs_drop_nlink(dir, inode);
}

bool f2fs_empty_dir(struct inode *dir)
{
        unsigned long bidx;
        struct page *dentry_page;
        unsigned int bit_pos;
        struct f2fs_dentry_block *dentry_blk;
        unsigned long nblock = dir_blocks(dir);

        if (f2fs_has_inline_dentry(dir))
                return f2fs_empty_inline_dir(dir);

        for (bidx = 0; bidx < nblock; bidx++) {
                dentry_page = f2fs_get_lock_data_page(dir, bidx, false);
                if (IS_ERR(dentry_page)) {
                        if (PTR_ERR(dentry_page) == -ENOENT)
                                continue;
                        else
                                return false;
                }

                dentry_blk = page_address(dentry_page);
                if (bidx == 0)
                        bit_pos = 2;
                else
                        bit_pos = 0;
                bit_pos = find_next_bit_le(&dentry_blk->dentry_bitmap,
                                                NR_DENTRY_IN_BLOCK,
                                                bit_pos);

                f2fs_put_page(dentry_page, 1);

                if (bit_pos < NR_DENTRY_IN_BLOCK)
                        return false;
        }
        return true;
}

int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d,
                        unsigned int start_pos, struct fscrypt_str *fstr)
{
        unsigned char d_type = DT_UNKNOWN;
        unsigned int bit_pos;
        struct f2fs_dir_entry *de = NULL;
        struct fscrypt_str de_name = FSTR_INIT(NULL, 0);
        struct f2fs_sb_info *sbi = F2FS_I_SB(d->inode);

        struct blk_plug plug;
        bool readdir_ra = sbi->readdir_ra == 1;
        bool found_valid_dirent = false;
        int err = 0;

        bit_pos = ((unsigned long)ctx->pos % d->max);

        if (readdir_ra)
                blk_start_plug(&plug);

        while (bit_pos < d->max) {
                bit_pos = find_next_bit_le(d->bitmap, d->max, bit_pos);
                if (bit_pos >= d->max)
                        break;

                de = &d->dentry[bit_pos];
                if (de->name_len == 0) {
                        if (found_valid_dirent || !bit_pos) {
                                printk_ratelimited(
                                        "%sF2FS-fs (%s): invalid namelen(0), ino:%u, run fsck to fix.",
                                        KERN_WARNING, sbi->sb->s_id,
                                        le32_to_cpu(de->ino));
                                set_sbi_flag(sbi, SBI_NEED_FSCK);
                        }
                        bit_pos++;
                        ctx->pos = start_pos + bit_pos;
                        continue;
                }

                d_type = f2fs_get_de_type(de);

                de_name.name = d->filename[bit_pos];
                de_name.len = le16_to_cpu(de->name_len);

                /* check memory boundary before moving forward */
                bit_pos += GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
                if (unlikely(bit_pos > d->max ||
                                le16_to_cpu(de->name_len) > F2FS_NAME_LEN)) {
                        f2fs_warn(sbi, "%s: corrupted namelen=%d, run fsck to fix.",
                                  __func__, le16_to_cpu(de->name_len));
                        set_sbi_flag(sbi, SBI_NEED_FSCK);
                        err = -EFSCORRUPTED;
                        goto out;
                }

                if (IS_ENCRYPTED(d->inode)) {
                        int save_len = fstr->len;

                        err = fscrypt_fname_disk_to_usr(d->inode,
                                                (u32)le32_to_cpu(de->hash_code),
                                                0, &de_name, fstr);
                        if (err)
                                goto out;

                        de_name = *fstr;
                        fstr->len = save_len;
                }

                if (!dir_emit(ctx, de_name.name, de_name.len,
                                        le32_to_cpu(de->ino), d_type)) {
                        err = 1;
                        goto out;
                }

                if (readdir_ra)
                        f2fs_ra_node_page(sbi, le32_to_cpu(de->ino));

                ctx->pos = start_pos + bit_pos;
                found_valid_dirent = true;
        }
out:
        if (readdir_ra)
                blk_finish_plug(&plug);
        return err;
}

static int f2fs_readdir(struct file *file, struct dir_context *ctx)
{
        struct inode *inode = file_inode(file);
        unsigned long npages = dir_blocks(inode);
        struct f2fs_dentry_block *dentry_blk = NULL;
        struct page *dentry_page = NULL;
        struct file_ra_state *ra = &file->f_ra;
        loff_t start_pos = ctx->pos;
        unsigned int n = ((unsigned long)ctx->pos / NR_DENTRY_IN_BLOCK);
        struct f2fs_dentry_ptr d;
        struct fscrypt_str fstr = FSTR_INIT(NULL, 0);
        int err = 0;

        if (IS_ENCRYPTED(inode)) {
                err = fscrypt_prepare_readdir(inode);
                if (err)
                        goto out;

                err = fscrypt_fname_alloc_buffer(F2FS_NAME_LEN, &fstr);
                if (err < 0)
                        goto out;
        }

        if (f2fs_has_inline_dentry(inode)) {
                err = f2fs_read_inline_dir(file, ctx, &fstr);
                goto out_free;
        }

        for (; n < npages; n++, ctx->pos = n * NR_DENTRY_IN_BLOCK) {

                /* allow readdir() to be interrupted */
                if (fatal_signal_pending(current)) {
                        err = -ERESTARTSYS;
                        goto out_free;
                }
                cond_resched();

                /* readahead for multi pages of dir */
                if (npages - n > 1 && !ra_has_index(ra, n))
                        page_cache_sync_readahead(inode->i_mapping, ra, file, n,
                                min(npages - n, (pgoff_t)MAX_DIR_RA_PAGES));

                dentry_page = f2fs_find_data_page(inode, n);
                if (IS_ERR(dentry_page)) {
                        err = PTR_ERR(dentry_page);
                        if (err == -ENOENT) {
                                err = 0;
                                continue;
                        } else {
                                goto out_free;
                        }
                }

                dentry_blk = page_address(dentry_page);

                make_dentry_ptr_block(inode, &d, dentry_blk);

                err = f2fs_fill_dentries(ctx, &d,
                                n * NR_DENTRY_IN_BLOCK, &fstr);
                if (err) {
                        f2fs_put_page(dentry_page, 0);
                        break;
                }

                f2fs_put_page(dentry_page, 0);
        }
out_free:
        fscrypt_fname_free_buffer(&fstr);
out:
        trace_f2fs_readdir(inode, start_pos, ctx->pos, err);
        return err < 0 ? err : 0;
}

const struct file_operations f2fs_dir_operations = {
        .llseek         = generic_file_llseek,
        .read           = generic_read_dir,
        .iterate_shared = f2fs_readdir,
        .fsync          = f2fs_sync_file,
        .unlocked_ioctl = f2fs_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = f2fs_compat_ioctl,
#endif
};