// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/ext2/dir.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/dir.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  ext2 directory handling functions
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 *
 * All code that works with directory layout had been switched to pagecache
 * and moved here. AV
 */

#include "ext2.h"
#include <linux/buffer_head.h>
#include <linux/pagemap.h>
#include <linux/swap.h>

typedef struct ext2_dir_entry_2 ext2_dirent;

/*
 * Tests against MAX_REC_LEN etc were put in place for 64k block
 * sizes; if that is not possible on this arch, we can skip
 * those tests and speed things up.
 */
static inline unsigned ext2_rec_len_from_disk(__le16 dlen)
{
        unsigned len = le16_to_cpu(dlen);

#if (PAGE_SIZE >= 65536)
        if (len == EXT2_MAX_REC_LEN)
                return 1 << 16;
#endif
        return len;
}

static inline __le16 ext2_rec_len_to_disk(unsigned len)
{
#if (PAGE_SIZE >= 65536)
        if (len == (1 << 16))
                return cpu_to_le16(EXT2_MAX_REC_LEN);
        else
                BUG_ON(len > (1 << 16));
#endif
        return cpu_to_le16(len);
}

/*
 * ext2 uses block-sized chunks. Arguably, sector-sized ones would be
 * more robust, but we have what we have
 */
static inline unsigned ext2_chunk_size(struct inode *inode)
{
        return inode->i_sb->s_blocksize;
}

static inline void ext2_put_page(struct page *page)
{
        kunmap(page);
        put_page(page);
}

/*
 * Return the offset into page `page_nr' of the last valid
 * byte in that page, plus one.
 */
static unsigned
ext2_last_byte(struct inode *inode, unsigned long page_nr)
{
        unsigned last_byte = inode->i_size;

        last_byte -= page_nr << PAGE_SHIFT;
        if (last_byte > PAGE_SIZE)
                last_byte = PAGE_SIZE;
        return last_byte;
}

static int ext2_commit_chunk(struct page *page, loff_t pos, unsigned len)
{
        struct address_space *mapping = page->mapping;
        struct inode *dir = mapping->host;
        int err = 0;

        dir->i_version++;
        block_write_end(NULL, mapping, pos, len, len, page, NULL);

        if (pos+len > dir->i_size) {
                i_size_write(dir, pos+len);
                mark_inode_dirty(dir);
        }

        if (IS_DIRSYNC(dir)) {
                err = write_one_page(page);
                if (!err)
                        err = sync_inode_metadata(dir, 1);
        } else {
                unlock_page(page);
        }

        return err;
}

static bool ext2_check_page(struct page *page, int quiet)
{
        struct inode *dir = page->mapping->host;
        struct super_block *sb = dir->i_sb;
        unsigned chunk_size = ext2_chunk_size(dir);
        char *kaddr = page_address(page);
        u32 max_inumber = le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count);
        unsigned offs, rec_len;
        unsigned limit = PAGE_SIZE;
        ext2_dirent *p;
        char *error;

        if ((dir->i_size >> PAGE_SHIFT) == page->index) {
                limit = dir->i_size & ~PAGE_MASK;
                if (limit & (chunk_size - 1))
                        goto Ebadsize;
                if (!limit)
                        goto out;
        }
        for (offs = 0; offs <= limit - EXT2_DIR_REC_LEN(1); offs += rec_len) {
                p = (ext2_dirent *)(kaddr + offs);
                rec_len = ext2_rec_len_from_disk(p->rec_len);

                if (unlikely(rec_len < EXT2_DIR_REC_LEN(1)))
                        goto Eshort;
                if (unlikely(rec_len & 3))
                        goto Ealign;
                if (unlikely(rec_len < EXT2_DIR_REC_LEN(p->name_len)))
                        goto Enamelen;
                if (unlikely(((offs + rec_len - 1) ^ offs) & ~(chunk_size-1)))
                        goto Espan;
                if (unlikely(le32_to_cpu(p->inode) > max_inumber))
                        goto Einumber;
        }
        if (offs != limit)
                goto Eend;
out:
        SetPageChecked(page);
        return true;

        /* Too bad, we had an error */

Ebadsize:
        if (!quiet)
                ext2_error(sb, __func__,
                        "size of directory #%lu is not a multiple "
                        "of chunk size", dir->i_ino);
        goto fail;
Eshort:
        error = "rec_len is smaller than minimal";
        goto bad_entry;
Ealign:
        error = "unaligned directory entry";
        goto bad_entry;
Enamelen:
        error = "rec_len is too small for name_len";
        goto bad_entry;
Espan:
        error = "directory entry across blocks";
        goto bad_entry;
Einumber:
        error = "inode out of bounds";
bad_entry:
        if (!quiet)
                ext2_error(sb, __func__, "bad entry in directory #%lu: : %s - "
                        "offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
                        dir->i_ino, error, (page->index<<PAGE_SHIFT)+offs,
                        (unsigned long) le32_to_cpu(p->inode),
                        rec_len, p->name_len);
        goto fail;
Eend:
        if (!quiet) {
                p = (ext2_dirent *)(kaddr + offs);
                ext2_error(sb, "ext2_check_page",
                        "entry in directory #%lu spans the page boundary"
                        "offset=%lu, inode=%lu",
                        dir->i_ino, (page->index<<PAGE_SHIFT)+offs,
                        (unsigned long) le32_to_cpu(p->inode));
        }
fail:
        SetPageError(page);
        return false;
}

static struct page * ext2_get_page(struct inode *dir, unsigned long n,
                                   int quiet)
{
        struct address_space *mapping = dir->i_mapping;
        struct page *page = read_mapping_page(mapping, n, NULL);
        if (!IS_ERR(page)) {
                kmap(page);
                if (unlikely(!PageChecked(page))) {
                        if (PageError(page) || !ext2_check_page(page, quiet))
                                goto fail;
                }
        }
        return page;

fail:
        ext2_put_page(page);
        return ERR_PTR(-EIO);
}

/*
 * NOTE! unlike strncmp, ext2_match returns 1 for success, 0 for failure.
 *
 * len <= EXT2_NAME_LEN and de != NULL are guaranteed by caller.
 */
static inline int ext2_match (int len, const char * const name,
                                        struct ext2_dir_entry_2 * de)
{
        if (len != de->name_len)
                return 0;
        if (!de->inode)
                return 0;
        return !memcmp(name, de->name, len);
}

/*
 * p is at least 6 bytes before the end of page
 */
static inline ext2_dirent *ext2_next_entry(ext2_dirent *p)
{
        return (ext2_dirent *)((char *)p +
                        ext2_rec_len_from_disk(p->rec_len));
}

static inline unsigned 
ext2_validate_entry(char *base, unsigned offset, unsigned mask)
{
        ext2_dirent *de = (ext2_dirent*)(base + offset);
        ext2_dirent *p = (ext2_dirent*)(base + (offset&mask));
        while ((char*)p < (char*)de) {
                if (p->rec_len == 0)
                        break;
                p = ext2_next_entry(p);
        }
        return (char *)p - base;
}

static unsigned char ext2_filetype_table[EXT2_FT_MAX] = {
        [EXT2_FT_UNKNOWN]       = DT_UNKNOWN,
        [EXT2_FT_REG_FILE]      = DT_REG,
        [EXT2_FT_DIR]           = DT_DIR,
        [EXT2_FT_CHRDEV]        = DT_CHR,
        [EXT2_FT_BLKDEV]        = DT_BLK,
        [EXT2_FT_FIFO]          = DT_FIFO,
        [EXT2_FT_SOCK]          = DT_SOCK,
        [EXT2_FT_SYMLINK]       = DT_LNK,
};

#define S_SHIFT 12
static unsigned char ext2_type_by_mode[S_IFMT >> S_SHIFT] = {
        [S_IFREG >> S_SHIFT]    = EXT2_FT_REG_FILE,
        [S_IFDIR >> S_SHIFT]    = EXT2_FT_DIR,
        [S_IFCHR >> S_SHIFT]    = EXT2_FT_CHRDEV,
        [S_IFBLK >> S_SHIFT]    = EXT2_FT_BLKDEV,
        [S_IFIFO >> S_SHIFT]    = EXT2_FT_FIFO,
        [S_IFSOCK >> S_SHIFT]   = EXT2_FT_SOCK,
        [S_IFLNK >> S_SHIFT]    = EXT2_FT_SYMLINK,
};

static inline void ext2_set_de_type(ext2_dirent *de, struct inode *inode)
{
        umode_t mode = inode->i_mode;
        if (EXT2_HAS_INCOMPAT_FEATURE(inode->i_sb, EXT2_FEATURE_INCOMPAT_FILETYPE))
                de->file_type = ext2_type_by_mode[(mode & S_IFMT)>>S_SHIFT];
        else
                de->file_type = 0;
}

static int
ext2_readdir(struct file *file, struct dir_context *ctx)
{
        loff_t pos = ctx->pos;
        struct inode *inode = file_inode(file);
        struct super_block *sb = inode->i_sb;
        unsigned int offset = pos & ~PAGE_MASK;
        unsigned long n = pos >> PAGE_SHIFT;
        unsigned long npages = dir_pages(inode);
        unsigned chunk_mask = ~(ext2_chunk_size(inode)-1);
        unsigned char *types = NULL;
        int need_revalidate = file->f_version != inode->i_version;

        if (pos > inode->i_size - EXT2_DIR_REC_LEN(1))
                return 0;

        if (EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_FILETYPE))
                types = ext2_filetype_table;

        for ( ; n < npages; n++, offset = 0) {
                char *kaddr, *limit;
                ext2_dirent *de;
                struct page *page = ext2_get_page(inode, n, 0);

                if (IS_ERR(page)) {
                        ext2_error(sb, __func__,
                                   "bad page in #%lu",
                                   inode->i_ino);
                        ctx->pos += PAGE_SIZE - offset;
                        return PTR_ERR(page);
                }
                kaddr = page_address(page);
                if (unlikely(need_revalidate)) {
                        if (offset) {
                                offset = ext2_validate_entry(kaddr, offset, chunk_mask);
                                ctx->pos = (n<<PAGE_SHIFT) + offset;
                        }
                        file->f_version = inode->i_version;
                        need_revalidate = 0;
                }
                de = (ext2_dirent *)(kaddr+offset);
                limit = kaddr + ext2_last_byte(inode, n) - EXT2_DIR_REC_LEN(1);
                for ( ;(char*)de <= limit; de = ext2_next_entry(de)) {
                        if (de->rec_len == 0) {
                                ext2_error(sb, __func__,
                                        "zero-length directory entry");
                                ext2_put_page(page);
                                return -EIO;
                        }
                        if (de->inode) {
                                unsigned char d_type = DT_UNKNOWN;

                                if (types && de->file_type < EXT2_FT_MAX)
                                        d_type = types[de->file_type];

                                if (!dir_emit(ctx, de->name, de->name_len,
                                                le32_to_cpu(de->inode),
                                                d_type)) {
                                        ext2_put_page(page);
                                        return 0;
                                }
                        }
                        ctx->pos += ext2_rec_len_from_disk(de->rec_len);
                }
                ext2_put_page(page);
        }
        return 0;
}

/*
 *      ext2_find_entry()
 *
 * finds an entry in the specified directory with the wanted name. It
 * returns the page in which 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 ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
                        const struct qstr *child, struct page **res_page)
{
        const char *name = child->name;
        int namelen = child->len;
        unsigned reclen = EXT2_DIR_REC_LEN(namelen);
        unsigned long start, n;
        unsigned long npages = dir_pages(dir);
        struct page *page = NULL;
        struct ext2_inode_info *ei = EXT2_I(dir);
        ext2_dirent * de;
        int dir_has_error = 0;

        if (npages == 0)
                goto out;

        /* OFFSET_CACHE */
        *res_page = NULL;

        start = ei->i_dir_start_lookup;
        if (start >= npages)
                start = 0;
        n = start;
        do {
                char *kaddr;
                page = ext2_get_page(dir, n, dir_has_error);
                if (!IS_ERR(page)) {
                        kaddr = page_address(page);
                        de = (ext2_dirent *) kaddr;
                        kaddr += ext2_last_byte(dir, n) - reclen;
                        while ((char *) de <= kaddr) {
                                if (de->rec_len == 0) {
                                        ext2_error(dir->i_sb, __func__,
                                                "zero-length directory entry");
                                        ext2_put_page(page);
                                        goto out;
                                }
                                if (ext2_match (namelen, name, de))
                                        goto found;
                                de = ext2_next_entry(de);
                        }
                        ext2_put_page(page);
                } else
                        dir_has_error = 1;

                if (++n >= npages)
                        n = 0;
                /* next page is past the blocks we've got */
                if (unlikely(n > (dir->i_blocks >> (PAGE_SHIFT - 9)))) {
                        ext2_error(dir->i_sb, __func__,
                                "dir %lu size %lld exceeds block count %llu",
                                dir->i_ino, dir->i_size,
                                (unsigned long long)dir->i_blocks);
                        goto out;
                }
        } while (n != start);
out:
        return NULL;

found:
        *res_page = page;
        ei->i_dir_start_lookup = n;
        return de;
}

struct ext2_dir_entry_2 * ext2_dotdot (struct inode *dir, struct page **p)
{
        struct page *page = ext2_get_page(dir, 0, 0);
        ext2_dirent *de = NULL;

        if (!IS_ERR(page)) {
                de = ext2_next_entry((ext2_dirent *) page_address(page));
                *p = page;
        }
        return de;
}

ino_t ext2_inode_by_name(struct inode *dir, const struct qstr *child)
{
        ino_t res = 0;
        struct ext2_dir_entry_2 *de;
        struct page *page;
        
        de = ext2_find_entry (dir, child, &page);
        if (de) {
                res = le32_to_cpu(de->inode);
                ext2_put_page(page);
        }
        return res;
}

static int ext2_prepare_chunk(struct page *page, loff_t pos, unsigned len)
{
        return __block_write_begin(page, pos, len, ext2_get_block);
}

/* Releases the page */
void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
                   struct page *page, struct inode *inode, int update_times)
{
        loff_t pos = page_offset(page) +
                        (char *) de - (char *) page_address(page);
        unsigned len = ext2_rec_len_from_disk(de->rec_len);
        int err;

        lock_page(page);
        err = ext2_prepare_chunk(page, pos, len);
        BUG_ON(err);
        de->inode = cpu_to_le32(inode->i_ino);
        ext2_set_de_type(de, inode);
        err = ext2_commit_chunk(page, pos, len);
        ext2_put_page(page);
        if (update_times)
                dir->i_mtime = dir->i_ctime = current_time(dir);
        EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
        mark_inode_dirty(dir);
}

/*
 *      Parent is locked.
 */
int ext2_add_link (struct dentry *dentry, struct inode *inode)
{
        struct inode *dir = d_inode(dentry->d_parent);
        const char *name = dentry->d_name.name;
        int namelen = dentry->d_name.len;
        unsigned chunk_size = ext2_chunk_size(dir);
        unsigned reclen = EXT2_DIR_REC_LEN(namelen);
        unsigned short rec_len, name_len;
        struct page *page = NULL;
        ext2_dirent * de;
        unsigned long npages = dir_pages(dir);
        unsigned long n;
        char *kaddr;
        loff_t pos;
        int err;

        /*
         * We take care of directory expansion in the same loop.
         * This code plays outside i_size, so it locks the page
         * to protect that region.
         */
        for (n = 0; n <= npages; n++) {
                char *dir_end;

                page = ext2_get_page(dir, n, 0);
                err = PTR_ERR(page);
                if (IS_ERR(page))
                        goto out;
                lock_page(page);
                kaddr = page_address(page);
                dir_end = kaddr + ext2_last_byte(dir, n);
                de = (ext2_dirent *)kaddr;
                kaddr += PAGE_SIZE - reclen;
                while ((char *)de <= kaddr) {
                        if ((char *)de == dir_end) {
                                /* We hit i_size */
                                name_len = 0;
                                rec_len = chunk_size;
                                de->rec_len = ext2_rec_len_to_disk(chunk_size);
                                de->inode = 0;
                                goto got_it;
                        }
                        if (de->rec_len == 0) {
                                ext2_error(dir->i_sb, __func__,
                                        "zero-length directory entry");
                                err = -EIO;
                                goto out_unlock;
                        }
                        err = -EEXIST;
                        if (ext2_match (namelen, name, de))
                                goto out_unlock;
                        name_len = EXT2_DIR_REC_LEN(de->name_len);
                        rec_len = ext2_rec_len_from_disk(de->rec_len);
                        if (!de->inode && rec_len >= reclen)
                                goto got_it;
                        if (rec_len >= name_len + reclen)
                                goto got_it;
                        de = (ext2_dirent *) ((char *) de + rec_len);
                }
                unlock_page(page);
                ext2_put_page(page);
        }
        BUG();
        return -EINVAL;

got_it:
        pos = page_offset(page) +
                (char*)de - (char*)page_address(page);
        err = ext2_prepare_chunk(page, pos, rec_len);
        if (err)
                goto out_unlock;
        if (de->inode) {
                ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
                de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
                de->rec_len = ext2_rec_len_to_disk(name_len);
                de = de1;
        }
        de->name_len = namelen;
        memcpy(de->name, name, namelen);
        de->inode = cpu_to_le32(inode->i_ino);
        ext2_set_de_type (de, inode);
        err = ext2_commit_chunk(page, pos, rec_len);
        dir->i_mtime = dir->i_ctime = current_time(dir);
        EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
        mark_inode_dirty(dir);
        /* OFFSET_CACHE */
out_put:
        ext2_put_page(page);
out:
        return err;
out_unlock:
        unlock_page(page);
        goto out_put;
}

/*
 * ext2_delete_entry deletes a directory entry by merging it with the
 * previous entry. Page is up-to-date. Releases the page.
 */
int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
{
        struct inode *inode = page->mapping->host;
        char *kaddr = page_address(page);
        unsigned from = ((char*)dir - kaddr) & ~(ext2_chunk_size(inode)-1);
        unsigned to = ((char *)dir - kaddr) +
                                ext2_rec_len_from_disk(dir->rec_len);
        loff_t pos;
        ext2_dirent * pde = NULL;
        ext2_dirent * de = (ext2_dirent *) (kaddr + from);
        int err;

        while ((char*)de < (char*)dir) {
                if (de->rec_len == 0) {
                        ext2_error(inode->i_sb, __func__,
                                "zero-length directory entry");
                        err = -EIO;
                        goto out;
                }
                pde = de;
                de = ext2_next_entry(de);
        }
        if (pde)
                from = (char*)pde - (char*)page_address(page);
        pos = page_offset(page) + from;
        lock_page(page);
        err = ext2_prepare_chunk(page, pos, to - from);
        BUG_ON(err);
        if (pde)
                pde->rec_len = ext2_rec_len_to_disk(to - from);
        dir->inode = 0;
        err = ext2_commit_chunk(page, pos, to - from);
        inode->i_ctime = inode->i_mtime = current_time(inode);
        EXT2_I(inode)->i_flags &= ~EXT2_BTREE_FL;
        mark_inode_dirty(inode);
out:
        ext2_put_page(page);
        return err;
}

/*
 * Set the first fragment of directory.
 */
int ext2_make_empty(struct inode *inode, struct inode *parent)
{
        struct page *page = grab_cache_page(inode->i_mapping, 0);
        unsigned chunk_size = ext2_chunk_size(inode);
        struct ext2_dir_entry_2 * de;
        int err;
        void *kaddr;

        if (!page)
                return -ENOMEM;

        err = ext2_prepare_chunk(page, 0, chunk_size);
        if (err) {
                unlock_page(page);
                goto fail;
        }
        kaddr = kmap_atomic(page);
        memset(kaddr, 0, chunk_size);
        de = (struct ext2_dir_entry_2 *)kaddr;
        de->name_len = 1;
        de->rec_len = ext2_rec_len_to_disk(EXT2_DIR_REC_LEN(1));
        memcpy (de->name, ".\0\0", 4);
        de->inode = cpu_to_le32(inode->i_ino);
        ext2_set_de_type (de, inode);

        de = (struct ext2_dir_entry_2 *)(kaddr + EXT2_DIR_REC_LEN(1));
        de->name_len = 2;
        de->rec_len = ext2_rec_len_to_disk(chunk_size - EXT2_DIR_REC_LEN(1));
        de->inode = cpu_to_le32(parent->i_ino);
        memcpy (de->name, "..\0", 4);
        ext2_set_de_type (de, inode);
        kunmap_atomic(kaddr);
        err = ext2_commit_chunk(page, 0, chunk_size);
fail:
        put_page(page);
        return err;
}

/*
 * routine to check that the specified directory is empty (for rmdir)
 */
int ext2_empty_dir (struct inode * inode)
{
        struct page *page = NULL;
        unsigned long i, npages = dir_pages(inode);
        int dir_has_error = 0;

        for (i = 0; i < npages; i++) {
                char *kaddr;
                ext2_dirent * de;
                page = ext2_get_page(inode, i, dir_has_error);

                if (IS_ERR(page)) {
                        dir_has_error = 1;
                        continue;
                }

                kaddr = page_address(page);
                de = (ext2_dirent *)kaddr;
                kaddr += ext2_last_byte(inode, i) - EXT2_DIR_REC_LEN(1);

                while ((char *)de <= kaddr) {
                        if (de->rec_len == 0) {
                                ext2_error(inode->i_sb, __func__,
                                        "zero-length directory entry");
                                printk("kaddr=%p, de=%p\n", kaddr, de);
                                goto not_empty;
                        }
                        if (de->inode != 0) {
                                /* check for . and .. */
                                if (de->name[0] != '.')
                                        goto not_empty;
                                if (de->name_len > 2)
                                        goto not_empty;
                                if (de->name_len < 2) {
                                        if (de->inode !=
                                            cpu_to_le32(inode->i_ino))
                                                goto not_empty;
                                } else if (de->name[1] != '.')
                                        goto not_empty;
                        }
                        de = ext2_next_entry(de);
                }
                ext2_put_page(page);
        }
        return 1;

not_empty:
        ext2_put_page(page);
        return 0;
}

const struct file_operations ext2_dir_operations = {
        .llseek         = generic_file_llseek,
        .read           = generic_read_dir,
        .iterate_shared = ext2_readdir,
        .unlocked_ioctl = ext2_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = ext2_compat_ioctl,
#endif
        .fsync          = ext2_fsync,
};