// SPDX-License-Identifier: GPL-2.0+
/*
 * NILFS directory entry operations
 *
 * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
 *
 * Modified for NILFS by Amagai Yoshiji.
 */
/*
 *  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 <linux/pagemap.h>
#include <linux/filelock.h>
#include "nilfs.h"
#include "page.h"

static inline unsigned int nilfs_rec_len_from_disk(__le16 dlen)
{
        unsigned int len = le16_to_cpu(dlen);

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

static inline __le16 nilfs_rec_len_to_disk(unsigned int len)
{
#if (PAGE_SIZE >= 65536)
        if (len == (1 << 16))
                return cpu_to_le16(NILFS_MAX_REC_LEN);

        BUG_ON(len > (1 << 16));
#endif
        return cpu_to_le16(len);
}

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

/*
 * Return the offset into page `page_nr' of the last valid
 * byte in that page, plus one.
 */
static unsigned int nilfs_last_byte(struct inode *inode, unsigned long page_nr)
{
        u64 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 nilfs_prepare_chunk(struct folio *folio, unsigned int from,
                               unsigned int to)
{
        loff_t pos = folio_pos(folio) + from;

        return __block_write_begin(folio, pos, to - from, nilfs_get_block);
}

static void nilfs_commit_chunk(struct folio *folio,
                struct address_space *mapping, size_t from, size_t to)
{
        struct inode *dir = mapping->host;
        loff_t pos = folio_pos(folio) + from;
        size_t copied, len = to - from;
        unsigned int nr_dirty;
        int err;

        nr_dirty = nilfs_page_count_clean_buffers(folio, from, to);
        copied = block_write_end(pos, len, len, folio);
        if (pos + copied > dir->i_size)
                i_size_write(dir, pos + copied);
        if (IS_DIRSYNC(dir))
                nilfs_set_transaction_flag(NILFS_TI_SYNC);
        err = nilfs_set_file_dirty(dir, nr_dirty);
        WARN_ON(err); /* do not happen */
        folio_unlock(folio);
}

static bool nilfs_check_folio(struct folio *folio, char *kaddr)
{
        struct inode *dir = folio->mapping->host;
        struct super_block *sb = dir->i_sb;
        unsigned int chunk_size = nilfs_chunk_size(dir);
        size_t offs, rec_len;
        size_t limit = folio_size(folio);
        struct nilfs_dir_entry *p;
        char *error;

        if (dir->i_size < folio_pos(folio) + limit) {
                limit = dir->i_size - folio_pos(folio);
                if (limit & (chunk_size - 1))
                        goto Ebadsize;
                if (!limit)
                        goto out;
        }
        for (offs = 0; offs <= limit - NILFS_DIR_REC_LEN(1); offs += rec_len) {
                p = (struct nilfs_dir_entry *)(kaddr + offs);
                rec_len = nilfs_rec_len_from_disk(p->rec_len);

                if (rec_len < NILFS_DIR_REC_LEN(1))
                        goto Eshort;
                if (rec_len & 3)
                        goto Ealign;
                if (rec_len < NILFS_DIR_REC_LEN(p->name_len))
                        goto Enamelen;
                if (((offs + rec_len - 1) ^ offs) & ~(chunk_size-1))
                        goto Espan;
                if (unlikely(p->inode &&
                             NILFS_PRIVATE_INODE(le64_to_cpu(p->inode))))
                        goto Einumber;
        }
        if (offs != limit)
                goto Eend;
out:
        folio_set_checked(folio);
        return true;

        /* Too bad, we had an error */

Ebadsize:
        nilfs_error(sb,
                    "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 = "disallowed inode number";
bad_entry:
        nilfs_error(sb,
                    "bad entry in directory #%lu: %s - offset=%lu, inode=%lu, rec_len=%zd, name_len=%d",
                    dir->i_ino, error, (folio->index << PAGE_SHIFT) + offs,
                    (unsigned long)le64_to_cpu(p->inode),
                    rec_len, p->name_len);
        goto fail;
Eend:
        p = (struct nilfs_dir_entry *)(kaddr + offs);
        nilfs_error(sb,
                    "entry in directory #%lu spans the page boundary offset=%lu, inode=%lu",
                    dir->i_ino, (folio->index << PAGE_SHIFT) + offs,
                    (unsigned long)le64_to_cpu(p->inode));
fail:
        return false;
}

static void *nilfs_get_folio(struct inode *dir, unsigned long n,
                struct folio **foliop)
{
        struct address_space *mapping = dir->i_mapping;
        struct folio *folio = read_mapping_folio(mapping, n, NULL);
        void *kaddr;

        if (IS_ERR(folio))
                return folio;

        kaddr = kmap_local_folio(folio, 0);
        if (unlikely(!folio_test_checked(folio))) {
                if (!nilfs_check_folio(folio, kaddr))
                        goto fail;
        }

        *foliop = folio;
        return kaddr;

fail:
        folio_release_kmap(folio, kaddr);
        return ERR_PTR(-EIO);
}

/*
 * NOTE! unlike strncmp, nilfs_match returns 1 for success, 0 for failure.
 *
 * len <= NILFS_NAME_LEN and de != NULL are guaranteed by caller.
 */
static int
nilfs_match(int len, const unsigned char *name, struct nilfs_dir_entry *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 struct nilfs_dir_entry *nilfs_next_entry(struct nilfs_dir_entry *p)
{
        return (struct nilfs_dir_entry *)((char *)p +
                                          nilfs_rec_len_from_disk(p->rec_len));
}

static int nilfs_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);

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

        for ( ; n < npages; n++, offset = 0) {
                char *kaddr, *limit;
                struct nilfs_dir_entry *de;
                struct folio *folio;

                kaddr = nilfs_get_folio(inode, n, &folio);
                if (IS_ERR(kaddr)) {
                        nilfs_error(sb, "bad page in #%lu", inode->i_ino);
                        ctx->pos += PAGE_SIZE - offset;
                        return -EIO;
                }
                de = (struct nilfs_dir_entry *)(kaddr + offset);
                limit = kaddr + nilfs_last_byte(inode, n) -
                        NILFS_DIR_REC_LEN(1);
                for ( ; (char *)de <= limit; de = nilfs_next_entry(de)) {
                        if (de->rec_len == 0) {
                                nilfs_error(sb, "zero-length directory entry");
                                folio_release_kmap(folio, kaddr);
                                return -EIO;
                        }
                        if (de->inode) {
                                unsigned char t;

                                t = fs_ftype_to_dtype(de->file_type);

                                if (!dir_emit(ctx, de->name, de->name_len,
                                                le64_to_cpu(de->inode), t)) {
                                        folio_release_kmap(folio, kaddr);
                                        return 0;
                                }
                        }
                        ctx->pos += nilfs_rec_len_from_disk(de->rec_len);
                }
                folio_release_kmap(folio, kaddr);
        }
        return 0;
}

/*
 * nilfs_find_entry()
 *
 * Finds an entry in the specified directory with the wanted name. It
 * returns the folio in which the entry was found, and the entry itself.
 * The folio is mapped and unlocked.  When the caller is finished with
 * the entry, it should call folio_release_kmap().
 *
 * On failure, returns an error pointer and the caller should ignore foliop.
 */
struct nilfs_dir_entry *nilfs_find_entry(struct inode *dir,
                const struct qstr *qstr, struct folio **foliop)
{
        const unsigned char *name = qstr->name;
        int namelen = qstr->len;
        unsigned int reclen = NILFS_DIR_REC_LEN(namelen);
        unsigned long start, n;
        unsigned long npages = dir_pages(dir);
        struct nilfs_inode_info *ei = NILFS_I(dir);
        struct nilfs_dir_entry *de;

        if (npages == 0)
                goto out;

        start = ei->i_dir_start_lookup;
        if (start >= npages)
                start = 0;
        n = start;
        do {
                char *kaddr = nilfs_get_folio(dir, n, foliop);

                if (IS_ERR(kaddr))
                        return ERR_CAST(kaddr);

                de = (struct nilfs_dir_entry *)kaddr;
                kaddr += nilfs_last_byte(dir, n) - reclen;
                while ((char *)de <= kaddr) {
                        if (de->rec_len == 0) {
                                nilfs_error(dir->i_sb,
                                            "zero-length directory entry");
                                folio_release_kmap(*foliop, kaddr);
                                goto out;
                        }
                        if (nilfs_match(namelen, name, de))
                                goto found;
                        de = nilfs_next_entry(de);
                }
                folio_release_kmap(*foliop, kaddr);

                if (++n >= npages)
                        n = 0;
                /* next folio is past the blocks we've got */
                if (unlikely(n > (dir->i_blocks >> (PAGE_SHIFT - 9)))) {
                        nilfs_error(dir->i_sb,
                               "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 ERR_PTR(-ENOENT);

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

struct nilfs_dir_entry *nilfs_dotdot(struct inode *dir, struct folio **foliop)
{
        struct folio *folio;
        struct nilfs_dir_entry *de, *next_de;
        size_t limit;
        char *msg;

        de = nilfs_get_folio(dir, 0, &folio);
        if (IS_ERR(de))
                return NULL;

        limit = nilfs_last_byte(dir, 0);  /* is a multiple of chunk size */
        if (unlikely(!limit || le64_to_cpu(de->inode) != dir->i_ino ||
                     !nilfs_match(1, ".", de))) {
                msg = "missing '.'";
                goto fail;
        }

        next_de = nilfs_next_entry(de);
        /*
         * If "next_de" has not reached the end of the chunk, there is
         * at least one more record.  Check whether it matches "..".
         */
        if (unlikely((char *)next_de == (char *)de + nilfs_chunk_size(dir) ||
                     !nilfs_match(2, "..", next_de))) {
                msg = "missing '..'";
                goto fail;
        }
        *foliop = folio;
        return next_de;

fail:
        nilfs_error(dir->i_sb, "directory #%lu %s", dir->i_ino, msg);
        folio_release_kmap(folio, de);
        return NULL;
}

int nilfs_inode_by_name(struct inode *dir, const struct qstr *qstr, ino_t *ino)
{
        struct nilfs_dir_entry *de;
        struct folio *folio;

        de = nilfs_find_entry(dir, qstr, &folio);
        if (IS_ERR(de))
                return PTR_ERR(de);

        *ino = le64_to_cpu(de->inode);
        folio_release_kmap(folio, de);
        return 0;
}

int nilfs_set_link(struct inode *dir, struct nilfs_dir_entry *de,
                    struct folio *folio, struct inode *inode)
{
        size_t from = offset_in_folio(folio, de);
        size_t to = from + nilfs_rec_len_from_disk(de->rec_len);
        struct address_space *mapping = folio->mapping;
        int err;

        folio_lock(folio);
        err = nilfs_prepare_chunk(folio, from, to);
        if (unlikely(err)) {
                folio_unlock(folio);
                return err;
        }
        de->inode = cpu_to_le64(inode->i_ino);
        de->file_type = fs_umode_to_ftype(inode->i_mode);
        nilfs_commit_chunk(folio, mapping, from, to);
        inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
        return 0;
}

/*
 *      Parent is locked.
 */
int nilfs_add_link(struct dentry *dentry, struct inode *inode)
{
        struct inode *dir = d_inode(dentry->d_parent);
        const unsigned char *name = dentry->d_name.name;
        int namelen = dentry->d_name.len;
        unsigned int chunk_size = nilfs_chunk_size(dir);
        unsigned int reclen = NILFS_DIR_REC_LEN(namelen);
        unsigned short rec_len, name_len;
        struct folio *folio = NULL;
        struct nilfs_dir_entry *de;
        unsigned long npages = dir_pages(dir);
        unsigned long n;
        size_t from, to;
        int err;

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

                if (IS_ERR(kaddr))
                        return PTR_ERR(kaddr);
                folio_lock(folio);
                dir_end = kaddr + nilfs_last_byte(dir, n);
                de = (struct nilfs_dir_entry *)kaddr;
                kaddr += folio_size(folio) - reclen;
                while ((char *)de <= kaddr) {
                        if ((char *)de == dir_end) {
                                /* We hit i_size */
                                name_len = 0;
                                rec_len = chunk_size;
                                de->rec_len = nilfs_rec_len_to_disk(chunk_size);
                                de->inode = 0;
                                goto got_it;
                        }
                        if (de->rec_len == 0) {
                                nilfs_error(dir->i_sb,
                                            "zero-length directory entry");
                                err = -EIO;
                                goto out_unlock;
                        }
                        err = -EEXIST;
                        if (nilfs_match(namelen, name, de))
                                goto out_unlock;
                        name_len = NILFS_DIR_REC_LEN(de->name_len);
                        rec_len = nilfs_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 = (struct nilfs_dir_entry *)((char *)de + rec_len);
                }
                folio_unlock(folio);
                folio_release_kmap(folio, kaddr);
        }
        BUG();
        return -EINVAL;

got_it:
        from = offset_in_folio(folio, de);
        to = from + rec_len;
        err = nilfs_prepare_chunk(folio, from, to);
        if (err)
                goto out_unlock;
        if (de->inode) {
                struct nilfs_dir_entry *de1;

                de1 = (struct nilfs_dir_entry *)((char *)de + name_len);
                de1->rec_len = nilfs_rec_len_to_disk(rec_len - name_len);
                de->rec_len = nilfs_rec_len_to_disk(name_len);
                de = de1;
        }
        de->name_len = namelen;
        memcpy(de->name, name, namelen);
        de->inode = cpu_to_le64(inode->i_ino);
        de->file_type = fs_umode_to_ftype(inode->i_mode);
        nilfs_commit_chunk(folio, folio->mapping, from, to);
        inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
        nilfs_mark_inode_dirty(dir);
        /* OFFSET_CACHE */
out_put:
        folio_release_kmap(folio, de);
        return err;
out_unlock:
        folio_unlock(folio);
        goto out_put;
}

/*
 * nilfs_delete_entry deletes a directory entry by merging it with the
 * previous entry. Folio is up-to-date.
 */
int nilfs_delete_entry(struct nilfs_dir_entry *dir, struct folio *folio)
{
        struct address_space *mapping = folio->mapping;
        struct inode *inode = mapping->host;
        char *kaddr = (char *)((unsigned long)dir & ~(folio_size(folio) - 1));
        size_t from, to;
        struct nilfs_dir_entry *de, *pde = NULL;
        int err;

        from = ((char *)dir - kaddr) & ~(nilfs_chunk_size(inode) - 1);
        to = ((char *)dir - kaddr) + nilfs_rec_len_from_disk(dir->rec_len);
        de = (struct nilfs_dir_entry *)(kaddr + from);

        while ((char *)de < (char *)dir) {
                if (de->rec_len == 0) {
                        nilfs_error(inode->i_sb,
                                    "zero-length directory entry");
                        err = -EIO;
                        goto out;
                }
                pde = de;
                de = nilfs_next_entry(de);
        }
        if (pde)
                from = (char *)pde - kaddr;
        folio_lock(folio);
        err = nilfs_prepare_chunk(folio, from, to);
        if (unlikely(err)) {
                folio_unlock(folio);
                goto out;
        }
        if (pde)
                pde->rec_len = nilfs_rec_len_to_disk(to - from);
        dir->inode = 0;
        nilfs_commit_chunk(folio, mapping, from, to);
        inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
out:
        return err;
}

/*
 * Set the first fragment of directory.
 */
int nilfs_make_empty(struct inode *inode, struct inode *parent)
{
        struct address_space *mapping = inode->i_mapping;
        struct folio *folio = filemap_grab_folio(mapping, 0);
        unsigned int chunk_size = nilfs_chunk_size(inode);
        struct nilfs_dir_entry *de;
        int err;
        void *kaddr;

        if (IS_ERR(folio))
                return PTR_ERR(folio);

        err = nilfs_prepare_chunk(folio, 0, chunk_size);
        if (unlikely(err)) {
                folio_unlock(folio);
                goto fail;
        }
        kaddr = kmap_local_folio(folio, 0);
        memset(kaddr, 0, chunk_size);
        de = (struct nilfs_dir_entry *)kaddr;
        de->name_len = 1;
        de->rec_len = nilfs_rec_len_to_disk(NILFS_DIR_REC_LEN(1));
        memcpy(de->name, ".\0\0", 4);
        de->inode = cpu_to_le64(inode->i_ino);
        de->file_type = fs_umode_to_ftype(inode->i_mode);

        de = (struct nilfs_dir_entry *)(kaddr + NILFS_DIR_REC_LEN(1));
        de->name_len = 2;
        de->rec_len = nilfs_rec_len_to_disk(chunk_size - NILFS_DIR_REC_LEN(1));
        de->inode = cpu_to_le64(parent->i_ino);
        memcpy(de->name, "..\0", 4);
        de->file_type = fs_umode_to_ftype(inode->i_mode);
        kunmap_local(kaddr);
        nilfs_commit_chunk(folio, mapping, 0, chunk_size);
fail:
        folio_put(folio);
        return err;
}

/*
 * routine to check that the specified directory is empty (for rmdir)
 */
int nilfs_empty_dir(struct inode *inode)
{
        struct folio *folio = NULL;
        char *kaddr;
        unsigned long i, npages = dir_pages(inode);

        for (i = 0; i < npages; i++) {
                struct nilfs_dir_entry *de;

                kaddr = nilfs_get_folio(inode, i, &folio);
                if (IS_ERR(kaddr))
                        return 0;

                de = (struct nilfs_dir_entry *)kaddr;
                kaddr += nilfs_last_byte(inode, i) - NILFS_DIR_REC_LEN(1);

                while ((char *)de <= kaddr) {
                        if (de->rec_len == 0) {
                                nilfs_error(inode->i_sb,
                                            "zero-length directory entry (kaddr=%p, de=%p)",
                                            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_le64(inode->i_ino))
                                                goto not_empty;
                                } else if (de->name[1] != '.')
                                        goto not_empty;
                        }
                        de = nilfs_next_entry(de);
                }
                folio_release_kmap(folio, kaddr);
        }
        return 1;

not_empty:
        folio_release_kmap(folio, kaddr);
        return 0;
}

const struct file_operations nilfs_dir_operations = {
        .llseek         = generic_file_llseek,
        .read           = generic_read_dir,
        .iterate_shared = nilfs_readdir,
        .unlocked_ioctl = nilfs_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = nilfs_compat_ioctl,
#endif  /* CONFIG_COMPAT */
        .fsync          = nilfs_sync_file,
        .setlease       = generic_setlease,
};