/*
 * dir.c - NILFS directory entry operations
 *
 * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * 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 "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;
}

static inline void nilfs_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 int nilfs_last_byte(struct inode *inode, unsigned long page_nr)
{
        unsigned int 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 page *page, unsigned int from,
                               unsigned int to)
{
        loff_t pos = page_offset(page) + from;

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

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

        nr_dirty = nilfs_page_count_clean_buffers(page, from, to);
        copied = block_write_end(NULL, mapping, pos, len, len, page, NULL);
        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 */
        unlock_page(page);
}

static bool nilfs_check_page(struct page *page)
{
        struct inode *dir = page->mapping->host;
        struct super_block *sb = dir->i_sb;
        unsigned int chunk_size = nilfs_chunk_size(dir);
        char *kaddr = page_address(page);
        unsigned int offs, rec_len;
        unsigned int limit = PAGE_SIZE;
        struct nilfs_dir_entry *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 - 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 (offs != limit)
                goto Eend;
out:
        SetPageChecked(page);
        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";
bad_entry:
        nilfs_error(sb,
                    "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)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, (page->index << PAGE_SHIFT) + offs,
                    (unsigned long)le64_to_cpu(p->inode));
fail:
        SetPageError(page);
        return false;
}

static struct page *nilfs_get_page(struct inode *dir, unsigned long n)
{
        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) || !nilfs_check_page(page))
                                goto fail;
                }
        }
        return page;

fail:
        nilfs_put_page(page);
        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 unsigned char
nilfs_filetype_table[NILFS_FT_MAX] = {
        [NILFS_FT_UNKNOWN]      = DT_UNKNOWN,
        [NILFS_FT_REG_FILE]     = DT_REG,
        [NILFS_FT_DIR]          = DT_DIR,
        [NILFS_FT_CHRDEV]       = DT_CHR,
        [NILFS_FT_BLKDEV]       = DT_BLK,
        [NILFS_FT_FIFO]         = DT_FIFO,
        [NILFS_FT_SOCK]         = DT_SOCK,
        [NILFS_FT_SYMLINK]      = DT_LNK,
};

#define S_SHIFT 12
static unsigned char
nilfs_type_by_mode[S_IFMT >> S_SHIFT] = {
        [S_IFREG >> S_SHIFT]    = NILFS_FT_REG_FILE,
        [S_IFDIR >> S_SHIFT]    = NILFS_FT_DIR,
        [S_IFCHR >> S_SHIFT]    = NILFS_FT_CHRDEV,
        [S_IFBLK >> S_SHIFT]    = NILFS_FT_BLKDEV,
        [S_IFIFO >> S_SHIFT]    = NILFS_FT_FIFO,
        [S_IFSOCK >> S_SHIFT]   = NILFS_FT_SOCK,
        [S_IFLNK >> S_SHIFT]    = NILFS_FT_SYMLINK,
};

static void nilfs_set_de_type(struct nilfs_dir_entry *de, struct inode *inode)
{
        umode_t mode = inode->i_mode;

        de->file_type = nilfs_type_by_mode[(mode & S_IFMT)>>S_SHIFT];
}

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 page *page = nilfs_get_page(inode, n);

                if (IS_ERR(page)) {
                        nilfs_error(sb, "bad page in #%lu", inode->i_ino);
                        ctx->pos += PAGE_SIZE - offset;
                        return -EIO;
                }
                kaddr = page_address(page);
                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");
                                nilfs_put_page(page);
                                return -EIO;
                        }
                        if (de->inode) {
                                unsigned char t;

                                if (de->file_type < NILFS_FT_MAX)
                                        t = nilfs_filetype_table[de->file_type];
                                else
                                        t = DT_UNKNOWN;

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

/*
 *      nilfs_find_entry()
 *
 * finds an entry in the specified directory with the wanted name. It
 * returns the page in which the entry was found, and the entry itself
 * (as a parameter - res_dir). Page is returned mapped and unlocked.
 * Entry is guaranteed to be valid.
 */
struct nilfs_dir_entry *
nilfs_find_entry(struct inode *dir, const struct qstr *qstr,
                 struct page **res_page)
{
        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 page *page = NULL;
        struct nilfs_inode_info *ei = NILFS_I(dir);
        struct nilfs_dir_entry *de;

        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 = nilfs_get_page(dir, n);
                if (!IS_ERR(page)) {
                        kaddr = page_address(page);
                        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");
                                        nilfs_put_page(page);
                                        goto out;
                                }
                                if (nilfs_match(namelen, name, de))
                                        goto found;
                                de = nilfs_next_entry(de);
                        }
                        nilfs_put_page(page);
                }
                if (++n >= npages)
                        n = 0;
                /* next page 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 NULL;

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

struct nilfs_dir_entry *nilfs_dotdot(struct inode *dir, struct page **p)
{
        struct page *page = nilfs_get_page(dir, 0);
        struct nilfs_dir_entry *de = NULL;

        if (!IS_ERR(page)) {
                de = nilfs_next_entry(
                        (struct nilfs_dir_entry *)page_address(page));
                *p = page;
        }
        return de;
}

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

        de = nilfs_find_entry(dir, qstr, &page);
        if (de) {
                res = le64_to_cpu(de->inode);
                kunmap(page);
                put_page(page);
        }
        return res;
}

/* Releases the page */
void nilfs_set_link(struct inode *dir, struct nilfs_dir_entry *de,
                    struct page *page, struct inode *inode)
{
        unsigned int from = (char *)de - (char *)page_address(page);
        unsigned int to = from + nilfs_rec_len_from_disk(de->rec_len);
        struct address_space *mapping = page->mapping;
        int err;

        lock_page(page);
        err = nilfs_prepare_chunk(page, from, to);
        BUG_ON(err);
        de->inode = cpu_to_le64(inode->i_ino);
        nilfs_set_de_type(de, inode);
        nilfs_commit_chunk(page, mapping, from, to);
        nilfs_put_page(page);
        dir->i_mtime = dir->i_ctime = current_time(dir);
}

/*
 *      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 page *page = NULL;
        struct nilfs_dir_entry *de;
        unsigned long npages = dir_pages(dir);
        unsigned long n;
        char *kaddr;
        unsigned int from, to;
        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 = nilfs_get_page(dir, n);
                err = PTR_ERR(page);
                if (IS_ERR(page))
                        goto out;
                lock_page(page);
                kaddr = page_address(page);
                dir_end = kaddr + nilfs_last_byte(dir, n);
                de = (struct nilfs_dir_entry *)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 = 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);
                }
                unlock_page(page);
                nilfs_put_page(page);
        }
        BUG();
        return -EINVAL;

got_it:
        from = (char *)de - (char *)page_address(page);
        to = from + rec_len;
        err = nilfs_prepare_chunk(page, 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);
        nilfs_set_de_type(de, inode);
        nilfs_commit_chunk(page, page->mapping, from, to);
        dir->i_mtime = dir->i_ctime = current_time(dir);
        nilfs_mark_inode_dirty(dir);
        /* OFFSET_CACHE */
out_put:
        nilfs_put_page(page);
out:
        return err;
out_unlock:
        unlock_page(page);
        goto out_put;
}

/*
 * nilfs_delete_entry deletes a directory entry by merging it with the
 * previous entry. Page is up-to-date. Releases the page.
 */
int nilfs_delete_entry(struct nilfs_dir_entry *dir, struct page *page)
{
        struct address_space *mapping = page->mapping;
        struct inode *inode = mapping->host;
        char *kaddr = page_address(page);
        unsigned int 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 - (char *)page_address(page);
        lock_page(page);
        err = nilfs_prepare_chunk(page, from, to);
        BUG_ON(err);
        if (pde)
                pde->rec_len = nilfs_rec_len_to_disk(to - from);
        dir->inode = 0;
        nilfs_commit_chunk(page, mapping, from, to);
        inode->i_ctime = inode->i_mtime = current_time(inode);
out:
        nilfs_put_page(page);
        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 page *page = grab_cache_page(mapping, 0);
        unsigned int chunk_size = nilfs_chunk_size(inode);
        struct nilfs_dir_entry *de;
        int err;
        void *kaddr;

        if (!page)
                return -ENOMEM;

        err = nilfs_prepare_chunk(page, 0, chunk_size);
        if (unlikely(err)) {
                unlock_page(page);
                goto fail;
        }
        kaddr = kmap_atomic(page);
        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);
        nilfs_set_de_type(de, inode);

        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);
        nilfs_set_de_type(de, inode);
        kunmap_atomic(kaddr);
        nilfs_commit_chunk(page, mapping, 0, chunk_size);
fail:
        put_page(page);
        return err;
}

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

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

                page = nilfs_get_page(inode, i);
                if (IS_ERR(page))
                        continue;

                kaddr = page_address(page);
                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);
                }
                nilfs_put_page(page);
        }
        return 1;

not_empty:
        nilfs_put_page(page);
        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,

};