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/*

 *  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/fs.h>

#include <linux/ext2_fs.h>

#include <linux/pagemap.h>

typedef struct ext2_dir_entry_2 ext2_dirent;

/*

 * 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);

        page_cache_release(page);

}

static inline unsigned long dir_pages(struct inode *inode)

{

        return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;

}

static int ext2_commit_chunk(struct page *page, unsigned from, unsigned to)

{

        struct inode *dir = page->mapping->host;

        int err = 0;

        dir->i_version = ++event;

        page->mapping->a_ops->commit_write(NULL, page, from, to);

        if (IS_SYNC(dir)) {

                int err2;

                err = writeout_one_page(page);

                err2 = waitfor_one_page(page);

                if (err == 0)

                        err = err2;

        }

        return err;

}

static void ext2_check_page(struct page *page)

{

        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(sb->u.ext2_sb.s_es->s_inodes_count);

        unsigned offs, rec_len;

        unsigned limit = PAGE_CACHE_SIZE;

        ext2_dirent *p;

        char *error;

        if ((dir->i_size >> PAGE_CACHE_SHIFT) == page->index) {

                limit = dir->i_size & ~PAGE_CACHE_MASK;

                if (limit & (chunk_size - 1))

                        goto Ebadsize;

                for (offs = limit; offs<PAGE_CACHE_SIZE; offs += chunk_size) {

                        ext2_dirent *p = (ext2_dirent*)(kaddr + offs);

                        p->rec_len = cpu_to_le16(chunk_size);

                }

                if (!limit)

                        goto out;

        }

        for (offs = 0; offs <= limit - EXT2_DIR_REC_LEN(1); offs += rec_len) {

                p = (ext2_dirent *)(kaddr + offs);

                rec_len = le16_to_cpu(p->rec_len);

                if (rec_len < EXT2_DIR_REC_LEN(1))

                        goto Eshort;

                if (rec_len & 3)

                        goto Ealign;

                if (rec_len < EXT2_DIR_REC_LEN(p->name_len))

                        goto Enamelen;

                if (((offs + rec_len - 1) ^ offs) & ~(chunk_size-1))

                        goto Espan;

                if (le32_to_cpu(p->inode) > max_inumber)

                        goto Einumber;

        }

        if (offs != limit)

                goto Eend;

out:

        SetPageChecked(page);

        return;

        /* Too bad, we had an error */

Ebadsize:

        ext2_error(sb, "ext2_check_page",

                "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:

        ext2_error (sb, "ext2_check_page", "bad entry in directory #%lu: %s - "

                "offset=%lu, inode=%lu, rec_len=%d, name_len=%d",

                dir->i_ino, error, (page->index<<PAGE_CACHE_SHIFT)+offs,

                (unsigned long) le32_to_cpu(p->inode),

                rec_len, p->name_len);

        goto fail;

Eend:

        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_CACHE_SHIFT)+offs,

                (unsigned long) le32_to_cpu(p->inode));

fail:

        SetPageChecked(page);

        SetPageError(page);

}

static struct page * ext2_get_page(struct inode *dir, unsigned long n)

{

        struct address_space *mapping = dir->i_mapping;

        struct page *page = read_cache_page(mapping, n,

                                (filler_t*)mapping->a_ops->readpage, NULL);

        if (!IS_ERR(page)) {

                wait_on_page(page);

                kmap(page);

                if (!Page_Uptodate(page))

                        goto fail;

                if (!PageChecked(page))

                        ext2_check_page(page);

                if (PageError(page))

                        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 + le16_to_cpu(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)

                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)

{

        mode_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 * filp, void * dirent, filldir_t filldir)

{

        loff_t pos = filp->f_pos;

        struct inode *inode = filp->f_dentry->d_inode;

        struct super_block *sb = inode->i_sb;

        unsigned offset = pos & ~PAGE_CACHE_MASK;

        unsigned long n = pos >> PAGE_CACHE_SHIFT;

        unsigned long npages = dir_pages(inode);

        unsigned chunk_mask = ~(ext2_chunk_size(inode)-1);

        unsigned char *types = NULL;

        int need_revalidate = (filp->f_version != inode->i_version);

        if (pos > inode->i_size - EXT2_DIR_REC_LEN(1))

                goto done;

        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);

                if (IS_ERR(page))

                        continue;

                kaddr = page_address(page);

                if (need_revalidate) {

                        offset = ext2_validate_entry(kaddr, offset, chunk_mask);

                        need_revalidate = 0;

                }

                de = (ext2_dirent *)(kaddr+offset);

                limit = kaddr + PAGE_CACHE_SIZE - EXT2_DIR_REC_LEN(1);

                for ( ;(char*)de <= limit; de = ext2_next_entry(de))

                        if (de->inode) {

                                int over;

                                unsigned char d_type = DT_UNKNOWN;

                                if (types && de->file_type < EXT2_FT_MAX)

                                        d_type = types[de->file_type];

                                offset = (char *)de - kaddr;

                                over = filldir(dirent, de->name, de->name_len,

                                                (n<<PAGE_CACHE_SHIFT) | offset,

                                                le32_to_cpu(de->inode), d_type);

                                if (over) {

                                        ext2_put_page(page);

                                        goto done;

                                }

                        }

                ext2_put_page(page);

        }

done:

        filp->f_pos = (n << PAGE_CACHE_SHIFT) | offset;

        filp->f_version = inode->i_version;

        UPDATE_ATIME(inode);

        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, and the entry itself

 * (as a parameter - res_dir). Page is returned mapped and unlocked.

 * Entry is guaranteed to be valid.

 */

struct ext2_dir_entry_2 * ext2_find_entry (struct inode * dir,

                        struct dentry *dentry, struct page ** res_page)

{

        const char *name = dentry->d_name.name;

        int namelen = dentry->d_name.len;

        unsigned reclen = EXT2_DIR_REC_LEN(namelen);

        unsigned long start, n;

        unsigned long npages = dir_pages(dir);

        struct page *page = NULL;

        ext2_dirent * de;

        /* OFFSET_CACHE */

        *res_page = NULL;

        start = dir->u.ext2_i.i_dir_start_lookup;

        if (start >= npages)

                start = 0;

        n = start;

        do {

                char *kaddr;

                page = ext2_get_page(dir, n);

                if (!IS_ERR(page)) {

                        kaddr = page_address(page);

                        de = (ext2_dirent *) kaddr;

                        kaddr += PAGE_CACHE_SIZE - reclen;

                        while ((char *) de <= kaddr) {

                                if (ext2_match (namelen, name, de))

                                        goto found;

                                de = ext2_next_entry(de);

                        }

                        ext2_put_page(page);

                }

                if (++n >= npages)

                        n = 0;

        } while (n != start);

        return NULL;

found:

        *res_page = page;

        dir->u.ext2_i.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);

        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, struct dentry *dentry)

{

        ino_t res = 0;

        struct ext2_dir_entry_2 * de;

        struct page *page;

        de = ext2_find_entry (dir, dentry, &page);

        if (de) {

                res = le32_to_cpu(de->inode);

                kunmap(page);

                page_cache_release(page);

        }

        return res;

}

/* Releases the page */

void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,

                        struct page *page, struct inode *inode)

{

        unsigned from = (char *) de - (char *) page_address(page);

        unsigned to = from + le16_to_cpu(de->rec_len);

        int err;

        lock_page(page);

        err = page->mapping->a_ops->prepare_write(NULL, page, from, to);

        if (err)

                BUG();

        de->inode = cpu_to_le32(inode->i_ino);

        ext2_set_de_type (de, inode);

        err = ext2_commit_chunk(page, from, to);

        UnlockPage(page);

        ext2_put_page(page);

        dir->i_mtime = dir->i_ctime = CURRENT_TIME;

        dir->u.ext2_i.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 = dentry->d_parent->d_inode;

        const char *name = dentry->d_name.name;

        int namelen = dentry->d_name.len;

        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;

        unsigned from, to;

        int err;

        /* We take care of directory expansion in the same loop */

        for (n = 0; n <= npages; n++) {

                page = ext2_get_page(dir, n);

                err = PTR_ERR(page);

                if (IS_ERR(page))

                        goto out;

                kaddr = page_address(page);

                de = (ext2_dirent *)kaddr;

                kaddr += PAGE_CACHE_SIZE - reclen;

                while ((char *)de <= kaddr) {

                        err = -EEXIST;

                        if (ext2_match (namelen, name, de))

                                goto out_page;

                        name_len = EXT2_DIR_REC_LEN(de->name_len);

                        rec_len = le16_to_cpu(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);

                }

                ext2_put_page(page);

        }

        BUG();

        return -EINVAL;

got_it:

        from = (char*)de - (char*)page_address(page);

        to = from + rec_len;

        lock_page(page);

        err = page->mapping->a_ops->prepare_write(NULL, page, from, to);

        if (err)

                goto out_unlock;

        if (de->inode) {

                ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);

                de1->rec_len = cpu_to_le16(rec_len - name_len);

                de->rec_len = cpu_to_le16(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, from, to);

        dir->i_mtime = dir->i_ctime = CURRENT_TIME;

        dir->u.ext2_i.i_flags &= ~EXT2_BTREE_FL;

        mark_inode_dirty(dir);

        /* OFFSET_CACHE */

out_unlock:

        UnlockPage(page);

out_page:

        ext2_put_page(page);

out:

        return err;

}

/*

 * 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 address_space *mapping = page->mapping;

        struct inode *inode = mapping->host;

        char *kaddr = page_address(page);

        unsigned from = ((char*)dir - kaddr) & ~(ext2_chunk_size(inode)-1);

        unsigned to = ((char*)dir - kaddr) + le16_to_cpu(dir->rec_len);

        ext2_dirent * pde = NULL;

        ext2_dirent * de = (ext2_dirent *) (kaddr + from);

        int err;

        while ((char*)de < (char*)dir) {

                pde = de;

                de = ext2_next_entry(de);

        }

        if (pde)

                from = (char*)pde - (char*)page_address(page);

        lock_page(page);

        err = mapping->a_ops->prepare_write(NULL, page, from, to);

        if (err)

                BUG();

        if (pde)

                pde->rec_len = cpu_to_le16(to-from);

        dir->inode = 0;

        err = ext2_commit_chunk(page, from, to);

        UnlockPage(page);

        ext2_put_page(page);

        inode->i_ctime = inode->i_mtime = CURRENT_TIME;

        inode->u.ext2_i.i_flags &= ~EXT2_BTREE_FL;

        mark_inode_dirty(inode);

        return err;

}

/*

 * Set the first fragment of directory.

 */

int ext2_make_empty(struct inode *inode, struct inode *parent)

{

        struct address_space *mapping = inode->i_mapping;

        struct page *page = grab_cache_page(mapping, 0);

        unsigned chunk_size = ext2_chunk_size(inode);

        struct ext2_dir_entry_2 * de;

        char *base;

        int err;

        if (!page)

                return -ENOMEM;

        err = mapping->a_ops->prepare_write(NULL, page, 0, chunk_size);

        if (err)

                goto fail;

        base = page_address(page);

        de = (struct ext2_dir_entry_2 *) base;

        de->name_len = 1;

        de->rec_len = cpu_to_le16(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 *) (base + EXT2_DIR_REC_LEN(1));

        de->name_len = 2;

        de->rec_len = cpu_to_le16(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);

        err = ext2_commit_chunk(page, 0, chunk_size);

fail:

        UnlockPage(page);

        page_cache_release(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);

        for (i = 0; i < npages; i++) {

                char *kaddr;

                ext2_dirent * de;

                page = ext2_get_page(inode, i);

                if (IS_ERR(page))

                        continue;

                kaddr = page_address(page);

                de = (ext2_dirent *)kaddr;

                kaddr += PAGE_CACHE_SIZE-EXT2_DIR_REC_LEN(1);

                while ((char *)de <= kaddr) {

                        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;

}

struct file_operations ext2_dir_operations = {

        read:           generic_read_dir,

        readdir:        ext2_readdir,

        ioctl:          ext2_ioctl,

        fsync:          ext2_sync_file,

};