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/*

 *  linux/fs/minix/dir.c

 *

 *  Copyright (C) 1991, 1992 Linus Torvalds

 *

 *  minix directory handling functions

 */

#include <linux/fs.h>

#include <linux/minix_fs.h>

#include <linux/pagemap.h>

typedef struct minix_dir_entry minix_dirent;

static int minix_readdir(struct file *, void *, filldir_t);

struct file_operations minix_dir_operations = {

        read:           generic_read_dir,

        readdir:        minix_readdir,

        fsync:          minix_sync_file,

};

static inline void dir_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 dir_commit_chunk(struct page *page, unsigned from, unsigned to)

{

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

        int err = 0;

        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 struct page * dir_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;

        }

        return page;

fail:

        dir_put_page(page);

        return ERR_PTR(-EIO);

}

static inline void *minix_next_entry(void *de, struct minix_sb_info *sbi)

{

        return (void*)((char*)de + sbi->s_dirsize);

}

static int minix_readdir(struct file * filp, void * dirent, filldir_t filldir)

{

        unsigned long 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);

        struct minix_sb_info *sbi = &sb->u.minix_sb;

        unsigned chunk_size = sbi->s_dirsize;

        pos = (pos + chunk_size-1) & ~(chunk_size-1);

        if (pos >= inode->i_size)

                goto done;

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

                char *p, *kaddr, *limit;

                struct page *page = dir_get_page(inode, n);

                if (IS_ERR(page))

                        continue;

                kaddr = (char *)page_address(page);

                p = kaddr+offset;

                limit = kaddr + PAGE_CACHE_SIZE - chunk_size;

                for ( ; p <= limit ; p = minix_next_entry(p, sbi)) {

                        minix_dirent *de = (minix_dirent *)p;

                        if (de->inode) {

                                int over;

                                unsigned l = strnlen(de->name,sbi->s_namelen);

                                offset = p - kaddr;

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

                                                (n<<PAGE_CACHE_SHIFT) | offset,

                                                de->inode, DT_UNKNOWN);

                                if (over) {

                                        dir_put_page(page);

                                        goto done;

                                }

                        }

                }

                dir_put_page(page);

        }

done:

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

        UPDATE_ATIME(inode);

        return 0;

}

static inline int namecompare(int len, int maxlen,

        const char * name, const char * buffer)

{

        if (len < maxlen && buffer[len])

                return 0;

        return !memcmp(name, buffer, len);

}

/*

 *      minix_find_entry()

 *

 * finds an entry in the specified directory with the wanted name. It

 * returns the cache buffer in which the entry was found, and the entry

 * itself (as a parameter - res_dir). It does NOT read the inode of the

 * entry - you'll have to do that yourself if you want to.

 */

minix_dirent *minix_find_entry(struct dentry *dentry, struct page **res_page)

{

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

        int namelen = dentry->d_name.len;

        struct inode * dir = dentry->d_parent->d_inode;

        struct super_block * sb = dir->i_sb;

        struct minix_sb_info * sbi = &sb->u.minix_sb;

        unsigned long n;

        unsigned long npages = dir_pages(dir);

        struct page *page = NULL;

        struct minix_dir_entry *de;

        *res_page = NULL;

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

                char *kaddr;

                page = dir_get_page(dir, n);

                if (IS_ERR(page))

                        continue;

                kaddr = (char*)page_address(page);

                de = (struct minix_dir_entry *) kaddr;

                kaddr += PAGE_CACHE_SIZE - sbi->s_dirsize;

                for ( ; (char *) de <= kaddr ; de = minix_next_entry(de,sbi)) {

                        if (!de->inode)

                                continue;

                        if (namecompare(namelen,sbi->s_namelen,name,de->name))

                                goto found;

                }

                dir_put_page(page);

        }

        return NULL;

found:

        *res_page = page;

        return de;

}

int minix_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;

        struct super_block * sb = dir->i_sb;

        struct minix_sb_info * sbi = &sb->u.minix_sb;

        struct page *page = NULL;

        struct minix_dir_entry * 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 = dir_get_page(dir, n);

                err = PTR_ERR(page);

                if (IS_ERR(page))

                        goto out;

                kaddr = (char*)page_address(page);

                de = (minix_dirent *)kaddr;

                kaddr += PAGE_CACHE_SIZE - sbi->s_dirsize;

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

                        if (!de->inode)

                                goto got_it;

                        err = -EEXIST;

                        if (namecompare(namelen,sbi->s_namelen,name,de->name))

                                goto out_page;

                        de = minix_next_entry(de, sbi);

                }

                dir_put_page(page);

        }

        BUG();

        return -EINVAL;

got_it:

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

        to = from + sbi->s_dirsize;

        lock_page(page);

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

        if (err)

                goto out_unlock;

        memcpy (de->name, name, namelen);

        memset (de->name + namelen, 0, sbi->s_dirsize - namelen - 2);

        de->inode = inode->i_ino;

        err = dir_commit_chunk(page, from, to);

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

        mark_inode_dirty(dir);

out_unlock:

        UnlockPage(page);

out_page:

        dir_put_page(page);

out:

        return err;

}

int minix_delete_entry(struct minix_dir_entry *de, struct page *page)

{

        struct address_space *mapping = page->mapping;

        struct inode *inode = (struct inode*)mapping->host;

        char *kaddr = (char*)page_address(page);

        unsigned from = (char*)de - kaddr;

        unsigned to = from + inode->i_sb->u.minix_sb.s_dirsize;

        int err;

        lock_page(page);

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

        if (err == 0) {

                de->inode = 0;

                err = dir_commit_chunk(page, from, to);

        }

        UnlockPage(page);

        dir_put_page(page);

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

        mark_inode_dirty(inode);

        return err;

}

int minix_make_empty(struct inode *inode, struct inode *dir)

{

        struct address_space *mapping = inode->i_mapping;

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

        struct minix_sb_info * sbi = &inode->i_sb->u.minix_sb;

        struct minix_dir_entry * de;

        char *base;

        int err;

        if (!page)

                return -ENOMEM;

        err = mapping->a_ops->prepare_write(NULL, page, 0, 2 * sbi->s_dirsize);

        if (err)

                goto fail;

        base = (char*)page_address(page);

        memset(base, 0, PAGE_CACHE_SIZE);

        de = (struct minix_dir_entry *) base;

        de->inode = inode->i_ino;

        strcpy(de->name,".");

        de = minix_next_entry(de, sbi);

        de->inode = dir->i_ino;

        strcpy(de->name,"..");

        err = dir_commit_chunk(page, 0, 2 * sbi->s_dirsize);

fail:

        UnlockPage(page);

        page_cache_release(page);

        return err;

}

/*

 * routine to check that the specified directory is empty (for rmdir)

 */

int minix_empty_dir(struct inode * inode)

{

        struct page *page = NULL;

        unsigned long i, npages = dir_pages(inode);

        struct minix_sb_info *sbi = &inode->i_sb->u.minix_sb;

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

                char *kaddr;

                minix_dirent * de;

                page = dir_get_page(inode, i);

                if (IS_ERR(page))

                        continue;

                kaddr = (char *)page_address(page);

                de = (minix_dirent *)kaddr;

                kaddr += PAGE_CACHE_SIZE - sbi->s_dirsize;

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

                        if (de->inode != 0) {

                                /* check for . and .. */

                                if (de->name[0] != '.')

                                        goto not_empty;

                                if (!de->name[1]) {

                                        if (de->inode != inode->i_ino)

                                                goto not_empty;

                                } else if (de->name[1] != '.')

                                        goto not_empty;

                                else if (de->name[2])

                                        goto not_empty;

                        }

                        de = minix_next_entry(de, sbi);

                }

                dir_put_page(page);

        }

        return 1;

not_empty:

        dir_put_page(page);

        return 0;

}

/* Releases the page */

void minix_set_link(struct minix_dir_entry *de, struct page *page,

        struct inode *inode)

{

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

        struct minix_sb_info *sbi = &dir->i_sb->u.minix_sb;

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

        unsigned to = from + sbi->s_dirsize;

        int err;

        lock_page(page);

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

        if (err == 0) {

                de->inode = inode->i_ino;

                err = dir_commit_chunk(page, from, to);

        }

        UnlockPage(page);

        dir_put_page(page);

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

        mark_inode_dirty(dir);

}

struct minix_dir_entry * minix_dotdot (struct inode *dir, struct page **p)

{

        struct page *page = dir_get_page(dir, 0);

        struct minix_sb_info *sbi = &dir->i_sb->u.minix_sb;

        struct minix_dir_entry *de = NULL;

        if (!IS_ERR(page)) {

                de = minix_next_entry(page_address(page), sbi);

                *p = page;

        }

        return de;

}

ino_t minix_inode_by_name(struct dentry *dentry)

{

        struct page *page;

        struct minix_dir_entry *de = minix_find_entry(dentry, &page);

        ino_t res = 0;

        if (de) {

                res = de->inode;

                dir_put_page(page);

        }

        return res;

}