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[linux/fpc-iii.git] / fs / sysv / dir.c

/*
 *  linux/fs/sysv/dir.c
 *
 *  minix/dir.c
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  coh/dir.c
 *  Copyright (C) 1993  Pascal Haible, Bruno Haible
 *
 *  sysv/dir.c
 *  Copyright (C) 1993  Bruno Haible
 *
 *  SystemV/Coherent directory handling functions
 */

#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/swap.h>
#include "sysv.h"

static int sysv_readdir(struct file *, struct dir_context *);

const struct file_operations sysv_dir_operations = {
        .llseek         = generic_file_llseek,
        .read           = generic_read_dir,
        .iterate        = sysv_readdir,
        .fsync          = generic_file_fsync,
};

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

        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, 1);
        else
                unlock_page(page);
        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_mapping_page(mapping, n, NULL);
        if (!IS_ERR(page))
                kmap(page);
        return page;
}

static int sysv_readdir(struct file *file, struct dir_context *ctx)
{
        unsigned long pos = ctx->pos;
        struct inode *inode = file_inode(file);
        struct super_block *sb = inode->i_sb;
        unsigned long npages = dir_pages(inode);
        unsigned offset;
        unsigned long n;

        ctx->pos = pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
        if (pos >= inode->i_size)
                return 0;

        offset = pos & ~PAGE_CACHE_MASK;
        n = pos >> PAGE_CACHE_SHIFT;

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

                if (IS_ERR(page))
                        continue;
                kaddr = (char *)page_address(page);
                de = (struct sysv_dir_entry *)(kaddr+offset);
                limit = kaddr + PAGE_CACHE_SIZE - SYSV_DIRSIZE;
                for ( ;(char*)de <= limit; de++, ctx->pos += sizeof(*de)) {
                        char *name = de->name;

                        if (!de->inode)
                                continue;

                        if (!dir_emit(ctx, name, strnlen(name,SYSV_NAMELEN),
                                        fs16_to_cpu(SYSV_SB(sb), de->inode),
                                        DT_UNKNOWN)) {
                                dir_put_page(page);
                                return 0;
                        }
                }
                dir_put_page(page);
        }
        return 0;
}

/* compare strings: name[0..len-1] (not zero-terminated) and
 * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
 */
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);
}

/*
 *      sysv_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.
 */
struct sysv_dir_entry *sysv_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;
        unsigned long start, n;
        unsigned long npages = dir_pages(dir);
        struct page *page = NULL;
        struct sysv_dir_entry *de;

        *res_page = NULL;

        start = SYSV_I(dir)->i_dir_start_lookup;
        if (start >= npages)
                start = 0;
        n = start;

        do {
                char *kaddr;
                page = dir_get_page(dir, n);
                if (!IS_ERR(page)) {
                        kaddr = (char*)page_address(page);
                        de = (struct sysv_dir_entry *) kaddr;
                        kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
                        for ( ; (char *) de <= kaddr ; de++) {
                                if (!de->inode)
                                        continue;
                                if (namecompare(namelen, SYSV_NAMELEN,
                                                        name, de->name))
                                        goto found;
                        }
                        dir_put_page(page);
                }

                if (++n >= npages)
                        n = 0;
        } while (n != start);

        return NULL;

found:
        SYSV_I(dir)->i_dir_start_lookup = n;
        *res_page = page;
        return de;
}

int sysv_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 page *page = NULL;
        struct sysv_dir_entry * 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 */
        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 = (struct sysv_dir_entry *)kaddr;
                kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
                while ((char *)de <= kaddr) {
                        if (!de->inode)
                                goto got_it;
                        err = -EEXIST;
                        if (namecompare(namelen, SYSV_NAMELEN, name, de->name)) 
                                goto out_page;
                        de++;
                }
                dir_put_page(page);
        }
        BUG();
        return -EINVAL;

got_it:
        pos = page_offset(page) +
                        (char*)de - (char*)page_address(page);
        lock_page(page);
        err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
        if (err)
                goto out_unlock;
        memcpy (de->name, name, namelen);
        memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
        de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
        err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
        dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
        mark_inode_dirty(dir);
out_page:
        dir_put_page(page);
out:
        return err;
out_unlock:
        unlock_page(page);
        goto out_page;
}

int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
{
        struct inode *inode = page->mapping->host;
        char *kaddr = (char*)page_address(page);
        loff_t pos = page_offset(page) + (char *)de - kaddr;
        int err;

        lock_page(page);
        err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
        BUG_ON(err);
        de->inode = 0;
        err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
        dir_put_page(page);
        inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
        mark_inode_dirty(inode);
        return err;
}

int sysv_make_empty(struct inode *inode, struct inode *dir)
{
        struct page *page = grab_cache_page(inode->i_mapping, 0);
        struct sysv_dir_entry * de;
        char *base;
        int err;

        if (!page)
                return -ENOMEM;
        err = sysv_prepare_chunk(page, 0, 2 * SYSV_DIRSIZE);
        if (err) {
                unlock_page(page);
                goto fail;
        }
        kmap(page);

        base = (char*)page_address(page);
        memset(base, 0, PAGE_CACHE_SIZE);

        de = (struct sysv_dir_entry *) base;
        de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
        strcpy(de->name,".");
        de++;
        de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
        strcpy(de->name,"..");

        kunmap(page);
        err = dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
fail:
        page_cache_release(page);
        return err;
}

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

        for (i = 0; i < npages; i++) {
                char *kaddr;
                struct sysv_dir_entry * de;
                page = dir_get_page(inode, i);

                if (IS_ERR(page))
                        continue;

                kaddr = (char *)page_address(page);
                de = (struct sysv_dir_entry *)kaddr;
                kaddr += PAGE_CACHE_SIZE-SYSV_DIRSIZE;

                for ( ;(char *)de <= kaddr; de++) {
                        if (!de->inode)
                                continue;
                        /* check for . and .. */
                        if (de->name[0] != '.')
                                goto not_empty;
                        if (!de->name[1]) {
                                if (de->inode == cpu_to_fs16(SYSV_SB(sb),
                                                        inode->i_ino))
                                        continue;
                                goto not_empty;
                        }
                        if (de->name[1] != '.' || de->name[2])
                                goto not_empty;
                }
                dir_put_page(page);
        }
        return 1;

not_empty:
        dir_put_page(page);
        return 0;
}

/* Releases the page */
void sysv_set_link(struct sysv_dir_entry *de, struct page *page,
        struct inode *inode)
{
        struct inode *dir = page->mapping->host;
        loff_t pos = page_offset(page) +
                        (char *)de-(char*)page_address(page);
        int err;

        lock_page(page);
        err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
        BUG_ON(err);
        de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
        err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
        dir_put_page(page);
        dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
        mark_inode_dirty(dir);
}

struct sysv_dir_entry * sysv_dotdot (struct inode *dir, struct page **p)
{
        struct page *page = dir_get_page(dir, 0);
        struct sysv_dir_entry *de = NULL;

        if (!IS_ERR(page)) {
                de = (struct sysv_dir_entry*) page_address(page) + 1;
                *p = page;
        }
        return de;
}

ino_t sysv_inode_by_name(struct dentry *dentry)
{
        struct page *page;
        struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
        ino_t res = 0;
        
        if (de) {
                res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
                dir_put_page(page);
        }
        return res;
}