dir.c

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/*
 *  linux/fs/minix/dir.c
 *
 *  Copyright (C) 1991, 1992 Linus Torvalds
 *
 *  minix directory handling functions
 *
 *  Updated to filesystem version 3 by Daniel Aragones
 */

#include "minix.h"
#include <linux/buffer_head.h>
#include <linux/highmem.h>
#include <linux/swap.h>

typedef struct minix_dir_entry minix_dirent;
typedef struct minix3_dir_entry minix3_dirent;

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

const struct file_operations minix_dir_operations = {
    .llseek     = generic_file_llseek,
    .read       = generic_read_dir,
    .readdir    = minix_readdir,
    .fsync      = generic_file_fsync,
};

static inline void dir_put_page(struct page *page)
{
    kunmap(page);
    page_cache_release(page);
}

/*
 * Return the offset into page `page_nr' of the last valid
 * byte in that page, plus one.
 */
static unsigned
minix_last_byte(struct inode *inode, unsigned long page_nr)
{
    unsigned last_byte = PAGE_CACHE_SIZE;

    if (page_nr == (inode->i_size >> PAGE_CACHE_SHIFT))
        last_byte = inode->i_size & (PAGE_CACHE_SIZE - 1);
    return last_byte;
}

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 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_path.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 = minix_sb(sb);
    unsigned chunk_size = sbi->s_dirsize;
    char *name;
    __u32 inumber;

    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 + minix_last_byte(inode, n) - chunk_size;
        for ( ; p <= limit; p = minix_next_entry(p, sbi)) {
            if (sbi->s_version == MINIX_V3) {
                minix3_dirent *de3 = (minix3_dirent *)p;
                name = de3->name;
                inumber = de3->inode;
            } else {
                minix_dirent *de = (minix_dirent *)p;
                name = de->name;
                inumber = de->inode;
            }
            if (inumber) {
                int over;

                unsigned l = strnlen(name, sbi->s_namelen);
                offset = p - kaddr;
                over = filldir(dirent, name, l,
                    (n << PAGE_CACHE_SHIFT) | offset,
                    inumber, DT_UNKNOWN);
                if (over) {
                    dir_put_page(page);
                    goto done;
                }
            }
        }
        dir_put_page(page);
    }

done:
    filp->f_pos = (n << PAGE_CACHE_SHIFT) | offset;
    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 = minix_sb(sb);
    unsigned long n;
    unsigned long npages = dir_pages(dir);
    struct page *page = NULL;
    char *p;

    char *namx;
    __u32 inumber;
    *res_page = NULL;

    for (n = 0; n < npages; n++) {
        char *kaddr, *limit;

        page = dir_get_page(dir, n);
        if (IS_ERR(page))
            continue;

        kaddr = (char*)page_address(page);
        limit = kaddr + minix_last_byte(dir, n) - sbi->s_dirsize;
        for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
            if (sbi->s_version == MINIX_V3) {
                minix3_dirent *de3 = (minix3_dirent *)p;
                namx = de3->name;
                inumber = de3->inode;
            } else {
                minix_dirent *de = (minix_dirent *)p;
                namx = de->name;
                inumber = de->inode;
            }
            if (!inumber)
                continue;
            if (namecompare(namelen, sbi->s_namelen, name, namx))
                goto found;
        }
        dir_put_page(page);
    }
    return NULL;

found:
    *res_page = page;
    return (minix_dirent *)p;
}

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 = minix_sb(sb);
    struct page *page = NULL;
    unsigned long npages = dir_pages(dir);
    unsigned long n;
    char *kaddr, *p;
    minix_dirent *de;
    minix3_dirent *de3;
    loff_t pos;
    int err;
    char *namx = NULL;
    __u32 inumber;

    /*
     * 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 *limit, *dir_end;

        page = dir_get_page(dir, n);
        err = PTR_ERR(page);
        if (IS_ERR(page))
            goto out;
        lock_page(page);
        kaddr = (char*)page_address(page);
        dir_end = kaddr + minix_last_byte(dir, n);
        limit = kaddr + PAGE_CACHE_SIZE - sbi->s_dirsize;
        for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
            de = (minix_dirent *)p;
            de3 = (minix3_dirent *)p;
            if (sbi->s_version == MINIX_V3) {
                namx = de3->name;
                inumber = de3->inode;
            } else {
                namx = de->name;
                inumber = de->inode;
            }
            if (p == dir_end) {
                /* We hit i_size */
                if (sbi->s_version == MINIX_V3)
                    de3->inode = 0;
                else
                    de->inode = 0;
                goto got_it;
            }
            if (!inumber)
                goto got_it;
            err = -EEXIST;
            if (namecompare(namelen, sbi->s_namelen, name, namx))
                goto out_unlock;
        }
        unlock_page(page);
        dir_put_page(page);
    }
    BUG();
    return -EINVAL;

got_it:
    pos = page_offset(page) + p - (char *)page_address(page);
    err = minix_prepare_chunk(page, pos, sbi->s_dirsize);
    if (err)
        goto out_unlock;
    memcpy (namx, name, namelen);
    if (sbi->s_version == MINIX_V3) {
        memset (namx + namelen, 0, sbi->s_dirsize - namelen - 4);
        de3->inode = inode->i_ino;
    } else {
        memset (namx + namelen, 0, sbi->s_dirsize - namelen - 2);
        de->inode = inode->i_ino;
    }
    err = dir_commit_chunk(page, pos, sbi->s_dirsize);
    dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
    mark_inode_dirty(dir);
out_put:
    dir_put_page(page);
out:
    return err;
out_unlock:
    unlock_page(page);
    goto out_put;
}

int minix_delete_entry(struct minix_dir_entry *de, struct page *page)
{
    struct inode *inode = page->mapping->host;
    char *kaddr = page_address(page);
    loff_t pos = page_offset(page) + (char*)de - kaddr;
    struct minix_sb_info *sbi = minix_sb(inode->i_sb);
    unsigned len = sbi->s_dirsize;
    int err;

    lock_page(page);
    err = minix_prepare_chunk(page, pos, len);
    if (err == 0) {
        if (sbi->s_version == MINIX_V3)
            ((minix3_dirent *) de)->inode = 0;
        else
            de->inode = 0;
        err = dir_commit_chunk(page, pos, len);
    } else {
        unlock_page(page);
    }
    dir_put_page(page);
    inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
    mark_inode_dirty(inode);
    return err;
}

int minix_make_empty(struct inode *inode, struct inode *dir)
{
    struct page *page = grab_cache_page(inode->i_mapping, 0);
    struct minix_sb_info *sbi = minix_sb(inode->i_sb);
    char *kaddr;
    int err;

    if (!page)
        return -ENOMEM;
    err = minix_prepare_chunk(page, 0, 2 * sbi->s_dirsize);
    if (err) {
        unlock_page(page);
        goto fail;
    }

    kaddr = kmap_atomic(page);
    memset(kaddr, 0, PAGE_CACHE_SIZE);

    if (sbi->s_version == MINIX_V3) {
        minix3_dirent *de3 = (minix3_dirent *)kaddr;

        de3->inode = inode->i_ino;
        strcpy(de3->name, ".");
        de3 = minix_next_entry(de3, sbi);
        de3->inode = dir->i_ino;
        strcpy(de3->name, "..");
    } else {
        minix_dirent *de = (minix_dirent *)kaddr;

        de->inode = inode->i_ino;
        strcpy(de->name, ".");
        de = minix_next_entry(de, sbi);
        de->inode = dir->i_ino;
        strcpy(de->name, "..");
    }
    kunmap_atomic(kaddr);

    err = dir_commit_chunk(page, 0, 2 * sbi->s_dirsize);
fail:
    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 = minix_sb(inode->i_sb);
    char *name;
    __u32 inumber;

    for (i = 0; i < npages; i++) {
        char *p, *kaddr, *limit;

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

        kaddr = (char *)page_address(page);
        limit = kaddr + minix_last_byte(inode, i) - sbi->s_dirsize;
        for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
            if (sbi->s_version == MINIX_V3) {
                minix3_dirent *de3 = (minix3_dirent *)p;
                name = de3->name;
                inumber = de3->inode;
            } else {
                minix_dirent *de = (minix_dirent *)p;
                name = de->name;
                inumber = de->inode;
            }

            if (inumber != 0) {
                /* check for . and .. */
                if (name[0] != '.')
                    goto not_empty;
                if (!name[1]) {
                    if (inumber != inode->i_ino)
                        goto not_empty;
                } else if (name[1] != '.')
                    goto not_empty;
                else if (name[2])
                    goto not_empty;
            }
        }
        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 = page->mapping->host;
    struct minix_sb_info *sbi = minix_sb(dir->i_sb);
    loff_t pos = page_offset(page) +
            (char *)de-(char*)page_address(page);
    int err;

    lock_page(page);

    err = minix_prepare_chunk(page, pos, sbi->s_dirsize);
    if (err == 0) {
        if (sbi->s_version == MINIX_V3)
            ((minix3_dirent *) de)->inode = inode->i_ino;
        else
            de->inode = inode->i_ino;
        err = dir_commit_chunk(page, pos, sbi->s_dirsize);
    } else {
        unlock_page(page);
    }
    dir_put_page(page);
    dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
    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 = minix_sb(dir->i_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) {
        struct address_space *mapping = page->mapping;
        struct inode *inode = mapping->host;
        struct minix_sb_info *sbi = minix_sb(inode->i_sb);

        if (sbi->s_version == MINIX_V3)
            res = ((minix3_dirent *) de)->inode;
        else
            res = de->inode;
        dir_put_page(page);
    }
    return res;
}