dir.c

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/*
 *  linux/fs/ext2/dir.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card ([email protected])
 * 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 ([email protected]), 1995
 *
 * All code that works with directory layout had been switched to pagecache
 * and moved here. AV
 */

#include "ext2.h"
#include <linux/buffer_head.h>
#include <linux/pagemap.h>
#include <linux/swap.h>

typedef struct ext2_dir_entry_2 ext2_dirent;

/*
 * Tests against MAX_REC_LEN etc were put in place for 64k block
 * sizes; if that is not possible on this arch, we can skip
 * those tests and speed things up.
 */
static inline unsigned ext2_rec_len_from_disk(__le16 dlen)
{
    unsigned len = le16_to_cpu(dlen);

#if (PAGE_CACHE_SIZE >= 65536)
    if (len == EXT2_MAX_REC_LEN)
        return 1 << 16;
#endif
    return len;
}

static inline __le16 ext2_rec_len_to_disk(unsigned len)
{
#if (PAGE_CACHE_SIZE >= 65536)
    if (len == (1 << 16))
        return cpu_to_le16(EXT2_MAX_REC_LEN);
    else
        BUG_ON(len > (1 << 16));
#endif
    return cpu_to_le16(len);
}

/*
 * 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;
}

/*
 * Return the offset into page `page_nr' of the last valid
 * byte in that page, plus one.
 */
static unsigned
ext2_last_byte(struct inode *inode, unsigned long page_nr)
{
    unsigned last_byte = inode->i_size;

    last_byte -= page_nr << PAGE_CACHE_SHIFT;
    if (last_byte > PAGE_CACHE_SIZE)
        last_byte = PAGE_CACHE_SIZE;
    return last_byte;
}

static int ext2_commit_chunk(struct page *page, loff_t pos, unsigned len)
{
    struct address_space *mapping = page->mapping;
    struct inode *dir = mapping->host;
    int err = 0;

    dir->i_version++;
    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);
        if (!err)
            err = sync_inode_metadata(dir, 1);
    } else {
        unlock_page(page);
    }

    return err;
}

static void ext2_check_page(struct page *page, int quiet)
{
    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(EXT2_SB(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;
        if (!limit)
            goto out;
    }
    for (offs = 0; offs <= limit - EXT2_DIR_REC_LEN(1); offs += rec_len) {
        p = (ext2_dirent *)(kaddr + offs);
        rec_len = ext2_rec_len_from_disk(p->rec_len);

        if (unlikely(rec_len < EXT2_DIR_REC_LEN(1)))
            goto Eshort;
        if (unlikely(rec_len & 3))
            goto Ealign;
        if (unlikely(rec_len < EXT2_DIR_REC_LEN(p->name_len)))
            goto Enamelen;
        if (unlikely(((offs + rec_len - 1) ^ offs) & ~(chunk_size-1)))
            goto Espan;
        if (unlikely(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:
    if (!quiet)
        ext2_error(sb, __func__,
            "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:
    if (!quiet)
        ext2_error(sb, __func__, "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:
    if (!quiet) {
        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,
                   int quiet)
{
    struct address_space *mapping = dir->i_mapping;
    struct page *page = read_mapping_page(mapping, n, NULL);
    if (!IS_ERR(page)) {
        kmap(page);
        if (!PageChecked(page))
            ext2_check_page(page, quiet);
        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 +
            ext2_rec_len_from_disk(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) {
        if (p->rec_len == 0)
            break;
        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)
{
    umode_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_path.dentry->d_inode;
    struct super_block *sb = inode->i_sb;
    unsigned int 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))
        return 0;

    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, 0);

        if (IS_ERR(page)) {
            ext2_error(sb, __func__,
                   "bad page in #%lu",
                   inode->i_ino);
            filp->f_pos += PAGE_CACHE_SIZE - offset;
            return PTR_ERR(page);
        }
        kaddr = page_address(page);
        if (unlikely(need_revalidate)) {
            if (offset) {
                offset = ext2_validate_entry(kaddr, offset, chunk_mask);
                filp->f_pos = (n<<PAGE_CACHE_SHIFT) + offset;
            }
            filp->f_version = inode->i_version;
            need_revalidate = 0;
        }
        de = (ext2_dirent *)(kaddr+offset);
        limit = kaddr + ext2_last_byte(inode, n) - EXT2_DIR_REC_LEN(1);
        for ( ;(char*)de <= limit; de = ext2_next_entry(de)) {
            if (de->rec_len == 0) {
                ext2_error(sb, __func__,
                    "zero-length directory entry");
                ext2_put_page(page);
                return -EIO;
            }
            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);
                    return 0;
                }
            }
            filp->f_pos += ext2_rec_len_from_disk(de->rec_len);
        }
        ext2_put_page(page);
    }
    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 (as a parameter - res_page),
 * and the entry itself. Page is returned mapped and unlocked.
 * Entry is guaranteed to be valid.
 */
struct ext2_dir_entry_2 *ext2_find_entry (struct inode * dir,
            struct qstr *child, struct page ** res_page)
{
    const char *name = child->name;
    int namelen = child->len;
    unsigned reclen = EXT2_DIR_REC_LEN(namelen);
    unsigned long start, n;
    unsigned long npages = dir_pages(dir);
    struct page *page = NULL;
    struct ext2_inode_info *ei = EXT2_I(dir);
    ext2_dirent * de;
    int dir_has_error = 0;

    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 = ext2_get_page(dir, n, dir_has_error);
        if (!IS_ERR(page)) {
            kaddr = page_address(page);
            de = (ext2_dirent *) kaddr;
            kaddr += ext2_last_byte(dir, n) - reclen;
            while ((char *) de <= kaddr) {
                if (de->rec_len == 0) {
                    ext2_error(dir->i_sb, __func__,
                        "zero-length directory entry");
                    ext2_put_page(page);
                    goto out;
                }
                if (ext2_match (namelen, name, de))
                    goto found;
                de = ext2_next_entry(de);
            }
            ext2_put_page(page);
        } else
            dir_has_error = 1;

        if (++n >= npages)
            n = 0;
        /* next page is past the blocks we've got */
        if (unlikely(n > (dir->i_blocks >> (PAGE_CACHE_SHIFT - 9)))) {
            ext2_error(dir->i_sb, __func__,
                "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 ext2_dir_entry_2 * ext2_dotdot (struct inode *dir, struct page **p)
{
    struct page *page = ext2_get_page(dir, 0, 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 qstr *child)
{
    ino_t res = 0;
    struct ext2_dir_entry_2 *de;
    struct page *page;
    
    de = ext2_find_entry (dir, child, &page);
    if (de) {
        res = le32_to_cpu(de->inode);
        ext2_put_page(page);
    }
    return res;
}

static int ext2_prepare_chunk(struct page *page, loff_t pos, unsigned len)
{
    return __block_write_begin(page, pos, len, ext2_get_block);
}

/* Releases the page */
void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
           struct page *page, struct inode *inode, int update_times)
{
    loff_t pos = page_offset(page) +
            (char *) de - (char *) page_address(page);
    unsigned len = ext2_rec_len_from_disk(de->rec_len);
    int err;

    lock_page(page);
    err = ext2_prepare_chunk(page, pos, len);
    BUG_ON(err);
    de->inode = cpu_to_le32(inode->i_ino);
    ext2_set_de_type(de, inode);
    err = ext2_commit_chunk(page, pos, len);
    ext2_put_page(page);
    if (update_times)
        dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
    EXT2_I(dir)->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 chunk_size = ext2_chunk_size(dir);
    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;
    loff_t pos;
    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 = ext2_get_page(dir, n, 0);
        err = PTR_ERR(page);
        if (IS_ERR(page))
            goto out;
        lock_page(page);
        kaddr = page_address(page);
        dir_end = kaddr + ext2_last_byte(dir, n);
        de = (ext2_dirent *)kaddr;
        kaddr += PAGE_CACHE_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 = ext2_rec_len_to_disk(chunk_size);
                de->inode = 0;
                goto got_it;
            }
            if (de->rec_len == 0) {
                ext2_error(dir->i_sb, __func__,
                    "zero-length directory entry");
                err = -EIO;
                goto out_unlock;
            }
            err = -EEXIST;
            if (ext2_match (namelen, name, de))
                goto out_unlock;
            name_len = EXT2_DIR_REC_LEN(de->name_len);
            rec_len = ext2_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 = (ext2_dirent *) ((char *) de + rec_len);
        }
        unlock_page(page);
        ext2_put_page(page);
    }
    BUG();
    return -EINVAL;

got_it:
    pos = page_offset(page) +
        (char*)de - (char*)page_address(page);
    err = ext2_prepare_chunk(page, pos, rec_len);
    if (err)
        goto out_unlock;
    if (de->inode) {
        ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
        de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
        de->rec_len = ext2_rec_len_to_disk(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, pos, rec_len);
    dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
    EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
    mark_inode_dirty(dir);
    /* OFFSET_CACHE */
out_put:
    ext2_put_page(page);
out:
    return err;
out_unlock:
    unlock_page(page);
    goto out_put;
}

/*
 * 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 inode *inode = page->mapping->host;
    char *kaddr = page_address(page);
    unsigned from = ((char*)dir - kaddr) & ~(ext2_chunk_size(inode)-1);
    unsigned to = ((char *)dir - kaddr) +
                ext2_rec_len_from_disk(dir->rec_len);
    loff_t pos;
    ext2_dirent * pde = NULL;
    ext2_dirent * de = (ext2_dirent *) (kaddr + from);
    int err;

    while ((char*)de < (char*)dir) {
        if (de->rec_len == 0) {
            ext2_error(inode->i_sb, __func__,
                "zero-length directory entry");
            err = -EIO;
            goto out;
        }
        pde = de;
        de = ext2_next_entry(de);
    }
    if (pde)
        from = (char*)pde - (char*)page_address(page);
    pos = page_offset(page) + from;
    lock_page(page);
    err = ext2_prepare_chunk(page, pos, to - from);
    BUG_ON(err);
    if (pde)
        pde->rec_len = ext2_rec_len_to_disk(to - from);
    dir->inode = 0;
    err = ext2_commit_chunk(page, pos, to - from);
    inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
    EXT2_I(inode)->i_flags &= ~EXT2_BTREE_FL;
    mark_inode_dirty(inode);
out:
    ext2_put_page(page);
    return err;
}

/*
 * Set the first fragment of directory.
 */
int ext2_make_empty(struct inode *inode, struct inode *parent)
{
    struct page *page = grab_cache_page(inode->i_mapping, 0);
    unsigned chunk_size = ext2_chunk_size(inode);
    struct ext2_dir_entry_2 * de;
    int err;
    void *kaddr;

    if (!page)
        return -ENOMEM;

    err = ext2_prepare_chunk(page, 0, chunk_size);
    if (err) {
        unlock_page(page);
        goto fail;
    }
    kaddr = kmap_atomic(page);
    memset(kaddr, 0, chunk_size);
    de = (struct ext2_dir_entry_2 *)kaddr;
    de->name_len = 1;
    de->rec_len = ext2_rec_len_to_disk(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 *)(kaddr + EXT2_DIR_REC_LEN(1));
    de->name_len = 2;
    de->rec_len = ext2_rec_len_to_disk(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);
    kunmap_atomic(kaddr);
    err = ext2_commit_chunk(page, 0, chunk_size);
fail:
    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);
    int dir_has_error = 0;

    for (i = 0; i < npages; i++) {
        char *kaddr;
        ext2_dirent * de;
        page = ext2_get_page(inode, i, dir_has_error);

        if (IS_ERR(page)) {
            dir_has_error = 1;
            continue;
        }

        kaddr = page_address(page);
        de = (ext2_dirent *)kaddr;
        kaddr += ext2_last_byte(inode, i) - EXT2_DIR_REC_LEN(1);

        while ((char *)de <= kaddr) {
            if (de->rec_len == 0) {
                ext2_error(inode->i_sb, __func__,
                    "zero-length directory entry");
                printk("kaddr=%p, de=%p\n", 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_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;
}

const struct file_operations ext2_dir_operations = {
    .llseek     = generic_file_llseek,
    .read       = generic_read_dir,
    .readdir    = ext2_readdir,
    .unlocked_ioctl = ext2_ioctl,
#ifdef CONFIG_COMPAT
    .compat_ioctl   = ext2_compat_ioctl,
#endif
    .fsync      = ext2_fsync,
};