dir.c

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/*
 *  linux/fs/ufs/ufs_dir.c
 *
 * Copyright (C) 1996
 * Adrian Rodriguez ([email protected])
 * Laboratory for Computer Science Research Computing Facility
 * Rutgers, The State University of New Jersey
 *
 * swab support by Francois-Rene Rideau <[email protected]> 19970406
 *
 * 4.4BSD (FreeBSD) support added on February 1st 1998 by
 * Niels Kristian Bech Jensen <[email protected]> partially based
 * on code by Martin von Loewis <[email protected]>.
 *
 * Migration to usage of "page cache" on May 2006 by
 * Evgeniy Dushistov <[email protected]> based on ext2 code base.
 */

#include <linux/time.h>
#include <linux/fs.h>
#include <linux/swap.h>

#include "ufs_fs.h"
#include "ufs.h"
#include "swab.h"
#include "util.h"

/*
 * NOTE! unlike strncmp, ufs_match returns 1 for success, 0 for failure.
 *
 * len <= UFS_MAXNAMLEN and de != NULL are guaranteed by caller.
 */
static inline int ufs_match(struct super_block *sb, int len,
        const unsigned char *name, struct ufs_dir_entry *de)
{
    if (len != ufs_get_de_namlen(sb, de))
        return 0;
    if (!de->d_ino)
        return 0;
    return !memcmp(name, de->d_name, len);
}

static int ufs_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);
    else
        unlock_page(page);
    return err;
}

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

static inline unsigned long ufs_dir_pages(struct inode *inode)
{
    return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
}

ino_t ufs_inode_by_name(struct inode *dir, const struct qstr *qstr)
{
    ino_t res = 0;
    struct ufs_dir_entry *de;
    struct page *page;
    
    de = ufs_find_entry(dir, qstr, &page);
    if (de) {
        res = fs32_to_cpu(dir->i_sb, de->d_ino);
        ufs_put_page(page);
    }
    return res;
}


/* Releases the page */
void ufs_set_link(struct inode *dir, struct ufs_dir_entry *de,
          struct page *page, struct inode *inode)
{
    loff_t pos = page_offset(page) +
            (char *) de - (char *) page_address(page);
    unsigned len = fs16_to_cpu(dir->i_sb, de->d_reclen);
    int err;

    lock_page(page);
    err = ufs_prepare_chunk(page, pos, len);
    BUG_ON(err);

    de->d_ino = cpu_to_fs32(dir->i_sb, inode->i_ino);
    ufs_set_de_type(dir->i_sb, de, inode->i_mode);

    err = ufs_commit_chunk(page, pos, len);
    ufs_put_page(page);
    dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
    mark_inode_dirty(dir);
}


static void ufs_check_page(struct page *page)
{
    struct inode *dir = page->mapping->host;
    struct super_block *sb = dir->i_sb;
    char *kaddr = page_address(page);
    unsigned offs, rec_len;
    unsigned limit = PAGE_CACHE_SIZE;
    const unsigned chunk_mask = UFS_SB(sb)->s_uspi->s_dirblksize - 1;
    struct ufs_dir_entry *p;
    char *error;

    if ((dir->i_size >> PAGE_CACHE_SHIFT) == page->index) {
        limit = dir->i_size & ~PAGE_CACHE_MASK;
        if (limit & chunk_mask)
            goto Ebadsize;
        if (!limit)
            goto out;
    }
    for (offs = 0; offs <= limit - UFS_DIR_REC_LEN(1); offs += rec_len) {
        p = (struct ufs_dir_entry *)(kaddr + offs);
        rec_len = fs16_to_cpu(sb, p->d_reclen);

        if (rec_len < UFS_DIR_REC_LEN(1))
            goto Eshort;
        if (rec_len & 3)
            goto Ealign;
        if (rec_len < UFS_DIR_REC_LEN(ufs_get_de_namlen(sb, p)))
            goto Enamelen;
        if (((offs + rec_len - 1) ^ offs) & ~chunk_mask)
            goto Espan;
        if (fs32_to_cpu(sb, p->d_ino) > (UFS_SB(sb)->s_uspi->s_ipg *
                          UFS_SB(sb)->s_uspi->s_ncg))
            goto Einumber;
    }
    if (offs != limit)
        goto Eend;
out:
    SetPageChecked(page);
    return;

    /* Too bad, we had an error */

Ebadsize:
    ufs_error(sb, "ufs_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:
    ufs_error (sb, "ufs_check_page", "bad entry in directory #%lu: %s - "
           "offset=%lu, rec_len=%d, name_len=%d",
           dir->i_ino, error, (page->index<<PAGE_CACHE_SHIFT)+offs,
           rec_len, ufs_get_de_namlen(sb, p));
    goto fail;
Eend:
    p = (struct ufs_dir_entry *)(kaddr + offs);
    ufs_error(sb, __func__,
           "entry in directory #%lu spans the page boundary"
           "offset=%lu",
           dir->i_ino, (page->index<<PAGE_CACHE_SHIFT)+offs);
fail:
    SetPageChecked(page);
    SetPageError(page);
}

static struct page *ufs_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);
        if (!PageChecked(page))
            ufs_check_page(page);
        if (PageError(page))
            goto fail;
    }
    return page;

fail:
    ufs_put_page(page);
    return ERR_PTR(-EIO);
}

/*
 * Return the offset into page `page_nr' of the last valid
 * byte in that page, plus one.
 */
static unsigned
ufs_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 inline struct ufs_dir_entry *
ufs_next_entry(struct super_block *sb, struct ufs_dir_entry *p)
{
    return (struct ufs_dir_entry *)((char *)p +
                    fs16_to_cpu(sb, p->d_reclen));
}

struct ufs_dir_entry *ufs_dotdot(struct inode *dir, struct page **p)
{
    struct page *page = ufs_get_page(dir, 0);
    struct ufs_dir_entry *de = NULL;

    if (!IS_ERR(page)) {
        de = ufs_next_entry(dir->i_sb,
                    (struct ufs_dir_entry *)page_address(page));
        *p = page;
    }
    return de;
}

/*
 *  ufs_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 ufs_dir_entry *ufs_find_entry(struct inode *dir, const struct qstr *qstr,
                     struct page **res_page)
{
    struct super_block *sb = dir->i_sb;
    const unsigned char *name = qstr->name;
    int namelen = qstr->len;
    unsigned reclen = UFS_DIR_REC_LEN(namelen);
    unsigned long start, n;
    unsigned long npages = ufs_dir_pages(dir);
    struct page *page = NULL;
    struct ufs_inode_info *ui = UFS_I(dir);
    struct ufs_dir_entry *de;

    UFSD("ENTER, dir_ino %lu, name %s, namlen %u\n", dir->i_ino, name, namelen);

    if (npages == 0 || namelen > UFS_MAXNAMLEN)
        goto out;

    /* OFFSET_CACHE */
    *res_page = NULL;

    start = ui->i_dir_start_lookup;

    if (start >= npages)
        start = 0;
    n = start;
    do {
        char *kaddr;
        page = ufs_get_page(dir, n);
        if (!IS_ERR(page)) {
            kaddr = page_address(page);
            de = (struct ufs_dir_entry *) kaddr;
            kaddr += ufs_last_byte(dir, n) - reclen;
            while ((char *) de <= kaddr) {
                if (de->d_reclen == 0) {
                    ufs_error(dir->i_sb, __func__,
                          "zero-length directory entry");
                    ufs_put_page(page);
                    goto out;
                }
                if (ufs_match(sb, namelen, name, de))
                    goto found;
                de = ufs_next_entry(sb, de);
            }
            ufs_put_page(page);
        }
        if (++n >= npages)
            n = 0;
    } while (n != start);
out:
    return NULL;

found:
    *res_page = page;
    ui->i_dir_start_lookup = n;
    return de;
}

/*
 *  Parent is locked.
 */
int ufs_add_link(struct dentry *dentry, struct inode *inode)
{
    struct inode *dir = dentry->d_parent->d_inode;
    const unsigned char *name = dentry->d_name.name;
    int namelen = dentry->d_name.len;
    struct super_block *sb = dir->i_sb;
    unsigned reclen = UFS_DIR_REC_LEN(namelen);
    const unsigned int chunk_size = UFS_SB(sb)->s_uspi->s_dirblksize;
    unsigned short rec_len, name_len;
    struct page *page = NULL;
    struct ufs_dir_entry *de;
    unsigned long npages = ufs_dir_pages(dir);
    unsigned long n;
    char *kaddr;
    loff_t pos;
    int err;

    UFSD("ENTER, name %s, namelen %u\n", name, namelen);

    /*
     * 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 = ufs_get_page(dir, n);
        err = PTR_ERR(page);
        if (IS_ERR(page))
            goto out;
        lock_page(page);
        kaddr = page_address(page);
        dir_end = kaddr + ufs_last_byte(dir, n);
        de = (struct ufs_dir_entry *)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->d_reclen = cpu_to_fs16(sb, chunk_size);
                de->d_ino = 0;
                goto got_it;
            }
            if (de->d_reclen == 0) {
                ufs_error(dir->i_sb, __func__,
                      "zero-length directory entry");
                err = -EIO;
                goto out_unlock;
            }
            err = -EEXIST;
            if (ufs_match(sb, namelen, name, de))
                goto out_unlock;
            name_len = UFS_DIR_REC_LEN(ufs_get_de_namlen(sb, de));
            rec_len = fs16_to_cpu(sb, de->d_reclen);
            if (!de->d_ino && rec_len >= reclen)
                goto got_it;
            if (rec_len >= name_len + reclen)
                goto got_it;
            de = (struct ufs_dir_entry *) ((char *) de + rec_len);
        }
        unlock_page(page);
        ufs_put_page(page);
    }
    BUG();
    return -EINVAL;

got_it:
    pos = page_offset(page) +
            (char*)de - (char*)page_address(page);
    err = ufs_prepare_chunk(page, pos, rec_len);
    if (err)
        goto out_unlock;
    if (de->d_ino) {
        struct ufs_dir_entry *de1 =
            (struct ufs_dir_entry *) ((char *) de + name_len);
        de1->d_reclen = cpu_to_fs16(sb, rec_len - name_len);
        de->d_reclen = cpu_to_fs16(sb, name_len);

        de = de1;
    }

    ufs_set_de_namlen(sb, de, namelen);
    memcpy(de->d_name, name, namelen + 1);
    de->d_ino = cpu_to_fs32(sb, inode->i_ino);
    ufs_set_de_type(sb, de, inode->i_mode);

    err = ufs_commit_chunk(page, pos, rec_len);
    dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;

    mark_inode_dirty(dir);
    /* OFFSET_CACHE */
out_put:
    ufs_put_page(page);
out:
    return err;
out_unlock:
    unlock_page(page);
    goto out_put;
}

static inline unsigned
ufs_validate_entry(struct super_block *sb, char *base,
           unsigned offset, unsigned mask)
{
    struct ufs_dir_entry *de = (struct ufs_dir_entry*)(base + offset);
    struct ufs_dir_entry *p = (struct ufs_dir_entry*)(base + (offset&mask));
    while ((char*)p < (char*)de) {
        if (p->d_reclen == 0)
            break;
        p = ufs_next_entry(sb, p);
    }
    return (char *)p - base;
}


/*
 * This is blatantly stolen from ext2fs
 */
static int
ufs_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 = ufs_dir_pages(inode);
    unsigned chunk_mask = ~(UFS_SB(sb)->s_uspi->s_dirblksize - 1);
    int need_revalidate = filp->f_version != inode->i_version;
    unsigned flags = UFS_SB(sb)->s_flags;

    UFSD("BEGIN\n");

    if (pos > inode->i_size - UFS_DIR_REC_LEN(1))
        return 0;

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

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

        if (IS_ERR(page)) {
            ufs_error(sb, __func__,
                  "bad page in #%lu",
                  inode->i_ino);
            filp->f_pos += PAGE_CACHE_SIZE - offset;
            return -EIO;
        }
        kaddr = page_address(page);
        if (unlikely(need_revalidate)) {
            if (offset) {
                offset = ufs_validate_entry(sb, kaddr, offset, chunk_mask);
                filp->f_pos = (n<<PAGE_CACHE_SHIFT) + offset;
            }
            filp->f_version = inode->i_version;
            need_revalidate = 0;
        }
        de = (struct ufs_dir_entry *)(kaddr+offset);
        limit = kaddr + ufs_last_byte(inode, n) - UFS_DIR_REC_LEN(1);
        for ( ;(char*)de <= limit; de = ufs_next_entry(sb, de)) {
            if (de->d_reclen == 0) {
                ufs_error(sb, __func__,
                    "zero-length directory entry");
                ufs_put_page(page);
                return -EIO;
            }
            if (de->d_ino) {
                int over;
                unsigned char d_type = DT_UNKNOWN;

                offset = (char *)de - kaddr;

                UFSD("filldir(%s,%u)\n", de->d_name,
                      fs32_to_cpu(sb, de->d_ino));
                UFSD("namlen %u\n", ufs_get_de_namlen(sb, de));

                if ((flags & UFS_DE_MASK) == UFS_DE_44BSD)
                    d_type = de->d_u.d_44.d_type;

                over = filldir(dirent, de->d_name,
                           ufs_get_de_namlen(sb, de),
                        (n<<PAGE_CACHE_SHIFT) | offset,
                           fs32_to_cpu(sb, de->d_ino), d_type);
                if (over) {
                    ufs_put_page(page);
                    return 0;
                }
            }
            filp->f_pos += fs16_to_cpu(sb, de->d_reclen);
        }
        ufs_put_page(page);
    }
    return 0;
}


/*
 * ufs_delete_entry deletes a directory entry by merging it with the
 * previous entry.
 */
int ufs_delete_entry(struct inode *inode, struct ufs_dir_entry *dir,
             struct page * page)
{
    struct super_block *sb = inode->i_sb;
    char *kaddr = page_address(page);
    unsigned from = ((char*)dir - kaddr) & ~(UFS_SB(sb)->s_uspi->s_dirblksize - 1);
    unsigned to = ((char*)dir - kaddr) + fs16_to_cpu(sb, dir->d_reclen);
    loff_t pos;
    struct ufs_dir_entry *pde = NULL;
    struct ufs_dir_entry *de = (struct ufs_dir_entry *) (kaddr + from);
    int err;

    UFSD("ENTER\n");

    UFSD("ino %u, reclen %u, namlen %u, name %s\n",
          fs32_to_cpu(sb, de->d_ino),
          fs16_to_cpu(sb, de->d_reclen),
          ufs_get_de_namlen(sb, de), de->d_name);

    while ((char*)de < (char*)dir) {
        if (de->d_reclen == 0) {
            ufs_error(inode->i_sb, __func__,
                  "zero-length directory entry");
            err = -EIO;
            goto out;
        }
        pde = de;
        de = ufs_next_entry(sb, de);
    }
    if (pde)
        from = (char*)pde - (char*)page_address(page);

    pos = page_offset(page) + from;
    lock_page(page);
    err = ufs_prepare_chunk(page, pos, to - from);
    BUG_ON(err);
    if (pde)
        pde->d_reclen = cpu_to_fs16(sb, to - from);
    dir->d_ino = 0;
    err = ufs_commit_chunk(page, pos, to - from);
    inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
    mark_inode_dirty(inode);
out:
    ufs_put_page(page);
    UFSD("EXIT\n");
    return err;
}

int ufs_make_empty(struct inode * inode, struct inode *dir)
{
    struct super_block * sb = dir->i_sb;
    struct address_space *mapping = inode->i_mapping;
    struct page *page = grab_cache_page(mapping, 0);
    const unsigned int chunk_size = UFS_SB(sb)->s_uspi->s_dirblksize;
    struct ufs_dir_entry * de;
    char *base;
    int err;

    if (!page)
        return -ENOMEM;

    err = ufs_prepare_chunk(page, 0, chunk_size);
    if (err) {
        unlock_page(page);
        goto fail;
    }

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

    de = (struct ufs_dir_entry *) base;

    de->d_ino = cpu_to_fs32(sb, inode->i_ino);
    ufs_set_de_type(sb, de, inode->i_mode);
    ufs_set_de_namlen(sb, de, 1);
    de->d_reclen = cpu_to_fs16(sb, UFS_DIR_REC_LEN(1));
    strcpy (de->d_name, ".");
    de = (struct ufs_dir_entry *)
        ((char *)de + fs16_to_cpu(sb, de->d_reclen));
    de->d_ino = cpu_to_fs32(sb, dir->i_ino);
    ufs_set_de_type(sb, de, dir->i_mode);
    de->d_reclen = cpu_to_fs16(sb, chunk_size - UFS_DIR_REC_LEN(1));
    ufs_set_de_namlen(sb, de, 2);
    strcpy (de->d_name, "..");
    kunmap(page);

    err = ufs_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 ufs_empty_dir(struct inode * inode)
{
    struct super_block *sb = inode->i_sb;
    struct page *page = NULL;
    unsigned long i, npages = ufs_dir_pages(inode);

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

        if (IS_ERR(page))
            continue;

        kaddr = page_address(page);
        de = (struct ufs_dir_entry *)kaddr;
        kaddr += ufs_last_byte(inode, i) - UFS_DIR_REC_LEN(1);

        while ((char *)de <= kaddr) {
            if (de->d_reclen == 0) {
                ufs_error(inode->i_sb, __func__,
                    "zero-length directory entry: "
                    "kaddr=%p, de=%p\n", kaddr, de);
                goto not_empty;
            }
            if (de->d_ino) {
                u16 namelen=ufs_get_de_namlen(sb, de);
                /* check for . and .. */
                if (de->d_name[0] != '.')
                    goto not_empty;
                if (namelen > 2)
                    goto not_empty;
                if (namelen < 2) {
                    if (inode->i_ino !=
                        fs32_to_cpu(sb, de->d_ino))
                        goto not_empty;
                } else if (de->d_name[1] != '.')
                    goto not_empty;
            }
            de = ufs_next_entry(sb, de);
        }
        ufs_put_page(page);
    }
    return 1;

not_empty:
    ufs_put_page(page);
    return 0;
}

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