dir.c

Go to the documentation of this file.

/*
 * dir.c - NILFS directory entry operations
 *
 * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Modified for NILFS by Amagai Yoshiji <[email protected]>
 */
/*
 *  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 <linux/pagemap.h>
#include "nilfs.h"
#include "page.h"

/*
 * nilfs uses block-sized chunks. Arguably, sector-sized ones would be
 * more robust, but we have what we have
 */
static inline unsigned nilfs_chunk_size(struct inode *inode)
{
    return inode->i_sb->s_blocksize;
}

static inline void nilfs_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 nilfs_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 nilfs_prepare_chunk(struct page *page, unsigned from, unsigned to)
{
    loff_t pos = page_offset(page) + from;
    return __block_write_begin(page, pos, to - from, nilfs_get_block);
}

static void nilfs_commit_chunk(struct page *page,
                   struct address_space *mapping,
                   unsigned from, unsigned to)
{
    struct inode *dir = mapping->host;
    loff_t pos = page_offset(page) + from;
    unsigned len = to - from;
    unsigned nr_dirty, copied;
    int err;

    nr_dirty = nilfs_page_count_clean_buffers(page, from, to);
    copied = block_write_end(NULL, mapping, pos, len, len, page, NULL);
    if (pos + copied > dir->i_size)
        i_size_write(dir, pos + copied);
    if (IS_DIRSYNC(dir))
        nilfs_set_transaction_flag(NILFS_TI_SYNC);
    err = nilfs_set_file_dirty(dir, nr_dirty);
    WARN_ON(err); /* do not happen */
    unlock_page(page);
}

static void nilfs_check_page(struct page *page)
{
    struct inode *dir = page->mapping->host;
    struct super_block *sb = dir->i_sb;
    unsigned chunk_size = nilfs_chunk_size(dir);
    char *kaddr = page_address(page);
    unsigned offs, rec_len;
    unsigned limit = PAGE_CACHE_SIZE;
    struct nilfs_dir_entry *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 - NILFS_DIR_REC_LEN(1); offs += rec_len) {
        p = (struct nilfs_dir_entry *)(kaddr + offs);
        rec_len = nilfs_rec_len_from_disk(p->rec_len);

        if (rec_len < NILFS_DIR_REC_LEN(1))
            goto Eshort;
        if (rec_len & 3)
            goto Ealign;
        if (rec_len < NILFS_DIR_REC_LEN(p->name_len))
            goto Enamelen;
        if (((offs + rec_len - 1) ^ offs) & ~(chunk_size-1))
            goto Espan;
    }
    if (offs != limit)
        goto Eend;
out:
    SetPageChecked(page);
    return;

    /* Too bad, we had an error */

Ebadsize:
    nilfs_error(sb, "nilfs_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";
bad_entry:
    nilfs_error(sb, "nilfs_check_page", "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) le64_to_cpu(p->inode),
            rec_len, p->name_len);
    goto fail;
Eend:
    p = (struct nilfs_dir_entry *)(kaddr + offs);
    nilfs_error(sb, "nilfs_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) le64_to_cpu(p->inode));
fail:
    SetPageChecked(page);
    SetPageError(page);
}

static struct page *nilfs_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))
            nilfs_check_page(page);
        if (PageError(page))
            goto fail;
    }
    return page;

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

/*
 * NOTE! unlike strncmp, nilfs_match returns 1 for success, 0 for failure.
 *
 * len <= NILFS_NAME_LEN and de != NULL are guaranteed by caller.
 */
static int
nilfs_match(int len, const unsigned char *name, struct nilfs_dir_entry *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 struct nilfs_dir_entry *nilfs_next_entry(struct nilfs_dir_entry *p)
{
    return (struct nilfs_dir_entry *)((char *)p +
                      nilfs_rec_len_from_disk(p->rec_len));
}

static unsigned char
nilfs_filetype_table[NILFS_FT_MAX] = {
    [NILFS_FT_UNKNOWN]  = DT_UNKNOWN,
    [NILFS_FT_REG_FILE] = DT_REG,
    [NILFS_FT_DIR]      = DT_DIR,
    [NILFS_FT_CHRDEV]   = DT_CHR,
    [NILFS_FT_BLKDEV]   = DT_BLK,
    [NILFS_FT_FIFO]     = DT_FIFO,
    [NILFS_FT_SOCK]     = DT_SOCK,
    [NILFS_FT_SYMLINK]  = DT_LNK,
};

#define S_SHIFT 12
static unsigned char
nilfs_type_by_mode[S_IFMT >> S_SHIFT] = {
    [S_IFREG >> S_SHIFT]    = NILFS_FT_REG_FILE,
    [S_IFDIR >> S_SHIFT]    = NILFS_FT_DIR,
    [S_IFCHR >> S_SHIFT]    = NILFS_FT_CHRDEV,
    [S_IFBLK >> S_SHIFT]    = NILFS_FT_BLKDEV,
    [S_IFIFO >> S_SHIFT]    = NILFS_FT_FIFO,
    [S_IFSOCK >> S_SHIFT]   = NILFS_FT_SOCK,
    [S_IFLNK >> S_SHIFT]    = NILFS_FT_SYMLINK,
};

static void nilfs_set_de_type(struct nilfs_dir_entry *de, struct inode *inode)
{
    umode_t mode = inode->i_mode;

    de->file_type = nilfs_type_by_mode[(mode & S_IFMT)>>S_SHIFT];
}

static int nilfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
    loff_t pos = filp->f_pos;
    struct inode *inode = filp->f_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 = ~(nilfs_chunk_size(inode)-1); */
    unsigned char *types = NULL;
    int ret;

    if (pos > inode->i_size - NILFS_DIR_REC_LEN(1))
        goto success;

    types = nilfs_filetype_table;

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

        if (IS_ERR(page)) {
            nilfs_error(sb, __func__, "bad page in #%lu",
                    inode->i_ino);
            filp->f_pos += PAGE_CACHE_SIZE - offset;
            ret = -EIO;
            goto done;
        }
        kaddr = page_address(page);
        de = (struct nilfs_dir_entry *)(kaddr + offset);
        limit = kaddr + nilfs_last_byte(inode, n) -
            NILFS_DIR_REC_LEN(1);
        for ( ; (char *)de <= limit; de = nilfs_next_entry(de)) {
            if (de->rec_len == 0) {
                nilfs_error(sb, __func__,
                        "zero-length directory entry");
                ret = -EIO;
                nilfs_put_page(page);
                goto done;
            }
            if (de->inode) {
                int over;
                unsigned char d_type = DT_UNKNOWN;

                if (types && de->file_type < NILFS_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,
                        le64_to_cpu(de->inode), d_type);
                if (over) {
                    nilfs_put_page(page);
                    goto success;
                }
            }
            filp->f_pos += nilfs_rec_len_from_disk(de->rec_len);
        }
        nilfs_put_page(page);
    }

success:
    ret = 0;
done:
    return ret;
}

/*
 *  nilfs_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 nilfs_dir_entry *
nilfs_find_entry(struct inode *dir, const struct qstr *qstr,
         struct page **res_page)
{
    const unsigned char *name = qstr->name;
    int namelen = qstr->len;
    unsigned reclen = NILFS_DIR_REC_LEN(namelen);
    unsigned long start, n;
    unsigned long npages = dir_pages(dir);
    struct page *page = NULL;
    struct nilfs_inode_info *ei = NILFS_I(dir);
    struct nilfs_dir_entry *de;

    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 = nilfs_get_page(dir, n);
        if (!IS_ERR(page)) {
            kaddr = page_address(page);
            de = (struct nilfs_dir_entry *)kaddr;
            kaddr += nilfs_last_byte(dir, n) - reclen;
            while ((char *) de <= kaddr) {
                if (de->rec_len == 0) {
                    nilfs_error(dir->i_sb, __func__,
                        "zero-length directory entry");
                    nilfs_put_page(page);
                    goto out;
                }
                if (nilfs_match(namelen, name, de))
                    goto found;
                de = nilfs_next_entry(de);
            }
            nilfs_put_page(page);
        }
        if (++n >= npages)
            n = 0;
        /* next page is past the blocks we've got */
        if (unlikely(n > (dir->i_blocks >> (PAGE_CACHE_SHIFT - 9)))) {
            nilfs_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 nilfs_dir_entry *nilfs_dotdot(struct inode *dir, struct page **p)
{
    struct page *page = nilfs_get_page(dir, 0);
    struct nilfs_dir_entry *de = NULL;

    if (!IS_ERR(page)) {
        de = nilfs_next_entry(
            (struct nilfs_dir_entry *)page_address(page));
        *p = page;
    }
    return de;
}

ino_t nilfs_inode_by_name(struct inode *dir, const struct qstr *qstr)
{
    ino_t res = 0;
    struct nilfs_dir_entry *de;
    struct page *page;

    de = nilfs_find_entry(dir, qstr, &page);
    if (de) {
        res = le64_to_cpu(de->inode);
        kunmap(page);
        page_cache_release(page);
    }
    return res;
}

/* Releases the page */
void nilfs_set_link(struct inode *dir, struct nilfs_dir_entry *de,
            struct page *page, struct inode *inode)
{
    unsigned from = (char *) de - (char *) page_address(page);
    unsigned to = from + nilfs_rec_len_from_disk(de->rec_len);
    struct address_space *mapping = page->mapping;
    int err;

    lock_page(page);
    err = nilfs_prepare_chunk(page, from, to);
    BUG_ON(err);
    de->inode = cpu_to_le64(inode->i_ino);
    nilfs_set_de_type(de, inode);
    nilfs_commit_chunk(page, mapping, from, to);
    nilfs_put_page(page);
    dir->i_mtime = dir->i_ctime = CURRENT_TIME;
}

/*
 *  Parent is locked.
 */
int nilfs_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;
    unsigned chunk_size = nilfs_chunk_size(dir);
    unsigned reclen = NILFS_DIR_REC_LEN(namelen);
    unsigned short rec_len, name_len;
    struct page *page = NULL;
    struct nilfs_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.
     * 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 = nilfs_get_page(dir, n);
        err = PTR_ERR(page);
        if (IS_ERR(page))
            goto out;
        lock_page(page);
        kaddr = page_address(page);
        dir_end = kaddr + nilfs_last_byte(dir, n);
        de = (struct nilfs_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->rec_len = nilfs_rec_len_to_disk(chunk_size);
                de->inode = 0;
                goto got_it;
            }
            if (de->rec_len == 0) {
                nilfs_error(dir->i_sb, __func__,
                        "zero-length directory entry");
                err = -EIO;
                goto out_unlock;
            }
            err = -EEXIST;
            if (nilfs_match(namelen, name, de))
                goto out_unlock;
            name_len = NILFS_DIR_REC_LEN(de->name_len);
            rec_len = nilfs_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 = (struct nilfs_dir_entry *)((char *)de + rec_len);
        }
        unlock_page(page);
        nilfs_put_page(page);
    }
    BUG();
    return -EINVAL;

got_it:
    from = (char *)de - (char *)page_address(page);
    to = from + rec_len;
    err = nilfs_prepare_chunk(page, from, to);
    if (err)
        goto out_unlock;
    if (de->inode) {
        struct nilfs_dir_entry *de1;

        de1 = (struct nilfs_dir_entry *)((char *)de + name_len);
        de1->rec_len = nilfs_rec_len_to_disk(rec_len - name_len);
        de->rec_len = nilfs_rec_len_to_disk(name_len);
        de = de1;
    }
    de->name_len = namelen;
    memcpy(de->name, name, namelen);
    de->inode = cpu_to_le64(inode->i_ino);
    nilfs_set_de_type(de, inode);
    nilfs_commit_chunk(page, page->mapping, from, to);
    dir->i_mtime = dir->i_ctime = CURRENT_TIME;
    nilfs_mark_inode_dirty(dir);
    /* OFFSET_CACHE */
out_put:
    nilfs_put_page(page);
out:
    return err;
out_unlock:
    unlock_page(page);
    goto out_put;
}

/*
 * nilfs_delete_entry deletes a directory entry by merging it with the
 * previous entry. Page is up-to-date. Releases the page.
 */
int nilfs_delete_entry(struct nilfs_dir_entry *dir, struct page *page)
{
    struct address_space *mapping = page->mapping;
    struct inode *inode = mapping->host;
    char *kaddr = page_address(page);
    unsigned from = ((char *)dir - kaddr) & ~(nilfs_chunk_size(inode) - 1);
    unsigned to = ((char *)dir - kaddr) +
        nilfs_rec_len_from_disk(dir->rec_len);
    struct nilfs_dir_entry *pde = NULL;
    struct nilfs_dir_entry *de = (struct nilfs_dir_entry *)(kaddr + from);
    int err;

    while ((char *)de < (char *)dir) {
        if (de->rec_len == 0) {
            nilfs_error(inode->i_sb, __func__,
                    "zero-length directory entry");
            err = -EIO;
            goto out;
        }
        pde = de;
        de = nilfs_next_entry(de);
    }
    if (pde)
        from = (char *)pde - (char *)page_address(page);
    lock_page(page);
    err = nilfs_prepare_chunk(page, from, to);
    BUG_ON(err);
    if (pde)
        pde->rec_len = nilfs_rec_len_to_disk(to - from);
    dir->inode = 0;
    nilfs_commit_chunk(page, mapping, from, to);
    inode->i_ctime = inode->i_mtime = CURRENT_TIME;
out:
    nilfs_put_page(page);
    return err;
}

/*
 * Set the first fragment of directory.
 */
int nilfs_make_empty(struct inode *inode, struct inode *parent)
{
    struct address_space *mapping = inode->i_mapping;
    struct page *page = grab_cache_page(mapping, 0);
    unsigned chunk_size = nilfs_chunk_size(inode);
    struct nilfs_dir_entry *de;
    int err;
    void *kaddr;

    if (!page)
        return -ENOMEM;

    err = nilfs_prepare_chunk(page, 0, chunk_size);
    if (unlikely(err)) {
        unlock_page(page);
        goto fail;
    }
    kaddr = kmap_atomic(page);
    memset(kaddr, 0, chunk_size);
    de = (struct nilfs_dir_entry *)kaddr;
    de->name_len = 1;
    de->rec_len = nilfs_rec_len_to_disk(NILFS_DIR_REC_LEN(1));
    memcpy(de->name, ".\0\0", 4);
    de->inode = cpu_to_le64(inode->i_ino);
    nilfs_set_de_type(de, inode);

    de = (struct nilfs_dir_entry *)(kaddr + NILFS_DIR_REC_LEN(1));
    de->name_len = 2;
    de->rec_len = nilfs_rec_len_to_disk(chunk_size - NILFS_DIR_REC_LEN(1));
    de->inode = cpu_to_le64(parent->i_ino);
    memcpy(de->name, "..\0", 4);
    nilfs_set_de_type(de, inode);
    kunmap_atomic(kaddr);
    nilfs_commit_chunk(page, mapping, 0, chunk_size);
fail:
    page_cache_release(page);
    return err;
}

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

    for (i = 0; i < npages; i++) {
        char *kaddr;
        struct nilfs_dir_entry *de;

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

        kaddr = page_address(page);
        de = (struct nilfs_dir_entry *)kaddr;
        kaddr += nilfs_last_byte(inode, i) - NILFS_DIR_REC_LEN(1);

        while ((char *)de <= kaddr) {
            if (de->rec_len == 0) {
                nilfs_error(inode->i_sb, __func__,
                        "zero-length directory entry "
                        "(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_le64(inode->i_ino))
                        goto not_empty;
                } else if (de->name[1] != '.')
                    goto not_empty;
            }
            de = nilfs_next_entry(de);
        }
        nilfs_put_page(page);
    }
    return 1;

not_empty:
    nilfs_put_page(page);
    return 0;
}

const struct file_operations nilfs_dir_operations = {
    .llseek     = generic_file_llseek,
    .read       = generic_read_dir,
    .readdir    = nilfs_readdir,
    .unlocked_ioctl = nilfs_ioctl,
#ifdef CONFIG_COMPAT
    .compat_ioctl   = nilfs_compat_ioctl,
#endif  /* CONFIG_COMPAT */
    .fsync      = nilfs_sync_file,

};