dir.c

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/*
 * Copyright (C) 2005, 2006
 * Avishay Traeger ([email protected])
 * Copyright (C) 2008, 2009
 * Boaz Harrosh <[email protected]>
 *
 * Copyrights for code taken from ext2:
 *     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/inode.c
 *     Copyright (C) 1991, 1992  Linus Torvalds
 *
 * This file is part of exofs.
 *
 * exofs 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.  Since it is based on ext2, and the only
 * valid version of GPL for the Linux kernel is version 2, the only valid
 * version of GPL for exofs is version 2.
 *
 * exofs 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 exofs; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include "exofs.h"

static inline unsigned exofs_chunk_size(struct inode *inode)
{
    return inode->i_sb->s_blocksize;
}

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

/* Accesses dir's inode->i_size must be called under inode lock */
static inline unsigned long dir_pages(struct inode *inode)
{
    return (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
}

static unsigned exofs_last_byte(struct inode *inode, unsigned long page_nr)
{
    loff_t 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 exofs_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++;

    if (!PageUptodate(page))
        SetPageUptodate(page);

    if (pos+len > dir->i_size) {
        i_size_write(dir, pos+len);
        mark_inode_dirty(dir);
    }
    set_page_dirty(page);

    if (IS_DIRSYNC(dir))
        err = write_one_page(page, 1);
    else
        unlock_page(page);

    return err;
}

static void exofs_check_page(struct page *page)
{
    struct inode *dir = page->mapping->host;
    unsigned chunk_size = exofs_chunk_size(dir);
    char *kaddr = page_address(page);
    unsigned offs, rec_len;
    unsigned limit = PAGE_CACHE_SIZE;
    struct exofs_dir_entry *p;
    char *error;

    /* if the page is the last one in the directory */
    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 - EXOFS_DIR_REC_LEN(1); offs += rec_len) {
        p = (struct exofs_dir_entry *)(kaddr + offs);
        rec_len = le16_to_cpu(p->rec_len);

        if (rec_len < EXOFS_DIR_REC_LEN(1))
            goto Eshort;
        if (rec_len & 3)
            goto Ealign;
        if (rec_len < EXOFS_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;

Ebadsize:
    EXOFS_ERR("ERROR [exofs_check_page]: "
        "size of directory(0x%lx) is not a multiple of chunk size\n",
        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;
bad_entry:
    EXOFS_ERR(
        "ERROR [exofs_check_page]: bad entry in directory(0x%lx): %s - "
        "offset=%lu, inode=0x%llu, rec_len=%d, name_len=%d\n",
        dir->i_ino, error, (page->index<<PAGE_CACHE_SHIFT)+offs,
        _LLU(le64_to_cpu(p->inode_no)),
        rec_len, p->name_len);
    goto fail;
Eend:
    p = (struct exofs_dir_entry *)(kaddr + offs);
    EXOFS_ERR("ERROR [exofs_check_page]: "
        "entry in directory(0x%lx) spans the page boundary"
        "offset=%lu, inode=0x%llx\n",
        dir->i_ino, (page->index<<PAGE_CACHE_SHIFT)+offs,
        _LLU(le64_to_cpu(p->inode_no)));
fail:
    SetPageChecked(page);
    SetPageError(page);
}

static struct page *exofs_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))
            exofs_check_page(page);
        if (PageError(page))
            goto fail;
    }
    return page;

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

static inline int exofs_match(int len, const unsigned char *name,
                    struct exofs_dir_entry *de)
{
    if (len != de->name_len)
        return 0;
    if (!de->inode_no)
        return 0;
    return !memcmp(name, de->name, len);
}

static inline
struct exofs_dir_entry *exofs_next_entry(struct exofs_dir_entry *p)
{
    return (struct exofs_dir_entry *)((char *)p + le16_to_cpu(p->rec_len));
}

static inline unsigned
exofs_validate_entry(char *base, unsigned offset, unsigned mask)
{
    struct exofs_dir_entry *de = (struct exofs_dir_entry *)(base + offset);
    struct exofs_dir_entry *p =
            (struct exofs_dir_entry *)(base + (offset&mask));
    while ((char *)p < (char *)de) {
        if (p->rec_len == 0)
            break;
        p = exofs_next_entry(p);
    }
    return (char *)p - base;
}

static unsigned char exofs_filetype_table[EXOFS_FT_MAX] = {
    [EXOFS_FT_UNKNOWN]  = DT_UNKNOWN,
    [EXOFS_FT_REG_FILE] = DT_REG,
    [EXOFS_FT_DIR]      = DT_DIR,
    [EXOFS_FT_CHRDEV]   = DT_CHR,
    [EXOFS_FT_BLKDEV]   = DT_BLK,
    [EXOFS_FT_FIFO]     = DT_FIFO,
    [EXOFS_FT_SOCK]     = DT_SOCK,
    [EXOFS_FT_SYMLINK]  = DT_LNK,
};

#define S_SHIFT 12
static unsigned char exofs_type_by_mode[S_IFMT >> S_SHIFT] = {
    [S_IFREG >> S_SHIFT]    = EXOFS_FT_REG_FILE,
    [S_IFDIR >> S_SHIFT]    = EXOFS_FT_DIR,
    [S_IFCHR >> S_SHIFT]    = EXOFS_FT_CHRDEV,
    [S_IFBLK >> S_SHIFT]    = EXOFS_FT_BLKDEV,
    [S_IFIFO >> S_SHIFT]    = EXOFS_FT_FIFO,
    [S_IFSOCK >> S_SHIFT]   = EXOFS_FT_SOCK,
    [S_IFLNK >> S_SHIFT]    = EXOFS_FT_SYMLINK,
};

static inline
void exofs_set_de_type(struct exofs_dir_entry *de, struct inode *inode)
{
    umode_t mode = inode->i_mode;
    de->file_type = exofs_type_by_mode[(mode & S_IFMT) >> S_SHIFT];
}

static int
exofs_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
    loff_t pos = filp->f_pos;
    struct inode *inode = filp->f_path.dentry->d_inode;
    unsigned int offset = pos & ~PAGE_CACHE_MASK;
    unsigned long n = pos >> PAGE_CACHE_SHIFT;
    unsigned long npages = dir_pages(inode);
    unsigned chunk_mask = ~(exofs_chunk_size(inode)-1);
    unsigned char *types = NULL;
    int need_revalidate = (filp->f_version != inode->i_version);

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

    types = exofs_filetype_table;

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

        if (IS_ERR(page)) {
            EXOFS_ERR("ERROR: bad page in directory(0x%lx)\n",
                  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 = exofs_validate_entry(kaddr, offset,
                                chunk_mask);
                filp->f_pos = (n<<PAGE_CACHE_SHIFT) + offset;
            }
            filp->f_version = inode->i_version;
            need_revalidate = 0;
        }
        de = (struct exofs_dir_entry *)(kaddr + offset);
        limit = kaddr + exofs_last_byte(inode, n) -
                            EXOFS_DIR_REC_LEN(1);
        for (; (char *)de <= limit; de = exofs_next_entry(de)) {
            if (de->rec_len == 0) {
                EXOFS_ERR("ERROR: "
                     "zero-length entry in directory(0x%lx)\n",
                     inode->i_ino);
                exofs_put_page(page);
                return -EIO;
            }
            if (de->inode_no) {
                int over;
                unsigned char d_type = DT_UNKNOWN;

                if (types && de->file_type < EXOFS_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_no),
                        d_type);
                if (over) {
                    exofs_put_page(page);
                    return 0;
                }
            }
            filp->f_pos += le16_to_cpu(de->rec_len);
        }
        exofs_put_page(page);
    }

    return 0;
}

struct exofs_dir_entry *exofs_find_entry(struct inode *dir,
            struct dentry *dentry, struct page **res_page)
{
    const unsigned char *name = dentry->d_name.name;
    int namelen = dentry->d_name.len;
    unsigned reclen = EXOFS_DIR_REC_LEN(namelen);
    unsigned long start, n;
    unsigned long npages = dir_pages(dir);
    struct page *page = NULL;
    struct exofs_i_info *oi = exofs_i(dir);
    struct exofs_dir_entry *de;

    if (npages == 0)
        goto out;

    *res_page = NULL;

    start = oi->i_dir_start_lookup;
    if (start >= npages)
        start = 0;
    n = start;
    do {
        char *kaddr;
        page = exofs_get_page(dir, n);
        if (!IS_ERR(page)) {
            kaddr = page_address(page);
            de = (struct exofs_dir_entry *) kaddr;
            kaddr += exofs_last_byte(dir, n) - reclen;
            while ((char *) de <= kaddr) {
                if (de->rec_len == 0) {
                    EXOFS_ERR("ERROR: zero-length entry in "
                          "directory(0x%lx)\n",
                          dir->i_ino);
                    exofs_put_page(page);
                    goto out;
                }
                if (exofs_match(namelen, name, de))
                    goto found;
                de = exofs_next_entry(de);
            }
            exofs_put_page(page);
        }
        if (++n >= npages)
            n = 0;
    } while (n != start);
out:
    return NULL;

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

struct exofs_dir_entry *exofs_dotdot(struct inode *dir, struct page **p)
{
    struct page *page = exofs_get_page(dir, 0);
    struct exofs_dir_entry *de = NULL;

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

ino_t exofs_parent_ino(struct dentry *child)
{
    struct page *page;
    struct exofs_dir_entry *de;
    ino_t ino;

    de = exofs_dotdot(child->d_inode, &page);
    if (!de)
        return 0;

    ino = le64_to_cpu(de->inode_no);
    exofs_put_page(page);
    return ino;
}

ino_t exofs_inode_by_name(struct inode *dir, struct dentry *dentry)
{
    ino_t res = 0;
    struct exofs_dir_entry *de;
    struct page *page;

    de = exofs_find_entry(dir, dentry, &page);
    if (de) {
        res = le64_to_cpu(de->inode_no);
        exofs_put_page(page);
    }
    return res;
}

int exofs_set_link(struct inode *dir, struct exofs_dir_entry *de,
            struct page *page, struct inode *inode)
{
    loff_t pos = page_offset(page) +
            (char *) de - (char *) page_address(page);
    unsigned len = le16_to_cpu(de->rec_len);
    int err;

    lock_page(page);
    err = exofs_write_begin(NULL, page->mapping, pos, len,
                AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
    if (err)
        EXOFS_ERR("exofs_set_link: exofs_write_begin FAILED => %d\n",
              err);

    de->inode_no = cpu_to_le64(inode->i_ino);
    exofs_set_de_type(de, inode);
    if (likely(!err))
        err = exofs_commit_chunk(page, pos, len);
    exofs_put_page(page);
    dir->i_mtime = dir->i_ctime = CURRENT_TIME;
    mark_inode_dirty(dir);
    return err;
}

int exofs_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 = exofs_chunk_size(dir);
    unsigned reclen = EXOFS_DIR_REC_LEN(namelen);
    unsigned short rec_len, name_len;
    struct page *page = NULL;
    struct exofs_sb_info *sbi = inode->i_sb->s_fs_info;
    struct exofs_dir_entry *de;
    unsigned long npages = dir_pages(dir);
    unsigned long n;
    char *kaddr;
    loff_t pos;
    int err;

    for (n = 0; n <= npages; n++) {
        char *dir_end;

        page = exofs_get_page(dir, n);
        err = PTR_ERR(page);
        if (IS_ERR(page))
            goto out;
        lock_page(page);
        kaddr = page_address(page);
        dir_end = kaddr + exofs_last_byte(dir, n);
        de = (struct exofs_dir_entry *)kaddr;
        kaddr += PAGE_CACHE_SIZE - reclen;
        while ((char *)de <= kaddr) {
            if ((char *)de == dir_end) {
                name_len = 0;
                rec_len = chunk_size;
                de->rec_len = cpu_to_le16(chunk_size);
                de->inode_no = 0;
                goto got_it;
            }
            if (de->rec_len == 0) {
                EXOFS_ERR("ERROR: exofs_add_link: "
                      "zero-length entry in directory(0x%lx)\n",
                      inode->i_ino);
                err = -EIO;
                goto out_unlock;
            }
            err = -EEXIST;
            if (exofs_match(namelen, name, de))
                goto out_unlock;
            name_len = EXOFS_DIR_REC_LEN(de->name_len);
            rec_len = le16_to_cpu(de->rec_len);
            if (!de->inode_no && rec_len >= reclen)
                goto got_it;
            if (rec_len >= name_len + reclen)
                goto got_it;
            de = (struct exofs_dir_entry *) ((char *) de + rec_len);
        }
        unlock_page(page);
        exofs_put_page(page);
    }

    EXOFS_ERR("exofs_add_link: BAD dentry=%p or inode=0x%lx\n",
          dentry, inode->i_ino);
    return -EINVAL;

got_it:
    pos = page_offset(page) +
        (char *)de - (char *)page_address(page);
    err = exofs_write_begin(NULL, page->mapping, pos, rec_len, 0,
                            &page, NULL);
    if (err)
        goto out_unlock;
    if (de->inode_no) {
        struct exofs_dir_entry *de1 =
            (struct exofs_dir_entry *)((char *)de + name_len);
        de1->rec_len = cpu_to_le16(rec_len - name_len);
        de->rec_len = cpu_to_le16(name_len);
        de = de1;
    }
    de->name_len = namelen;
    memcpy(de->name, name, namelen);
    de->inode_no = cpu_to_le64(inode->i_ino);
    exofs_set_de_type(de, inode);
    err = exofs_commit_chunk(page, pos, rec_len);
    dir->i_mtime = dir->i_ctime = CURRENT_TIME;
    mark_inode_dirty(dir);
    sbi->s_numfiles++;

out_put:
    exofs_put_page(page);
out:
    return err;
out_unlock:
    unlock_page(page);
    goto out_put;
}

int exofs_delete_entry(struct exofs_dir_entry *dir, struct page *page)
{
    struct address_space *mapping = page->mapping;
    struct inode *inode = mapping->host;
    struct exofs_sb_info *sbi = inode->i_sb->s_fs_info;
    char *kaddr = page_address(page);
    unsigned from = ((char *)dir - kaddr) & ~(exofs_chunk_size(inode)-1);
    unsigned to = ((char *)dir - kaddr) + le16_to_cpu(dir->rec_len);
    loff_t pos;
    struct exofs_dir_entry *pde = NULL;
    struct exofs_dir_entry *de = (struct exofs_dir_entry *) (kaddr + from);
    int err;

    while (de < dir) {
        if (de->rec_len == 0) {
            EXOFS_ERR("ERROR: exofs_delete_entry:"
                  "zero-length entry in directory(0x%lx)\n",
                  inode->i_ino);
            err = -EIO;
            goto out;
        }
        pde = de;
        de = exofs_next_entry(de);
    }
    if (pde)
        from = (char *)pde - (char *)page_address(page);
    pos = page_offset(page) + from;
    lock_page(page);
    err = exofs_write_begin(NULL, page->mapping, pos, to - from, 0,
                            &page, NULL);
    if (err)
        EXOFS_ERR("exofs_delete_entry: exofs_write_begin FAILED => %d\n",
              err);
    if (pde)
        pde->rec_len = cpu_to_le16(to - from);
    dir->inode_no = 0;
    if (likely(!err))
        err = exofs_commit_chunk(page, pos, to - from);
    inode->i_ctime = inode->i_mtime = CURRENT_TIME;
    mark_inode_dirty(inode);
    sbi->s_numfiles--;
out:
    exofs_put_page(page);
    return err;
}

/* kept aligned on 4 bytes */
#define THIS_DIR ".\0\0"
#define PARENT_DIR "..\0"

int exofs_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 = exofs_chunk_size(inode);
    struct exofs_dir_entry *de;
    int err;
    void *kaddr;

    if (!page)
        return -ENOMEM;

    err = exofs_write_begin(NULL, page->mapping, 0, chunk_size, 0,
                            &page, NULL);
    if (err) {
        unlock_page(page);
        goto fail;
    }

    kaddr = kmap_atomic(page);
    de = (struct exofs_dir_entry *)kaddr;
    de->name_len = 1;
    de->rec_len = cpu_to_le16(EXOFS_DIR_REC_LEN(1));
    memcpy(de->name, THIS_DIR, sizeof(THIS_DIR));
    de->inode_no = cpu_to_le64(inode->i_ino);
    exofs_set_de_type(de, inode);

    de = (struct exofs_dir_entry *)(kaddr + EXOFS_DIR_REC_LEN(1));
    de->name_len = 2;
    de->rec_len = cpu_to_le16(chunk_size - EXOFS_DIR_REC_LEN(1));
    de->inode_no = cpu_to_le64(parent->i_ino);
    memcpy(de->name, PARENT_DIR, sizeof(PARENT_DIR));
    exofs_set_de_type(de, inode);
    kunmap_atomic(kaddr);
    err = exofs_commit_chunk(page, 0, chunk_size);
fail:
    page_cache_release(page);
    return err;
}

int exofs_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 exofs_dir_entry *de;
        page = exofs_get_page(inode, i);

        if (IS_ERR(page))
            continue;

        kaddr = page_address(page);
        de = (struct exofs_dir_entry *)kaddr;
        kaddr += exofs_last_byte(inode, i) - EXOFS_DIR_REC_LEN(1);

        while ((char *)de <= kaddr) {
            if (de->rec_len == 0) {
                EXOFS_ERR("ERROR: exofs_empty_dir: "
                      "zero-length directory entry"
                      "kaddr=%p, de=%p\n", kaddr, de);
                goto not_empty;
            }
            if (de->inode_no != 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 (le64_to_cpu(de->inode_no) !=
                        inode->i_ino)
                        goto not_empty;
                } else if (de->name[1] != '.')
                    goto not_empty;
            }
            de = exofs_next_entry(de);
        }
        exofs_put_page(page);
    }
    return 1;

not_empty:
    exofs_put_page(page);
    return 0;
}

const struct file_operations exofs_dir_operations = {
    .llseek     = generic_file_llseek,
    .read       = generic_read_dir,
    .readdir    = exofs_readdir,
};