namei.c

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/*
 * linux/fs/ext2/namei.c
 *
 * Rewrite to pagecache. Almost all code had been changed, so blame me
 * if the things go wrong. Please, send bug reports to
 * [email protected]
 *
 * Stuff here is basically a glue between the VFS and generic UNIXish
 * filesystem that keeps everything in pagecache. All knowledge of the
 * directory layout is in fs/ext2/dir.c - it turned out to be easily separatable
 * and it's easier to debug that way. In principle we might want to
 * generalize that a bit and turn it into a library. Or not.
 *
 * The only non-static object here is ext2_dir_inode_operations.
 *
 * TODO: get rid of kmap() use, add readahead.
 *
 * 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/namei.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller ([email protected]), 1995
 */

#include <linux/pagemap.h>
#include <linux/quotaops.h>
#include "ext2.h"
#include "xattr.h"
#include "acl.h"
#include "xip.h"

static inline int ext2_add_nondir(struct dentry *dentry, struct inode *inode)
{
    int err = ext2_add_link(dentry, inode);
    if (!err) {
        unlock_new_inode(inode);
        d_instantiate(dentry, inode);
        return 0;
    }
    inode_dec_link_count(inode);
    unlock_new_inode(inode);
    iput(inode);
    return err;
}

/*
 * Methods themselves.
 */

static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry, unsigned int flags)
{
    struct inode * inode;
    ino_t ino;
    
    if (dentry->d_name.len > EXT2_NAME_LEN)
        return ERR_PTR(-ENAMETOOLONG);

    ino = ext2_inode_by_name(dir, &dentry->d_name);
    inode = NULL;
    if (ino) {
        inode = ext2_iget(dir->i_sb, ino);
        if (inode == ERR_PTR(-ESTALE)) {
            ext2_error(dir->i_sb, __func__,
                    "deleted inode referenced: %lu",
                    (unsigned long) ino);
            return ERR_PTR(-EIO);
        }
    }
    return d_splice_alias(inode, dentry);
}

struct dentry *ext2_get_parent(struct dentry *child)
{
    struct qstr dotdot = QSTR_INIT("..", 2);
    unsigned long ino = ext2_inode_by_name(child->d_inode, &dotdot);
    if (!ino)
        return ERR_PTR(-ENOENT);
    return d_obtain_alias(ext2_iget(child->d_inode->i_sb, ino));
} 

/*
 * By the time this is called, we already have created
 * the directory cache entry for the new file, but it
 * is so far negative - it has no inode.
 *
 * If the create succeeds, we fill in the inode information
 * with d_instantiate(). 
 */
static int ext2_create (struct inode * dir, struct dentry * dentry, umode_t mode, bool excl)
{
    struct inode *inode;

    dquot_initialize(dir);

    inode = ext2_new_inode(dir, mode, &dentry->d_name);
    if (IS_ERR(inode))
        return PTR_ERR(inode);

    inode->i_op = &ext2_file_inode_operations;
    if (ext2_use_xip(inode->i_sb)) {
        inode->i_mapping->a_ops = &ext2_aops_xip;
        inode->i_fop = &ext2_xip_file_operations;
    } else if (test_opt(inode->i_sb, NOBH)) {
        inode->i_mapping->a_ops = &ext2_nobh_aops;
        inode->i_fop = &ext2_file_operations;
    } else {
        inode->i_mapping->a_ops = &ext2_aops;
        inode->i_fop = &ext2_file_operations;
    }
    mark_inode_dirty(inode);
    return ext2_add_nondir(dentry, inode);
}

static int ext2_mknod (struct inode * dir, struct dentry *dentry, umode_t mode, dev_t rdev)
{
    struct inode * inode;
    int err;

    if (!new_valid_dev(rdev))
        return -EINVAL;

    dquot_initialize(dir);

    inode = ext2_new_inode (dir, mode, &dentry->d_name);
    err = PTR_ERR(inode);
    if (!IS_ERR(inode)) {
        init_special_inode(inode, inode->i_mode, rdev);
#ifdef CONFIG_EXT2_FS_XATTR
        inode->i_op = &ext2_special_inode_operations;
#endif
        mark_inode_dirty(inode);
        err = ext2_add_nondir(dentry, inode);
    }
    return err;
}

static int ext2_symlink (struct inode * dir, struct dentry * dentry,
    const char * symname)
{
    struct super_block * sb = dir->i_sb;
    int err = -ENAMETOOLONG;
    unsigned l = strlen(symname)+1;
    struct inode * inode;

    if (l > sb->s_blocksize)
        goto out;

    dquot_initialize(dir);

    inode = ext2_new_inode (dir, S_IFLNK | S_IRWXUGO, &dentry->d_name);
    err = PTR_ERR(inode);
    if (IS_ERR(inode))
        goto out;

    if (l > sizeof (EXT2_I(inode)->i_data)) {
        /* slow symlink */
        inode->i_op = &ext2_symlink_inode_operations;
        if (test_opt(inode->i_sb, NOBH))
            inode->i_mapping->a_ops = &ext2_nobh_aops;
        else
            inode->i_mapping->a_ops = &ext2_aops;
        err = page_symlink(inode, symname, l);
        if (err)
            goto out_fail;
    } else {
        /* fast symlink */
        inode->i_op = &ext2_fast_symlink_inode_operations;
        memcpy((char*)(EXT2_I(inode)->i_data),symname,l);
        inode->i_size = l-1;
    }
    mark_inode_dirty(inode);

    err = ext2_add_nondir(dentry, inode);
out:
    return err;

out_fail:
    inode_dec_link_count(inode);
    unlock_new_inode(inode);
    iput (inode);
    goto out;
}

static int ext2_link (struct dentry * old_dentry, struct inode * dir,
    struct dentry *dentry)
{
    struct inode *inode = old_dentry->d_inode;
    int err;

    dquot_initialize(dir);

    inode->i_ctime = CURRENT_TIME_SEC;
    inode_inc_link_count(inode);
    ihold(inode);

    err = ext2_add_link(dentry, inode);
    if (!err) {
        d_instantiate(dentry, inode);
        return 0;
    }
    inode_dec_link_count(inode);
    iput(inode);
    return err;
}

static int ext2_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
{
    struct inode * inode;
    int err;

    dquot_initialize(dir);

    inode_inc_link_count(dir);

    inode = ext2_new_inode(dir, S_IFDIR | mode, &dentry->d_name);
    err = PTR_ERR(inode);
    if (IS_ERR(inode))
        goto out_dir;

    inode->i_op = &ext2_dir_inode_operations;
    inode->i_fop = &ext2_dir_operations;
    if (test_opt(inode->i_sb, NOBH))
        inode->i_mapping->a_ops = &ext2_nobh_aops;
    else
        inode->i_mapping->a_ops = &ext2_aops;

    inode_inc_link_count(inode);

    err = ext2_make_empty(inode, dir);
    if (err)
        goto out_fail;

    err = ext2_add_link(dentry, inode);
    if (err)
        goto out_fail;

    unlock_new_inode(inode);
    d_instantiate(dentry, inode);
out:
    return err;

out_fail:
    inode_dec_link_count(inode);
    inode_dec_link_count(inode);
    unlock_new_inode(inode);
    iput(inode);
out_dir:
    inode_dec_link_count(dir);
    goto out;
}

static int ext2_unlink(struct inode * dir, struct dentry *dentry)
{
    struct inode * inode = dentry->d_inode;
    struct ext2_dir_entry_2 * de;
    struct page * page;
    int err = -ENOENT;

    dquot_initialize(dir);

    de = ext2_find_entry (dir, &dentry->d_name, &page);
    if (!de)
        goto out;

    err = ext2_delete_entry (de, page);
    if (err)
        goto out;

    inode->i_ctime = dir->i_ctime;
    inode_dec_link_count(inode);
    err = 0;
out:
    return err;
}

static int ext2_rmdir (struct inode * dir, struct dentry *dentry)
{
    struct inode * inode = dentry->d_inode;
    int err = -ENOTEMPTY;

    if (ext2_empty_dir(inode)) {
        err = ext2_unlink(dir, dentry);
        if (!err) {
            inode->i_size = 0;
            inode_dec_link_count(inode);
            inode_dec_link_count(dir);
        }
    }
    return err;
}

static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
    struct inode * new_dir, struct dentry * new_dentry )
{
    struct inode * old_inode = old_dentry->d_inode;
    struct inode * new_inode = new_dentry->d_inode;
    struct page * dir_page = NULL;
    struct ext2_dir_entry_2 * dir_de = NULL;
    struct page * old_page;
    struct ext2_dir_entry_2 * old_de;
    int err = -ENOENT;

    dquot_initialize(old_dir);
    dquot_initialize(new_dir);

    old_de = ext2_find_entry (old_dir, &old_dentry->d_name, &old_page);
    if (!old_de)
        goto out;

    if (S_ISDIR(old_inode->i_mode)) {
        err = -EIO;
        dir_de = ext2_dotdot(old_inode, &dir_page);
        if (!dir_de)
            goto out_old;
    }

    if (new_inode) {
        struct page *new_page;
        struct ext2_dir_entry_2 *new_de;

        err = -ENOTEMPTY;
        if (dir_de && !ext2_empty_dir (new_inode))
            goto out_dir;

        err = -ENOENT;
        new_de = ext2_find_entry (new_dir, &new_dentry->d_name, &new_page);
        if (!new_de)
            goto out_dir;
        ext2_set_link(new_dir, new_de, new_page, old_inode, 1);
        new_inode->i_ctime = CURRENT_TIME_SEC;
        if (dir_de)
            drop_nlink(new_inode);
        inode_dec_link_count(new_inode);
    } else {
        err = ext2_add_link(new_dentry, old_inode);
        if (err)
            goto out_dir;
        if (dir_de)
            inode_inc_link_count(new_dir);
    }

    /*
     * Like most other Unix systems, set the ctime for inodes on a
     * rename.
     */
    old_inode->i_ctime = CURRENT_TIME_SEC;
    mark_inode_dirty(old_inode);

    ext2_delete_entry (old_de, old_page);

    if (dir_de) {
        if (old_dir != new_dir)
            ext2_set_link(old_inode, dir_de, dir_page, new_dir, 0);
        else {
            kunmap(dir_page);
            page_cache_release(dir_page);
        }
        inode_dec_link_count(old_dir);
    }
    return 0;


out_dir:
    if (dir_de) {
        kunmap(dir_page);
        page_cache_release(dir_page);
    }
out_old:
    kunmap(old_page);
    page_cache_release(old_page);
out:
    return err;
}

const struct inode_operations ext2_dir_inode_operations = {
    .create     = ext2_create,
    .lookup     = ext2_lookup,
    .link       = ext2_link,
    .unlink     = ext2_unlink,
    .symlink    = ext2_symlink,
    .mkdir      = ext2_mkdir,
    .rmdir      = ext2_rmdir,
    .mknod      = ext2_mknod,
    .rename     = ext2_rename,
#ifdef CONFIG_EXT2_FS_XATTR
    .setxattr   = generic_setxattr,
    .getxattr   = generic_getxattr,
    .listxattr  = ext2_listxattr,
    .removexattr    = generic_removexattr,
#endif
    .setattr    = ext2_setattr,
    .get_acl    = ext2_get_acl,
};

const struct inode_operations ext2_special_inode_operations = {
#ifdef CONFIG_EXT2_FS_XATTR
    .setxattr   = generic_setxattr,
    .getxattr   = generic_getxattr,
    .listxattr  = ext2_listxattr,
    .removexattr    = generic_removexattr,
#endif
    .setattr    = ext2_setattr,
    .get_acl    = ext2_get_acl,
};