// SPDX-License-Identifier: GPL-2.0
/*
 * 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
 * viro@parcelfarce.linux.theplanet.co.uk
 *
 * 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 (card@masi.ibp.fr)
 * 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 (davem@caip.rutgers.edu), 1995
 */

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

static inline int ext2_add_nondir(struct dentry *dentry, struct inode *inode)
{
        int err = ext2_add_link(dentry, inode);
        if (!err) {
                d_instantiate_new(dentry, inode);
                return 0;
        }
        inode_dec_link_count(inode);
        discard_new_inode(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;
        int res;
        
        if (dentry->d_name.len > EXT2_NAME_LEN)
                return ERR_PTR(-ENAMETOOLONG);

        res = ext2_inode_by_name(dir, &dentry->d_name, &ino);
        if (res) {
                if (res != -ENOENT)
                        return ERR_PTR(res);
                inode = NULL;
        } else {
                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);
        ino_t ino;
        int res;

        res = ext2_inode_by_name(d_inode(child), &dotdot, &ino);
        if (res)
                return ERR_PTR(res);

        return d_obtain_alias(ext2_iget(child->d_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;
        int err;

        err = dquot_initialize(dir);
        if (err)
                return err;

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

        ext2_set_file_ops(inode);
        mark_inode_dirty(inode);
        return ext2_add_nondir(dentry, inode);
}

static int ext2_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
{
        struct inode *inode = ext2_new_inode(dir, mode, NULL);
        if (IS_ERR(inode))
                return PTR_ERR(inode);

        ext2_set_file_ops(inode);
        mark_inode_dirty(inode);
        d_tmpfile(dentry, inode);
        unlock_new_inode(inode);
        return 0;
}

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

        err = dquot_initialize(dir);
        if (err)
                return err;

        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);
                inode->i_op = &ext2_special_inode_operations;
                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;

        err = dquot_initialize(dir);
        if (err)
                goto out;

        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;
                inode_nohighmem(inode);
                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;
                inode->i_link = (char*)EXT2_I(inode)->i_data;
                memcpy(inode->i_link, 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);
        discard_new_inode(inode);
        goto out;
}

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

        err = dquot_initialize(dir);
        if (err)
                return err;

        inode->i_ctime = current_time(inode);
        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;

        err = dquot_initialize(dir);
        if (err)
                return err;

        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;

        d_instantiate_new(dentry, inode);
out:
        return err;

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

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

        err = dquot_initialize(dir);
        if (err)
                goto out;

        de = ext2_find_entry(dir, &dentry->d_name, &page);
        if (IS_ERR(de)) {
                err = PTR_ERR(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 = d_inode(dentry);
        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,
                        unsigned int flags)
{
        struct inode * old_inode = d_inode(old_dentry);
        struct inode * new_inode = d_inode(new_dentry);
        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;

        if (flags & ~RENAME_NOREPLACE)
                return -EINVAL;

        err = dquot_initialize(old_dir);
        if (err)
                goto out;

        err = dquot_initialize(new_dir);
        if (err)
                goto out;

        old_de = ext2_find_entry(old_dir, &old_dentry->d_name, &old_page);
        if (IS_ERR(old_de)) {
                err = PTR_ERR(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;

                new_de = ext2_find_entry(new_dir, &new_dentry->d_name, &new_page);
                if (IS_ERR(new_de)) {
                        err = PTR_ERR(new_de);
                        goto out_dir;
                }
                ext2_set_link(new_dir, new_de, new_page, old_inode, 1);
                new_inode->i_ctime = current_time(new_inode);
                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(old_inode);
        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);
                        put_page(dir_page);
                }
                inode_dec_link_count(old_dir);
        }
        return 0;


out_dir:
        if (dir_de) {
                kunmap(dir_page);
                put_page(dir_page);
        }
out_old:
        kunmap(old_page);
        put_page(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,
        .listxattr      = ext2_listxattr,
        .getattr        = ext2_getattr,
        .setattr        = ext2_setattr,
        .get_acl        = ext2_get_acl,
        .set_acl        = ext2_set_acl,
        .tmpfile        = ext2_tmpfile,
};

const struct inode_operations ext2_special_inode_operations = {
        .listxattr      = ext2_listxattr,
        .getattr        = ext2_getattr,
        .setattr        = ext2_setattr,
        .get_acl        = ext2_get_acl,
        .set_acl        = ext2_set_acl,
};