// SPDX-License-Identifier: GPL-2.0

/*
 * Directory operations for Coda filesystem
 * Original version: (C) 1996 P. Braam and M. Callahan
 * Rewritten for Linux 2.1. (C) 1997 Carnegie Mellon University
 * 
 * Carnegie Mellon encourages users to contribute improvements to
 * the Coda project. Contact Peter Braam (coda@cs.cmu.edu).
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/spinlock.h>
#include <linux/namei.h>
#include <linux/uaccess.h>

#include <linux/coda.h>
#include "coda_psdev.h"
#include "coda_linux.h"
#include "coda_cache.h"

#include "coda_int.h"

/* same as fs/bad_inode.c */
static int coda_return_EIO(void)
{
        return -EIO;
}
#define CODA_EIO_ERROR ((void *) (coda_return_EIO))

/* inode operations for directories */
/* access routines: lookup, readlink, permission */
static struct dentry *coda_lookup(struct inode *dir, struct dentry *entry, unsigned int flags)
{
        struct super_block *sb = dir->i_sb;
        const char *name = entry->d_name.name;
        size_t length = entry->d_name.len;
        struct inode *inode;
        int type = 0;

        if (length > CODA_MAXNAMLEN) {
                pr_err("name too long: lookup, %s %zu\n",
                       coda_i2s(dir), length);
                return ERR_PTR(-ENAMETOOLONG);
        }

        /* control object, create inode on the fly */
        if (is_root_inode(dir) && coda_iscontrol(name, length)) {
                inode = coda_cnode_makectl(sb);
                type = CODA_NOCACHE;
        } else {
                struct CodaFid fid = { { 0, } };
                int error = venus_lookup(sb, coda_i2f(dir), name, length,
                                     &type, &fid);
                inode = !error ? coda_cnode_make(&fid, sb) : ERR_PTR(error);
        }

        if (!IS_ERR(inode) && (type & CODA_NOCACHE))
                coda_flag_inode(inode, C_VATTR | C_PURGE);

        if (inode == ERR_PTR(-ENOENT))
                inode = NULL;

        return d_splice_alias(inode, entry);
}


int coda_permission(struct user_namespace *mnt_userns, struct inode *inode,
                    int mask)
{
        int error;

        if (mask & MAY_NOT_BLOCK)
                return -ECHILD;

        mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
 
        if (!mask)
                return 0;

        if ((mask & MAY_EXEC) && !execute_ok(inode))
                return -EACCES;

        if (coda_cache_check(inode, mask))
                return 0;

        error = venus_access(inode->i_sb, coda_i2f(inode), mask);
    
        if (!error)
                coda_cache_enter(inode, mask);

        return error;
}


static inline void coda_dir_update_mtime(struct inode *dir)
{
#ifdef REQUERY_VENUS_FOR_MTIME
        /* invalidate the directory cnode's attributes so we refetch the
         * attributes from venus next time the inode is referenced */
        coda_flag_inode(dir, C_VATTR);
#else
        /* optimistically we can also act as if our nose bleeds. The
         * granularity of the mtime is coarse anyways so we might actually be
         * right most of the time. Note: we only do this for directories. */
        dir->i_mtime = dir->i_ctime = current_time(dir);
#endif
}

/* we have to wrap inc_nlink/drop_nlink because sometimes userspace uses a
 * trick to fool GNU find's optimizations. If we can't be sure of the link
 * (because of volume mount points) we set i_nlink to 1 which forces find
 * to consider every child as a possible directory. We should also never
 * see an increment or decrement for deleted directories where i_nlink == 0 */
static inline void coda_dir_inc_nlink(struct inode *dir)
{
        if (dir->i_nlink >= 2)
                inc_nlink(dir);
}

static inline void coda_dir_drop_nlink(struct inode *dir)
{
        if (dir->i_nlink > 2)
                drop_nlink(dir);
}

/* creation routines: create, mknod, mkdir, link, symlink */
static int coda_create(struct user_namespace *mnt_userns, struct inode *dir,
                       struct dentry *de, umode_t mode, bool excl)
{
        int error;
        const char *name=de->d_name.name;
        int length=de->d_name.len;
        struct inode *inode;
        struct CodaFid newfid;
        struct coda_vattr attrs;

        if (is_root_inode(dir) && coda_iscontrol(name, length))
                return -EPERM;

        error = venus_create(dir->i_sb, coda_i2f(dir), name, length, 
                                0, mode, &newfid, &attrs);
        if (error)
                goto err_out;

        inode = coda_iget(dir->i_sb, &newfid, &attrs);
        if (IS_ERR(inode)) {
                error = PTR_ERR(inode);
                goto err_out;
        }

        /* invalidate the directory cnode's attributes */
        coda_dir_update_mtime(dir);
        d_instantiate(de, inode);
        return 0;
err_out:
        d_drop(de);
        return error;
}

static int coda_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
                      struct dentry *de, umode_t mode)
{
        struct inode *inode;
        struct coda_vattr attrs;
        const char *name = de->d_name.name;
        int len = de->d_name.len;
        int error;
        struct CodaFid newfid;

        if (is_root_inode(dir) && coda_iscontrol(name, len))
                return -EPERM;

        attrs.va_mode = mode;
        error = venus_mkdir(dir->i_sb, coda_i2f(dir), 
                               name, len, &newfid, &attrs);
        if (error)
                goto err_out;
         
        inode = coda_iget(dir->i_sb, &newfid, &attrs);
        if (IS_ERR(inode)) {
                error = PTR_ERR(inode);
                goto err_out;
        }

        /* invalidate the directory cnode's attributes */
        coda_dir_inc_nlink(dir);
        coda_dir_update_mtime(dir);
        d_instantiate(de, inode);
        return 0;
err_out:
        d_drop(de);
        return error;
}

/* try to make de an entry in dir_inodde linked to source_de */ 
static int coda_link(struct dentry *source_de, struct inode *dir_inode, 
          struct dentry *de)
{
        struct inode *inode = d_inode(source_de);
        const char * name = de->d_name.name;
        int len = de->d_name.len;
        int error;

        if (is_root_inode(dir_inode) && coda_iscontrol(name, len))
                return -EPERM;

        error = venus_link(dir_inode->i_sb, coda_i2f(inode),
                           coda_i2f(dir_inode), (const char *)name, len);
        if (error) {
                d_drop(de);
                return error;
        }

        coda_dir_update_mtime(dir_inode);
        ihold(inode);
        d_instantiate(de, inode);
        inc_nlink(inode);
        return 0;
}


static int coda_symlink(struct user_namespace *mnt_userns,
                        struct inode *dir_inode, struct dentry *de,
                        const char *symname)
{
        const char *name = de->d_name.name;
        int len = de->d_name.len;
        int symlen;
        int error;

        if (is_root_inode(dir_inode) && coda_iscontrol(name, len))
                return -EPERM;

        symlen = strlen(symname);
        if (symlen > CODA_MAXPATHLEN)
                return -ENAMETOOLONG;

        /*
         * This entry is now negative. Since we do not create
         * an inode for the entry we have to drop it.
         */
        d_drop(de);
        error = venus_symlink(dir_inode->i_sb, coda_i2f(dir_inode), name, len,
                              symname, symlen);

        /* mtime is no good anymore */
        if (!error)
                coda_dir_update_mtime(dir_inode);

        return error;
}

/* destruction routines: unlink, rmdir */
static int coda_unlink(struct inode *dir, struct dentry *de)
{
        int error;
        const char *name = de->d_name.name;
        int len = de->d_name.len;

        error = venus_remove(dir->i_sb, coda_i2f(dir), name, len);
        if (error)
                return error;

        coda_dir_update_mtime(dir);
        drop_nlink(d_inode(de));
        return 0;
}

static int coda_rmdir(struct inode *dir, struct dentry *de)
{
        const char *name = de->d_name.name;
        int len = de->d_name.len;
        int error;

        error = venus_rmdir(dir->i_sb, coda_i2f(dir), name, len);
        if (!error) {
                /* VFS may delete the child */
                if (d_really_is_positive(de))
                        clear_nlink(d_inode(de));

                /* fix the link count of the parent */
                coda_dir_drop_nlink(dir);
                coda_dir_update_mtime(dir);
        }
        return error;
}

/* rename */
static int coda_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
                       struct dentry *old_dentry, struct inode *new_dir,
                       struct dentry *new_dentry, unsigned int flags)
{
        const char *old_name = old_dentry->d_name.name;
        const char *new_name = new_dentry->d_name.name;
        int old_length = old_dentry->d_name.len;
        int new_length = new_dentry->d_name.len;
        int error;

        if (flags)
                return -EINVAL;

        error = venus_rename(old_dir->i_sb, coda_i2f(old_dir),
                             coda_i2f(new_dir), old_length, new_length,
                             (const char *) old_name, (const char *)new_name);
        if (!error) {
                if (d_really_is_positive(new_dentry)) {
                        if (d_is_dir(new_dentry)) {
                                coda_dir_drop_nlink(old_dir);
                                coda_dir_inc_nlink(new_dir);
                        }
                        coda_dir_update_mtime(old_dir);
                        coda_dir_update_mtime(new_dir);
                        coda_flag_inode(d_inode(new_dentry), C_VATTR);
                } else {
                        coda_flag_inode(old_dir, C_VATTR);
                        coda_flag_inode(new_dir, C_VATTR);
                }
        }
        return error;
}

static inline unsigned int CDT2DT(unsigned char cdt)
{
        unsigned int dt;

        switch(cdt) {
        case CDT_UNKNOWN: dt = DT_UNKNOWN; break;
        case CDT_FIFO:    dt = DT_FIFO;    break;
        case CDT_CHR:     dt = DT_CHR;     break;
        case CDT_DIR:     dt = DT_DIR;     break;
        case CDT_BLK:     dt = DT_BLK;     break;
        case CDT_REG:     dt = DT_REG;     break;
        case CDT_LNK:     dt = DT_LNK;     break;
        case CDT_SOCK:    dt = DT_SOCK;    break;
        case CDT_WHT:     dt = DT_WHT;     break;
        default:          dt = DT_UNKNOWN; break;
        }
        return dt;
}

/* support routines */
static int coda_venus_readdir(struct file *coda_file, struct dir_context *ctx)
{
        struct coda_file_info *cfi;
        struct coda_inode_info *cii;
        struct file *host_file;
        struct venus_dirent *vdir;
        unsigned long vdir_size = offsetof(struct venus_dirent, d_name);
        unsigned int type;
        struct qstr name;
        ino_t ino;
        int ret;

        cfi = coda_ftoc(coda_file);
        host_file = cfi->cfi_container;

        cii = ITOC(file_inode(coda_file));

        vdir = kmalloc(sizeof(*vdir), GFP_KERNEL);
        if (!vdir) return -ENOMEM;

        if (!dir_emit_dots(coda_file, ctx))
                goto out;

        while (1) {
                loff_t pos = ctx->pos - 2;

                /* read entries from the directory file */
                ret = kernel_read(host_file, vdir, sizeof(*vdir), &pos);
                if (ret < 0) {
                        pr_err("%s: read dir %s failed %d\n",
                               __func__, coda_f2s(&cii->c_fid), ret);
                        break;
                }
                if (ret == 0) break; /* end of directory file reached */

                /* catch truncated reads */
                if (ret < vdir_size || ret < vdir_size + vdir->d_namlen) {
                        pr_err("%s: short read on %s\n",
                               __func__, coda_f2s(&cii->c_fid));
                        ret = -EBADF;
                        break;
                }
                /* validate whether the directory file actually makes sense */
                if (vdir->d_reclen < vdir_size + vdir->d_namlen) {
                        pr_err("%s: invalid dir %s\n",
                               __func__, coda_f2s(&cii->c_fid));
                        ret = -EBADF;
                        break;
                }

                name.len = vdir->d_namlen;
                name.name = vdir->d_name;

                /* Make sure we skip '.' and '..', we already got those */
                if (name.name[0] == '.' && (name.len == 1 ||
                    (name.name[1] == '.' && name.len == 2)))
                        vdir->d_fileno = name.len = 0;

                /* skip null entries */
                if (vdir->d_fileno && name.len) {
                        ino = vdir->d_fileno;
                        type = CDT2DT(vdir->d_type);
                        if (!dir_emit(ctx, name.name, name.len, ino, type))
                                break;
                }
                /* we'll always have progress because d_reclen is unsigned and
                 * we've already established it is non-zero. */
                ctx->pos += vdir->d_reclen;
        }
out:
        kfree(vdir);
        return 0;
}

/* file operations for directories */
static int coda_readdir(struct file *coda_file, struct dir_context *ctx)
{
        struct coda_file_info *cfi;
        struct file *host_file;
        int ret;

        cfi = coda_ftoc(coda_file);
        host_file = cfi->cfi_container;

        if (host_file->f_op->iterate || host_file->f_op->iterate_shared) {
                struct inode *host_inode = file_inode(host_file);
                ret = -ENOENT;
                if (!IS_DEADDIR(host_inode)) {
                        if (host_file->f_op->iterate_shared) {
                                inode_lock_shared(host_inode);
                                ret = host_file->f_op->iterate_shared(host_file, ctx);
                                file_accessed(host_file);
                                inode_unlock_shared(host_inode);
                        } else {
                                inode_lock(host_inode);
                                ret = host_file->f_op->iterate(host_file, ctx);
                                file_accessed(host_file);
                                inode_unlock(host_inode);
                        }
                }
                return ret;
        }
        /* Venus: we must read Venus dirents from a file */
        return coda_venus_readdir(coda_file, ctx);
}

/* called when a cache lookup succeeds */
static int coda_dentry_revalidate(struct dentry *de, unsigned int flags)
{
        struct inode *inode;
        struct coda_inode_info *cii;

        if (flags & LOOKUP_RCU)
                return -ECHILD;

        inode = d_inode(de);
        if (!inode || is_root_inode(inode))
                goto out;
        if (is_bad_inode(inode))
                goto bad;

        cii = ITOC(d_inode(de));
        if (!(cii->c_flags & (C_PURGE | C_FLUSH)))
                goto out;

        shrink_dcache_parent(de);

        /* propagate for a flush */
        if (cii->c_flags & C_FLUSH) 
                coda_flag_inode_children(inode, C_FLUSH);

        if (d_count(de) > 1)
                /* pretend it's valid, but don't change the flags */
                goto out;

        /* clear the flags. */
        spin_lock(&cii->c_lock);
        cii->c_flags &= ~(C_VATTR | C_PURGE | C_FLUSH);
        spin_unlock(&cii->c_lock);
bad:
        return 0;
out:
        return 1;
}

/*
 * This is the callback from dput() when d_count is going to 0.
 * We use this to unhash dentries with bad inodes.
 */
static int coda_dentry_delete(const struct dentry * dentry)
{
        int flags;

        if (d_really_is_negative(dentry)) 
                return 0;

        flags = (ITOC(d_inode(dentry))->c_flags) & C_PURGE;
        if (is_bad_inode(d_inode(dentry)) || flags) {
                return 1;
        }
        return 0;
}



/*
 * This is called when we want to check if the inode has
 * changed on the server.  Coda makes this easy since the
 * cache manager Venus issues a downcall to the kernel when this 
 * happens 
 */
int coda_revalidate_inode(struct inode *inode)
{
        struct coda_vattr attr;
        int error;
        int old_mode;
        ino_t old_ino;
        struct coda_inode_info *cii = ITOC(inode);

        if (!cii->c_flags)
                return 0;

        if (cii->c_flags & (C_VATTR | C_PURGE | C_FLUSH)) {
                error = venus_getattr(inode->i_sb, &(cii->c_fid), &attr);
                if (error)
                        return -EIO;

                /* this inode may be lost if:
                   - it's ino changed 
                   - type changes must be permitted for repair and
                   missing mount points.
                */
                old_mode = inode->i_mode;
                old_ino = inode->i_ino;
                coda_vattr_to_iattr(inode, &attr);

                if ((old_mode & S_IFMT) != (inode->i_mode & S_IFMT)) {
                        pr_warn("inode %ld, fid %s changed type!\n",
                                inode->i_ino, coda_f2s(&(cii->c_fid)));
                }

                /* the following can happen when a local fid is replaced 
                   with a global one, here we lose and declare the inode bad */
                if (inode->i_ino != old_ino)
                        return -EIO;
                
                coda_flag_inode_children(inode, C_FLUSH);

                spin_lock(&cii->c_lock);
                cii->c_flags &= ~(C_VATTR | C_PURGE | C_FLUSH);
                spin_unlock(&cii->c_lock);
        }
        return 0;
}

const struct dentry_operations coda_dentry_operations = {
        .d_revalidate   = coda_dentry_revalidate,
        .d_delete       = coda_dentry_delete,
};

const struct inode_operations coda_dir_inode_operations = {
        .create         = coda_create,
        .lookup         = coda_lookup,
        .link           = coda_link,
        .unlink         = coda_unlink,
        .symlink        = coda_symlink,
        .mkdir          = coda_mkdir,
        .rmdir          = coda_rmdir,
        .mknod          = CODA_EIO_ERROR,
        .rename         = coda_rename,
        .permission     = coda_permission,
        .getattr        = coda_getattr,
        .setattr        = coda_setattr,
};

const struct file_operations coda_dir_operations = {
        .llseek         = generic_file_llseek,
        .read           = generic_read_dir,
        .iterate        = coda_readdir,
        .open           = coda_open,
        .release        = coda_release,
        .fsync          = coda_fsync,
};