kernel-hacking-2024-linux-steffo/fs/autofs4/inode.c

/* -*- c -*- --------------------------------------------------------------- *
 *
 * linux/fs/autofs/inode.c
 *
 *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
 *  Copyright 2005-2006 Ian Kent <raven@themaw.net>
 *
 * This file is part of the Linux kernel and is made available under
 * the terms of the GNU General Public License, version 2, or at your
 * option, any later version, incorporated herein by reference.
 *
 * ------------------------------------------------------------------------- */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/seq_file.h>
#include <linux/pagemap.h>
#include <linux/parser.h>
#include <linux/bitops.h>
#include <linux/magic.h>
#include "autofs_i.h"
#include <linux/module.h>

static void ino_lnkfree(struct autofs_info *ino)
{
	kfree(ino->u.symlink);
	ino->u.symlink = NULL;
}

struct autofs_info *autofs4_init_ino(struct autofs_info *ino,
				     struct autofs_sb_info *sbi, mode_t mode)
{
	int reinit = 1;

	if (ino == NULL) {
		reinit = 0;
		ino = kmalloc(sizeof(*ino), GFP_KERNEL);
	}

	if (ino == NULL)
		return NULL;

	ino->flags = 0;
	ino->mode = mode;
	ino->inode = NULL;
	ino->dentry = NULL;
	ino->size = 0;

	INIT_LIST_HEAD(&ino->expiring);

	ino->last_used = jiffies;
	atomic_set(&ino->count, 0);

	ino->sbi = sbi;

	if (reinit && ino->free)
		(ino->free)(ino);

	memset(&ino->u, 0, sizeof(ino->u));

	ino->free = NULL;

	if (S_ISLNK(mode))
		ino->free = ino_lnkfree;

	return ino;
}

void autofs4_free_ino(struct autofs_info *ino)
{
	struct autofs_info *p_ino;

	if (ino->dentry) {
		ino->dentry->d_fsdata = NULL;
		if (ino->dentry->d_inode) {
			struct dentry *parent = ino->dentry->d_parent;
			if (atomic_dec_and_test(&ino->count)) {
				p_ino = autofs4_dentry_ino(parent);
				if (p_ino && parent != ino->dentry)
					atomic_dec(&p_ino->count);
			}
			dput(ino->dentry);
		}
		ino->dentry = NULL;
	}
	if (ino->free)
		(ino->free)(ino);
	kfree(ino);
}

/*
 * Deal with the infamous "Busy inodes after umount ..." message.
 *
 * Clean up the dentry tree. This happens with autofs if the user
 * space program goes away due to a SIGKILL, SIGSEGV etc.
 */
static void autofs4_force_release(struct autofs_sb_info *sbi)
{
	struct dentry *this_parent = sbi->sb->s_root;
	struct list_head *next;

	if (!sbi->sb->s_root)
		return;

	spin_lock(&dcache_lock);
repeat:
	next = this_parent->d_subdirs.next;
resume:
	while (next != &this_parent->d_subdirs) {
		struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);

		/* Negative dentry - don`t care */
		if (!simple_positive(dentry)) {
			next = next->next;
			continue;
		}

		if (!list_empty(&dentry->d_subdirs)) {
			this_parent = dentry;
			goto repeat;
		}

		next = next->next;
		spin_unlock(&dcache_lock);

		DPRINTK("dentry %p %.*s",
			dentry, (int)dentry->d_name.len, dentry->d_name.name);

		dput(dentry);
		spin_lock(&dcache_lock);
	}

	if (this_parent != sbi->sb->s_root) {
		struct dentry *dentry = this_parent;

		next = this_parent->d_u.d_child.next;
		this_parent = this_parent->d_parent;
		spin_unlock(&dcache_lock);
		DPRINTK("parent dentry %p %.*s",
			dentry, (int)dentry->d_name.len, dentry->d_name.name);
		dput(dentry);
		spin_lock(&dcache_lock);
		goto resume;
	}
	spin_unlock(&dcache_lock);
}

void autofs4_kill_sb(struct super_block *sb)
{
	struct autofs_sb_info *sbi = autofs4_sbi(sb);

	/*
	 * In the event of a failure in get_sb_nodev the superblock
	 * info is not present so nothing else has been setup, so
	 * just call kill_anon_super when we are called from
	 * deactivate_super.
	 */
	if (!sbi)
		goto out_kill_sb;

	if (!sbi->catatonic)
		autofs4_catatonic_mode(sbi); /* Free wait queues, close pipe */

	/* Clean up and release dangling references */
	autofs4_force_release(sbi);

	sb->s_fs_info = NULL;
	kfree(sbi);

out_kill_sb:
	DPRINTK("shutting down");
	kill_anon_super(sb);
}

static int autofs4_show_options(struct seq_file *m, struct vfsmount *mnt)
{
	struct autofs_sb_info *sbi = autofs4_sbi(mnt->mnt_sb);
	struct inode *root_inode = mnt->mnt_sb->s_root->d_inode;

	if (!sbi)
		return 0;

	seq_printf(m, ",fd=%d", sbi->pipefd);
	if (root_inode->i_uid != 0)
		seq_printf(m, ",uid=%u", root_inode->i_uid);
	if (root_inode->i_gid != 0)
		seq_printf(m, ",gid=%u", root_inode->i_gid);
	seq_printf(m, ",pgrp=%d", sbi->oz_pgrp);
	seq_printf(m, ",timeout=%lu", sbi->exp_timeout/HZ);
	seq_printf(m, ",minproto=%d", sbi->min_proto);
	seq_printf(m, ",maxproto=%d", sbi->max_proto);

	if (sbi->type & AUTOFS_TYPE_OFFSET)
		seq_printf(m, ",offset");
	else if (sbi->type & AUTOFS_TYPE_DIRECT)
		seq_printf(m, ",direct");
	else
		seq_printf(m, ",indirect");

	return 0;
}

static const struct super_operations autofs4_sops = {
	.statfs		= simple_statfs,
	.show_options	= autofs4_show_options,
};

enum {Opt_err, Opt_fd, Opt_uid, Opt_gid, Opt_pgrp, Opt_minproto, Opt_maxproto,
	Opt_indirect, Opt_direct, Opt_offset};

static match_table_t tokens = {
	{Opt_fd, "fd=%u"},
	{Opt_uid, "uid=%u"},
	{Opt_gid, "gid=%u"},
	{Opt_pgrp, "pgrp=%u"},
	{Opt_minproto, "minproto=%u"},
	{Opt_maxproto, "maxproto=%u"},
	{Opt_indirect, "indirect"},
	{Opt_direct, "direct"},
	{Opt_offset, "offset"},
	{Opt_err, NULL}
};

static int parse_options(char *options, int *pipefd, uid_t *uid, gid_t *gid,
		pid_t *pgrp, unsigned int *type, int *minproto, int *maxproto)
{
	char *p;
	substring_t args[MAX_OPT_ARGS];
	int option;

	*uid = current->uid;
	*gid = current->gid;
	*pgrp = task_pgrp_nr(current);

	*minproto = AUTOFS_MIN_PROTO_VERSION;
	*maxproto = AUTOFS_MAX_PROTO_VERSION;

	*pipefd = -1;

	if (!options)
		return 1;

	while ((p = strsep(&options, ",")) != NULL) {
		int token;
		if (!*p)
			continue;

		token = match_token(p, tokens, args);
		switch (token) {
		case Opt_fd:
			if (match_int(args, pipefd))
				return 1;
			break;
		case Opt_uid:
			if (match_int(args, &option))
				return 1;
			*uid = option;
			break;
		case Opt_gid:
			if (match_int(args, &option))
				return 1;
			*gid = option;
			break;
		case Opt_pgrp:
			if (match_int(args, &option))
				return 1;
			*pgrp = option;
			break;
		case Opt_minproto:
			if (match_int(args, &option))
				return 1;
			*minproto = option;
			break;
		case Opt_maxproto:
			if (match_int(args, &option))
				return 1;
			*maxproto = option;
			break;
		case Opt_indirect:
			*type = AUTOFS_TYPE_INDIRECT;
			break;
		case Opt_direct:
			*type = AUTOFS_TYPE_DIRECT;
			break;
		case Opt_offset:
			*type = AUTOFS_TYPE_DIRECT | AUTOFS_TYPE_OFFSET;
			break;
		default:
			return 1;
		}
	}
	return (*pipefd < 0);
}

static struct autofs_info *autofs4_mkroot(struct autofs_sb_info *sbi)
{
	struct autofs_info *ino;

	ino = autofs4_init_ino(NULL, sbi, S_IFDIR | 0755);
	if (!ino)
		return NULL;

	return ino;
}

static struct dentry_operations autofs4_sb_dentry_operations = {
	.d_release      = autofs4_dentry_release,
};

int autofs4_fill_super(struct super_block *s, void *data, int silent)
{
	struct inode * root_inode;
	struct dentry * root;
	struct file * pipe;
	int pipefd;
	struct autofs_sb_info *sbi;
	struct autofs_info *ino;

	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
	if (!sbi)
		goto fail_unlock;
	DPRINTK("starting up, sbi = %p",sbi);

	s->s_fs_info = sbi;
	sbi->magic = AUTOFS_SBI_MAGIC;
	sbi->pipefd = -1;
	sbi->pipe = NULL;
	sbi->catatonic = 1;
	sbi->exp_timeout = 0;
	sbi->oz_pgrp = task_pgrp_nr(current);
	sbi->sb = s;
	sbi->version = 0;
	sbi->sub_version = 0;
	sbi->type = 0;
	sbi->min_proto = 0;
	sbi->max_proto = 0;
	mutex_init(&sbi->wq_mutex);
	spin_lock_init(&sbi->fs_lock);
	sbi->queues = NULL;
	spin_lock_init(&sbi->lookup_lock);
	INIT_LIST_HEAD(&sbi->expiring_list);
	s->s_blocksize = 1024;
	s->s_blocksize_bits = 10;
	s->s_magic = AUTOFS_SUPER_MAGIC;
	s->s_op = &autofs4_sops;
	s->s_time_gran = 1;

	/*
	 * Get the root inode and dentry, but defer checking for errors.
	 */
	ino = autofs4_mkroot(sbi);
	if (!ino)
		goto fail_free;
	root_inode = autofs4_get_inode(s, ino);
	if (!root_inode)
		goto fail_ino;

	root = d_alloc_root(root_inode);
	if (!root)
		goto fail_iput;
	pipe = NULL;

	root->d_op = &autofs4_sb_dentry_operations;
	root->d_fsdata = ino;

	/* Can this call block? */
	if (parse_options(data, &pipefd, &root_inode->i_uid, &root_inode->i_gid,
				&sbi->oz_pgrp, &sbi->type, &sbi->min_proto,
				&sbi->max_proto)) {
		printk("autofs: called with bogus options\n");
		goto fail_dput;
	}

	root_inode->i_fop = &autofs4_root_operations;
	root_inode->i_op = sbi->type & AUTOFS_TYPE_DIRECT ?
			&autofs4_direct_root_inode_operations :
			&autofs4_indirect_root_inode_operations;

	/* Couldn't this be tested earlier? */
	if (sbi->max_proto < AUTOFS_MIN_PROTO_VERSION ||
	    sbi->min_proto > AUTOFS_MAX_PROTO_VERSION) {
		printk("autofs: kernel does not match daemon version "
		       "daemon (%d, %d) kernel (%d, %d)\n",
			sbi->min_proto, sbi->max_proto,
			AUTOFS_MIN_PROTO_VERSION, AUTOFS_MAX_PROTO_VERSION);
		goto fail_dput;
	}

	/* Establish highest kernel protocol version */
	if (sbi->max_proto > AUTOFS_MAX_PROTO_VERSION)
		sbi->version = AUTOFS_MAX_PROTO_VERSION;
	else
		sbi->version = sbi->max_proto;
	sbi->sub_version = AUTOFS_PROTO_SUBVERSION;

	DPRINTK("pipe fd = %d, pgrp = %u", pipefd, sbi->oz_pgrp);
	pipe = fget(pipefd);
	
	if (!pipe) {
		printk("autofs: could not open pipe file descriptor\n");
		goto fail_dput;
	}
	if (!pipe->f_op || !pipe->f_op->write)
		goto fail_fput;
	sbi->pipe = pipe;
	sbi->pipefd = pipefd;
	sbi->catatonic = 0;

	/*
	 * Success! Install the root dentry now to indicate completion.
	 */
	s->s_root = root;
	return 0;
	
	/*
	 * Failure ... clean up.
	 */
fail_fput:
	printk("autofs: pipe file descriptor does not contain proper ops\n");
	fput(pipe);
	/* fall through */
fail_dput:
	dput(root);
	goto fail_free;
fail_iput:
	printk("autofs: get root dentry failed\n");
	iput(root_inode);
fail_ino:
	kfree(ino);
fail_free:
	kfree(sbi);
	s->s_fs_info = NULL;
fail_unlock:
	return -EINVAL;
}

struct inode *autofs4_get_inode(struct super_block *sb,
				struct autofs_info *inf)
{
	struct inode *inode = new_inode(sb);

	if (inode == NULL)
		return NULL;

	inf->inode = inode;
	inode->i_mode = inf->mode;
	if (sb->s_root) {
		inode->i_uid = sb->s_root->d_inode->i_uid;
		inode->i_gid = sb->s_root->d_inode->i_gid;
	} else {
		inode->i_uid = 0;
		inode->i_gid = 0;
	}
	inode->i_blocks = 0;
	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;

	if (S_ISDIR(inf->mode)) {
		inode->i_nlink = 2;
		inode->i_op = &autofs4_dir_inode_operations;
		inode->i_fop = &autofs4_dir_operations;
	} else if (S_ISLNK(inf->mode)) {
		inode->i_size = inf->size;
		inode->i_op = &autofs4_symlink_inode_operations;
	}

	return inode;
}