/*
   * POSIX message queues filesystem for Linux.
   *
   * Copyright (C) 2003,2004  Krzysztof Benedyczak    (golbi@mat.uni.torun.pl)

   *                          Michal Wronski          (michal.wronski@gmail.com)

   *
   * Spinlocks:               Mohamed Abbas           (abbas.mohamed@intel.com)
   * Lockless receive & send, fd based notify:
   * 			    Manfred Spraul	    (manfred@colorfullife.com)
   *

   * Audit:                   George Wilson           (ltcgcw@us.ibm.com)
   *

   * This file is released under the GPL.
   */

  #include <linux/capability.h>

  #include <linux/init.h>
  #include <linux/pagemap.h>
  #include <linux/file.h>
  #include <linux/mount.h>
  #include <linux/namei.h>
  #include <linux/sysctl.h>
  #include <linux/poll.h>
  #include <linux/mqueue.h>
  #include <linux/msg.h>
  #include <linux/skbuff.h>
  #include <linux/netlink.h>
  #include <linux/syscalls.h>

  #include <linux/audit.h>

  #include <linux/signal.h>

  #include <linux/mutex.h>

  #include <linux/nsproxy.h>
  #include <linux/pid.h>

  #include <net/sock.h>
  #include "util.h"
  
  #define MQUEUE_MAGIC	0x19800202
  #define DIRENT_SIZE	20
  #define FILENT_SIZE	80
  
  #define SEND		0
  #define RECV		1
  
  #define STATE_NONE	0
  #define STATE_PENDING	1
  #define STATE_READY	2

  /* default values */
  #define DFLT_QUEUESMAX	256	/* max number of message queues */
  #define DFLT_MSGMAX 	10	/* max number of messages in each queue */
  #define HARD_MSGMAX 	(131072/sizeof(void*))
  #define DFLT_MSGSIZEMAX 8192	/* max message size */

  
  struct ext_wait_queue {		/* queue of sleeping tasks */
  	struct task_struct *task;
  	struct list_head list;
  	struct msg_msg *msg;	/* ptr of loaded message */
  	int state;		/* one of STATE_* values */
  };
  
  struct mqueue_inode_info {
  	spinlock_t lock;
  	struct inode vfs_inode;
  	wait_queue_head_t wait_q;
  
  	struct msg_msg **messages;
  	struct mq_attr attr;
  
  	struct sigevent notify;

  	struct pid* notify_owner;

  	struct user_struct *user;	/* user who created, for accounting */

  	struct sock *notify_sock;
  	struct sk_buff *notify_cookie;
  
  	/* for tasks waiting for free space and messages, respectively */
  	struct ext_wait_queue e_wait_q[2];
  
  	unsigned long qsize; /* size of queue in memory (sum of all msgs) */
  };

  static const struct inode_operations mqueue_dir_inode_operations;

  static const struct file_operations mqueue_file_operations;

  static struct super_operations mqueue_super_ops;
  static void remove_notification(struct mqueue_inode_info *info);
  
  static spinlock_t mq_lock;

  static struct kmem_cache *mqueue_inode_cachep;

  static struct vfsmount *mqueue_mnt;
  
  static unsigned int queues_count;
  static unsigned int queues_max 	= DFLT_QUEUESMAX;
  static unsigned int msg_max 	= DFLT_MSGMAX;
  static unsigned int msgsize_max = DFLT_MSGSIZEMAX;
  
  static struct ctl_table_header * mq_sysctl_table;
  
  static inline struct mqueue_inode_info *MQUEUE_I(struct inode *inode)
  {
  	return container_of(inode, struct mqueue_inode_info, vfs_inode);
  }
  
  static struct inode *mqueue_get_inode(struct super_block *sb, int mode,
  							struct mq_attr *attr)
  {
  	struct inode *inode;
  
  	inode = new_inode(sb);
  	if (inode) {
  		inode->i_mode = mode;
  		inode->i_uid = current->fsuid;
  		inode->i_gid = current->fsgid;

  		inode->i_blocks = 0;
  		inode->i_mtime = inode->i_ctime = inode->i_atime =
  				CURRENT_TIME;
  
  		if (S_ISREG(mode)) {
  			struct mqueue_inode_info *info;
  			struct task_struct *p = current;
  			struct user_struct *u = p->user;
  			unsigned long mq_bytes, mq_msg_tblsz;
  
  			inode->i_fop = &mqueue_file_operations;
  			inode->i_size = FILENT_SIZE;
  			/* mqueue specific info */
  			info = MQUEUE_I(inode);
  			spin_lock_init(&info->lock);
  			init_waitqueue_head(&info->wait_q);
  			INIT_LIST_HEAD(&info->e_wait_q[0].list);
  			INIT_LIST_HEAD(&info->e_wait_q[1].list);
  			info->messages = NULL;

  			info->notify_owner = NULL;

  			info->qsize = 0;
  			info->user = NULL;	/* set when all is ok */
  			memset(&info->attr, 0, sizeof(info->attr));
  			info->attr.mq_maxmsg = DFLT_MSGMAX;
  			info->attr.mq_msgsize = DFLT_MSGSIZEMAX;
  			if (attr) {
  				info->attr.mq_maxmsg = attr->mq_maxmsg;
  				info->attr.mq_msgsize = attr->mq_msgsize;
  			}
  			mq_msg_tblsz = info->attr.mq_maxmsg * sizeof(struct msg_msg *);
  			mq_bytes = (mq_msg_tblsz +
  				(info->attr.mq_maxmsg * info->attr.mq_msgsize));
  
  			spin_lock(&mq_lock);
  			if (u->mq_bytes + mq_bytes < u->mq_bytes ||
  		 	    u->mq_bytes + mq_bytes >
  			    p->signal->rlim[RLIMIT_MSGQUEUE].rlim_cur) {
  				spin_unlock(&mq_lock);
  				goto out_inode;
  			}
  			u->mq_bytes += mq_bytes;
  			spin_unlock(&mq_lock);
  
  			info->messages = kmalloc(mq_msg_tblsz, GFP_KERNEL);
  			if (!info->messages) {
  				spin_lock(&mq_lock);
  				u->mq_bytes -= mq_bytes;
  				spin_unlock(&mq_lock);
  				goto out_inode;
  			}
  			/* all is ok */
  			info->user = get_uid(u);
  		} else if (S_ISDIR(mode)) {

  			inc_nlink(inode);

  			/* Some things misbehave if size == 0 on a directory */
  			inode->i_size = 2 * DIRENT_SIZE;
  			inode->i_op = &mqueue_dir_inode_operations;
  			inode->i_fop = &simple_dir_operations;
  		}
  	}
  	return inode;
  out_inode:
  	make_bad_inode(inode);
  	iput(inode);
  	return NULL;
  }
  
  static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
  {
  	struct inode *inode;
  
  	sb->s_blocksize = PAGE_CACHE_SIZE;
  	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
  	sb->s_magic = MQUEUE_MAGIC;
  	sb->s_op = &mqueue_super_ops;
  
  	inode = mqueue_get_inode(sb, S_IFDIR | S_ISVTX | S_IRWXUGO, NULL);
  	if (!inode)
  		return -ENOMEM;
  
  	sb->s_root = d_alloc_root(inode);
  	if (!sb->s_root) {
  		iput(inode);
  		return -ENOMEM;
  	}
  
  	return 0;
  }

  static int mqueue_get_sb(struct file_system_type *fs_type,
  			 int flags, const char *dev_name,
  			 void *data, struct vfsmount *mnt)

  {

  	return get_sb_single(fs_type, flags, data, mqueue_fill_super, mnt);

  }

  static void init_once(void *foo)

  {
  	struct mqueue_inode_info *p = (struct mqueue_inode_info *) foo;

  	inode_init_once(&p->vfs_inode);

  }
  
  static struct inode *mqueue_alloc_inode(struct super_block *sb)
  {
  	struct mqueue_inode_info *ei;

  	ei = kmem_cache_alloc(mqueue_inode_cachep, GFP_KERNEL);

  	if (!ei)
  		return NULL;
  	return &ei->vfs_inode;
  }
  
  static void mqueue_destroy_inode(struct inode *inode)
  {
  	kmem_cache_free(mqueue_inode_cachep, MQUEUE_I(inode));
  }
  
  static void mqueue_delete_inode(struct inode *inode)
  {
  	struct mqueue_inode_info *info;
  	struct user_struct *user;
  	unsigned long mq_bytes;
  	int i;
  
  	if (S_ISDIR(inode->i_mode)) {
  		clear_inode(inode);
  		return;
  	}
  	info = MQUEUE_I(inode);
  	spin_lock(&info->lock);
  	for (i = 0; i < info->attr.mq_curmsgs; i++)
  		free_msg(info->messages[i]);
  	kfree(info->messages);
  	spin_unlock(&info->lock);
  
  	clear_inode(inode);
  
  	mq_bytes = (info->attr.mq_maxmsg * sizeof(struct msg_msg *) +
  		   (info->attr.mq_maxmsg * info->attr.mq_msgsize));
  	user = info->user;
  	if (user) {
  		spin_lock(&mq_lock);
  		user->mq_bytes -= mq_bytes;
  		queues_count--;
  		spin_unlock(&mq_lock);
  		free_uid(user);
  	}
  }
  
  static int mqueue_create(struct inode *dir, struct dentry *dentry,
  				int mode, struct nameidata *nd)
  {
  	struct inode *inode;
  	struct mq_attr *attr = dentry->d_fsdata;
  	int error;
  
  	spin_lock(&mq_lock);
  	if (queues_count >= queues_max && !capable(CAP_SYS_RESOURCE)) {
  		error = -ENOSPC;
  		goto out_lock;
  	}
  	queues_count++;
  	spin_unlock(&mq_lock);
  
  	inode = mqueue_get_inode(dir->i_sb, mode, attr);
  	if (!inode) {
  		error = -ENOMEM;
  		spin_lock(&mq_lock);
  		queues_count--;
  		goto out_lock;
  	}
  
  	dir->i_size += DIRENT_SIZE;
  	dir->i_ctime = dir->i_mtime = dir->i_atime = CURRENT_TIME;
  
  	d_instantiate(dentry, inode);
  	dget(dentry);
  	return 0;
  out_lock:
  	spin_unlock(&mq_lock);
  	return error;
  }
  
  static int mqueue_unlink(struct inode *dir, struct dentry *dentry)
  {
    	struct inode *inode = dentry->d_inode;
  
  	dir->i_ctime = dir->i_mtime = dir->i_atime = CURRENT_TIME;
  	dir->i_size -= DIRENT_SIZE;

    	drop_nlink(inode);

    	dput(dentry);
    	return 0;
  }
  
  /*
  *	This is routine for system read from queue file.
  *	To avoid mess with doing here some sort of mq_receive we allow
  *	to read only queue size & notification info (the only values
  *	that are interesting from user point of view and aren't accessible
  *	through std routines)
  */
  static ssize_t mqueue_read_file(struct file *filp, char __user *u_data,

  				size_t count, loff_t *off)

  {

  	struct mqueue_inode_info *info = MQUEUE_I(filp->f_path.dentry->d_inode);

  	char buffer[FILENT_SIZE];

  	ssize_t ret;

  
  	spin_lock(&info->lock);
  	snprintf(buffer, sizeof(buffer),
  			"QSIZE:%-10lu NOTIFY:%-5d SIGNO:%-5d NOTIFY_PID:%-6d
  ",
  			info->qsize,
  			info->notify_owner ? info->notify.sigev_notify : 0,
  			(info->notify_owner &&
  			 info->notify.sigev_notify == SIGEV_SIGNAL) ?
  				info->notify.sigev_signo : 0,

  			pid_vnr(info->notify_owner));

  	spin_unlock(&info->lock);
  	buffer[sizeof(buffer)-1] = '\0';

  	ret = simple_read_from_buffer(u_data, count, off, buffer,
  				strlen(buffer));
  	if (ret <= 0)
  		return ret;

  	filp->f_path.dentry->d_inode->i_atime = filp->f_path.dentry->d_inode->i_ctime = CURRENT_TIME;

  	return ret;

  }

  static int mqueue_flush_file(struct file *filp, fl_owner_t id)

  {

  	struct mqueue_inode_info *info = MQUEUE_I(filp->f_path.dentry->d_inode);

  
  	spin_lock(&info->lock);

  	if (task_tgid(current) == info->notify_owner)

  		remove_notification(info);
  
  	spin_unlock(&info->lock);
  	return 0;
  }
  
  static unsigned int mqueue_poll_file(struct file *filp, struct poll_table_struct *poll_tab)
  {

  	struct mqueue_inode_info *info = MQUEUE_I(filp->f_path.dentry->d_inode);

  	int retval = 0;
  
  	poll_wait(filp, &info->wait_q, poll_tab);
  
  	spin_lock(&info->lock);
  	if (info->attr.mq_curmsgs)
  		retval = POLLIN | POLLRDNORM;
  
  	if (info->attr.mq_curmsgs < info->attr.mq_maxmsg)
  		retval |= POLLOUT | POLLWRNORM;
  	spin_unlock(&info->lock);
  
  	return retval;
  }
  
  /* Adds current to info->e_wait_q[sr] before element with smaller prio */
  static void wq_add(struct mqueue_inode_info *info, int sr,
  			struct ext_wait_queue *ewp)
  {
  	struct ext_wait_queue *walk;
  
  	ewp->task = current;
  
  	list_for_each_entry(walk, &info->e_wait_q[sr].list, list) {
  		if (walk->task->static_prio <= current->static_prio) {
  			list_add_tail(&ewp->list, &walk->list);
  			return;
  		}
  	}
  	list_add_tail(&ewp->list, &info->e_wait_q[sr].list);
  }
  
  /*
   * Puts current task to sleep. Caller must hold queue lock. After return
   * lock isn't held.
   * sr: SEND or RECV
   */
  static int wq_sleep(struct mqueue_inode_info *info, int sr,
  			long timeout, struct ext_wait_queue *ewp)
  {
  	int retval;
  	signed long time;
  
  	wq_add(info, sr, ewp);
  
  	for (;;) {
  		set_current_state(TASK_INTERRUPTIBLE);
  
  		spin_unlock(&info->lock);
  		time = schedule_timeout(timeout);
  
  		while (ewp->state == STATE_PENDING)
  			cpu_relax();
  
  		if (ewp->state == STATE_READY) {
  			retval = 0;
  			goto out;
  		}
  		spin_lock(&info->lock);
  		if (ewp->state == STATE_READY) {
  			retval = 0;
  			goto out_unlock;
  		}
  		if (signal_pending(current)) {
  			retval = -ERESTARTSYS;
  			break;
  		}
  		if (time == 0) {
  			retval = -ETIMEDOUT;
  			break;
  		}
  	}
  	list_del(&ewp->list);
  out_unlock:
  	spin_unlock(&info->lock);
  out:
  	return retval;
  }
  
  /*
   * Returns waiting task that should be serviced first or NULL if none exists
   */
  static struct ext_wait_queue *wq_get_first_waiter(
  		struct mqueue_inode_info *info, int sr)
  {
  	struct list_head *ptr;
  
  	ptr = info->e_wait_q[sr].list.prev;
  	if (ptr == &info->e_wait_q[sr].list)
  		return NULL;
  	return list_entry(ptr, struct ext_wait_queue, list);
  }
  
  /* Auxiliary functions to manipulate messages' list */
  static void msg_insert(struct msg_msg *ptr, struct mqueue_inode_info *info)
  {
  	int k;
  
  	k = info->attr.mq_curmsgs - 1;
  	while (k >= 0 && info->messages[k]->m_type >= ptr->m_type) {
  		info->messages[k + 1] = info->messages[k];
  		k--;
  	}
  	info->attr.mq_curmsgs++;
  	info->qsize += ptr->m_ts;
  	info->messages[k + 1] = ptr;
  }
  
  static inline struct msg_msg *msg_get(struct mqueue_inode_info *info)
  {
  	info->qsize -= info->messages[--info->attr.mq_curmsgs]->m_ts;
  	return info->messages[info->attr.mq_curmsgs];
  }
  
  static inline void set_cookie(struct sk_buff *skb, char code)
  {
  	((char*)skb->data)[NOTIFY_COOKIE_LEN-1] = code;
  }
  
  /*
   * The next function is only to split too long sys_mq_timedsend
   */
  static void __do_notify(struct mqueue_inode_info *info)
  {
  	/* notification
  	 * invoked when there is registered process and there isn't process
  	 * waiting synchronously for message AND state of queue changed from
  	 * empty to not empty. Here we are sure that no one is waiting
  	 * synchronously. */
  	if (info->notify_owner &&
  	    info->attr.mq_curmsgs == 1) {
  		struct siginfo sig_i;
  		switch (info->notify.sigev_notify) {
  		case SIGEV_NONE:
  			break;
  		case SIGEV_SIGNAL:
  			/* sends signal */
  
  			sig_i.si_signo = info->notify.sigev_signo;
  			sig_i.si_errno = 0;
  			sig_i.si_code = SI_MESGQ;
  			sig_i.si_value = info->notify.sigev_value;

  			sig_i.si_pid = task_tgid_vnr(current);

  			sig_i.si_uid = current->uid;

  			kill_pid_info(info->notify.sigev_signo,
  				      &sig_i, info->notify_owner);

  			break;
  		case SIGEV_THREAD:
  			set_cookie(info->notify_cookie, NOTIFY_WOKENUP);

  			netlink_sendskb(info->notify_sock, info->notify_cookie);

  			break;
  		}
  		/* after notification unregisters process */

  		put_pid(info->notify_owner);
  		info->notify_owner = NULL;

  	}
  	wake_up(&info->wait_q);
  }
  
  static long prepare_timeout(const struct timespec __user *u_arg)
  {
  	struct timespec ts, nowts;
  	long timeout;
  
  	if (u_arg) {
  		if (unlikely(copy_from_user(&ts, u_arg,
  					sizeof(struct timespec))))
  			return -EFAULT;
  
  		if (unlikely(ts.tv_nsec < 0 || ts.tv_sec < 0
  			|| ts.tv_nsec >= NSEC_PER_SEC))
  			return -EINVAL;
  		nowts = CURRENT_TIME;
  		/* first subtract as jiffies can't be too big */
  		ts.tv_sec -= nowts.tv_sec;
  		if (ts.tv_nsec < nowts.tv_nsec) {
  			ts.tv_nsec += NSEC_PER_SEC;
  			ts.tv_sec--;
  		}
  		ts.tv_nsec -= nowts.tv_nsec;
  		if (ts.tv_sec < 0)
  			return 0;
  
  		timeout = timespec_to_jiffies(&ts) + 1;
  	} else
  		return MAX_SCHEDULE_TIMEOUT;
  
  	return timeout;
  }
  
  static void remove_notification(struct mqueue_inode_info *info)
  {

  	if (info->notify_owner != NULL &&

  	    info->notify.sigev_notify == SIGEV_THREAD) {
  		set_cookie(info->notify_cookie, NOTIFY_REMOVED);

  		netlink_sendskb(info->notify_sock, info->notify_cookie);

  	}

  	put_pid(info->notify_owner);
  	info->notify_owner = NULL;

  }
  
  static int mq_attr_ok(struct mq_attr *attr)
  {
  	if (attr->mq_maxmsg <= 0 || attr->mq_msgsize <= 0)
  		return 0;
  	if (capable(CAP_SYS_RESOURCE)) {
  		if (attr->mq_maxmsg > HARD_MSGMAX)
  			return 0;
  	} else {
  		if (attr->mq_maxmsg > msg_max ||
  				attr->mq_msgsize > msgsize_max)
  			return 0;
  	}
  	/* check for overflow */
  	if (attr->mq_msgsize > ULONG_MAX/attr->mq_maxmsg)
  		return 0;
  	if ((unsigned long)(attr->mq_maxmsg * attr->mq_msgsize) +
  	    (attr->mq_maxmsg * sizeof (struct msg_msg *)) <
  	    (unsigned long)(attr->mq_maxmsg * attr->mq_msgsize))
  		return 0;
  	return 1;
  }
  
  /*
   * Invoked when creating a new queue via sys_mq_open
   */
  static struct file *do_create(struct dentry *dir, struct dentry *dentry,
  			int oflag, mode_t mode, struct mq_attr __user *u_attr)
  {

  	struct mq_attr attr;

  	struct file *result;

  	int ret;

  	if (u_attr) {
  		ret = -EFAULT;

  		if (copy_from_user(&attr, u_attr, sizeof(attr)))

  			goto out;
  		ret = -EINVAL;

  		if (!mq_attr_ok(&attr))

  			goto out;

  		/* store for use during create */
  		dentry->d_fsdata = &attr;
  	}

  	mode &= ~current->fs->umask;

  	ret = mnt_want_write(mqueue_mnt);
  	if (ret)
  		goto out;

  	ret = vfs_create(dir->d_inode, dentry, mode, NULL);
  	dentry->d_fsdata = NULL;
  	if (ret)

  		goto out_drop_write;
  
  	result = dentry_open(dentry, mqueue_mnt, oflag);
  	/*
  	 * dentry_open() took a persistent mnt_want_write(),
  	 * so we can now drop this one.
  	 */
  	mnt_drop_write(mqueue_mnt);
  	return result;
  
  out_drop_write:
  	mnt_drop_write(mqueue_mnt);

  out:
  	dput(dentry);
  	mntput(mqueue_mnt);
  	return ERR_PTR(ret);

  }
  
  /* Opens existing queue */
  static struct file *do_open(struct dentry *dentry, int oflag)
  {
  static int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE,
  					MAY_READ | MAY_WRITE };

  	if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY)) {
  		dput(dentry);
  		mntput(mqueue_mnt);

  		return ERR_PTR(-EINVAL);

  	}

  	if (inode_permission(dentry->d_inode, oflag2acc[oflag & O_ACCMODE])) {

  		dput(dentry);
  		mntput(mqueue_mnt);

  		return ERR_PTR(-EACCES);

  	}

  	return dentry_open(dentry, mqueue_mnt, oflag);

  }
  
  asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode,
  				struct mq_attr __user *u_attr)
  {
  	struct dentry *dentry;
  	struct file *filp;
  	char *name;
  	int fd, error;

  	error = audit_mq_open(oflag, mode, u_attr);
  	if (error != 0)
  		return error;

  	if (IS_ERR(name = getname(u_name)))
  		return PTR_ERR(name);

  	fd = get_unused_fd_flags(O_CLOEXEC);

  	if (fd < 0)
  		goto out_putname;

  	mutex_lock(&mqueue_mnt->mnt_root->d_inode->i_mutex);

  	dentry = lookup_one_len(name, mqueue_mnt->mnt_root, strlen(name));
  	if (IS_ERR(dentry)) {
  		error = PTR_ERR(dentry);
  		goto out_err;
  	}
  	mntget(mqueue_mnt);
  
  	if (oflag & O_CREAT) {
  		if (dentry->d_inode) {	/* entry already exists */

  			audit_inode(name, dentry);

  			error = -EEXIST;
  			if (oflag & O_EXCL)
  				goto out;
  			filp = do_open(dentry, oflag);

  		} else {
  			filp = do_create(mqueue_mnt->mnt_root, dentry,
  						oflag, mode, u_attr);
  		}

  	} else {
  		error = -ENOENT;
  		if (!dentry->d_inode)
  			goto out;

  		audit_inode(name, dentry);

  		filp = do_open(dentry, oflag);
  	}

  
  	if (IS_ERR(filp)) {
  		error = PTR_ERR(filp);
  		goto out_putfd;
  	}

  	fd_install(fd, filp);
  	goto out_upsem;

  out:
  	dput(dentry);

  	mntput(mqueue_mnt);

  out_putfd:

  	put_unused_fd(fd);
  out_err:
  	fd = error;
  out_upsem:

  	mutex_unlock(&mqueue_mnt->mnt_root->d_inode->i_mutex);

  out_putname:
  	putname(name);
  	return fd;
  }
  
  asmlinkage long sys_mq_unlink(const char __user *u_name)
  {
  	int err;
  	char *name;
  	struct dentry *dentry;
  	struct inode *inode = NULL;
  
  	name = getname(u_name);
  	if (IS_ERR(name))
  		return PTR_ERR(name);

  	mutex_lock_nested(&mqueue_mnt->mnt_root->d_inode->i_mutex,
  			I_MUTEX_PARENT);

  	dentry = lookup_one_len(name, mqueue_mnt->mnt_root, strlen(name));
  	if (IS_ERR(dentry)) {
  		err = PTR_ERR(dentry);
  		goto out_unlock;
  	}
  
  	if (!dentry->d_inode) {
  		err = -ENOENT;
  		goto out_err;
  	}
  
  	inode = dentry->d_inode;
  	if (inode)
  		atomic_inc(&inode->i_count);

  	err = mnt_want_write(mqueue_mnt);
  	if (err)
  		goto out_err;

  	err = vfs_unlink(dentry->d_parent->d_inode, dentry);

  	mnt_drop_write(mqueue_mnt);

  out_err:
  	dput(dentry);
  
  out_unlock:

  	mutex_unlock(&mqueue_mnt->mnt_root->d_inode->i_mutex);

  	putname(name);
  	if (inode)
  		iput(inode);
  
  	return err;
  }
  
  /* Pipelined send and receive functions.
   *
   * If a receiver finds no waiting message, then it registers itself in the
   * list of waiting receivers. A sender checks that list before adding the new
   * message into the message array. If there is a waiting receiver, then it
   * bypasses the message array and directly hands the message over to the
   * receiver.
   * The receiver accepts the message and returns without grabbing the queue
   * spinlock. Therefore an intermediate STATE_PENDING state and memory barriers
   * are necessary. The same algorithm is used for sysv semaphores, see

   * ipc/sem.c for more details.

   *
   * The same algorithm is used for senders.
   */
  
  /* pipelined_send() - send a message directly to the task waiting in
   * sys_mq_timedreceive() (without inserting message into a queue).
   */
  static inline void pipelined_send(struct mqueue_inode_info *info,
  				  struct msg_msg *message,
  				  struct ext_wait_queue *receiver)
  {
  	receiver->msg = message;
  	list_del(&receiver->list);
  	receiver->state = STATE_PENDING;
  	wake_up_process(receiver->task);

  	smp_wmb();

  	receiver->state = STATE_READY;
  }
  
  /* pipelined_receive() - if there is task waiting in sys_mq_timedsend()
   * gets its message and put to the queue (we have one free place for sure). */
  static inline void pipelined_receive(struct mqueue_inode_info *info)
  {
  	struct ext_wait_queue *sender = wq_get_first_waiter(info, SEND);
  
  	if (!sender) {
  		/* for poll */
  		wake_up_interruptible(&info->wait_q);
  		return;
  	}
  	msg_insert(sender->msg, info);
  	list_del(&sender->list);
  	sender->state = STATE_PENDING;
  	wake_up_process(sender->task);

  	smp_wmb();

  	sender->state = STATE_READY;
  }
  
  asmlinkage long sys_mq_timedsend(mqd_t mqdes, const char __user *u_msg_ptr,
  	size_t msg_len, unsigned int msg_prio,
  	const struct timespec __user *u_abs_timeout)
  {
  	struct file *filp;
  	struct inode *inode;
  	struct ext_wait_queue wait;
  	struct ext_wait_queue *receiver;
  	struct msg_msg *msg_ptr;
  	struct mqueue_inode_info *info;
  	long timeout;
  	int ret;

  	ret = audit_mq_timedsend(mqdes, msg_len, msg_prio, u_abs_timeout);
  	if (ret != 0)
  		return ret;

  	if (unlikely(msg_prio >= (unsigned long) MQ_PRIO_MAX))
  		return -EINVAL;
  
  	timeout = prepare_timeout(u_abs_timeout);
  
  	ret = -EBADF;
  	filp = fget(mqdes);
  	if (unlikely(!filp))
  		goto out;

  	inode = filp->f_path.dentry->d_inode;

  	if (unlikely(filp->f_op != &mqueue_file_operations))
  		goto out_fput;
  	info = MQUEUE_I(inode);

  	audit_inode(NULL, filp->f_path.dentry);

  
  	if (unlikely(!(filp->f_mode & FMODE_WRITE)))
  		goto out_fput;
  
  	if (unlikely(msg_len > info->attr.mq_msgsize)) {
  		ret = -EMSGSIZE;
  		goto out_fput;
  	}
  
  	/* First try to allocate memory, before doing anything with
  	 * existing queues. */
  	msg_ptr = load_msg(u_msg_ptr, msg_len);
  	if (IS_ERR(msg_ptr)) {
  		ret = PTR_ERR(msg_ptr);
  		goto out_fput;
  	}
  	msg_ptr->m_ts = msg_len;
  	msg_ptr->m_type = msg_prio;
  
  	spin_lock(&info->lock);
  
  	if (info->attr.mq_curmsgs == info->attr.mq_maxmsg) {
  		if (filp->f_flags & O_NONBLOCK) {
  			spin_unlock(&info->lock);
  			ret = -EAGAIN;
  		} else if (unlikely(timeout < 0)) {
  			spin_unlock(&info->lock);
  			ret = timeout;
  		} else {
  			wait.task = current;
  			wait.msg = (void *) msg_ptr;
  			wait.state = STATE_NONE;
  			ret = wq_sleep(info, SEND, timeout, &wait);
  		}
  		if (ret < 0)
  			free_msg(msg_ptr);
  	} else {
  		receiver = wq_get_first_waiter(info, RECV);
  		if (receiver) {
  			pipelined_send(info, msg_ptr, receiver);
  		} else {
  			/* adds message to the queue */
  			msg_insert(msg_ptr, info);
  			__do_notify(info);
  		}
  		inode->i_atime = inode->i_mtime = inode->i_ctime =
  				CURRENT_TIME;
  		spin_unlock(&info->lock);
  		ret = 0;
  	}
  out_fput:
  	fput(filp);
  out:
  	return ret;
  }
  
  asmlinkage ssize_t sys_mq_timedreceive(mqd_t mqdes, char __user *u_msg_ptr,
  	size_t msg_len, unsigned int __user *u_msg_prio,
  	const struct timespec __user *u_abs_timeout)
  {
  	long timeout;
  	ssize_t ret;
  	struct msg_msg *msg_ptr;
  	struct file *filp;
  	struct inode *inode;
  	struct mqueue_inode_info *info;
  	struct ext_wait_queue wait;

  	ret = audit_mq_timedreceive(mqdes, msg_len, u_msg_prio, u_abs_timeout);
  	if (ret != 0)
  		return ret;

  	timeout = prepare_timeout(u_abs_timeout);
  
  	ret = -EBADF;
  	filp = fget(mqdes);
  	if (unlikely(!filp))
  		goto out;

  	inode = filp->f_path.dentry->d_inode;

  	if (unlikely(filp->f_op != &mqueue_file_operations))
  		goto out_fput;
  	info = MQUEUE_I(inode);

  	audit_inode(NULL, filp->f_path.dentry);

  
  	if (unlikely(!(filp->f_mode & FMODE_READ)))
  		goto out_fput;
  
  	/* checks if buffer is big enough */
  	if (unlikely(msg_len < info->attr.mq_msgsize)) {
  		ret = -EMSGSIZE;
  		goto out_fput;
  	}
  
  	spin_lock(&info->lock);
  	if (info->attr.mq_curmsgs == 0) {
  		if (filp->f_flags & O_NONBLOCK) {
  			spin_unlock(&info->lock);
  			ret = -EAGAIN;
  			msg_ptr = NULL;
  		} else if (unlikely(timeout < 0)) {
  			spin_unlock(&info->lock);
  			ret = timeout;
  			msg_ptr = NULL;
  		} else {
  			wait.task = current;
  			wait.state = STATE_NONE;
  			ret = wq_sleep(info, RECV, timeout, &wait);
  			msg_ptr = wait.msg;
  		}
  	} else {
  		msg_ptr = msg_get(info);
  
  		inode->i_atime = inode->i_mtime = inode->i_ctime =
  				CURRENT_TIME;
  
  		/* There is now free space in queue. */
  		pipelined_receive(info);
  		spin_unlock(&info->lock);
  		ret = 0;
  	}
  	if (ret == 0) {
  		ret = msg_ptr->m_ts;
  
  		if ((u_msg_prio && put_user(msg_ptr->m_type, u_msg_prio)) ||
  			store_msg(u_msg_ptr, msg_ptr, msg_ptr->m_ts)) {
  			ret = -EFAULT;
  		}
  		free_msg(msg_ptr);
  	}
  out_fput:
  	fput(filp);
  out:
  	return ret;
  }
  
  /*
   * Notes: the case when user wants us to deregister (with NULL as pointer)
   * and he isn't currently owner of notification, will be silently discarded.
   * It isn't explicitly defined in the POSIX.
   */
  asmlinkage long sys_mq_notify(mqd_t mqdes,
  				const struct sigevent __user *u_notification)
  {
  	int ret;
  	struct file *filp;
  	struct sock *sock;
  	struct inode *inode;
  	struct sigevent notification;
  	struct mqueue_inode_info *info;
  	struct sk_buff *nc;

  	ret = audit_mq_notify(mqdes, u_notification);
  	if (ret != 0)
  		return ret;

  	nc = NULL;
  	sock = NULL;
  	if (u_notification != NULL) {
  		if (copy_from_user(&notification, u_notification,
  					sizeof(struct sigevent)))
  			return -EFAULT;
  
  		if (unlikely(notification.sigev_notify != SIGEV_NONE &&
  			     notification.sigev_notify != SIGEV_SIGNAL &&
  			     notification.sigev_notify != SIGEV_THREAD))
  			return -EINVAL;
  		if (notification.sigev_notify == SIGEV_SIGNAL &&

  			!valid_signal(notification.sigev_signo)) {

  			return -EINVAL;
  		}
  		if (notification.sigev_notify == SIGEV_THREAD) {

  			long timeo;

  			/* create the notify skb */
  			nc = alloc_skb(NOTIFY_COOKIE_LEN, GFP_KERNEL);
  			ret = -ENOMEM;
  			if (!nc)
  				goto out;
  			ret = -EFAULT;
  			if (copy_from_user(nc->data,
  					notification.sigev_value.sival_ptr,
  					NOTIFY_COOKIE_LEN)) {
  				goto out;
  			}
  
  			/* TODO: add a header? */
  			skb_put(nc, NOTIFY_COOKIE_LEN);
  			/* and attach it to the socket */
  retry:
  			filp = fget(notification.sigev_signo);
  			ret = -EBADF;
  			if (!filp)
  				goto out;
  			sock = netlink_getsockbyfilp(filp);
  			fput(filp);
  			if (IS_ERR(sock)) {
  				ret = PTR_ERR(sock);
  				sock = NULL;
  				goto out;
  			}

  			timeo = MAX_SCHEDULE_TIMEOUT;

  			ret = netlink_attachskb(sock, nc, &timeo, NULL);

  			if (ret == 1)
  		       		goto retry;
  			if (ret) {
  				sock = NULL;
  				nc = NULL;
  				goto out;
  			}
  		}
  	}
  
  	ret = -EBADF;
  	filp = fget(mqdes);
  	if (!filp)
  		goto out;

  	inode = filp->f_path.dentry->d_inode;

  	if (unlikely(filp->f_op != &mqueue_file_operations))
  		goto out_fput;
  	info = MQUEUE_I(inode);
  
  	ret = 0;
  	spin_lock(&info->lock);
  	if (u_notification == NULL) {

  		if (info->notify_owner == task_tgid(current)) {

  			remove_notification(info);
  			inode->i_atime = inode->i_ctime = CURRENT_TIME;
  		}

  	} else if (info->notify_owner != NULL) {

  		ret = -EBUSY;
  	} else {
  		switch (notification.sigev_notify) {
  		case SIGEV_NONE:
  			info->notify.sigev_notify = SIGEV_NONE;
  			break;
  		case SIGEV_THREAD:
  			info->notify_sock = sock;
  			info->notify_cookie = nc;
  			sock = NULL;
  			nc = NULL;
  			info->notify.sigev_notify = SIGEV_THREAD;
  			break;
  		case SIGEV_SIGNAL:
  			info->notify.sigev_signo = notification.sigev_signo;
  			info->notify.sigev_value = notification.sigev_value;
  			info->notify.sigev_notify = SIGEV_SIGNAL;
  			break;
  		}

  
  		info->notify_owner = get_pid(task_tgid(current));

  		inode->i_atime = inode->i_ctime = CURRENT_TIME;
  	}
  	spin_unlock(&info->lock);
  out_fput:
  	fput(filp);
  out:
  	if (sock) {
  		netlink_detachskb(sock, nc);
  	} else if (nc) {
  		dev_kfree_skb(nc);
  	}
  	return ret;
  }
  
  asmlinkage long sys_mq_getsetattr(mqd_t mqdes,
  			const struct mq_attr __user *u_mqstat,
  			struct mq_attr __user *u_omqstat)
  {
  	int ret;
  	struct mq_attr mqstat, omqstat;
  	struct file *filp;
  	struct inode *inode;
  	struct mqueue_inode_info *info;
  
  	if (u_mqstat != NULL) {
  		if (copy_from_user(&mqstat, u_mqstat, sizeof(struct mq_attr)))
  			return -EFAULT;
  		if (mqstat.mq_flags & (~O_NONBLOCK))
  			return -EINVAL;
  	}
  
  	ret = -EBADF;
  	filp = fget(mqdes);
  	if (!filp)
  		goto out;

  	inode = filp->f_path.dentry->d_inode;

  	if (unlikely(filp->f_op != &mqueue_file_operations))
  		goto out_fput;
  	info = MQUEUE_I(inode);
  
  	spin_lock(&info->lock);
  
  	omqstat = info->attr;
  	omqstat.mq_flags = filp->f_flags & O_NONBLOCK;
  	if (u_mqstat) {

  		ret = audit_mq_getsetattr(mqdes, &mqstat);

  		if (ret != 0) {
  			spin_unlock(&info->lock);
  			goto out_fput;
  		}

  		if (mqstat.mq_flags & O_NONBLOCK)
  			filp->f_flags |= O_NONBLOCK;
  		else
  			filp->f_flags &= ~O_NONBLOCK;
  
  		inode->i_atime = inode->i_ctime = CURRENT_TIME;
  	}
  
  	spin_unlock(&info->lock);
  
  	ret = 0;
  	if (u_omqstat != NULL && copy_to_user(u_omqstat, &omqstat,
  						sizeof(struct mq_attr)))
  		ret = -EFAULT;
  
  out_fput:
  	fput(filp);
  out:
  	return ret;
  }

  static const struct inode_operations mqueue_dir_inode_operations = {

  	.lookup = simple_lookup,
  	.create = mqueue_create,
  	.unlink = mqueue_unlink,
  };

  static const struct file_operations mqueue_file_operations = {

  	.flush = mqueue_flush_file,
  	.poll = mqueue_poll_file,
  	.read = mqueue_read_file,
  };
  
  static struct super_operations mqueue_super_ops = {
  	.alloc_inode = mqueue_alloc_inode,
  	.destroy_inode = mqueue_destroy_inode,
  	.statfs = simple_statfs,
  	.delete_inode = mqueue_delete_inode,
  	.drop_inode = generic_delete_inode,
  };
  
  static struct file_system_type mqueue_fs_type = {
  	.name = "mqueue",
  	.get_sb = mqueue_get_sb,
  	.kill_sb = kill_litter_super,
  };
  
  static int msg_max_limit_min = DFLT_MSGMAX;
  static int msg_max_limit_max = HARD_MSGMAX;
  
  static int msg_maxsize_limit_min = DFLT_MSGSIZEMAX;
  static int msg_maxsize_limit_max = INT_MAX;
  
  static ctl_table mq_sysctls[] = {
  	{

  		.procname	= "queues_max",
  		.data		= &queues_max,
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= &proc_dointvec,
  	},
  	{

  		.procname	= "msg_max",
  		.data		= &msg_max,
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= &proc_dointvec_minmax,
  		.extra1		= &msg_max_limit_min,
  		.extra2		= &msg_max_limit_max,
  	},
  	{

  		.procname	= "msgsize_max",
  		.data		= &msgsize_max,
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= &proc_dointvec_minmax,
  		.extra1		= &msg_maxsize_limit_min,
  		.extra2		= &msg_maxsize_limit_max,
  	},
  	{ .ctl_name = 0 }
  };
  
  static ctl_table mq_sysctl_dir[] = {
  	{

  		.procname	= "mqueue",
  		.mode		= 0555,
  		.child		= mq_sysctls,
  	},
  	{ .ctl_name = 0 }
  };
  
  static ctl_table mq_sysctl_root[] = {
  	{
  		.ctl_name	= CTL_FS,
  		.procname	= "fs",
  		.mode		= 0555,
  		.child		= mq_sysctl_dir,
  	},
  	{ .ctl_name = 0 }
  };
  
  static int __init init_mqueue_fs(void)
  {
  	int error;
  
  	mqueue_inode_cachep = kmem_cache_create("mqueue_inode_cache",
  				sizeof(struct mqueue_inode_info), 0,

  				SLAB_HWCACHE_ALIGN, init_once);

  	if (mqueue_inode_cachep == NULL)
  		return -ENOMEM;
  
  	/* ignore failues - they are not fatal */

  	mq_sysctl_table = register_sysctl_table(mq_sysctl_root);

  
  	error = register_filesystem(&mqueue_fs_type);
  	if (error)
  		goto out_sysctl;
  
  	if (IS_ERR(mqueue_mnt = kern_mount(&mqueue_fs_type))) {
  		error = PTR_ERR(mqueue_mnt);
  		goto out_filesystem;
  	}
  
  	/* internal initialization - not common for vfs */
  	queues_count = 0;
  	spin_lock_init(&mq_lock);
  
  	return 0;
  
  out_filesystem:
  	unregister_filesystem(&mqueue_fs_type);
  out_sysctl:
  	if (mq_sysctl_table)
  		unregister_sysctl_table(mq_sysctl_table);

  	kmem_cache_destroy(mqueue_inode_cachep);

  	return error;
  }
  
  __initcall(init_mqueue_fs);