[linux-2.6-block.git] / fs / autofs4 / expire.c

/* -*- c -*- --------------------------------------------------------------- *
 *
 * linux/fs/autofs/expire.c
 *
 *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
 *  Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
 *  Copyright 2001-2006 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 "autofs_i.h"

static unsigned long now;

/* Check if a dentry can be expired */
static inline int autofs4_can_expire(struct dentry *dentry,
					unsigned long timeout, int do_now)
{
	struct autofs_info *ino = autofs4_dentry_ino(dentry);

	/* dentry in the process of being deleted */
	if (ino == NULL)
		return 0;

	if (!do_now) {
		/* Too young to die */
		if (!timeout || time_after(ino->last_used + timeout, now))
			return 0;

		/* update last_used here :-
		   - obviously makes sense if it is in use now
		   - less obviously, prevents rapid-fire expire
		     attempts if expire fails the first time */
		ino->last_used = now;
	}
	return 1;
}

/* Check a mount point for busyness */
static int autofs4_mount_busy(struct vfsmount *mnt, struct dentry *dentry)
{
	struct dentry *top = dentry;
	struct path path = {.mnt = mnt, .dentry = dentry};
	int status = 1;

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

	path_get(&path);

	if (!follow_down_one(&path))
		goto done;

	if (is_autofs4_dentry(path.dentry)) {
		struct autofs_sb_info *sbi = autofs4_sbi(path.dentry->d_sb);

		/* This is an autofs submount, we can't expire it */
		if (autofs_type_indirect(sbi->type))
			goto done;
	}

	/* Update the expiry counter if fs is busy */
	if (!may_umount_tree(path.mnt)) {
		struct autofs_info *ino = autofs4_dentry_ino(top);
		ino->last_used = jiffies;
		goto done;
	}

	status = 0;
done:
	DPRINTK("returning = %d", status);
	path_put(&path);
	return status;
}

/*
 * Calculate and dget next entry in the subdirs list under root.
 */
static struct dentry *get_next_positive_subdir(struct dentry *prev,
						struct dentry *root)
{
	struct autofs_sb_info *sbi = autofs4_sbi(root->d_sb);
	struct list_head *next;
	struct dentry *q;

	spin_lock(&sbi->lookup_lock);
	spin_lock(&root->d_lock);

	if (prev)
		next = prev->d_u.d_child.next;
	else {
		prev = dget_dlock(root);
		next = prev->d_subdirs.next;
	}

cont:
	if (next == &root->d_subdirs) {
		spin_unlock(&root->d_lock);
		spin_unlock(&sbi->lookup_lock);
		dput(prev);
		return NULL;
	}

	q = list_entry(next, struct dentry, d_u.d_child);

	spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
	/* Already gone or negative dentry (under construction) - try next */
	if (!d_count(q) || !simple_positive(q)) {
		spin_unlock(&q->d_lock);
		next = q->d_u.d_child.next;
		goto cont;
	}
	dget_dlock(q);
	spin_unlock(&q->d_lock);
	spin_unlock(&root->d_lock);
	spin_unlock(&sbi->lookup_lock);

	dput(prev);

	return q;
}

/*
 * Calculate and dget next entry in top down tree traversal.
 */
static struct dentry *get_next_positive_dentry(struct dentry *prev,
						struct dentry *root)
{
	struct autofs_sb_info *sbi = autofs4_sbi(root->d_sb);
	struct list_head *next;
	struct dentry *p, *ret;

	if (prev == NULL)
		return dget(root);

	spin_lock(&sbi->lookup_lock);
relock:
	p = prev;
	spin_lock(&p->d_lock);
again:
	next = p->d_subdirs.next;
	if (next == &p->d_subdirs) {
		while (1) {
			struct dentry *parent;

			if (p == root) {
				spin_unlock(&p->d_lock);
				spin_unlock(&sbi->lookup_lock);
				dput(prev);
				return NULL;
			}

			parent = p->d_parent;
			if (!spin_trylock(&parent->d_lock)) {
				spin_unlock(&p->d_lock);
				cpu_relax();
				goto relock;
			}
			spin_unlock(&p->d_lock);
			next = p->d_u.d_child.next;
			p = parent;
			if (next != &parent->d_subdirs)
				break;
		}
	}
	ret = list_entry(next, struct dentry, d_u.d_child);

	spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
	/* Negative dentry - try next */
	if (!simple_positive(ret)) {
		spin_unlock(&p->d_lock);
		lock_set_subclass(&ret->d_lock.dep_map, 0, _RET_IP_);
		p = ret;
		goto again;
	}
	dget_dlock(ret);
	spin_unlock(&ret->d_lock);
	spin_unlock(&p->d_lock);
	spin_unlock(&sbi->lookup_lock);

	dput(prev);

	return ret;
}

/*
 * Check a direct mount point for busyness.
 * Direct mounts have similar expiry semantics to tree mounts.
 * The tree is not busy iff no mountpoints are busy and there are no
 * autofs submounts.
 */
static int autofs4_direct_busy(struct vfsmount *mnt,
				struct dentry *top,
				unsigned long timeout,
				int do_now)
{
	DPRINTK("top %p %.*s",
		top, (int) top->d_name.len, top->d_name.name);

	/* If it's busy update the expiry counters */
	if (!may_umount_tree(mnt)) {
		struct autofs_info *ino = autofs4_dentry_ino(top);
		if (ino)
			ino->last_used = jiffies;
		return 1;
	}

	/* Timeout of a direct mount is determined by its top dentry */
	if (!autofs4_can_expire(top, timeout, do_now))
		return 1;

	return 0;
}

/* Check a directory tree of mount points for busyness
 * The tree is not busy iff no mountpoints are busy
 */
static int autofs4_tree_busy(struct vfsmount *mnt,
	       		     struct dentry *top,
			     unsigned long timeout,
			     int do_now)
{
	struct autofs_info *top_ino = autofs4_dentry_ino(top);
	struct dentry *p;

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

	/* Negative dentry - give up */
	if (!simple_positive(top))
		return 1;

	p = NULL;
	while ((p = get_next_positive_dentry(p, top))) {
		DPRINTK("dentry %p %.*s",
			p, (int) p->d_name.len, p->d_name.name);

		/*
		 * Is someone visiting anywhere in the subtree ?
		 * If there's no mount we need to check the usage
		 * count for the autofs dentry.
		 * If the fs is busy update the expiry counter.
		 */
		if (d_mountpoint(p)) {
			if (autofs4_mount_busy(mnt, p)) {
				top_ino->last_used = jiffies;
				dput(p);
				return 1;
			}
		} else {
			struct autofs_info *ino = autofs4_dentry_ino(p);
			unsigned int ino_count = atomic_read(&ino->count);

			/* allow for dget above and top is already dgot */
			if (p == top)
				ino_count += 2;
			else
				ino_count++;

			if (d_count(p) > ino_count) {
				top_ino->last_used = jiffies;
				dput(p);
				return 1;
			}
		}
	}

	/* Timeout of a tree mount is ultimately determined by its top dentry */
	if (!autofs4_can_expire(top, timeout, do_now))
		return 1;

	return 0;
}

static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
					   struct dentry *parent,
					   unsigned long timeout,
					   int do_now)
{
	struct dentry *p;

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

	p = NULL;
	while ((p = get_next_positive_dentry(p, parent))) {
		DPRINTK("dentry %p %.*s",
			p, (int) p->d_name.len, p->d_name.name);

		if (d_mountpoint(p)) {
			/* Can we umount this guy */
			if (autofs4_mount_busy(mnt, p))
				continue;

			/* Can we expire this guy */
			if (autofs4_can_expire(p, timeout, do_now))
				return p;
		}
	}
	return NULL;
}

/* Check if we can expire a direct mount (possibly a tree) */
struct dentry *autofs4_expire_direct(struct super_block *sb,
				     struct vfsmount *mnt,
				     struct autofs_sb_info *sbi,
				     int how)
{
	unsigned long timeout;
	struct dentry *root = dget(sb->s_root);
	int do_now = how & AUTOFS_EXP_IMMEDIATE;
	struct autofs_info *ino;

	if (!root)
		return NULL;

	now = jiffies;
	timeout = sbi->exp_timeout;

	spin_lock(&sbi->fs_lock);
	ino = autofs4_dentry_ino(root);
	/* No point expiring a pending mount */
	if (ino->flags & AUTOFS_INF_PENDING)
		goto out;
	if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
		ino->flags |= AUTOFS_INF_EXPIRING;
		init_completion(&ino->expire_complete);
		spin_unlock(&sbi->fs_lock);
		return root;
	}
out:
	spin_unlock(&sbi->fs_lock);
	dput(root);

	return NULL;
}

/*
 * Find an eligible tree to time-out
 * A tree is eligible if :-
 *  - it is unused by any user process
 *  - it has been unused for exp_timeout time
 */
struct dentry *autofs4_expire_indirect(struct super_block *sb,
				       struct vfsmount *mnt,
				       struct autofs_sb_info *sbi,
				       int how)
{
	unsigned long timeout;
	struct dentry *root = sb->s_root;
	struct dentry *dentry;
	struct dentry *expired = NULL;
	int do_now = how & AUTOFS_EXP_IMMEDIATE;
	int exp_leaves = how & AUTOFS_EXP_LEAVES;
	struct autofs_info *ino;
	unsigned int ino_count;

	if (!root)
		return NULL;

	now = jiffies;
	timeout = sbi->exp_timeout;

	dentry = NULL;
	while ((dentry = get_next_positive_subdir(dentry, root))) {
		spin_lock(&sbi->fs_lock);
		ino = autofs4_dentry_ino(dentry);
		/* No point expiring a pending mount */
		if (ino->flags & AUTOFS_INF_PENDING)
			goto next;

		/*
		 * Case 1: (i) indirect mount or top level pseudo direct mount
		 *	   (autofs-4.1).
		 *	   (ii) indirect mount with offset mount, check the "/"
		 *	   offset (autofs-5.0+).
		 */
		if (d_mountpoint(dentry)) {
			DPRINTK("checking mountpoint %p %.*s",
				dentry, (int)dentry->d_name.len, dentry->d_name.name);

			/* Can we umount this guy */
			if (autofs4_mount_busy(mnt, dentry))
				goto next;

			/* Can we expire this guy */
			if (autofs4_can_expire(dentry, timeout, do_now)) {
				expired = dentry;
				goto found;
			}
			goto next;
		}

		if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)) {
			DPRINTK("checking symlink %p %.*s",
				dentry, (int)dentry->d_name.len, dentry->d_name.name);
			/*
			 * A symlink can't be "busy" in the usual sense so
			 * just check last used for expire timeout.
			 */
			if (autofs4_can_expire(dentry, timeout, do_now)) {
				expired = dentry;
				goto found;
			}
			goto next;
		}

		if (simple_empty(dentry))
			goto next;

		/* Case 2: tree mount, expire iff entire tree is not busy */
		if (!exp_leaves) {
			/* Path walk currently on this dentry? */
			ino_count = atomic_read(&ino->count) + 1;
			if (d_count(dentry) > ino_count)
				goto next;

			if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
				expired = dentry;
				goto found;
			}
		/*
		 * Case 3: pseudo direct mount, expire individual leaves
		 *	   (autofs-4.1).
		 */
		} else {
			/* Path walk currently on this dentry? */
			ino_count = atomic_read(&ino->count) + 1;
			if (d_count(dentry) > ino_count)
				goto next;

			expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
			if (expired) {
				dput(dentry);
				goto found;
			}
		}
next:
		spin_unlock(&sbi->fs_lock);
	}
	return NULL;

found:
	DPRINTK("returning %p %.*s",
		expired, (int)expired->d_name.len, expired->d_name.name);
	ino = autofs4_dentry_ino(expired);
	ino->flags |= AUTOFS_INF_EXPIRING;
	init_completion(&ino->expire_complete);
	spin_unlock(&sbi->fs_lock);
	spin_lock(&sbi->lookup_lock);
	spin_lock(&expired->d_parent->d_lock);
	spin_lock_nested(&expired->d_lock, DENTRY_D_LOCK_NESTED);
	list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
	spin_unlock(&expired->d_lock);
	spin_unlock(&expired->d_parent->d_lock);
	spin_unlock(&sbi->lookup_lock);
	return expired;
}

int autofs4_expire_wait(struct dentry *dentry)
{
	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
	struct autofs_info *ino = autofs4_dentry_ino(dentry);
	int status;

	/* Block on any pending expire */
	spin_lock(&sbi->fs_lock);
	if (ino->flags & AUTOFS_INF_EXPIRING) {
		spin_unlock(&sbi->fs_lock);

		DPRINTK("waiting for expire %p name=%.*s",
			 dentry, dentry->d_name.len, dentry->d_name.name);

		status = autofs4_wait(sbi, dentry, NFY_NONE);
		wait_for_completion(&ino->expire_complete);

		DPRINTK("expire done status=%d", status);

		if (d_unhashed(dentry))
			return -EAGAIN;

		return status;
	}
	spin_unlock(&sbi->fs_lock);

	return 0;
}

/* Perform an expiry operation */
int autofs4_expire_run(struct super_block *sb,
		      struct vfsmount *mnt,
		      struct autofs_sb_info *sbi,
		      struct autofs_packet_expire __user *pkt_p)
{
	struct autofs_packet_expire pkt;
	struct autofs_info *ino;
	struct dentry *dentry;
	int ret = 0;

	memset(&pkt,0,sizeof pkt);

	pkt.hdr.proto_version = sbi->version;
	pkt.hdr.type = autofs_ptype_expire;

	if ((dentry = autofs4_expire_indirect(sb, mnt, sbi, 0)) == NULL)
		return -EAGAIN;

	pkt.len = dentry->d_name.len;
	memcpy(pkt.name, dentry->d_name.name, pkt.len);
	pkt.name[pkt.len] = '\0';
	dput(dentry);

	if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
		ret = -EFAULT;

	spin_lock(&sbi->fs_lock);
	ino = autofs4_dentry_ino(dentry);
	ino->flags &= ~AUTOFS_INF_EXPIRING;
	complete_all(&ino->expire_complete);
	spin_unlock(&sbi->fs_lock);

	return ret;
}

int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
			    struct autofs_sb_info *sbi, int when)
{
	struct dentry *dentry;
	int ret = -EAGAIN;

	if (autofs_type_trigger(sbi->type))
		dentry = autofs4_expire_direct(sb, mnt, sbi, when);
	else
		dentry = autofs4_expire_indirect(sb, mnt, sbi, when);

	if (dentry) {
		struct autofs_info *ino = autofs4_dentry_ino(dentry);

		/* This is synchronous because it makes the daemon a
                   little easier */
		ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);

		spin_lock(&sbi->fs_lock);
		ino->flags &= ~AUTOFS_INF_EXPIRING;
		complete_all(&ino->expire_complete);
		spin_unlock(&sbi->fs_lock);
		dput(dentry);
	}

	return ret;
}

/* Call repeatedly until it returns -EAGAIN, meaning there's nothing
   more to be done */
int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
			struct autofs_sb_info *sbi, int __user *arg)
{
	int do_now = 0;

	if (arg && get_user(do_now, arg))
		return -EFAULT;

	return autofs4_do_expire_multi(sb, mnt, sbi, do_now);
}
Commit	Line	Data
1da177e4 LT	1	/* -- c -- --------------------------------------------------------------- *
	2	*
	3	* linux/fs/autofs/expire.c
	4	*
	5	* Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
	6	* Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
3a15e2ab	7	* Copyright 2001-2006 Ian Kent <raven@themaw.net>
1da177e4 LT	8	*
	9	* This file is part of the Linux kernel and is made available under
	10	* the terms of the GNU General Public License, version 2, or at your
	11	* option, any later version, incorporated herein by reference.
	12	*
	13	* ------------------------------------------------------------------------- */
	14
	15	#include "autofs_i.h"
	16
	17	static unsigned long now;
	18
1f5f2c30	19	/* Check if a dentry can be expired */
1da177e4 LT	20	static inline int autofs4_can_expire(struct dentry *dentry,
	21	unsigned long timeout, int do_now)
	22	{
	23	struct autofs_info *ino = autofs4_dentry_ino(dentry);
	24
	25	/* dentry in the process of being deleted */
	26	if (ino == NULL)
	27	return 0;
	28
1da177e4 LT	29	if (!do_now) {
1da177e4 LT	30	/* Too young to die */
c0ba7e51	31	if (!timeout \|\| time_after(ino->last_used + timeout, now))
1da177e4 LT	32	return 0;
	33
	34	/* update last_used here :-
	35	- obviously makes sense if it is in use now
	36	- less obviously, prevents rapid-fire expire
	37	attempts if expire fails the first time */
	38	ino->last_used = now;
	39	}
1da177e4 LT	40	return 1;
	41	}
	42
1f5f2c30 IK	43	/* Check a mount point for busyness */
1f5f2c30 IK	44	static int autofs4_mount_busy(struct vfsmount mnt, struct dentry dentry)
1da177e4	45	{
e0a7aae9	46	struct dentry *top = dentry;
9393bd07	47	struct path path = {.mnt = mnt, .dentry = dentry};
1f5f2c30	48	int status = 1;
1da177e4 LT	49
	50	DPRINTK("dentry %p %.*s",
	51	dentry, (int)dentry->d_name.len, dentry->d_name.name);
	52
9393bd07	53	path_get(&path);
1da177e4	54
cc53ce53	55	if (!follow_down_one(&path))
1da177e4 LT	56	goto done;
1da177e4 LT	57
9393bd07 AV	58	if (is_autofs4_dentry(path.dentry)) {
9393bd07 AV	59	struct autofs_sb_info *sbi = autofs4_sbi(path.dentry->d_sb);
bc9c4068 IK	60
bc9c4068 IK	61	/* This is an autofs submount, we can't expire it */
a92daf6b	62	if (autofs_type_indirect(sbi->type))
bc9c4068	63	goto done;
bc9c4068	64	}
1da177e4	65
e0a7aae9	66	/* Update the expiry counter if fs is busy */
37d0892c	67	if (!may_umount_tree(path.mnt)) {
e0a7aae9 IK	68	struct autofs_info *ino = autofs4_dentry_ino(top);
	69	ino->last_used = jiffies;
	70	goto done;
	71	}
	72
	73	status = 0;
1da177e4 LT	74	done:
1da177e4 LT	75	DPRINTK("returning = %d", status);
9393bd07	76	path_put(&path);
1da177e4 LT	77	return status;
	78	}
	79
d4a85e35 IK	80	/*
	81	* Calculate and dget next entry in the subdirs list under root.
	82	*/
	83	static struct dentry get_next_positive_subdir(struct dentry prev,
	84	struct dentry *root)
	85	{
e7854723	86	struct autofs_sb_info *sbi = autofs4_sbi(root->d_sb);
d4a85e35	87	struct list_head *next;
a45440f0	88	struct dentry *q;
d4a85e35	89
e7854723	90	spin_lock(&sbi->lookup_lock);
a45440f0	91	spin_lock(&root->d_lock);
d4a85e35	92
a45440f0 IK	93	if (prev)
	94	next = prev->d_u.d_child.next;
	95	else {
d4a85e35 IK	96	prev = dget_dlock(root);
d4a85e35 IK	97	next = prev->d_subdirs.next;
d4a85e35 IK	98	}
d4a85e35 IK	99
a45440f0	100	cont:
d4a85e35	101	if (next == &root->d_subdirs) {
a45440f0	102	spin_unlock(&root->d_lock);
e7854723	103	spin_unlock(&sbi->lookup_lock);
d4a85e35 IK	104	dput(prev);
	105	return NULL;
	106	}
	107
	108	q = list_entry(next, struct dentry, d_u.d_child);
	109
	110	spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
a45440f0	111	/* Already gone or negative dentry (under construction) - try next */
84d08fa8	112	if (!d_count(q) \|\| !simple_positive(q)) {
a45440f0 IK	113	spin_unlock(&q->d_lock);
	114	next = q->d_u.d_child.next;
	115	goto cont;
d4a85e35 IK	116	}
	117	dget_dlock(q);
	118	spin_unlock(&q->d_lock);
a45440f0	119	spin_unlock(&root->d_lock);
e7854723	120	spin_unlock(&sbi->lookup_lock);
d4a85e35 IK	121
	122	dput(prev);
	123
	124	return q;
	125	}
	126
1ce12bad	127	/*
2fd6b7f5	128	* Calculate and dget next entry in top down tree traversal.
1ce12bad	129	*/
2fd6b7f5 NP	130	static struct dentry get_next_positive_dentry(struct dentry prev,
2fd6b7f5 NP	131	struct dentry *root)
1ce12bad	132	{
e7854723	133	struct autofs_sb_info *sbi = autofs4_sbi(root->d_sb);
2fd6b7f5 NP	134	struct list_head *next;
	135	struct dentry p, ret;
	136
	137	if (prev == NULL)
c14cc63a	138	return dget(root);
1ce12bad	139
e7854723	140	spin_lock(&sbi->lookup_lock);
2fd6b7f5 NP	141	relock:
	142	p = prev;
	143	spin_lock(&p->d_lock);
	144	again:
	145	next = p->d_subdirs.next;
1ce12bad IK	146	if (next == &p->d_subdirs) {
1ce12bad IK	147	while (1) {
2fd6b7f5 NP	148	struct dentry *parent;
	149
	150	if (p == root) {
	151	spin_unlock(&p->d_lock);
e7854723	152	spin_unlock(&sbi->lookup_lock);
2fd6b7f5	153	dput(prev);
1ce12bad	154	return NULL;
2fd6b7f5 NP	155	}
	156
	157	parent = p->d_parent;
	158	if (!spin_trylock(&parent->d_lock)) {
	159	spin_unlock(&p->d_lock);
	160	cpu_relax();
	161	goto relock;
	162	}
	163	spin_unlock(&p->d_lock);
1ce12bad	164	next = p->d_u.d_child.next;
2fd6b7f5 NP	165	p = parent;
2fd6b7f5 NP	166	if (next != &parent->d_subdirs)
1ce12bad	167	break;
1ce12bad IK	168	}
1ce12bad IK	169	}
2fd6b7f5 NP	170	ret = list_entry(next, struct dentry, d_u.d_child);
	171
	172	spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
	173	/* Negative dentry - try next */
	174	if (!simple_positive(ret)) {
c14cc63a	175	spin_unlock(&p->d_lock);
1d6f2097	176	lock_set_subclass(&ret->d_lock.dep_map, 0, _RET_IP_);
2fd6b7f5 NP	177	p = ret;
	178	goto again;
	179	}
	180	dget_dlock(ret);
	181	spin_unlock(&ret->d_lock);
	182	spin_unlock(&p->d_lock);
e7854723	183	spin_unlock(&sbi->lookup_lock);
2fd6b7f5 NP	184
	185	dput(prev);
	186
	187	return ret;
1ce12bad IK	188	}
1ce12bad IK	189
3a15e2ab IK	190	/*
	191	* Check a direct mount point for busyness.
	192	* Direct mounts have similar expiry semantics to tree mounts.
	193	* The tree is not busy iff no mountpoints are busy and there are no
	194	* autofs submounts.
	195	*/
	196	static int autofs4_direct_busy(struct vfsmount *mnt,
	197	struct dentry *top,
	198	unsigned long timeout,
	199	int do_now)
	200	{
	201	DPRINTK("top %p %.*s",
	202	top, (int) top->d_name.len, top->d_name.name);
	203
3a15e2ab IK	204	/* If it's busy update the expiry counters */
	205	if (!may_umount_tree(mnt)) {
	206	struct autofs_info *ino = autofs4_dentry_ino(top);
	207	if (ino)
	208	ino->last_used = jiffies;
	209	return 1;
	210	}
	211
	212	/* Timeout of a direct mount is determined by its top dentry */
	213	if (!autofs4_can_expire(top, timeout, do_now))
	214	return 1;
	215
	216	return 0;
	217	}
	218
1da177e4 LT	219	/* Check a directory tree of mount points for busyness
1da177e4 LT	220	* The tree is not busy iff no mountpoints are busy
1da177e4	221	*/
1f5f2c30 IK	222	static int autofs4_tree_busy(struct vfsmount *mnt,
	223	struct dentry *top,
	224	unsigned long timeout,
	225	int do_now)
1da177e4	226	{
e0a7aae9	227	struct autofs_info *top_ino = autofs4_dentry_ino(top);
1ce12bad	228	struct dentry *p;
1da177e4	229
1f5f2c30	230	DPRINTK("top %p %.*s",
1da177e4 LT	231	top, (int)top->d_name.len, top->d_name.name);
	232
	233	/* Negative dentry - give up */
	234	if (!simple_positive(top))
1f5f2c30	235	return 1;
1da177e4	236
2fd6b7f5 NP	237	p = NULL;
2fd6b7f5 NP	238	while ((p = get_next_positive_dentry(p, top))) {
1da177e4	239	DPRINTK("dentry %p %.*s",
1ce12bad	240	p, (int) p->d_name.len, p->d_name.name);
1da177e4	241
1aff3c8b IK	242	/*
	243	* Is someone visiting anywhere in the subtree ?
	244	* If there's no mount we need to check the usage
	245	* count for the autofs dentry.
e0a7aae9	246	* If the fs is busy update the expiry counter.
1aff3c8b	247	*/
1ce12bad	248	if (d_mountpoint(p)) {
1ce12bad	249	if (autofs4_mount_busy(mnt, p)) {
e0a7aae9	250	top_ino->last_used = jiffies;
1ce12bad	251	dput(p);
1f5f2c30	252	return 1;
1da177e4	253	}
1aff3c8b	254	} else {
e0a7aae9	255	struct autofs_info *ino = autofs4_dentry_ino(p);
1aff3c8b IK	256	unsigned int ino_count = atomic_read(&ino->count);
	257
	258	/* allow for dget above and top is already dgot */
	259	if (p == top)
	260	ino_count += 2;
	261	else
	262	ino_count++;
	263
84d08fa8	264	if (d_count(p) > ino_count) {
e0a7aae9	265	top_ino->last_used = jiffies;
1aff3c8b IK	266	dput(p);
	267	return 1;
	268	}
1da177e4	269	}
1da177e4	270	}
1aff3c8b IK	271
	272	/* Timeout of a tree mount is ultimately determined by its top dentry */
	273	if (!autofs4_can_expire(top, timeout, do_now))
	274	return 1;
	275
1f5f2c30	276	return 0;
1da177e4 LT	277	}
	278
	279	static struct dentry autofs4_check_leaves(struct vfsmount mnt,
	280	struct dentry *parent,
	281	unsigned long timeout,
	282	int do_now)
	283	{
1ce12bad	284	struct dentry *p;
1da177e4 LT	285
	286	DPRINTK("parent %p %.*s",
	287	parent, (int)parent->d_name.len, parent->d_name.name);
	288
2fd6b7f5 NP	289	p = NULL;
2fd6b7f5 NP	290	while ((p = get_next_positive_dentry(p, parent))) {
1da177e4	291	DPRINTK("dentry %p %.*s",
1ce12bad	292	p, (int) p->d_name.len, p->d_name.name);
1da177e4	293
1ce12bad	294	if (d_mountpoint(p)) {
e0a7aae9 IK	295	/* Can we umount this guy */
e0a7aae9 IK	296	if (autofs4_mount_busy(mnt, p))
2fd6b7f5	297	continue;
1da177e4	298
e0a7aae9 IK	299	/* Can we expire this guy */
e0a7aae9 IK	300	if (autofs4_can_expire(p, timeout, do_now))
1ce12bad	301	return p;
1da177e4	302	}
1da177e4	303	}
1da177e4 LT	304	return NULL;
	305	}
	306
3a15e2ab	307	/* Check if we can expire a direct mount (possibly a tree) */
8d7b48e0 IK	308	struct dentry autofs4_expire_direct(struct super_block sb,
	309	struct vfsmount *mnt,
	310	struct autofs_sb_info *sbi,
	311	int how)
3a15e2ab IK	312	{
	313	unsigned long timeout;
	314	struct dentry *root = dget(sb->s_root);
	315	int do_now = how & AUTOFS_EXP_IMMEDIATE;
b5b80177	316	struct autofs_info *ino;
3a15e2ab	317
c0ba7e51	318	if (!root)
3a15e2ab IK	319	return NULL;
	320
	321	now = jiffies;
	322	timeout = sbi->exp_timeout;
	323
3a15e2ab	324	spin_lock(&sbi->fs_lock);
b5b80177 IK	325	ino = autofs4_dentry_ino(root);
b5b80177 IK	326	/* No point expiring a pending mount */
f9398c23 IK	327	if (ino->flags & AUTOFS_INF_PENDING)
f9398c23 IK	328	goto out;
3a15e2ab	329	if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
3a15e2ab	330	ino->flags \|= AUTOFS_INF_EXPIRING;
6e60a9ab	331	init_completion(&ino->expire_complete);
3a15e2ab IK	332	spin_unlock(&sbi->fs_lock);
	333	return root;
	334	}
f9398c23	335	out:
3a15e2ab IK	336	spin_unlock(&sbi->fs_lock);
	337	dput(root);
	338
	339	return NULL;
	340	}
	341
1da177e4 LT	342	/*
	343	* Find an eligible tree to time-out
	344	* A tree is eligible if :-
	345	* - it is unused by any user process
	346	* - it has been unused for exp_timeout time
	347	*/
8d7b48e0 IK	348	struct dentry autofs4_expire_indirect(struct super_block sb,
	349	struct vfsmount *mnt,
	350	struct autofs_sb_info *sbi,
	351	int how)
1da177e4 LT	352	{
	353	unsigned long timeout;
	354	struct dentry *root = sb->s_root;
2fd6b7f5	355	struct dentry *dentry;
1da177e4	356	struct dentry *expired = NULL;
1da177e4 LT	357	int do_now = how & AUTOFS_EXP_IMMEDIATE;
1da177e4 LT	358	int exp_leaves = how & AUTOFS_EXP_LEAVES;
97e7449a IK	359	struct autofs_info *ino;
97e7449a IK	360	unsigned int ino_count;
1da177e4	361
c0ba7e51	362	if (!root)
1da177e4 LT	363	return NULL;
	364
	365	now = jiffies;
	366	timeout = sbi->exp_timeout;
	367
2fd6b7f5	368	dentry = NULL;
d4a85e35	369	while ((dentry = get_next_positive_subdir(dentry, root))) {
97e7449a IK	370	spin_lock(&sbi->fs_lock);
97e7449a IK	371	ino = autofs4_dentry_ino(dentry);
b5b80177 IK	372	/* No point expiring a pending mount */
b5b80177 IK	373	if (ino->flags & AUTOFS_INF_PENDING)
3c319985	374	goto next;
97e7449a	375
3a15e2ab IK	376	/*
	377	* Case 1: (i) indirect mount or top level pseudo direct mount
	378	* (autofs-4.1).
	379	* (ii) indirect mount with offset mount, check the "/"
	380	* offset (autofs-5.0+).
	381	*/
1da177e4 LT	382	if (d_mountpoint(dentry)) {
	383	DPRINTK("checking mountpoint %p %.*s",
	384	dentry, (int)dentry->d_name.len, dentry->d_name.name);
	385
e0a7aae9 IK	386	/* Can we umount this guy */
e0a7aae9 IK	387	if (autofs4_mount_busy(mnt, dentry))
1da177e4 LT	388	goto next;
1da177e4 LT	389
e0a7aae9 IK	390	/* Can we expire this guy */
e0a7aae9 IK	391	if (autofs4_can_expire(dentry, timeout, do_now)) {
1da177e4	392	expired = dentry;
afec570c	393	goto found;
1da177e4 LT	394	}
	395	goto next;
	396	}
	397
8dc51fe5 IK	398	if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)) {
	399	DPRINTK("checking symlink %p %.*s",
	400	dentry, (int)dentry->d_name.len, dentry->d_name.name);
	401	/*
	402	* A symlink can't be "busy" in the usual sense so
	403	* just check last used for expire timeout.
	404	*/
	405	if (autofs4_can_expire(dentry, timeout, do_now)) {
	406	expired = dentry;
	407	goto found;
	408	}
	409	goto next;
	410	}
	411
1f5f2c30	412	if (simple_empty(dentry))
1da177e4 LT	413	goto next;
	414
	415	/* Case 2: tree mount, expire iff entire tree is not busy */
	416	if (!exp_leaves) {
97e7449a IK	417	/* Path walk currently on this dentry? */
97e7449a IK	418	ino_count = atomic_read(&ino->count) + 1;
84d08fa8	419	if (d_count(dentry) > ino_count)
97e7449a	420	goto next;
3a9720ce	421
97e7449a	422	if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
3a9720ce	423	expired = dentry;
afec570c	424	goto found;
1da177e4	425	}
3a15e2ab IK	426	/*
	427	* Case 3: pseudo direct mount, expire individual leaves
	428	* (autofs-4.1).
	429	*/
1da177e4	430	} else {
97e7449a IK	431	/* Path walk currently on this dentry? */
97e7449a IK	432	ino_count = atomic_read(&ino->count) + 1;
84d08fa8	433	if (d_count(dentry) > ino_count)
97e7449a IK	434	goto next;
97e7449a IK	435
1da177e4 LT	436	expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
	437	if (expired) {
	438	dput(dentry);
afec570c	439	goto found;
1da177e4 LT	440	}
	441	}
	442	next:
97e7449a	443	spin_unlock(&sbi->fs_lock);
1da177e4	444	}
1da177e4	445	return NULL;
afec570c IK	446
	447	found:
	448	DPRINTK("returning %p %.*s",
	449	expired, (int)expired->d_name.len, expired->d_name.name);
97e7449a IK	450	ino = autofs4_dentry_ino(expired);
97e7449a IK	451	ino->flags \|= AUTOFS_INF_EXPIRING;
6e60a9ab	452	init_completion(&ino->expire_complete);
97e7449a	453	spin_unlock(&sbi->fs_lock);
e7854723	454	spin_lock(&sbi->lookup_lock);
2fd6b7f5 NP	455	spin_lock(&expired->d_parent->d_lock);
2fd6b7f5 NP	456	spin_lock_nested(&expired->d_lock, DENTRY_D_LOCK_NESTED);
afec570c	457	list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
2fd6b7f5 NP	458	spin_unlock(&expired->d_lock);
2fd6b7f5 NP	459	spin_unlock(&expired->d_parent->d_lock);
e7854723	460	spin_unlock(&sbi->lookup_lock);
afec570c	461	return expired;
1da177e4 LT	462	}
1da177e4 LT	463
06a35985 IK	464	int autofs4_expire_wait(struct dentry *dentry)
	465	{
	466	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
	467	struct autofs_info *ino = autofs4_dentry_ino(dentry);
	468	int status;
	469
	470	/* Block on any pending expire */
	471	spin_lock(&sbi->fs_lock);
	472	if (ino->flags & AUTOFS_INF_EXPIRING) {
	473	spin_unlock(&sbi->fs_lock);
	474
	475	DPRINTK("waiting for expire %p name=%.*s",
	476	dentry, dentry->d_name.len, dentry->d_name.name);
	477
	478	status = autofs4_wait(sbi, dentry, NFY_NONE);
	479	wait_for_completion(&ino->expire_complete);
	480
	481	DPRINTK("expire done status=%d", status);
	482
4b1ae27a	483	if (d_unhashed(dentry))
06a35985 IK	484	return -EAGAIN;
	485
	486	return status;
	487	}
	488	spin_unlock(&sbi->fs_lock);
	489
	490	return 0;
	491	}
	492
1da177e4 LT	493	/* Perform an expiry operation */
	494	int autofs4_expire_run(struct super_block *sb,
	495	struct vfsmount *mnt,
	496	struct autofs_sb_info *sbi,
	497	struct autofs_packet_expire __user *pkt_p)
	498	{
	499	struct autofs_packet_expire pkt;
97e7449a	500	struct autofs_info *ino;
1da177e4	501	struct dentry *dentry;
97e7449a	502	int ret = 0;
1da177e4 LT	503
	504	memset(&pkt,0,sizeof pkt);
	505
	506	pkt.hdr.proto_version = sbi->version;
	507	pkt.hdr.type = autofs_ptype_expire;
	508
3a15e2ab	509	if ((dentry = autofs4_expire_indirect(sb, mnt, sbi, 0)) == NULL)
1da177e4 LT	510	return -EAGAIN;
	511
	512	pkt.len = dentry->d_name.len;
	513	memcpy(pkt.name, dentry->d_name.name, pkt.len);
	514	pkt.name[pkt.len] = '\0';
	515	dput(dentry);
	516
	517	if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
97e7449a	518	ret = -EFAULT;
1da177e4	519
97e7449a IK	520	spin_lock(&sbi->fs_lock);
	521	ino = autofs4_dentry_ino(dentry);
	522	ino->flags &= ~AUTOFS_INF_EXPIRING;
6e60a9ab	523	complete_all(&ino->expire_complete);
97e7449a IK	524	spin_unlock(&sbi->fs_lock);
	525
	526	return ret;
1da177e4 LT	527	}
1da177e4 LT	528
56fcef75 IK	529	int autofs4_do_expire_multi(struct super_block sb, struct vfsmount mnt,
56fcef75 IK	530	struct autofs_sb_info *sbi, int when)
1da177e4 LT	531	{
	532	struct dentry *dentry;
	533	int ret = -EAGAIN;
1da177e4	534
a92daf6b	535	if (autofs_type_trigger(sbi->type))
56fcef75	536	dentry = autofs4_expire_direct(sb, mnt, sbi, when);
3a15e2ab	537	else
56fcef75	538	dentry = autofs4_expire_indirect(sb, mnt, sbi, when);
3a15e2ab IK	539
3a15e2ab IK	540	if (dentry) {
1f5f2c30	541	struct autofs_info *ino = autofs4_dentry_ino(dentry);
1da177e4 LT	542
	543	/* This is synchronous because it makes the daemon a
	544	little easier */
1da177e4	545	ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
6e60a9ab	546
97e7449a	547	spin_lock(&sbi->fs_lock);
1f5f2c30	548	ino->flags &= ~AUTOFS_INF_EXPIRING;
6e60a9ab	549	complete_all(&ino->expire_complete);
97e7449a	550	spin_unlock(&sbi->fs_lock);
1da177e4 LT	551	dput(dentry);
1da177e4 LT	552	}
1f5f2c30	553
1da177e4 LT	554	return ret;
	555	}
	556
56fcef75 IK	557	/* Call repeatedly until it returns -EAGAIN, meaning there's nothing
	558	more to be done */
	559	int autofs4_expire_multi(struct super_block sb, struct vfsmount mnt,
	560	struct autofs_sb_info sbi, int __user arg)
	561	{
	562	int do_now = 0;
	563
	564	if (arg && get_user(do_now, arg))
	565	return -EFAULT;
	566
	567	return autofs4_do_expire_multi(sb, mnt, sbi, do_now);
	568	}
	569