aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/dirhash.c
blob: 60a3c6933b238821f1fb1a264441f3ade91caf18 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
/* -*- linux-c -*- --------------------------------------------------------- *
 *
 * linux/fs/autofs/dirhash.c
 *
 *  Copyright 1997 Transmeta Corporation -- All Rights Reserved
 *
 * 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"

/* Functions for maintenance of expiry queue */

static void autofs_init_usage(struct autofs_dirhash *dh,
			      struct autofs_dir_ent *ent)
{
	ent->exp_next = &dh->expiry_head;
	ent->exp_prev = dh->expiry_head.exp_prev;
	dh->expiry_head.exp_prev->exp_next = ent;
	dh->expiry_head.exp_prev = ent;
	ent->last_usage = jiffies;
}

static void autofs_delete_usage(struct autofs_dir_ent *ent)
{
	ent->exp_prev->exp_next = ent->exp_next;
	ent->exp_next->exp_prev = ent->exp_prev;
}

void autofs_update_usage(struct autofs_dirhash *dh,
			 struct autofs_dir_ent *ent)
{
	autofs_delete_usage(ent);   /* Unlink from current position */
	autofs_init_usage(dh,ent);  /* Relink at queue tail */
}

struct autofs_dir_ent *autofs_expire(struct autofs_dirhash *dh,
				     unsigned long timeout)
{
	struct autofs_dir_ent *ent;

	ent = dh->expiry_head.exp_next;

	if ( ent == &(dh->expiry_head) ) return NULL;
	return (jiffies - ent->last_usage >= timeout) ? ent : NULL;
}

void autofs_initialize_hash(struct autofs_dirhash *dh) {
	memset(&dh->h, 0, AUTOFS_HASH_SIZE*sizeof(struct autofs_dir_ent *));
	dh->expiry_head.exp_next = dh->expiry_head.exp_prev =
		&dh->expiry_head;
}

struct autofs_dir_ent *autofs_hash_lookup(const struct autofs_dirhash *dh, struct qstr *name)
{
	struct autofs_dir_ent *dhn;

	DPRINTK(("autofs_hash_lookup: hash = 0x%08x, name = ", name->hash));
	autofs_say(name->name,name->len);

	for ( dhn = dh->h[(unsigned) name->hash % AUTOFS_HASH_SIZE] ; dhn ; dhn = dhn->next ) {
		if ( name->hash == dhn->hash &&
		     name->len == dhn->len &&
		     !memcmp(name->name, dhn->name, name->len) )
			break;
	}

	return dhn;
}

void autofs_hash_insert(struct autofs_dirhash *dh, struct autofs_dir_ent *ent)
{
	struct autofs_dir_ent **dhnp;

	DPRINTK(("autofs_hash_insert: hash = 0x%08x, name = ", ent->hash));
	autofs_say(ent->name,ent->len);

	autofs_init_usage(dh,ent);

	dhnp = &dh->h[(unsigned) ent->hash % AUTOFS_HASH_SIZE];
	ent->next = *dhnp;
	ent->back = dhnp;
	*dhnp = ent;
}

void autofs_hash_delete(struct autofs_dir_ent *ent)
{
	*(ent->back) = ent->next;

	autofs_delete_usage(ent);

	kfree(ent->name);
	kfree(ent);
}

/*
 * Used by readdir().  We must validate "ptr", so we can't simply make it
 * a pointer.  Values below 0xffff are reserved; calling with any value
 * <= 0x10000 will return the first entry found.
 */
struct autofs_dir_ent *autofs_hash_enum(const struct autofs_dirhash *dh, off_t *ptr)
{
	int bucket, ecount, i;
	struct autofs_dir_ent *ent;

	bucket = (*ptr >> 16) - 1;
	ecount = *ptr & 0xffff;

	if ( bucket < 0 ) {
		bucket = ecount = 0;
	} 

	DPRINTK(("autofs_hash_enum: bucket %d, entry %d\n", bucket, ecount));

	ent = NULL;

	while  ( bucket < AUTOFS_HASH_SIZE ) {
		ent = dh->h[bucket];
		for ( i = ecount ; ent && i ; i-- )
			ent = ent->next;

		if (ent) {
			ecount++; /* Point to *next* entry */
			break;
		}

		bucket++; ecount = 0;
	}

#ifdef DEBUG
	if ( !ent )
		printk("autofs_hash_enum: nothing found\n");
	else {
		printk("autofs_hash_enum: found hash %08x, name", ent->hash);
		autofs_say(ent->name,ent->len);
	}
#endif

	*ptr = ((bucket+1) << 16) + ecount;
	return ent;
}

/* Delete everything.  This is used on filesystem destruction, so we
   make no attempt to keep the pointers valid */
void autofs_hash_nuke(struct autofs_dirhash *dh)
{
	int i;
	struct autofs_dir_ent *ent, *nent;

	for ( i = 0 ; i < AUTOFS_HASH_SIZE ; i++ ) {
		for ( ent = dh->h[i] ; ent ; ent = nent ) {
			nent = ent->next;
			kfree(ent->name);
			kfree(ent);
		}
	}
}