WebSVN – HelenOS-historic – Diff – /kernel/trunk/genarch/src/mm/page_ht.c


/*
 * Copyright (C) 2006 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
/**
 * @file    page_ht.c
 * @brief   Virtual Address Translation (VAT) for global page hash table.
 */
 
#include <genarch/mm/page_ht.h>
#include <mm/page.h>
#include <arch/mm/page.h>
#include <mm/frame.h>
#include <mm/slab.h>
#include <mm/as.h>
#include <arch/mm/asid.h>
#include <arch/types.h>
#include <typedefs.h>
#include <arch/asm.h>
#include <synch/spinlock.h>
#include <arch.h>
#include <debug.h>
#include <memstr.h>
#include <adt/hash_table.h>
#include <align.h>
 
static index_t hash(__native key[]);
static bool compare(__native key[], count_t keys, link_t *item);
static void remove_callback(link_t *item);
 
static void ht_mapping_insert(as_t *as, __address page, __address frame, int flags);
static void ht_mapping_remove(as_t *as, __address page);
static pte_t *ht_mapping_find(as_t *as, __address page);
 
/**
 * This lock protects the page hash table. It must be acquired
 * after address space lock and after any address space area
 * locks.
 */
SPINLOCK_INITIALIZE(page_ht_lock);
 
/**
 * Page hash table.
 * The page hash table may be accessed only when page_ht_lock is held.
 */
hash_table_t page_ht;
 
/** Hash table operations for page hash table. */
hash_table_operations_t ht_operations = {
    .hash = hash,
    .compare = compare,
    .remove_callback = remove_callback
};
 
/** Page mapping operations for page hash table architectures. */
page_mapping_operations_t ht_mapping_operations = {
    .mapping_insert = ht_mapping_insert,
    .mapping_remove = ht_mapping_remove,
    .mapping_find = ht_mapping_find
};
 
/** Compute page hash table index.
 *
 * @param key Array of two keys (i.e. page and address space).
 *
 * @return Index into page hash table.
 */
index_t hash(__native key[])
{
    as_t *as = (as_t *) key[KEY_AS];
    __address page = (__address) key[KEY_PAGE];
    index_t index;
   
    /*
     * Virtual page addresses have roughly the same probability
     * of occurring. Least significant bits of VPN compose the
     * hash index.
     */
    index = ((page >> PAGE_WIDTH) & (PAGE_HT_ENTRIES-1));
   
    /*
     * Address space structures are likely to be allocated from
     * similar addresses. Least significant bits compose the
     * hash index.
     */
    index |= ((__native) as) & (PAGE_HT_ENTRIES-1);
   
    return index;
}
 
/** Compare page hash table item with page and/or address space.
 *
 * @param key Array of one or two keys (i.e. page and/or address space).
 * @param keys Number of keys passed.
 * @param item Item to compare the keys with.
 *
 * @return true on match, false otherwise.
 */
bool compare(__native key[], count_t keys, link_t *item)
{
    pte_t *t;
 
    ASSERT(item);
    ASSERT((keys > 0) && (keys <= PAGE_HT_KEYS));
 
    /*
     * Convert item to PTE.
     */
    t = hash_table_get_instance(item, pte_t, link);
 
    if (keys == PAGE_HT_KEYS) {
        return (key[KEY_AS] == (__address) t->as) && (key[KEY_PAGE] == t->page);
    } else {
        return (key[KEY_AS] == (__address) t->as);
    }
}
 
/** Callback on page hash table item removal.
 *
 * @param item Page hash table item being removed.
 */
void remove_callback(link_t *item)
{
    pte_t *t;
 
    ASSERT(item);
 
    /*
     * Convert item to PTE.
     */
    t = hash_table_get_instance(item, pte_t, link);
 
    free(t);
}
 
/** Map page to frame using page hash table.
 *
 * Map virtual address page to physical address frame
 * using flags.
 *
 * The page table must be locked and interrupts must be disabled.
 *
 * @param as Address space to which page belongs.
 * @param page Virtual address of the page to be mapped.
 * @param frame Physical address of memory frame to which the mapping is done.
 * @param flags Flags to be used for mapping.
 */
void ht_mapping_insert(as_t *as, __address page, __address frame, int flags)
{
    pte_t *t;
    __native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
   
    if (!hash_table_find(&page_ht, key)) {
        t = (pte_t *) malloc(sizeof(pte_t), FRAME_ATOMIC);
        ASSERT(t != NULL);
 
        t->g = (flags & PAGE_GLOBAL) != 0;
        t->x = (flags & PAGE_EXEC) != 0;
        t->w = (flags & PAGE_WRITE) != 0;
        t->k = !(flags & PAGE_USER);
        t->c = (flags & PAGE_CACHEABLE) != 0;
        t->p = !(flags & PAGE_NOT_PRESENT);
 
        t->as = as;
        t->page = page;
        t->frame = frame;
 
        hash_table_insert(&page_ht, key, &t->link);
    }
}
 
/** Remove mapping of page from page hash table.
 *
 * Remove any mapping of page within address space as.
 * TLB shootdown should follow in order to make effects of
 * this call visible.
 *
 * The page table must be locked and interrupts must be disabled.
 *
 * @param as Address space to wich page belongs.
 * @param page Virtual address of the page to be demapped.
 */
void ht_mapping_remove(as_t *as, __address page)
{
    __native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
   
    /*
     * Note that removed PTE's will be freed
     * by remove_callback().
     */
    hash_table_remove(&page_ht, key, 2);
}
 
 
/** Find mapping for virtual page in page hash table.
 *
 * Find mapping for virtual page.
 *
 * The page table must be locked and interrupts must be disabled.
 *
 * @param as Address space to wich page belongs.
 * @param page Virtual page.
 *
 * @return NULL if there is no such mapping; requested mapping otherwise.
 */
pte_t *ht_mapping_find(as_t *as, __address page)
{
    link_t *hlp;
    pte_t *t = NULL;
    __native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
   
    hlp = hash_table_find(&page_ht, key);
    if (hlp)
        t = hash_table_get_instance(hlp, pte_t, link);
 
    return t;
}
 

Subversion Repositories HelenOS-historic

(root)/kernel/trunk/genarch/src/mm/page_ht.c – Rev 1248 → 1266

Rev 1248		Rev 1266
1	/*	1	/*
2	* Copyright (C) 2006 Jakub Jermar	2	* Copyright (C) 2006 Jakub Jermar
3	* All rights reserved.	3	* All rights reserved.
4	*	4	*
5	* Redistribution and use in source and binary forms, with or without	5	* Redistribution and use in source and binary forms, with or without
6	* modification, are permitted provided that the following conditions	6	* modification, are permitted provided that the following conditions
7	* are met:	7	* are met:
8	*	8	*
9	* - Redistributions of source code must retain the above copyright	9	* - Redistributions of source code must retain the above copyright
10	* notice, this list of conditions and the following disclaimer.	10	* notice, this list of conditions and the following disclaimer.
11	* - Redistributions in binary form must reproduce the above copyright	11	* - Redistributions in binary form must reproduce the above copyright
12	* notice, this list of conditions and the following disclaimer in the	12	* notice, this list of conditions and the following disclaimer in the
13	* documentation and/or other materials provided with the distribution.	13	* documentation and/or other materials provided with the distribution.
14	* - The name of the author may not be used to endorse or promote products	14	* - The name of the author may not be used to endorse or promote products
15	* derived from this software without specific prior written permission.	15	* derived from this software without specific prior written permission.
16	*	16	*
17	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR	17	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES	18	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.	19	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,	20	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT	21	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,	22	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY	23	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT	24	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF	25	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.	26	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27	*/	27	*/
28		28
-		29	/**
-		30	* @file page_ht.c
-		31	* @brief Virtual Address Translation (VAT) for global page hash table.
-		32	*/
-		33
29	#include <genarch/mm/page_ht.h>	34	#include <genarch/mm/page_ht.h>
30	#include <mm/page.h>	35	#include <mm/page.h>
31	#include <arch/mm/page.h>	36	#include <arch/mm/page.h>
32	#include <mm/frame.h>	37	#include <mm/frame.h>
33	#include <mm/slab.h>	38	#include <mm/slab.h>
34	#include <mm/as.h>	39	#include <mm/as.h>
35	#include <arch/mm/asid.h>	40	#include <arch/mm/asid.h>
36	#include <arch/types.h>	41	#include <arch/types.h>
37	#include <typedefs.h>	42	#include <typedefs.h>
38	#include <arch/asm.h>	43	#include <arch/asm.h>
39	#include <synch/spinlock.h>	44	#include <synch/spinlock.h>
40	#include <arch.h>	45	#include <arch.h>
41	#include <debug.h>	46	#include <debug.h>
42	#include <memstr.h>	47	#include <memstr.h>
43	#include <adt/hash_table.h>	48	#include <adt/hash_table.h>
44	#include <align.h>	49	#include <align.h>
45		50
46	static index_t hash(__native key[]);	51	static index_t hash(__native key[]);
47	static bool compare(__native key[], count_t keys, link_t *item);	52	static bool compare(__native key[], count_t keys, link_t *item);
48	static void remove_callback(link_t *item);	53	static void remove_callback(link_t *item);
49		54
50	static void ht_mapping_insert(as_t *as, __address page, __address frame, int flags);	55	static void ht_mapping_insert(as_t *as, __address page, __address frame, int flags);
51	static void ht_mapping_remove(as_t *as, __address page);	56	static void ht_mapping_remove(as_t *as, __address page);
52	static pte_t ht_mapping_find(as_t as, __address page);	57	static pte_t ht_mapping_find(as_t as, __address page);
53		58
54	/**	59	/**
55	* This lock protects the page hash table. It must be acquired	60	* This lock protects the page hash table. It must be acquired
56	* after address space lock and after any address space area	61	* after address space lock and after any address space area
57	* locks.	62	* locks.
58	*/	63	*/
59	SPINLOCK_INITIALIZE(page_ht_lock);	64	SPINLOCK_INITIALIZE(page_ht_lock);
60		65
61	/**	66	/**
62	* Page hash table.	67	* Page hash table.
63	* The page hash table may be accessed only when page_ht_lock is held.	68	* The page hash table may be accessed only when page_ht_lock is held.
64	*/	69	*/
65	hash_table_t page_ht;	70	hash_table_t page_ht;
66		71
67	/** Hash table operations for page hash table. */	72	/** Hash table operations for page hash table. */
68	hash_table_operations_t ht_operations = {	73	hash_table_operations_t ht_operations = {
69	.hash = hash,	74	.hash = hash,
70	.compare = compare,	75	.compare = compare,
71	.remove_callback = remove_callback	76	.remove_callback = remove_callback
72	};	77	};
73		78
74	/** Page mapping operations for page hash table architectures. */	79	/** Page mapping operations for page hash table architectures. */
75	page_mapping_operations_t ht_mapping_operations = {	80	page_mapping_operations_t ht_mapping_operations = {
76	.mapping_insert = ht_mapping_insert,	81	.mapping_insert = ht_mapping_insert,
77	.mapping_remove = ht_mapping_remove,	82	.mapping_remove = ht_mapping_remove,
78	.mapping_find = ht_mapping_find	83	.mapping_find = ht_mapping_find
79	};	84	};
80		85
81	/** Compute page hash table index.	86	/** Compute page hash table index.
82	*	87	*
83	* @param key Array of two keys (i.e. page and address space).	88	* @param key Array of two keys (i.e. page and address space).
84	*	89	*
85	* @return Index into page hash table.	90	* @return Index into page hash table.
86	*/	91	*/
87	index_t hash(__native key[])	92	index_t hash(__native key[])
88	{	93	{
89	as_t as = (as_t ) key[KEY_AS];	94	as_t as = (as_t ) key[KEY_AS];
90	__address page = (__address) key[KEY_PAGE];	95	__address page = (__address) key[KEY_PAGE];
91	index_t index;	96	index_t index;
92		97
93	/*	98	/*
94	* Virtual page addresses have roughly the same probability	99	* Virtual page addresses have roughly the same probability
95	* of occurring. Least significant bits of VPN compose the	100	* of occurring. Least significant bits of VPN compose the
96	* hash index.	101	* hash index.
97	*/	102	*/
98	index = ((page >> PAGE_WIDTH) & (PAGE_HT_ENTRIES-1));	103	index = ((page >> PAGE_WIDTH) & (PAGE_HT_ENTRIES-1));
99		104
100	/*	105	/*
101	* Address space structures are likely to be allocated from	106	* Address space structures are likely to be allocated from
102	* similar addresses. Least significant bits compose the	107	* similar addresses. Least significant bits compose the
103	* hash index.	108	* hash index.
104	*/	109	*/
105	index \|= ((__native) as) & (PAGE_HT_ENTRIES-1);	110	index \|= ((__native) as) & (PAGE_HT_ENTRIES-1);
106		111
107	return index;	112	return index;
108	}	113	}
109		114
110	/** Compare page hash table item with page and/or address space.	115	/** Compare page hash table item with page and/or address space.
111	*	116	*
112	* @param key Array of one or two keys (i.e. page and/or address space).	117	* @param key Array of one or two keys (i.e. page and/or address space).
113	* @param keys Number of keys passed.	118	* @param keys Number of keys passed.
114	* @param item Item to compare the keys with.	119	* @param item Item to compare the keys with.
115	*	120	*
116	* @return true on match, false otherwise.	121	* @return true on match, false otherwise.
117	*/	122	*/
118	bool compare(__native key[], count_t keys, link_t *item)	123	bool compare(__native key[], count_t keys, link_t *item)
119	{	124	{
120	pte_t *t;	125	pte_t *t;
121		126
122	ASSERT(item);	127	ASSERT(item);
123	ASSERT((keys > 0) && (keys <= PAGE_HT_KEYS));	128	ASSERT((keys > 0) && (keys <= PAGE_HT_KEYS));
124		129
125	/*	130	/*
126	* Convert item to PTE.	131	* Convert item to PTE.
127	*/	132	*/
128	t = hash_table_get_instance(item, pte_t, link);	133	t = hash_table_get_instance(item, pte_t, link);
129		134
130	if (keys == PAGE_HT_KEYS) {	135	if (keys == PAGE_HT_KEYS) {
131	return (key[KEY_AS] == (__address) t->as) && (key[KEY_PAGE] == t->page);	136	return (key[KEY_AS] == (__address) t->as) && (key[KEY_PAGE] == t->page);
132	} else {	137	} else {
133	return (key[KEY_AS] == (__address) t->as);	138	return (key[KEY_AS] == (__address) t->as);
134	}	139	}
135	}	140	}
136		141
137	/** Callback on page hash table item removal.	142	/** Callback on page hash table item removal.
138	*	143	*
139	* @param item Page hash table item being removed.	144	* @param item Page hash table item being removed.
140	*/	145	*/
141	void remove_callback(link_t *item)	146	void remove_callback(link_t *item)
142	{	147	{
143	pte_t *t;	148	pte_t *t;
144		149
145	ASSERT(item);	150	ASSERT(item);
146		151
147	/*	152	/*
148	* Convert item to PTE.	153	* Convert item to PTE.
149	*/	154	*/
150	t = hash_table_get_instance(item, pte_t, link);	155	t = hash_table_get_instance(item, pte_t, link);
151		156
152	free(t);	157	free(t);
153	}	158	}
154		159
155	/** Map page to frame using page hash table.	160	/** Map page to frame using page hash table.
156	*	161	*
157	* Map virtual address page to physical address frame	162	* Map virtual address page to physical address frame
158	* using flags.	163	* using flags.
159	*	164	*
160	* The page table must be locked and interrupts must be disabled.	165	* The page table must be locked and interrupts must be disabled.
161	*	166	*
162	* @param as Address space to which page belongs.	167	* @param as Address space to which page belongs.
163	* @param page Virtual address of the page to be mapped.	168	* @param page Virtual address of the page to be mapped.
164	* @param frame Physical address of memory frame to which the mapping is done.	169	* @param frame Physical address of memory frame to which the mapping is done.
165	* @param flags Flags to be used for mapping.	170	* @param flags Flags to be used for mapping.
166	*/	171	*/
167	void ht_mapping_insert(as_t *as, __address page, __address frame, int flags)	172	void ht_mapping_insert(as_t *as, __address page, __address frame, int flags)
168	{	173	{
169	pte_t *t;	174	pte_t *t;
170	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };	175	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
171		176
172	if (!hash_table_find(&page_ht, key)) {	177	if (!hash_table_find(&page_ht, key)) {
173	t = (pte_t *) malloc(sizeof(pte_t), FRAME_ATOMIC);	178	t = (pte_t *) malloc(sizeof(pte_t), FRAME_ATOMIC);
174	ASSERT(t != NULL);	179	ASSERT(t != NULL);
175		180
176	t->g = (flags & PAGE_GLOBAL) != 0;	181	t->g = (flags & PAGE_GLOBAL) != 0;
177	t->x = (flags & PAGE_EXEC) != 0;	182	t->x = (flags & PAGE_EXEC) != 0;
178	t->w = (flags & PAGE_WRITE) != 0;	183	t->w = (flags & PAGE_WRITE) != 0;
179	t->k = !(flags & PAGE_USER);	184	t->k = !(flags & PAGE_USER);
180	t->c = (flags & PAGE_CACHEABLE) != 0;	185	t->c = (flags & PAGE_CACHEABLE) != 0;
181	t->p = !(flags & PAGE_NOT_PRESENT);	186	t->p = !(flags & PAGE_NOT_PRESENT);
182		187
183	t->as = as;	188	t->as = as;
184	t->page = page;	189	t->page = page;
185	t->frame = frame;	190	t->frame = frame;
186		191
187	hash_table_insert(&page_ht, key, &t->link);	192	hash_table_insert(&page_ht, key, &t->link);
188	}	193	}
189	}	194	}
190		195
191	/** Remove mapping of page from page hash table.	196	/** Remove mapping of page from page hash table.
192	*	197	*
193	* Remove any mapping of page within address space as.	198	* Remove any mapping of page within address space as.
194	* TLB shootdown should follow in order to make effects of	199	* TLB shootdown should follow in order to make effects of
195	* this call visible.	200	* this call visible.
196	*	201	*
197	* The page table must be locked and interrupts must be disabled.	202	* The page table must be locked and interrupts must be disabled.
198	*	203	*
199	* @param as Address space to wich page belongs.	204	* @param as Address space to wich page belongs.
200	* @param page Virtual address of the page to be demapped.	205	* @param page Virtual address of the page to be demapped.
201	*/	206	*/
202	void ht_mapping_remove(as_t *as, __address page)	207	void ht_mapping_remove(as_t *as, __address page)
203	{	208	{
204	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };	209	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
205		210
206	/*	211	/*
207	* Note that removed PTE's will be freed	212	* Note that removed PTE's will be freed
208	* by remove_callback().	213	* by remove_callback().
209	*/	214	*/
210	hash_table_remove(&page_ht, key, 2);	215	hash_table_remove(&page_ht, key, 2);
211	}	216	}
212		217
213		218
214	/** Find mapping for virtual page in page hash table.	219	/** Find mapping for virtual page in page hash table.
215	*	220	*
216	* Find mapping for virtual page.	221	* Find mapping for virtual page.
217	*	222	*
218	* The page table must be locked and interrupts must be disabled.	223	* The page table must be locked and interrupts must be disabled.
219	*	224	*
220	* @param as Address space to wich page belongs.	225	* @param as Address space to wich page belongs.
221	* @param page Virtual page.	226	* @param page Virtual page.
222	*	227	*
223	* @return NULL if there is no such mapping; requested mapping otherwise.	228	* @return NULL if there is no such mapping; requested mapping otherwise.
224	*/	229	*/
225	pte_t ht_mapping_find(as_t as, __address page)	230	pte_t ht_mapping_find(as_t as, __address page)
226	{	231	{
227	link_t *hlp;	232	link_t *hlp;
228	pte_t *t = NULL;	233	pte_t *t = NULL;
229	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };	234	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
230		235
231	hlp = hash_table_find(&page_ht, key);	236	hlp = hash_table_find(&page_ht, key);
232	if (hlp)	237	if (hlp)
233	t = hash_table_get_instance(hlp, pte_t, link);	238	t = hash_table_get_instance(hlp, pte_t, link);
234		239
235	return t;	240	return t;
236	}	241	}
237		242