1 /*
2 * High memory handling common code and variables.
3 *
4 * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
5 * Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
6 *
7 *
8 * Redesigned the x86 32-bit VM architecture to deal with
9 * 64-bit physical space. With current x86 CPUs this
10 * means up to 64 Gigabytes physical RAM.
11 *
12 * Rewrote high memory support to move the page cache into
13 * high memory. Implemented permanent (schedulable) kmaps
14 * based on Linus' idea.
15 *
16 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
17 */
18
19 #include <linux/mm.h>
20 #include <linux/pagemap.h>
21 #include <linux/highmem.h>
22 #include <linux/swap.h>
23 #include <linux/slab.h>
24
25 /*
26 * Virtual_count is not a pure "count".
27 * 0 means that it is not mapped, and has not been mapped
28 * since a TLB flush - it is usable.
29 * 1 means that there are no users, but it has been mapped
30 * since the last TLB flush - so we can't use it.
31 * n means that there are (n-1) current users of it.
32 */
33 static int pkmap_count[LAST_PKMAP];
34 static unsigned int last_pkmap_nr;
35 static spinlock_t kmap_lock = SPIN_LOCK_UNLOCKED;
36
37 pte_t * pkmap_page_table;
38
39 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
40
41 static void flush_all_zero_pkmaps(void)
42 {
43 int i;
44
45 flush_cache_all();
46
47 for (i = 0; i < LAST_PKMAP; i++) {
48 struct page *page;
49 pte_t pte;
50 /*
51 * zero means we don't have anything to do,
52 * >1 means that it is still in use. Only
53 * a count of 1 means that it is free but
54 * needs to be unmapped
55 */
56 if (pkmap_count[i] != 1)
57 continue;
58 pkmap_count[i] = 0;
59 pte = ptep_get_and_clear(pkmap_page_table+i);
60 if (pte_none(pte))
61 BUG();
62 page = pte_page(pte);
63 page->virtual = NULL;
64 }
65 flush_tlb_all();
66 }
67
68 static inline unsigned long map_new_virtual(struct page *page)
69 {
70 unsigned long vaddr;
71 int count;
72
73 start:
74 count = LAST_PKMAP;
75 /* Find an empty entry */
76 for (;;) {
77 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
78 if (!last_pkmap_nr) {
79 flush_all_zero_pkmaps();
80 count = LAST_PKMAP;
81 }
82 if (!pkmap_count[last_pkmap_nr])
83 break; /* Found a usable entry */
84 if (--count)
85 continue;
86
87 /*
88 * Sleep for somebody else to unmap their entries
89 */
90 {
91 DECLARE_WAITQUEUE(wait, current);
92
93 current->state = TASK_UNINTERRUPTIBLE;
94 add_wait_queue(&pkmap_map_wait, &wait);
95 spin_unlock(&kmap_lock);
96 schedule();
97 remove_wait_queue(&pkmap_map_wait, &wait);
98 spin_lock(&kmap_lock);
99
100 /* Somebody else might have mapped it while we slept */
101 if (page->virtual)
102 return (unsigned long) page->virtual;
103
104 /* Re-start */
105 goto start;
106 }
107 }
108 vaddr = PKMAP_ADDR(last_pkmap_nr);
109 set_pte(&(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
110
111 pkmap_count[last_pkmap_nr] = 1;
112 page->virtual = (void *) vaddr;
113
114 return vaddr;
115 }
116
117 void *kmap_high(struct page *page)
118 {
119 unsigned long vaddr;
120
121 /*
122 * For highmem pages, we can't trust "virtual" until
123 * after we have the lock.
124 *
125 * We cannot call this from interrupts, as it may block
126 */
127 spin_lock(&kmap_lock);
128 vaddr = (unsigned long) page->virtual;
129 if (!vaddr)
130 vaddr = map_new_virtual(page);
131 pkmap_count[PKMAP_NR(vaddr)]++;
132 if (pkmap_count[PKMAP_NR(vaddr)] < 2)
133 BUG();
134 spin_unlock(&kmap_lock);
135 return (void*) vaddr;
136 }
137
138 void kunmap_high(struct page *page)
139 {
140 unsigned long vaddr;
141 unsigned long nr;
142
143 spin_lock(&kmap_lock);
144 vaddr = (unsigned long) page->virtual;
145 if (!vaddr)
146 BUG();
147 nr = PKMAP_NR(vaddr);
148
149 /*
150 * A count must never go down to zero
151 * without a TLB flush!
152 */
153 switch (--pkmap_count[nr]) {
154 case 0:
155 BUG();
156 case 1:
157 wake_up(&pkmap_map_wait);
158 }
159 spin_unlock(&kmap_lock);
160 }
161
162 /*
163 * Simple bounce buffer support for highmem pages.
164 * This will be moved to the block layer in 2.5.
165 */
166
167 static inline void copy_from_high_bh (struct buffer_head *to,
168 struct buffer_head *from)
169 {
170 struct page *p_from;
171 char *vfrom;
172 unsigned long flags;
173
174 p_from = from->b_page;
175
176 /*
177 * Since this can be executed from IRQ context, reentrance
178 * on the same CPU must be avoided:
179 */
180 __save_flags(flags);
181 __cli();
182 vfrom = kmap_atomic(p_from, KM_BOUNCE_WRITE);
183 memcpy(to->b_data, vfrom + bh_offset(from), to->b_size);
184 kunmap_atomic(vfrom, KM_BOUNCE_WRITE);
185 __restore_flags(flags);
186 }
187
188 static inline void copy_to_high_bh_irq (struct buffer_head *to,
189 struct buffer_head *from)
190 {
191 struct page *p_to;
192 char *vto;
193 unsigned long flags;
194
195 p_to = to->b_page;
196 __save_flags(flags);
197 __cli();
198 vto = kmap_atomic(p_to, KM_BOUNCE_READ);
199 memcpy(vto + bh_offset(to), from->b_data, to->b_size);
200 kunmap_atomic(vto, KM_BOUNCE_READ);
201 __restore_flags(flags);
202 }
203
204 static inline void bounce_end_io (struct buffer_head *bh, int uptodate)
205 {
206 struct buffer_head *bh_orig = (struct buffer_head *)(bh->b_private);
207
208 bh_orig->b_end_io(bh_orig, uptodate);
209 __free_page(bh->b_page);
210 kmem_cache_free(bh_cachep, bh);
211 }
212
213 static void bounce_end_io_write (struct buffer_head *bh, int uptodate)
214 {
215 bounce_end_io(bh, uptodate);
216 }
217
218 static void bounce_end_io_read (struct buffer_head *bh, int uptodate)
219 {
220 struct buffer_head *bh_orig = (struct buffer_head *)(bh->b_private);
221
222 if (uptodate)
223 copy_to_high_bh_irq(bh_orig, bh);
224 bounce_end_io(bh, uptodate);
225 }
226
227 struct buffer_head * create_bounce(int rw, struct buffer_head * bh_orig)
228 {
229 struct page *page;
230 struct buffer_head *bh;
231
232 if (!PageHighMem(bh_orig->b_page))
233 return bh_orig;
234
235 repeat_bh:
236 bh = kmem_cache_alloc(bh_cachep, SLAB_BUFFER);
237 if (!bh) {
238 wakeup_bdflush(1); /* Sets task->state to TASK_RUNNING */
239 goto repeat_bh;
240 }
241 /*
242 * This is wasteful for 1k buffers, but this is a stopgap measure
243 * and we are being ineffective anyway. This approach simplifies
244 * things immensly. On boxes with more than 4GB RAM this should
245 * not be an issue anyway.
246 */
247 repeat_page:
248 page = alloc_page(GFP_BUFFER);
249 if (!page) {
250 wakeup_bdflush(1); /* Sets task->state to TASK_RUNNING */
251 goto repeat_page;
252 }
253 set_bh_page(bh, page, 0);
254
255 bh->b_next = NULL;
256 bh->b_blocknr = bh_orig->b_blocknr;
257 bh->b_size = bh_orig->b_size;
258 bh->b_list = -1;
259 bh->b_dev = bh_orig->b_dev;
260 bh->b_count = bh_orig->b_count;
261 bh->b_rdev = bh_orig->b_rdev;
262 bh->b_state = bh_orig->b_state;
263 bh->b_flushtime = jiffies;
264 bh->b_next_free = NULL;
265 bh->b_prev_free = NULL;
266 /* bh->b_this_page */
267 bh->b_reqnext = NULL;
268 bh->b_pprev = NULL;
269 /* bh->b_page */
270 if (rw == WRITE) {
271 bh->b_end_io = bounce_end_io_write;
272 copy_from_high_bh(bh, bh_orig);
273 } else
274 bh->b_end_io = bounce_end_io_read;
275 bh->b_private = (void *)bh_orig;
276 bh->b_rsector = bh_orig->b_rsector;
277 memset(&bh->b_wait, -1, sizeof(bh->b_wait));
278
279 return bh;
280 }
281
282
This page was automatically generated by the
LXR engine.
Visit the LXR main site for more
information.