sparc/lib/bitext.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * bitext.c: kernel little helper (of bit shuffling variety).
0004  *
0005  * Copyright (C) 2002 Pete Zaitcev <zaitcev@yahoo.com>
0006  *
0007  * The algorithm to search a zero bit string is geared towards its application.
0008  * We expect a couple of fixed sizes of requests, so a rotating counter, reset
0009  * by align size, should provide fast enough search while maintaining low
0010  * fragmentation.
0011  */
0012
0013 #include <linux/string.h>
0014 #include <linux/bitmap.h>
0015
0016 #include <asm/bitext.h>
0017
0018 /**
0019  * bit_map_string_get - find and set a bit string in bit map.
0020  * @t: the bit map.
0021  * @len: requested string length
0022  * @align: requested alignment
0023  *
0024  * Returns offset in the map or -1 if out of space.
0025  *
0026  * Not safe to call from an interrupt (uses spin_lock).
0027  */
0028 int bit_map_string_get(struct bit_map *t, int len, int align)
0029 {
0030     int offset, count;  /* siamese twins */
0031     int off_new;
0032     int align1;
0033     int i, color;
0034
0035     if (t->num_colors) {
0036         /* align is overloaded to be the page color */
0037         color = align;
0038         align = t->num_colors;
0039     } else {
0040         color = 0;
0041         if (align == 0)
0042             align = 1;
0043     }
0044     align1 = align - 1;
0045     if ((align & align1) != 0)
0046         BUG();
0047     if (align < 0 || align >= t->size)
0048         BUG();
0049     if (len <= 0 || len > t->size)
0050         BUG();
0051     color &= align1;
0052
0053     spin_lock(&t->lock);
0054     if (len < t->last_size)
0055         offset = t->first_free;
0056     else
0057         offset = t->last_off & ~align1;
0058     count = 0;
0059     for (;;) {
0060         off_new = find_next_zero_bit(t->map, t->size, offset);
0061         off_new = ((off_new + align1) & ~align1) + color;
0062         count += off_new - offset;
0063         offset = off_new;
0064         if (offset >= t->size)
0065             offset = 0;
0066         if (count + len > t->size) {
0067             spin_unlock(&t->lock);
0068 /* P3 */ printk(KERN_ERR
0069   "bitmap out: size %d used %d off %d len %d align %d count %d\n",
0070   t->size, t->used, offset, len, align, count);
0071             return -1;
0072         }
0073
0074         if (offset + len > t->size) {
0075             count += t->size - offset;
0076             offset = 0;
0077             continue;
0078         }
0079
0080         i = 0;
0081         while (test_bit(offset + i, t->map) == 0) {
0082             i++;
0083             if (i == len) {
0084                 bitmap_set(t->map, offset, len);
0085                 if (offset == t->first_free)
0086                     t->first_free = find_next_zero_bit
0087                             (t->map, t->size,
0088                              t->first_free + len);
0089                 if ((t->last_off = offset + len) >= t->size)
0090                     t->last_off = 0;
0091                 t->used += len;
0092                 t->last_size = len;
0093                 spin_unlock(&t->lock);
0094                 return offset;
0095             }
0096         }
0097         count += i + 1;
0098         if ((offset += i + 1) >= t->size)
0099             offset = 0;
0100     }
0101 }
0102
0103 void bit_map_clear(struct bit_map *t, int offset, int len)
0104 {
0105     int i;
0106
0107     if (t->used < len)
0108         BUG();      /* Much too late to do any good, but alas... */
0109     spin_lock(&t->lock);
0110     for (i = 0; i < len; i++) {
0111         if (test_bit(offset + i, t->map) == 0)
0112             BUG();
0113         __clear_bit(offset + i, t->map);
0114     }
0115     if (offset < t->first_free)
0116         t->first_free = offset;
0117     t->used -= len;
0118     spin_unlock(&t->lock);
0119 }
0120
0121 void bit_map_init(struct bit_map *t, unsigned long *map, int size)
0122 {
0123     bitmap_zero(map, size);
0124     memset(t, 0, sizeof *t);
0125     spin_lock_init(&t->lock);
0126     t->map = map;
0127     t->size = size;
0128 }